Patent Publication Number: US-2022213132-A1

Title: Organometallic compound, organic light-emitting device including the same, and diagnostic composition including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 16/240,203, filed Jan. 4, 2019, which claims priority to Korean Patent Applications No. 10-2018-0001851, filed on Jan. 5, 2018, and No. 10-2019-0000390, filed on Jan. 2, 2019, in the Korean Intellectual Property Office, and all the benefits accruing therefrom under 35 U.S.C. § 119, the contents of which are incorporated herein in their entirety by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to an organometallic compound, an organic light-emitting device including the same, and a diagnostic composition including the organometallic compound. 
     2. Description of the Related Art 
     Organic light-emitting devices (OLEDs) are self-emission devices, which have improved characteristics in terms of a viewing angle, a response time, brightness, a driving voltage, and a response speed, and which produce full-color images. 
     In an example, an organic light-emitting device includes an anode, a cathode, and an organic layer disposed between the anode and the cathode, wherein the organic layer includes an emission layer. A hole transport region may be disposed between the anode and the emission layer, and an electron transport region may be disposed between the emission layer and the cathode. Holes provided from the anode may move toward the emission layer through the hole transport region, and electrons provided from the cathode may move toward the emission layer through the electron transport region. The holes and the electrons recombine in the emission layer to produce excitons. These excitons transition from an excited state to a ground state, thereby generating light. 
     Meanwhile, luminescent compounds, for example, phosphorescent compounds, may be used for monitoring, sensing, and detecting biological materials such as various cells and proteins. 
     Various types of organic light emitting devices are known. However, there still remains a need in OLEDs having low driving voltage, high efficiency, high brightness, and long lifespan. 
     SUMMARY 
     Provided are an organometallic compound, an organic light-emitting device including the organometallic compound, and a diagnostic composition including the organometallic compound. 
     Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments. 
     According to an aspect of an embodiment, an organometallic compound is represented by Formula 1: 
     
       
         
         
             
             
         
       
     
     In Formula 1, 
     M may be beryllium (Be), magnesium (Mg), aluminum (AI), calcium (Ca), titanium (Ti), manganese (Mn), cobalt (Co), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), rhenium (Re), platinum (Pt), or gold (Au),
         X 1  may be a chemical bond, O, S, N(R′), P(R′), B(R′), C(R′)(R″) or Si(R′)(R′), and when X 1  is a chemical bond, Y 1  may be directly bonded to M,   X 2  to X 4  may each independently be N or C, two selected from X 2  to X 4  may each be N, and the other may be C,   a bond between X 1  or Y and M may be a covalent bond, one bond selected from a bond between X 2  and M, a bond between X 3  and M, and a bond between X 4  and M may be a covalent bond, and the remaining two bonds may be coordinate bonds,   Y 1  and Y 3  to Y 5  may each independently be C or N,   among pairs of X 2  and Y 3 , X 2  and Y 4 , Y 4  and Y 5 , X 51  and Y 3 , and X 51  and Y 5 , the components in each pair may be linked via a chemical bond,   ring CY 1  to ring CY 5  may each independently be selected from a C 5 -C 30  carbocyclic group and a C 1 -C 30  heterocyclic group, and each of ring CY 1 , ring CY 3 , and ring CY 4  may not be a benzimidazole group,   a cyclometalated ring formed by ring CY 5 , ring CY 2 , ring CY 3 , and M may be a 6-membered ring,   X 51  may be selected from O, S, N—[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 )(R 8 ), Si(R 7 )(R 8 ), Ge(R 7 )(R 8 ), C(═O), N, C(R 7 ), Si(R 7 ), and Ge(R 7 ),   R 7  and R 8  may optionally be linked via a single bond, a double bond, or a first linking group to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a ,   T 1  and T 2  may each independently be a single bond, a double bond, *—N(R 9 )—*′, *—B(R 9 )—*′, *—P(R 9 )—*′, *—C(R 9 )(R 10 )—*′, *—Si(R 9 )(R 10 )—*′, *—Ge(R 9 )(R 10 )—*′, *—S—*′, *—Se—*′, *—O—*′, *—C(═O)—*′, *—S(═O)—*′, *—S(═O) 2 —*, *—C(R 9 )—*′, *═C(R 9 )—*′, *—C(R 9 )═C(R 10 )—*′, *—C(═S)—*′, or *—C≡C—*′,   L 1  to L 4  and L 7  may each independently be selected from a single bond, a substituted or unsubstituted C 5 -C 30  carbocyclic group, and a substituted or unsubstituted C 1 -C 30  heterocyclic group,   b1 to b4 and b7 may each independently be an integer from 1 to 5,   R 1  to R 4 , R 7  to R 10 , R′, and R″ may each independently be selected from hydrogen, deuterium, a deuterium-containing group, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group, a substituted or unsubstituted C 2 -C 60  alkynyl group, a substituted or unsubstituted C 1 -C 60  alkoxy group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted C 1 -C 1  heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 60  alkylaryl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 7 -C 60  arylalkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted C 2 -C 60  heteroarylalkyl group, a substituted or unsubstituted C 2 -C 60  alkylheteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q 1 )(Q 2 ), —Si(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), and —P(═O)(Q 8 )(Q 9 ),   c1 to c4 and c7 may each independently be an integer from 1 to 5,   Z 1  to Z 4  may each independently be deuterium or a deuterium-containing group,   a1 to a4 and n1 to n4 may each independently be an integer from 0 to 20,   i) when X 51  is O, S, C(═O), or N, the sum of n1 to n4 may be 1 or more, ii) when X 51  is N[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 ), Si(R 7 ), or Ge(R 7 ), a) R 7  may be deuterium or a deuterium-containing group; b) the sum of n1 to n4 may be 1 or more; or c) R 7  may be deuterium or a deuterium-containing group and the sum of n1 to n4 may be 1 or more, and iii) when X 51  is C(R 7 )(R 8 ), Si(R 7 )(R 8 ), or Ge(R 7 )(R 8 ), a) at least one selected from R 7  and R 8  may be deuterium or a deuterium-containing group; b) the sum of n1 to n4 may be 1 or more; or c) at least one selected from R 7  and R 8  may be deuterium or a deuterium-containing group and the sum of n1 to n4 may be 1 or more,   two of a plurality of neighboring groups R 1  may be optionally linked to each other to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a ,   two of a plurality of neighboring groups R 2  may be optionally linked to each other to form a C 5 -C 30  carbocyclic group that is unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group that is unsubstituted or substituted with at least one R 10a ,   two of a plurality of neighboring groups R 3  may be optionally linked to each other to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a ,   two of a plurality of neighboring groups R 4  may be optionally linked to each other to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a ,   two or more neighboring groups selected from R 1  to R 4 , R 7  to R 10 , R′, and R″ may be optionally linked to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a , R 10a  has the same definition as R 1 ,   at least one substituent of the substituted C 5 -C 30  carbocyclic group, substituted C 1 -C 30  heterocyclic group, substituted C 1 -C 60  alkyl group, substituted C 2 -C 60  alkenyl group, substituted C 2 -C 60  alkynyl group, substituted C 1 -C 60  alkoxy group, substituted C 3 -C 10  cycloalkyl group, substituted C 1 -C 10  heterocycloalkyl group, substituted C 3 -C 10  cycloalkenyl group, substituted C 1 -C 10  heterocycloalkenyl group, substituted C 6 -C 60  aryl group, substituted C 7 -C 60  alkylaryl group, substituted C 6 -C 60  aryloxy group, substituted C 6 -C 60  arylthio group, substituted C 7 -C 60  arylalkyl group, substituted C 1 -C 60  heteroaryl group, substituted C 1 -C 60  heteroaryloxy group, substituted C 1 -C 60  heteroarylthio group, substituted C 2 -C 60  heteroarylalkyl group, substituted C 2 -C 60  alkylheteroaryl group, substituted monovalent non-aromatic condensed polycyclic group and substituted monovalent non-aromatic condensed heteropolycyclic group may be selected from:   deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, and a C 1 -C 60  alkoxy group;   a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, and a C 1 -C 60  alkoxy group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkylaryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, a C 2 -C 60  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 11 )(Q 12 ), —Si(Q 13 )(Q 14 )(Q 15 ), —B(Q 16 )(Q 17 ), and —P(═O)(Q 18 )(Q 19 );   a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkylaryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, a C 2 -C 60  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group;   a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkylaryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, a C 2 -C 60  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkylaryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, a C 2 -C 60  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 21 )(Q 22 ), —Si(Q 23 )(Q 24 )(Q 25 ), —B(Q 26 )(Q 27 ) and —P(═O)(Q 28 )(Q 29 ); and   —N(Q 31 )(Q 32 ), —Si(Q 33 )(Q 34 )(Q 35 ), —B(Q 36 )(Q 37 ), and —P(═O)(Q 38 )(Q 39 );   wherein Q 1  to Q 9 , Q 11  to Q 19 , Q 21  to Q 29 , and Q 31  to Q 39  may each independently be selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 1 -C 60  alkyl group substituted with at least one selected from deuterium, a C 1 -C 60  alkyl group, and a C 6 -C 60  aryl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 6 -C 60  aryl group substituted with at least one selected from deuterium, a C 1 -C 60  alkyl group, and a C 6 -C 60  aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, a C 2 -C 60  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group.       

     According to an aspect of another embodiment, an organic light-emitting device includes: 
     a first electrode; 
     a second electrode; and 
     an organic layer disposed between the first electrode and the second electrode, 
     wherein the organic layer includes an emission layer and at least one organometallic compound represented by Formula 1. 
     The organometallic compound in the organic layer may function as a dopant. 
     According to an aspect of another embodiment, a diagnostic composition includes at least one organometallic compound represented by Formula 1. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the FIGURE which is a schematic cross-sectional view of an organic light-emitting device according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly in contact with the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present embodiments. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     The term “or” means “and/or.” It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this general inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims. 
     “About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ±30%, 20%, 10%, 5% of the stated value. 
     In an embodiment, an organometallic compound represented by Formula 1 below is provided: 
     
       
         
         
             
             
         
       
     
     M in Formula 1 may be beryllium (Be), magnesium (Mg), aluminum (Al), calcium (Ca), titanium (Ti), manganese (Mn), cobalt (Co), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), rhenium (Re), platinum (Pt), or gold (Au). 
     In an embodiment, M may be Pt, Pd, or Au, but embodiments of the present disclosure are not limited thereto. 
     X 1  in Formula 1 may be a chemical bond (for example, a single bond or a covalent bond), O, S, N(R′), P(R′), B(R′), C(R′)(R′), or Si(R′)(R″). R′ and R″ are the same as described above. When X 1  is a chemical bond, Y 1  and M may directly be linked to each other. 
     For example, X 1  may be O or S, but embodiments of the present disclosure are not limited thereto. 
     X 2  to X 4  in Formula 1 may each independently be N or C, two selected from X 2  to X 4  may each be N, and the remainder may be C. 
     A bond between X 1  or Y 1  and M in Formula 1 may be a covalent bond, one bond selected from a bond between X 2  and M, a bond between X 3  and M, and a bond between X 4  and M may be a covalent bond, and the remaining two bonds may be coordinate bonds. Thus, the organometallic compound represented by Formula 1 may be electrically neutral. 
     In one or more embodiments, in Formula 1,
         i) X 2  and X 4  may each be N, X 3  may be C, a bond between X 2  and M and a bond between X 4  and M may each be a coordinate bond, and a bond between X 3 , and M may be a covalent bond, or   i) X 2  and X 3  may each be N, X 4  may be C, a bond between X 2  and M and a bond between X 3  and M may each be a coordinate bond, and a bond between X 4  and M may be a covalent bond, or   iii) X 3  and X 4  may be N, X 2  may be C, a bond between X 3  and M and a bond between X 4  and M may each be a coordinate bond, and a bond between X 2  and M may be a covalent bond, but embodiments of the present disclosure are not limited thereto.       

     In Formula 1, Y 1  and Y 3  to Y 5  may each independently be C or N, and among pairs of X 2  and Y 3 , X 2  and Y 4 , Y 4  and Y 5 , X 51  and Y 3 , and X 51  and Y 5 , the components in each pair may be linked via a chemical bond. Accordingly, ring CY 5  in the Formula 1 may be a 5-membered ring condensed with ring CY 2 . 
     Ring CY 1  to ring CY 5  in Formula 1 may each independently be selected from a C 5 -C 30  carbocyclic group, and a C 1 -C 30  heterocyclic group, and each of ring CY 1 , ring CY 3 , and ring CY 4  may not be a benzimidazole group. 
     For example, ring CY 1  to ring CY 4  may each independently selected from: i) a first ring, ii) a second ring, iii) a condensed ring in which two or more first rings are condensed with each other, iv) a condensed ring in which two or more second rings are condensed with each other, and v) a condensed ring in which one or more first rings and one or more second rings are condensed with each other, wherein 
     the first ring may be selected from a cyclopentane group, a cyclopentadiene group, a furan group, a thiophene group, a pyrrole group, a silole group, an indene group, a benzofuran group, a benzothiophene group, an indole group, a benzosilole group, an oxazole group, an isoxazole group, an oxadiazole group, an isozadiazole group, an oxatriazole group, an isoxatriazole group, a thiazole group, an isothiazole group, a thiadiazole group, an isothiadiazole group, a thiatriazole group, an isothiatriazole group, a pyrazole group, an imidazole group, a triazole group, a tetrazole group, an azasilole group, a diazasilole group, and a triazasilole group, 
     the second ring may be selected from an adamantane group, a norbomane group, a norbomene group, a cyclohexane group, a cyclohexene group, a benzene group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, and a triazine group, and 
     each of ring CY 1  to ring CY 4  may not be a benzimidazole group. 
     In an embodiment, ring CY 1  to ring CY 4  may each independently be selected from a benzene group, a naphthalene group, an anthracene group, a phenanthrene group, a triphenylene group, a pyrene group, a chrysene group, cyclopentadiene group, a 1,2,3,4-tetrahydronaphthalene group, a furan group, a thiophene group, a silole group, an indene group, a fluorene group, an indole group, a carbazole group, a benzofuran group, a dibenzofuran group, a benzothiophene group, a dibenzothiophene group, a benzosilole group, a dibenzosilole group, an azafluorene group, an azacarbazole group, an azadibenzofuran group, an azadibenzothiophene group, an azadibenzosilole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a quinazoline group, a phenanthroline group, a pyrrole group, a pyrazole group, an imidazole group, a triazole group, an oxazole group, an isooxazole group, a thiazole group, an isothiazole group, an oxadiazole group, a thiadiazole group, a 5,6,7,8-tetrahydroisoquinoline group, and a 5,6,7,8-tetrahydroquinoline group, but embodiments of the present disclosure are not limited thereto. 
     A cyclometalated ring formed by ring CY 5 , ring CY 2 , ring CY 3 , and M in Formula 1 may be a 6-membered ring. 
     In an embodiment, X 2  of ring CY 5 , X 3  of ring CY 3 , and X 4  of ring CY 4  in Formula 1 may not constitute a carbine moiety. That is, regarding Formula 1, 1) when X 2  is C, a bond between X 2  and M may be a covalent bond, 2) when X 3  is C, a bond between X 3  and M may be a covalent bond, and 3) when X 4  is C, a bond between X 4  and M may be a covalent bond. 
     Regarding Formula 1, X 51  may be O, S, N—[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 )(R 8 ), Si(R 7 )(R 8 ), Ge(R 7 )(R 8 ), C(═O), N, C(R 7 ), Si(R 7 ), and Ge(R 7 ), and R 7  and R 8  may optionally be linked via a single bond, a double bond, or a first linking group to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a . Herein, the C 5 -C 30  carbocyclic group and the C 1 -C 30  heterocyclic group may be understood by referring to the descriptions about i) the first ring, ii) the second ring, iii) the condensed ring in which two or more first rings are condensed with each other, iv) the condensed ring in which two or more second rings are condensed with each other, and v) the condensed ring in which one or more first rings and one or more second rings are condensed with each other, and R 10a  may be understood by referring to the description about R 1 , and L 7 , b7, R 7 , R 8 , and c7 will be described in detail later. 
     The first linking group may be selected from *—O—*, *—S—*, *—C(R 5 )(R 6 )—*′, *—C(R 5 )═*′, *═C(R 6 )—*′, *—C(R 5 )═C(R 6 )—*′, *—C(═O)—*′, *—C(═S)—*′, *—C≡C—*′, *—N(R 5 )—*′, *—Si(R 5 )(R 6 )—*′, and *—P(R 5 )(R 6 )—*′, and R 5  and R 6  are the same as described in connection with R 1 , and each of * and *′ indicates a binding site to a neighboring atom. 
     In one or more embodiments, in Formula 1,
         i) Y 3  to Y 5  may each be C, a bond between X 51  and Y 3  and a bond between X 51  and Y 5  may each be a single bond, and X 51  may be O, S, N—[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 )(R 8 ), Si(R 7 )(R 8 ), Ge(R 7 )(R 8 ), or C(═O),   ii) Y 3  and Y 4  may each be C, Y 5  may be N, a bond between X 51  and Y 3  may be a double bond, a bond between X 51  and Y 5  may be a single bond, and X 51  may be N, C(R 7 ), Si(R 7 ), or Ge(R 7 ),   iii) Y 3  and Y 5  may each be C, Y 4  may be N, a bond between X 51  and Y 3  may be a single bond, a bond between X 51  and Y 5  may be a double bond, and X 51  may be N, C(R 7 ), Si(R 7 ), or Ge(R 7 ),   iv) Y 3  may be N, Y 4  and Y 5  may each be C, a bond between X 51  and Y 3  may be a single bond, a bond between X 51  and Y 5  may be a double bond, and X 51  may be N, C(R 7 ), Si(R 7 ), or Ge(R 7 ), or   v) Y 3  to Y 5  may each be C, a bond between X 51  and Y 3  may be a double bond, a bond between X 51  and Y 5  may be a single bond, and X 51  may be N, C(R 7 ), Si(R 7 ), or Ge(R 7 ), but embodiments are not limited thereto.       

     T 1  and T 2  in Formula 1 may each independently be a single bond, a double bond, *—N(R 9 )—*′, *—B(R 9 )—*′, *—P(R 9 )—*′, *—C(R 9 )(R 10 )—*′, *—Si(R 9 )(R 10 )—*′, *—Ge(R 9 )(R 10 )—*′, *—S—*′, *—Se—*′, *—O—*′, *—C(═O)—*′, *—S(═O)—*′, *—S(═O) 2 —*′, *—C(R 9 )═*′, *═C(R 9 )—*′, *—C(R 9 )═C(R 10 )—*′, *—C(═S)—*′, or *—C≡C—*′, R 9  and R 10  may optionally be linked via a single bond, a double bond, or a second linking group to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a . Herein, the C 5 -C 30  carbocyclic group and the C 1 -C 30  heterocyclic group may be understood by referring to the descriptions about i) the first ring, ii) the second ring, iii) the condensed ring in which two or more first rings are condensed with each other, iv) the condensed ring in which two or more second rings are condensed with each other, and v) the condensed ring in which one or more first rings and one or more second rings are condensed with each other, and R 10a  may be understood by referring to the description about R 1 , and the second linking group may be understood by referring to the description about the first linking group. 
     In an embodiment, T 1  and T 2  in Formula 1 may be a single bond, but embodiments are not limited thereto.
         L 1  to L 4  and L 7  in Formula 1 may each independently be selected from a single bond, a substituted or unsubstituted C 5 -C 30  carbocyclic group, and a substituted or unsubstituted C 1 -C 30  heterocyclic group.       

     For example, L 1  to L 4  and L 7  in Formula 1 may each independently be selected from:
         a single bond, a benzene group, a naphthalene group, an anthracene group, a phenanthrene group, a triphenylene group, a pyrene group, a chrysene group, cyclopentadiene group, a furan group, a thiophene group, a silole group, an indene group, a fluorene group, an indole group, a carbazole group, a benzofuran group, a dibenzofuran group, a benzothiophene group, a dibenzothiophene group, a benzosilole group, a dibenzosilole group, an azafluorene group, an azacarbazole group, an azadibenzofuran group, an azadibenzothiophene group, an azadibenzosilole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a quinazoline group, a phenanthroline group, a pyrrole group, a pyrazole group, an imidazole group, a triazole group, an oxazole group, an isooxazole group, a thiazole group, an isothiazole group, an oxadiazole group, a thiadiazole group, a benzopyrazole group, a benzimidazole group, a benzoxazole group, a benzothiazole group, a benzooxadiazole group and a benzothiadiazole group; and   a benzene group, a naphthalene group, an anthracene group, a phenanthrene group, a triphenylene group, a pyrene group, a chrysene group, cyclopentadiene group, a furan group, a thiophene group, a silole group, an indene group, a fluorene group, an indole group, a carbazole group, a benzofuran group, a dibenzofuran group, a benzothiophene group, a dibenzothiophene group, a benzosilole group, a dibenzosilole group, an azafluorene group, an azacarbazole group, an azadibenzofuran group, an azadibenzothiophene group, an azadibenzosilole group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, a triazine group, a quinoline group, an isoquinoline group, a quinoxaline group, a quinazoline group, a phenanthroline group, a pyrrole group, a pyrazole group, an imidazole group, a triazole group, an oxazole group, an isooxazole group, a thiazole group, an isothiazole group, an oxadiazole group, a thiadiazole group, a benzopyrazole group, a benzimidazole group, a benzoxazole group, a benzothiazole group, a benzooxadiazole group and a benzothiadiazole group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkyl group substituted with at least one deuterium, a C 1 -C 20  alkoxy group, a phenyl group, a phenyl group substituted with at least one deuterium, a biphenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a triazinyl group, a fluorenyl group, a dimethylfluorenyl group, a diphenylfluorenyl group, a carbazolyl group, a phenylcarbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, a dimethyldibenzosilolyl group, a diphenyldibenzosilolyl group, —N(Q 31 )(Q 32 ), —Si(Q 33 )(Q 34 )(Q 35 ), —B(Q 36 )(Q 37 ), and —P(═O)(Q 38 )(Q 39 );   Q 31  to Q 39  may each independently be selected from:   —CH 3 , —CD 3 , —CD 2 H, —CDH 2 , —CH 2 CH 3 , —CH 2 CD 3 , —CH 2 CD 2 H, —CH 2 CDH 2 , —CHDCH 3 , —CHDCD 2 H, —CHDCDH 2 , —CHDCD 3 , —CD 2 CH 3 , —CD 2 CD 3 , —CD 2 CD 2 H, and —CD 2 CDH 2 ;   an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from deuterium, a C 1  to C 10  alkyl group, and a phenyl group;   but embodiments of the present disclosure are not limited thereto.       

     b1 to b4 and b7 in Formula 1 indicate numbers of L 1  to L 4  and L 7 , respectively, and may each independently be an integer from 1 to 5. When b1 is two or more, two or more groups L 1  may be identical to or different from each other. b2 to b4 and b7 may each be the same as described in connection with b1. 
     In an embodiment, L 1  to L 4  and L 7  in Formula 1 may each independently be selected from:
         a single bond; and   a benzene group unsubstituted or substituted with at least one selected from deuterium, —F, a cyano group, a C 1 -C 20  alkyl group, a C 1 -C 20  alkyl group substituted with at least one deuterium, a phenyl group, a phenyl group substituted with at least one deuterium, a biphenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a triazinyl group, a fluorenyl group, a dimethylfluorenyl group, a diphenylfluorenyl group, a carbazolyl group, a phenylcarbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, a dimethyldibenzosilolyl group and a diphenyldibenzosilolyl group; and       

     b1 to b4 and b7 in Formula 1 may be 1 or 2, but embodiments of the present disclosure are not limited thereto. 
     In an embodiment, b1 to b4 and b7 in Formula 1 may be 1 or 2, but embodiments of the present disclosure are not limited thereto. 
     R 1  to R 4 , R 7  to R 10 , R′, and R″ may each independently be selected from hydrogen, deuterium, deuterium-containing group, —F, —Cl, —Br, —I, —SF 5 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group, a substituted or unsubstituted C 2 -C 60  alkynyl group, a substituted or unsubstituted C 1 -C 60  alkoxy group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 60  alkylaryl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 7 -C 60  arylalkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted C 2 -C 60  heteroarylalkyl group, a substituted or unsubstituted C 2 -C 60  alkylheteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q 1 )(Q 2 ), —Si(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), and —P(═O)(Q 8 )(Q 9 ). The deuterium-containing group and Q 1  to Q 9  are the same as described above. 
     For example, R 1  to R 4 , R 7  to R 10 , R′, and R″ may each independently be selected from:
         hydrogen, deuterium, a deuterium-containing group, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, —SF 5 , a C 1 -C 20  alkyl group, and a C 1 -C 20  alkoxy group;   a C 1 -C 20  alkyl group and a C 1 -C 20  alkoxy group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10  alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group;   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group;   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, and —Si(Q 33 )(Q 34 )(Q 35 ); and —N(Q 1 )(Q 2 ), —Si(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), and —P(═O)(Q 8 )(Q 9 );       

     Herein, Q 1  to Q 9  and Q 33  to Q 35  may be understood by referring to the description presented above. 
     In some embodiments, R 1  to R 4 , R 7  to R 10 , R′, and R″ may each independently be selected from:
         hydrogen, deuterium, deuterium-containing group, —F, a cyano group, a nitro group, —SF 5 , a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an isodecyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, and a dibenzosilolyl group;   a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an isohexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an isooctyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an isononyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an isodecyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, and a dibenzosilolyl group, each substituted with at least one selected from deuterium, —F, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a cyano group, a nitro group, a C 1 -C 10  alkyl group, a C 1 -C 10  alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a fluorenyl group, a carbazolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, and —Si(Q 33 )(Q 34 )(Q 35 ); and   —N(Q 1 )(Q 2 ), —Si(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), and —P(═O)(Q 8 )(Q 9 );   wherein Q 1  to Q 9  and Q 33  to Q 35  are the same as described above, but embodiments are not limited thereto.       

     c1 to c4 and c7 in Formula 1 indicate numbers of R 1  to R 4  and R 7 , respectively, and may each independently be an integer from 1 to 5 (for example, 1, 2, and 3). When c1 is two or more, two or more groups R 1  may be identical to or different from each other. c2 to c4 and c7 may be understood by referring to the description about c1. 
     Z 1  to Z 4  in Formula 1 may each independently be deuterium or a deuterium-containing group. 
     For example, the deuterium-containing group is a first group substituted with at least one deuterium, and the first group may be selected from a substituted or unsubstituted C 1 -C 60  alkyl group, a substituted or unsubstituted C 2 -C 60  alkenyl group, a substituted or unsubstituted C 2 -C 60  alkynyl group, a substituted or unsubstituted C 1 -C 60  alkoxy group, a substituted or unsubstituted C 3 -C 10  cycloalkyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkyl group, a substituted or unsubstituted C 3 -C 10  cycloalkenyl group, a substituted or unsubstituted C 1 -C 10  heterocycloalkenyl group, a substituted or unsubstituted C 6 -C 60  aryl group, a substituted or unsubstituted C 7 -C 60  alkylaryl group, a substituted or unsubstituted C 6 -C 60  aryloxy group, a substituted or unsubstituted C 6 -C 60  arylthio group, a substituted or unsubstituted C 7 -C 60  arylalkyl group, a substituted or unsubstituted C 1 -C 60  heteroaryl group, a substituted or unsubstituted C 1 -C 60  heteroaryloxy group, a substituted or unsubstituted C 1 -C 60  heteroarylthio group, a substituted or unsubstituted C 2 -C 60  heteroarylalkyl group, a substituted or unsubstituted C 2 -C 60  alkylheteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group. 
     The term “a deuterium-containing group” as used herein refers to any group including at least one deuterium, which may be further substituted with substituents other than deuterium. For example, the term “a deuterium-containing group” as used herein may include a phenyl group substituted with one deuterium, a phenyl group substituted with five deuterium and not containing hydrogen (see Formula 11-1), a phenyl group substituted with four deuterium and one tert-butyl group (see Formulae 11-10 to 11-12), a phenyl group substituted with four deuterium and one —C(CD 3 ) 3  and not containing hydrogen (see Formulae 11-7 to 11-9), —CDH 2 , —CD 3 , or the like. Herein, for example, the “phenyl group substituted with one deuterium” refers to a deuterium-containing group in which the first group is a “phenyl group,” and the “phenyl group substituted with four deuterium and one tert-butyl group” refers to a deuterium-containing group in which the first group is “a phenyl group substituted with a tert-butyl group.” 
     In an embodiment, the deuterium-containing group may be a first group substituted with at least one deuterium,
         the first group may be selected from:   a C 1 -C 20  alkyl group and a C 1 -C 20  alkoxy group;   a C 1 -C 20  alkyl group and a C 1 -C 20  alkoxy group, each substituted with at least one selected from —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10  alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group;   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group;   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group, each substituted with at least one selected from —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a dibenzosilolyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, and —Si(Q 33 )(Q 34 )(Q 35 ); and   —N(Q 1 )(Q 2 ), —Si(Q 3 )(Q 4 )(Q 5 ), —B(Q 6 )(Q 7 ), and —P(═O)(Q 8 )(Q 9 );       

     Herein, Q 1  to Q 9  and Q 33  to Q 35  may be understood by referring to the description presented above. 
     In an embodiment, the deuterium-containing group may be a first group substituted with at least one deuterium, and the first group may be selected from a C 1 -C 20  alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group and a terphenyl group, each unsubstituted or substituted with at least one selected from —F, —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a cyano group, a C 1 -C 10  alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cycloctyl group, an adamantanyl group, a norbomanyl group, a norbomenyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a bicyclo[1.1.1]pentyl group, a bicyclo[2.1.1]hexyl group, a bicyclo[2.2.1]heptyl group, a bicyclo[2.2.2]octyl group, a phenyl group, a (C 1 -C 20  alkyl)phenyl group, a biphenyl group and a terphenyl group. 
     In an embodiment, the deuterium-containing group i) may not include hydrogen or ii) may include at least one C 1 -C 10  alkyl group. 
     For example, in the deuterium-containing group, “all hydrogen” of the “first group” is replaced with “deuterium” and thus, hydrogen is not present (for example, such the deuterium-containing group may be selected from —CD 3 , —CD 2 (CD 3 ), —CD(CD 3 ) 2 , —C(CD 3 ) 3 , —CD 2 —C(CD 3 ) 3 , —CD 2 CD(CD 3 ) 2 , —CD 2 CD 2 (CD 3 ), —CD(CD 3 )—C(CD 3 ) 3 , —CD(CD 3 )—CD(CD 3 ) 2 , —CD(CD 3 )—CD 2 (CD 3 ), —C(CD 3 ) 2 —C(CD 3 ) 3 , —C(CD 3 ) 2 CD(CD 3 ) 2 , —C(CD 3 ) 2 CD 2 (CD 3 ), and Formulae 11-1 to 11-9). 
     In some embodiments, the deuterium-containing group may include at least one C 1 -C 10  alkyl group (for example, a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, an iso-butyl group, a tert-butyl group, a sec-butyl group, an n-pentyl group, an isopentyl group, a tert-pentyl group, a sec-pentyl group, etc.), and such a deuterium-containing group may be, for example, one of Formulae 11-10 to 11-12, but embodiments are not limited thereto. 
     In some embodiments, R 1  to R 4 , R 7  to R 10 , R′ and R″ may each independently selected from hydrogen, deuterium, —F, a cyano group, a nitro group, —SF 5 , —CH 3 , —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , —CD 2 (CD 3 ), —CD(CD 3 ) 2 , —C(CD 3 ) 3 , —CD 2 C(CD 3 ) 3 , —CD 2 —CD(CD 3 ) 2 , —CD 2 —CD 2 (CD 3 ), —CD(CD 3 )—C(CD 3 ) 3 , —CD(CD 3 )—CD(CD 3 ) 2 , —CD(CD 3 )—CD 2 (CD 3 ), —C(CD 3 ) 2 —C(CD 3 ) 3 , —C(CD 3 ) 2 CD(CD 3 ) 2 , —C(CD 3 ) 2 CD 2 (CD 3 ), a group represented by Formula 9-1 to 9-19, a group represented by Formulae 10-1 to 10-232, a group represented by Formulae 11-1 to 11-41, and —Si(Q 1 )(Q 2 )(Q 3 ) (Q 1  to Q 3  are the same as described above),
         Z 1  to Z 4  may each independently be deuterium, —CD 3 , —CD 2 H, —CDH 2 , —CD 2 (CD 3 ), —CD(CD 3 ) 2 , —C(CD 3 ) 3 , —CD 2 C(CD 3 ) 3 , —CD 2 —CD(CD 3 ) 2 , —CD 2 CD 2 (CD 3 ), —CD(CD 3 )—C(CD 3 ) 3 , —CD(CD 3 )—CD(CD 3 ) 2 , —CD(CD 3 )—CD 2 (CD 3 ), —C(CD 3 ) 2 —C(CD 3 ) 3 , —C(CD 3 ) 2 CD(CD 3 ) 2 , —C(CD 3 ) 2 CD 2 (CD 3 ), and a group represented by one of Formulae 9-14 to 9-19, 10-11, 10-12, and 11-1 to 11-41, but embodiments are not limited thereto:       

     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Regarding Formulae 9-1 to 9-19, 10-1 to 10-232 and 11-1 to 11-41, * indicates a binding site to neighboring atoms, Ph is a phenyl group, and TMS is a trimethylsilyl group. 
     In one or more embodiments, the deuterium-containing group may be selected from —CD 3 , —CD 2 (CD 3 ), —CD(CD 3 ) 2 , —C(CD 3 ) 3 , —CD 2 —C(CD 3 ) 3 , —CD 2 —CD(CD 3 ) 2 , —CD 2 —CD 2 (CD 3 ), —CD(CD 3 )—C(CD 3 ) 3 , —CD(CD 3 )—CD(CD 3 ) 2 , —CD(CD 3 )—CD 2 (CD 3 ), —C(CD 3 ) 2 —C(CD 3 ) 3 , —C(CD 3 ) 2 —CD(CD 3 ) 2 , —C(CD 3 ) 2 —CD 2 (CD 3 ), and a group represented by one of Formula 11-1 to 11-41, but embodiments are not limited thereto. 
     Regarding Formula 1, a1 to a4 respectively indicate numbers of *—[(L 1 ) b1 —(R 1 )C 1 ], *—[(L 2 ) b2 —(R 2 ) c2 ], *—[(L 3 ) b3 —(R 3 ) c3 ], and *—[(L 4 ) b4 —(R 4 ) c4 ], and n1 to n4 respectively indicate numbers of Z 1  to Z 4 , and a1 to a4 and n1 to n4 may each independently be an integer from 0 to 20. When a1 is two or more, two or more groups *—[(L 1 ) b1 —(R 1 ) c1 ] may be identical to or different from each other, when a2 is two or more, two or more groups *—[(L 2 ) b2 —(R 2 ) c2 ] may be identical to or different from each other, when a3 is two or more, two or more groups * [(L 3 ) b3 —(R 3 ) c3 ] may be identical to or different from each other, when a4 is two or more, two or more groups *—[(L 4 ) b4 —(R 4 ) c4 ] may be identical to or different from each other, when n1 is two or more, two or more groups Z 1  may be identical to or different from each other, when n2 is two or more, two or more groups Z 2  may be identical to or different from each other, when n3 is two or more, two or more groups Z 3  may be identical to or different from each other, and when n4 is two or more, two or more groups Z 4  may be identical to or different from each other. 
     In Formula 1,
         i) when X 51  is O, S, C(═O), or N, the sum of n1 to n4 may be 1 or more,   ii) when X 51  is N[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 ), Si(R 7 ), or Ge(R 7 ), a) R 7  is deuterium or a deuterium-containing group; b) the sum of n1 to n4 may be 1 or more; or c) R 7  is deuterium or a deuterium-containing group and the sum of n1 to n4 may be 1 or more,   iii) when X 51  is C(R 7 )(R 8 ), Si(R 7 )(R 8 ), or Ge(R 7 )(R 8 ), a) at least one selected from R 7  and R 8  may be a deuterium or a deuterium-containing group; b) the sum of n1 to n4 may be 1 or more; or c) at least one selected from R 7  and R 8  may be deuterium or a deuterium-containing group and the sum of n1 to n4 may be 1 or more.       

     That is, Formula 1 may essentially include at least one deuterium and/or at least one deuterium-containing group. 
     In one or more embodiments, in Formula 1,
         Y 3  to Y 5  may each be C,   a bond between X 51  and Y 3  and a bond between X 51  and Y 5  may each be a single bond, and   a) X 51  may be O or S, and the sum of n1 to n4 may be 1, 2, 3, or 4; b) X 51  may be N[(L 7 ) b7 —(R 7 ) c7 ] and R 7  may be deuterium or a deuterium-containing group; c) X 51  may be N[(L 7 ) b7 —(R 7 ) c7 ], and the sum of n1 to n4 may be 1, 2, 3, or 4; d) X 51  may be N[(L 7 ) b7 —(R 7 ) c7 ], R 7  may be deuterium or deuterium-containing group, and the sum of n1 to n4 may be 1, 2, 3, or 4; e) X 51  may be C(R 7 )(R 8 ), and at least one selected from R 7  and R 8  may be deuterium or a deuterium-containing group; or f) X 51  may be C(R 7 )(R 8 ), and the sum of n1 to n4 may be 1, 2, 3, or 4, but embodiments are not limited thereto.       

     In one or more embodiments, Formula 1 may satisfy at least one of Condition A to Condition D:
         Condition A   n1 may be 1, 2, 3 or 4.   Condition B   X 51  may be N[(L 7 ) b7 —(R 7 ) c7 ] and R 7  may be deuterium or a deuterium-containing group.   Condition C   n3 may be 1, 2 or 3.   Condition D   n4 may be 1, 2, 3 or 4.       

     In one or more embodiments, in Formula 1,
         i) n1=n2=n3=0, and n4 may be 1, 2, 3, or 4,   ii) n1=n2=n4=0, and n3 may be 1, 2, 3, or 4,   iii) n1=n3=n4=0, and n2 may be 1, 2, 3, or 4,   iv) n2=n3=n4=0, and n1 may be 1, 2, 3, or 4, or   v) n1=n2=n3=n4=0, X 51  may be N—[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 ), Si(R 7 ), or Ge(R 7 ), and R 7  may be deuterium or a deuterium-containing group; or   vi) n1=n2=0, and n3 and n4 may each independently be 1, 2, 3, or 4,   vii) n1=n2=n3=0, n4 may be 1, 2, 3, or 4, X 51  may be N—[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 ), Si(R 7 ), or Ge(R 7 ), and R 7  may be deuterium or a deuterium-containing group,   viii) n1=n2=n4=0, n3 may be 1, 2, 3, or 4, X 51  may be N—[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 ), Si(R 7 ), or Ge(R 7 ), and R 7  may be deuterium or a deuterium-containing group, or   ix) n2=n4=0, and n1 and n3 may each independently be 1, 2, 3, or 4, but embodiments are not limited thereto.       

     In one or more embodiments, regarding Formula 1,
         i) X 1  may be a chemical bond, and T 1  may be a single bond, a moiety represented by       

     
       
         
         
             
             
         
       
     
     may be a group represented by Formula CY1-B,
         ii) X 1  may be O, S, N(R′), P(R′), B(R′), C(R′)(R′), Si(R′)(R″), or N(R′)(R′), and T 1  may be a single bond, a moiety represented by       

     
       
         
         
             
             
         
       
     
     may be a group represented by Formula CY1-A, or
         iii) X 1  may be a chemical bond, and T 1  may be *—N(R 9 )—*′, *—B(R 9 )—*′, *—P(R 9 )—*′, *—C(R 9 )(R 10 )—*′, *—Si(R 9 )(R 10 )—*′, *—Ge(R 9 )(R 10 )—*′, *—S—*′, *—Se—*′, *—O—*′, *—C(═O)—*′, *—S(═O)—*′, *—S(═O) 2 —*′, *—C(R 9 )═*, *═C(R 9 )—*′, *—C(R 9 )═C(R 10 )—*′, *—C(═S)—*′, or *—C≡C—*, and a moiety represented by       

     
       
         
         
             
             
         
       
     
     may be a group represented by Formula CY1-A: 
     
       
         
         
             
             
         
       
     
     Regarding Formulae CY1-A and CY1-B, Y 1 , CY 1 , L 1 , b1, R 1 , c1, a1, Z 1 , and n1 are the same as described above, Y 2  and Y 6  may each independently be N or C, and a bond between Y 1  and Y 2 , a bond between Y 1  and Y 6 , and a bond between Y 6  and Y 2  may each be a chemical bond. 
     In one or more embodiments, regarding Formula 1, a moiety represented by 
     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY1-1 to CY1-40: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formula CY1-1 to CY1-40,
         Y 1 , R 1 , Z 1 , and n1 are the same as described above, and n1 may be an integer from 0 to 7,   X 19  may be C(R 19a )(R 19b ), N[(L 19 ) b19 —(R 19 ) c19 ], O, S, or Si(R 19a )(R 19b ),   L 19  may be the same as explained in connection with L 1 ;   b19 and c19 are the same as described in connection with b1 and c1,   R 11  to R 19 , R 19a  and R 19b  are the same as described in connection with R 1 .   a12 may be an integer from 0 to 2,   a13 may be an integer from 0 to 3,   a14 may be an integer from 0 to 4,   a15 may be an integer from 0 to 5,   a16 may be an integer from 0 to 6,   a17 may be an integer from 0 to 7,   *′ indicates a binding site to X 1  or M in Formula 1, and   * indicates a binding site to T 1  in Formula 1.       

     n1 in Formula CY1-1 to CY1-40 has been described based on when n1 has its maximum value, and n1 may be an integer from 0 to 7, varying depending on a corresponding chemical formula. For example, n1 in Formula CY1-1 may be 0, 1, 2, 3, or 4, n1 in Formula CY1-2 may be 0, 1, 2, or 3, and n1 in Formula CY1-27 may be 0, 1, 2, 3, 4, 5, 6, or 7. 
     In one or more embodiments, regarding Formula 1, a moiety represented by 
     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY2-1 to CY2-20: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae CY2-1 to CY2-20,
         X 2 , R 2 , Z 2 , and n2 are the same as described above, and n2 may be an integer from 0 to 3,   X 51  in Formulae CY2-1 to CY2-4 may be O, S, N—[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 )(R 8 ), Si(R 7 )(R 8 ), Ge(R 7 )(R 8 ), or C(═O),   X 51  in Formulae CY2-5 to CY2-20 may be N, C(R 7 ), Si(R 7 ), or Ge(R 7 ),   L 7 , b7, R 7 , and c7 may be the same as described above,   a22 is an integer from 0 to 2,   a23 is an integer from 0 to 3,   * indicates a binding site to T 1  in Formula 1,   *′ indicates a binding site to M in Formula 1, and   *″ indicates a binding site to ring CY 3  in Formula 1.       

     n2 in Formula CY2-1 to CY2-20 has been described based on when n2 has its maximum value, and n2 may be an integer from 0 to 3, varying depending on a corresponding chemical formula. For example, n2 in Formula CY2-1 may be 0, 1, 2, or 3, and n2 in Formula CY2-2 may be 0, 1, or 2. 
     In one or more embodiments, regarding Formula 1, a moiety represented by 
     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY3-1 to CY3-12: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae CY3-1 to CY3-12,
         X 3 , R 3 , Z 3 , and n3 are the same as described above, and n3 may be an integer from 0 to 5,   X 39  may be C(R 39a )(R 39b ), N[(L 39 ) b39 —(R 39 ) c39 ], O, S, or Si(R 39a )(R 39b ),   L 39  may be the same as explained in connection with L 3 ,   b39 and c39 may be the same as described in connection with b3 and c3,   R 39a  and R 39b  may be the same as described in connection with R 3 .   a32 may be an integer from 0 to 2,   a33 may be an integer from 0 to 3,   a34 may be an integer from 0 to 4,   a35 may be an integer from 0 to 5,   * indicates a binding site to T 2  in Formula 1,   *′ indicates a binding site to M in Formula 1, and   *″ indicates a binding site to ring CY 2  in Formula 1.       

     n3 in Formulae CY3-1 to CY3-12 has been described based on when n3 has its maximum value, and n3 may be an integer from 0 to 5, varying depending on a corresponding chemical formula. For example, n3 in Formula CY3-1 may be 0, 1, 2, or 3, and n3 in Formula CY3-9 may be 0, 1, 2, 3, 4, or 5. 
     In one or more embodiments, regarding Formula 1, a moiety represented by 
     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY4-1 to CY4-26: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae CY4-1 to CY4-26,
         X 4 , R 4 , Z 4 , and n4 may be the same as described above, and n4 may be 0, 1, 2, 3, 4, 5, or 6,   X 49  may be C(R 49a )(R 49b ), N[(L 49 ) b49 —(R 49 ) c49 ], O, S, or Si(R 49a )(R 49b ),   L 49  may be the same as explained in connection with L 4 ,   b49 and c49 are the same as described in connection with b4 and c4,   R 41  to R 49 , R 49a , and R 49b  are the same as described in connection with R 4 ,   a42 may be an integer from 0 to 2,   a43 may be an integer from 0 to 3,   a44 may be an integer from 0 to 4,   a45 may be an integer from 0 to 5,   a46 may be an integer from 0 to 6,   * indicates a binding site to T 2  in Formula 1, and   *′ indicates a binding site to M in Formula 1.       

     n4 in Formulae CY4-1 to CY4-26 has been described based on when n4 has its maximum value, and n4 may be an integer from 0 to 6, varying depending on a corresponding chemical formula. For example, n4 in Formula CY4-1 may be 0, 1, 2, 3, or 4, n4 in Formula CY4-2 may be 0, 1, 2, or 3, and n4 in Formula CY4-17 may be 0, 1, 2, 3, 4, 5, or 6. 
     In one or more embodiments, regarding Formula 1,
         a moiety represented by       

     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY1(1) to CY1(16) and CY1-d(1) to CY1-d(18), and (or),
         a moiety represented by       

     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY2(1) to CY2(20) and CY2-d(1) to CY2-d(15), and (or),
         a moiety represented by       

     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY3(1) to CY3(12) and CY3-d(1) to CY3-d(13), and (or),
         a moiety represented by       

     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY4(1) to CY4(10) and CY4-d(1) to CY4-d(18), but embodiments are not limited thereto. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formulae CY1(1) to CY1(16), CY1-d(1) to CY1-d(18), CY2(1) to CY2(20), CY2-d(1) to CY2-d(15), CY3(1) to CY3(12), CY3-d(1) to CY3-d(13), CY4(1) to CY4(10), and CY4-d(1) to CY4-d(18),
         X 2  to X 4 , Y 1 , X 51 , R 1  to R 4  and Z 1  to Z 4  may be the same as described above,   X 19  may be C(R 19a )(R 19b ), N[(L 19 ) b19 —(R 19 ) c19 ], O, S, or Si(R 19a )(R 19b ),   X 39  may be C(R 39a )(R 39b ), N[(L 39 ) b39 —(R 39 ) c39 ], O, S, or Si(R 39a )(R 39b ),   L 19 , b19, R 19 , and c19 are the same as described in connection with L 1 , b1, R 1 , and c1, respectively,   L 39 , b39, R 39 , and c39 are the same as described in connection with L 3 , b3, R 3 , and c3, respectively.       

     R 3a  to R 3c , R 19a , and R 19b  are the same as described in connection with R 1 ,
         R 3a  to R 3c , R 39a , and R 39b  are the same as described in connection with R 3 ,   R 4a  to R 4d  may be the same as described in connection with R 4 ,   each of R 1  to R 4 , R 1a  to R 1d , R 3a  to R 3c  and R 4a  to R 4d  is not hydrogen,   Z 1a  to Z 1d  are the same as described in connection with Z 1 ,   Z 3a  to Z 3c  are the same as described in connection with Z 3 ,   Z 4a  to Z 4d  are the same as described in connection with Z 4 ,   regarding Formula CY1(1) to CY1(16) and CY1-d(1) to CY1-d(18), * indicates a binding site to X 1  or M in Formula 1, and * indicates a binding site to T 1  in Formula 1,   regarding Formulae CY2(1) to CY2(20) and CY2-d(1) to CY2-d(15), * indicates a binding site to M in Formula 1, * indicates a binding site to T 1  in Formula 1, and *″ indicates a binding site to ring CY 3  in Formula 1,   regarding Formulae CY3(1) to CY3(12) and CY3-d(1) to CY3-d(13), * indicates a binding site to M in Formula 1, *″ indicates a binding site to ring CY 2  in Formula 1, and * indicates a binding site to T 2  in Formula 1, and   regarding Formulae CY4(1) to CY4(10) and CY4-d(1) to CY4-d(18), * indicates a binding site to M in Formula 1, and * indicates a binding site to T 2  in Formula 1.       

     In an embodiment, each of R 1  to R 4 , R 1a  to R 1d , R 3a  to R 3c  and R 4a  to R 4d  in Formulae CY1(1) to CY1(16), CY2(1) to CY2(20), CY3(1) to CY3(13) and CY4(1) to CY4(10) may not be deuterium and a deuterium-containing group. 
     In one or more embodiments, Formula 1 may satisfy at least one of Condition 1 to Condition 5:
         Condition 1       

     In Formula 1, a moiety represented by 
     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY1-d(1) to CY1-d(18).
         Condition 2       

     In Formula 1, a moiety represented by may be a 
     
       
         
         
             
             
         
       
     
     group represented by one of Formulae CY2-d(1) to CY2-d(15).
         Condition 3       

     In Formula 1, a moiety represented by 
     
       
         
         
             
             
         
       
     
     is a group represented by one of Formulae CY3-d(1) to CY3-d(13).
         Condition 4       

     In Formula 1, a moiety represented by 
     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY4-d(1) to CY4-d(18).
         Condition 5   a) in Formula 1, a moiety represented by       

     
       
         
         
             
             
         
       
     
     may be a group represented by one of Formulae CY2(1) to CY2(20), and b) regarding Formulae CY2(1) to CY2(20), i) X 51  is N—[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 ), Si(R 7 ), or Ge(R 7 ), and R 7  is deuterium or a deuterium-containing group, or ii) X 51  is C(R 7 )(R 8 ), Si(R 7 )(R 8 ), or Ge(R 7 )(R 8 ), and at least one of R 7  and R 8  is deuterium or a deuterium-containing group. 
     Regarding Formula 1, i) two of a plurality of neighboring groups R 1  may optionally be linked to each other to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a , ii) two of a plurality of neighboring groups R 2  may optionally be linked to each other to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a , iii) two of a plurality of neighboring groups R 3  may optionally be linked to each other to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a , iv) two of a plurality of neighboring groups R 4  may optionally be linked to each other to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a , and v) two or more neighboring substituents selected from R 1  to R 4 , R 7  to R 10 , R′ and R″ may optionally be linked to each other to form a C 5 -C 30  carbocyclic group unsubstituted or substituted with at least one R 10a  or a C 1 -C 30  heterocyclic group unsubstituted or substituted with at least one R 10a . Herein, the C 5 -C 30  carbocyclic group and the C 1 -C 30  heterocyclic group may be understood by referring to the descriptions about i) the first ring, ii) the second ring, iii) the condensed ring in which two or more first rings are condensed with each other, iv) the condensed ring in which two or more second rings are condensed with each other, and v) the condensed ring in which one or more first rings and one or more second rings are condensed with each other, and R 10a  may be understood by referring to the description about R 1 . 
     “An azabenzothiophene, an azabenzofuran, an azaindene, an azaindole, an azabenzosilole, an azadibenzothiophene, an azadibenzofuran, an azafluorene, an azacarbazole, and an azadibenzosilole” may have the same backbone as those of “a benzothiophene, a benzofuran, an indene, an indole, a benzosilole, a dibenzothiophene, a dibenzofuran, a fluorene, a carbazole, and a dibenzosilole,” respectively, and may each be a heteroring in which at least one of ring-forming carbon atoms is substituted with nitrogen. 
     In one embodiment, the organometallic compound represented by Formula 1 may be represented by Formula 1A as follows: 
     
       
         
         
             
             
         
       
     
     In Formula 1A, the descriptions for M, X 1  to X 4 , Y 1 , X 51 , L 1  to L 4 , b1 to b4, R 1  to R 4 , c1 to c4, Z 1  to Z 4 , a1 to a4 and n1 to n4 may be the same as described in this disclosure. 
     For example, the organometallic compound represented by Formula 1 may be one of Compounds 1 to 666 below, but embodiments of the present disclosure are not limited thereto. 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Z 1  to Z 4  in Formula 1 may each independently be deuterium or a deuterium-containing group, and i) when X 51  is O, S, C(═O), or N, the sum of n1 to n4 may be 1 or more, ii) when X 51  is N[(L 7 ) b7 —(R 7 ) c7 ], C(R 7 ), Si(R 7 ), or Ge(R 7 ), a) R 7  is deuterium or a deuterium-containing group; b) the sum of n1 to n4 may be 1 or more; or c) R 7  is deuterium or a deuterium-containing group and the sum of n1 to n4 is 1 or more, and iii) when X 51  is C(R 7 )(R 8 ), Si(R 7 )(R 8 ), or Ge(R 7 )(R 8 ), a) at least one of R 7  and R 8  may be deuterium or a deuterium-containing group; b) the sum of n1 to n4 is 1 or more; or c) at least one of R 7  and R 8  is deuterium or a deuterium-containing group and the sum of n1 to n4 is 1 or more. That is, the organometallic compound represented by Formula 1 may essentially include at least one deuterium. Accordingly, the reduced mass of the organometallic compound represented by Formula 1 is changed, and thus, a molecular structure change caused by energy quenching caused due to vibration of the organometallic compound being in an excited state is decreased. Due to the decrease in the molecular structure change, an electronic device including the organometallic compound represented by Formula 1, for example, an organic light-emitting device including the organometallic compound represented by Formula 1 may have improved lifespan characteristics. 
     In one or more embodiments, X 2  to X 4  in Formula 1 may each independently be N or C, two selected from X 2  to X 4  may each be N, and the remaining one may be C, and a bond between X 1  or Y 1  and M may be a covalent bond, and one bond selected from a bond between X 2  and M, a bond between X 3  and M, and a bond between X 4  and M may be a covalent bond, and the remaining two bonds may each be a coordinate bond. In an embodiment, X 2  of ring CY 5 , X 3  of ring CY 3 , and X 4  of ring CY 4  in Formula 1 may not constitute a carbine moiety. That is, regarding Formula 1, 1) when X 2  is C, a bond between X 2  and M may be a covalent bond, 2) when X 3  is C, a bond between X 3  and M may be a covalent bond, and 3) when X 4  is C, a bond between X 4  and M may be a covalent bond. Therefore, the structural change of the main emission moiety of the organometallic compound represented by Formula in an exited state is decreased, and thus, color purity of an electronic device including the organometallic compound, for example, an organic light-emitting device including the organometallic compound may be improved. 
     Furthermore, each of ring CY 1 , ring CY 3 , and ring CY 4  in Formula 1 may not be a benzimidazole group. Accordingly, since the steric hindrance of a ligand surrounding the center metal M is improved, an electronic device including the organometallic compound, for example, an organic light-emitting device including the organometallic compound may have an improved lifespan characteristic and a sharp electroluminescence peak. 
     For example, HOMO, LUMO, singlet (S 1 ) and triplet (T 1 ) energy levels of Compounds 1 to 10 and 13 were evaluated by using a DFT method of Gaussian program (structurally optimized at a level of B3LYP, 6-31G(d,p)). Evaluation results are shown in Table 1 below. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 HOMO 
                 LUMO 
                 Energy gap 
                 S 1  energy 
                 T 1  energy 
               
               
                 Compound No. 
                 (eV) 
                 (eV) 
                 (eV) 
                 level (eV) 
                 level (eV) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 1 
                 −4.85 
                 −1.546 
                 3.304 
                 2.751 
                 2.517 
               
               
                 2 
                 −4.85 
                 −1.546 
                 3.304 
                 2.751 
                 2.517 
               
               
                 3 
                 −4.85 
                 −1.546 
                 3.304 
                 2.751 
                 2.517 
               
               
                 4 
                 −4.869 
                 −1.589 
                 3.280 
                 2.728 
                 2.472 
               
               
                 5 
                 −4.869 
                 −1.589 
                 3.280 
                 2.728 
                 2.472 
               
               
                 6 
                 −4.869 
                 −1.589 
                 3.280 
                 2.728 
                 2.472 
               
               
                 7 
                 −4.994 
                 −1.793 
                 3.201 
                 2.661 
                 2.439 
               
               
                 8 
                 −4.994 
                 −1.793 
                 3.201 
                 2.661 
                 2.439 
               
               
                 9 
                 −4.994 
                 −1.793 
                 3.201 
                 2.661 
                 2.439 
               
               
                 10 
                 −4.794 
                 −1.528 
                 3.266 
                 2.721 
                 2.47 
               
               
                 13 
                 −4.782 
                 −1.528 
                 3.254 
                 2.719 
                 2.466 
               
               
                   
               
            
           
         
       
     
     From Table 1, it is confirmed that the organometallic compound represented by Formula 1 has such electric characteristics that are suitable for use as a dopant for an electronic device, for example, an organic light-emitting device. 
     Synthesis methods of the organometallic compound represented by Formula 1 may be recognizable by one of ordinary skill in the art by referring to Synthesis Examples provided below. 
     The organometallic compound represented by Formula 1 is suitable for use in an organic layer of an organic light-emitting device, for example, for use as a dopant in an emission layer of the organic layer. Thus, another aspect provides an organic light-emitting device that includes: a first electrode; a second electrode; and an organic layer that is located between the first electrode and the second electrode, wherein the organic layer includes an emission layer and at least one organometallic compound represented by Formula 1. 
     The organic light-emitting device may have, due to the inclusion of an organic layer including the organometallic compound represented by Formula 1, a low driving voltage, high efficiency, high power efficiency, high quantum efficiency, a long lifespan, a low roll-off ratio, and excellent color purity. 
     The organometallic compound of Formula 1 may be used between a pair of electrodes of an organic light-emitting device. For example, the organometallic compound represented by Formula 1 may be included in the emission layer. In this regard, the organometallic compound may act as a dopant, and the emission layer may further include a host (that is, an amount of the organometallic compound represented by Formula 1 is smaller than an amount of the host). 
     The expression “(an organic layer) includes at least one organometallic compounds” as used herein may include an embodiment in which “(an organic layer) includes identical organometallic compounds represented by Formula 1” and an embodiment in which “(an organic layer) includes two or more different organometallic compounds represented by Formula 1.” 
     For example, the organic layer may include, as the organometallic compound, only Compound 1. In this regard, Compound 1 may be included in an emission layer of the organic light-emitting device. In one or more embodiments, the organic layer may include, as the organometallic compound, Compound 1 and Compound 2. In this regard, Compound 1 and Compound 2 may be included in an identical layer (for example, Compound 1 and Compound 2 may all be included in an emission layer). 
     The first electrode may be an anode, which is a hole injection electrode, and the second electrode may be a cathode, which is an electron injection electrode; or the first electrode may be a cathode, which is an electron injection electrode, and the second electrode may be an anode, which is a hole injection electrode. 
     In an embodiment, in the organic light-emitting device, the first electrode is an anode, and the second electrode is a cathode, and the organic layer further includes a hole transport region disposed between the first electrode and the emission layer and an electron transport region disposed between the emission layer and the second electrode, wherein the hole transport region includes a hole injection layer, a hole transport layer, an electron blocking layer, or any combination thereof, and the electron transport region includes a hole blocking layer, an electron transport layer, an electron injection layer, or any combination thereof. 
     The term “organic layer” as used herein refers to a single layer and/or a plurality of layers disposed between the first electrode and the second electrode of the organic light-emitting device. The “organic layer” may include, in addition to an organic compound, an organometallic complex including metal. 
     The FIGURE is a schematic view of an organic light-emitting device  10  according to an embodiment. Hereinafter, the structure of an organic light-emitting device according to an embodiment and a method of manufacturing an organic light-emitting device according to an embodiment will be described in connection with the FIGURE. The organic light-emitting device  10  includes a first electrode  11 , an organic layer  15 , and a second electrode  19 , which are sequentially stacked. 
     A substrate may be additionally located under the first electrode  11  or above the second electrode  19 . For use as the substrate, any substrate that is used in general organic light-emitting devices may be used, and the substrate may be a glass substrate or a transparent plastic substrate, each having excellent mechanical strength, thermal stability, transparency, surface smoothness, ease of handling, and water resistance. 
     In one or more embodiments, the first electrode  11  may be formed by depositing or sputtering a material for forming the first electrode  11  on the substrate. The first electrode  11  may be an anode. The material for forming the first electrode  11  may be selected from materials with a high work function to facilitate hole injection. The first electrode  11  may be a reflective electrode, a semi-transmissive electrode, or a transmissive electrode. The material for forming the first electrode  11  may be indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO 2 ), or zinc oxide (ZnO). In one or more embodiments, the material for forming the first electrode  11  may be metal, such as magnesium (Mg), aluminum (AI), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), or magnesium-silver (Mg—Ag). 
     The first electrode  11  may have a single-layered structure or a multi-layered structure including two or more layers. For example, the first electrode  11  may have a three-layered structure of ITO/Ag/ITO, but the structure of the first electrode  11  is not limited thereto. 
     The organic layer  15  is located on the first electrode  11 . 
     The organic layer  15  may include a hole transport region, an emission layer, and an electron transport region. 
     The hole transport region may be between the first electrode  11  and the emission layer. 
     The hole transport region may include a hole injection layer, a hole transport layer, an electron blocking layer, a buffer layer, or any combination thereof. 
     The hole transport region may include only either a hole injection layer or a hole transport layer. In one or more embodiments, the hole transport region may have a hole injection layer/hole transport layer structure or a hole injection layer/hole transport layer/electron blocking layer structure, which are sequentially stacked in this stated order from the first electrode  11 . 
     When the hole transport region includes a hole injection layer (HIL), the hole injection layer may be formed on the first electrode  11  by using one or more suitable methods, for example, vacuum deposition, spin coating, casting, and/or Langmuir-Blodgett (LB) deposition. 
     When a hole injection layer is formed by vacuum deposition, the deposition conditions may vary according to a material that is used to form the hole injection layer, and the structure and thermal characteristics of the hole injection layer. For example, the deposition conditions may include a deposition temperature of about 100 to about 500° C., a vacuum pressure of about 10 −8  torr to about 10 −3  torr, and a deposition rate of about 0.01 Angstroms per second (Å/sec) to about 100 Å/sec. However, the deposition conditions are not limited thereto. 
     When the hole injection layer is formed using spin coating, coating conditions may vary according to the material used to form the hole injection layer, and the structure and thermal properties of the hole injection layer. For example, a coating speed may be from about 2,000 revolutions per minute (rpm) to about 5,000 rpm, and a temperature at which a heat treatment is performed to remove a solvent after coating may be from about 80° C. to about 200° C. However, the coating conditions are not limited thereto. 
     Conditions for forming a hole transport layer and an electron blocking layer may be understood by referring to conditions for forming the hole injection layer. 
     The hole transport region may include at least one selected from m-MTDATA, TDATA, 2-TNATA, NPB, P-NPB, TPD, Spiro-TPD, Spiro-NPB, methylated-NPB, TAPC, HMTPD, 4,4′,4″-tis(N-carbazolyl)triphenylamine (TCTA), polyaniline/dodecylbenzene sulfonic acid (PANI/DBSA), poly(3,4-ethylenedioxythiophene)/poly(4-styrene sulfonate) (PEDOT/PSS), polyaniline/camphor sulfonic acid (PANI/CSA), polyaniline/poly(4-styrene sulfonate) (PANI/PSS), a compound represented by Formula 201 below, and a compound represented by Formula 202 below: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Ar 101  to Ar 102  in Formula 201 may each independently be selected from 
     a phenylene group, a pentalenylene group, an indenylene group, a naphthylene group, an azulenylene group, a heptalenylene group, an acenaphthylene group, a fluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, and a pentacenylene group; and 
     a phenylene group, a pentalenylene group, an indenylene group, a naphthylene group, an azulenylene group, a heptalenylene group, an acenaphthylene group, a fluorenylene group, a phenalenylene group, a phenanthrenylene group, an anthracenylene group, a fluoranthenylene group, a triphenylenylene group, a pyrenylene group, a chrysenylenylene group, a naphthacenylene group, a picenylene group, a perylenylene group, and a pentacenylene group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 1 -C 60  heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group. 
     xa and xb in Formula 201 may each independently be an integer from 0 to 5, or 0, 1 or 2. For example, xa may be 1 and xb may be 0, but xa and xb are not limited thereto. 
     R 101  to R 108 , R 111  to R 119  and R 121  to R 124  in Formulae 201 and 202 may each independently be selected from: 
     hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10  alkyl group (for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, and so on), or a C 1 -C 10  alkoxy group (for example, a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a pentoxy group, and so on); 
     a C 1 -C 10  alkyl group or a C 1 -C 10  alkoxy group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, and a phosphoric acid group or a salt thereof; 
     a phenyl group, a naphthyl group, an anthracenyl group, a fluorenyl group, or a pyrenyl group; and 
     a phenyl group, a naphthyl group, an anthracenyl group, a fluorenyl group, and a pyrenyl group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 10  alkyl group, and a C 1 -C 10  alkoxy group, 
     but embodiments of the present disclosure are not limited thereto. 
     R 109  in Formula 201 may be selected from: 
     a phenyl group, a naphthyl group, an anthracenyl group, and a pyridinyl group; and 
     a phenyl group, a naphthyl group, an anthracenyl group, and a pyridinyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid or a salt thereof, a sulfonic acid or a salt thereof, a phosphoric acid or a salt thereof, a C 1 -C 20  alkyl group, a C 1 -C 20  alkoxy group, a phenyl group, a naphthyl group, an anthracenyl group, and a pyridinyl group. 
     According to an embodiment, the compound represented by Formula 201 may be represented by Formula 201A below, but embodiments of the present disclosure are not limited thereto: 
     
       
         
         
             
             
         
       
     
     R 101 , R 111 , R 112 , and R 109  in Formula 201A may be understood by referring to the description provided herein. 
     For example, the compound represented by Formula 201, and the compound represented by Formula 202 may include compounds HT1 to HT20 illustrated below, but are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the hole transport region may be in a range of about 100 Å to about 10,000 Å, for example, about 100 Å to about 1,000 Å. When the hole transport region includes at least one of a hole injection layer and a hole transport layer, a thickness of the hole injection layer may be in a range of about 100 Å to about 10,000 Å, for example, about 100 Å to about 1,000 Å, and a thickness of the hole transport layer may be in a range of about 50 Å to about 2,000 Å, for example about 100 Å to about 1,500 Å. While not wishing to be bound by theory, it is understood that when the thicknesses of the hole transport region, the hole injection layer and the hole transport layer are within these ranges, satisfactory hole transporting characteristics may be obtained without a substantial increase in driving voltage. 
     The hole transport region may further include, in addition to these materials, a charge-generation material for the improvement of conductive properties. The charge-generation material may be homogeneously or non-homogeneously dispersed in the hole transport region. 
     The charge-generation material may be, for example, a p-dopant. The p-dopant may be one selected from a quinone derivative, a metal oxide, and a cyano group-containing compound, but embodiments of the present disclosure are not limited thereto. Non-limiting examples of the p-dopant are a quinone derivative, such as tetracyanoquinonedimethane (TCNQ) or 2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinonedimethane (F4-TCNQ); a metal oxide, such as a tungsten oxide or a molybdenium oxide; and a cyano group-containing compound, such as Compound HT-D1 below, but are not limited thereto. 
     
       
         
         
             
             
         
       
     
     The hole transport region may include a buffer layer. 
     Also, the buffer layer may compensate for an optical resonance distance according to a wavelength of light emitted from the emission layer, and thus, efficiency of a formed organic light-emitting device may be improved. 
     Then, an emission layer (EML) may be formed on the hole transport region by vacuum deposition, spin coating, casting, LB deposition, or the like. When the emission layer is formed by vacuum deposition or spin coating, the deposition or coating conditions may be similar to those applied in forming the hole injection layer although the deposition or coating conditions may vary according to a material that is used to form the hole transport layer. 
     Meanwhile, when the hole transport region includes an electron blocking layer, a material for the electron blocking layer may be selected from materials for the hole transport region described above and materials for a host to be explained later. However, the material for the electron blocking layer is not limited thereto. For example, when the hole transport region includes an electron blocking layer, a material for the electron blocking layer may be mCP, which will be explained later. 
     The emission layer may include a host and a dopant, and the dopant may include the organometallic compound represented by Formula 1. 
     The host may include at least one selected from TPBi, TBADN, ADN (also referred to as “DNA”), CBP, CDBP, TCP, mCP, Compound H50, and Compound H51: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In one or more embodiments, the host may further include a compound represented by Formula 301 below. 
     
       
         
         
             
             
         
       
     
     Ar 111  and Ar 112  in Formula 301 may each independently be selected from: 
     a phenylene group, a naphthylene group, a phenanthrenylene group, and a pyrenylene group; and 
     a phenylene group, a naphthylene group, a phenanthrenylene group, and a pyrenylene group, each substituted with at least one selected from a phenyl group, a naphthyl group, and an anthracenyl group. 
     Ar 113  to Ar 116  in Formula 301 may each independently be selected from: 
     a C 1 -C 10  alkyl group, a phenyl group, a naphthyl group, a phenanthrenyl group, and a pyrenyl group; and 
     a phenyl group, a naphthyl group, a phenanthrenyl group, and a pyrenyl group, each substituted with at least one selected from a phenyl group, a naphthyl group, and an anthracenyl group. 
     g, h, i, and j in Formula 301 may each independently be an integer from 0 to 4, and may be, for example, 0, 1, or 2. 
     Ar 113  and Ar 116  in Formula 301 may each independently be selected from 
     a C 1 -C 10  alkyl group, substituted with at least one selected from a phenyl group, a naphthyl group, and an anthracenyl group; 
     a phenyl group, a naphthyl group, an anthracenyl group, a pyrenyl, a phenanthrenyl group, and a fluorenyl group; 
     a phenyl group, a naphthyl group, an anthracenyl group, a pyrenyl group, a phenanthrenyl group, and a fluorenyl group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a phenyl group, a naphthyl group, an anthracenyl group, a pyrenyl group, a phenanthrenyl group, and a fluorenyl group; and 
     
       
         
         
             
             
         
       
     
     but embodiments of the present disclosure are not limited thereto. 
     In one or more embodiments, the host may include a compound represented by Formula 302 below: 
     Formula 302 
     
       
         
         
             
             
         
       
     
     Ar 122  to Ar 125  in Formula 302 are the same as described in detail in connection with Ar 113  in Formula 301. 
     Ar 126  and Ar 127  in Formula 302 may each independently be a C 1 -C 10  alkyl group (for example, a methyl group, an ethyl group, or a propyl group). 
     k and l in Formula 302 may each independently be an integer from 0 to 4. For example, k and l may be 0, 1, or 2. 
     When the organic light-emitting device is a full-color organic light-emitting device, the emission layer may be patterned into a red emission layer, a green emission layer, and a blue emission layer. In one or more embodiments, due to a stacked structure including a red emission layer, a green emission layer, and/or a blue emission layer, the emission layer may emit white light. 
     When the emission layer includes a host and a dopant, an amount of the dopant may be in a range of about 0.01 parts by weight to about 15 parts by weight based on 100 parts by weight of the host, but embodiments of the present disclosure are not limited thereto. 
     A thickness of the emission layer may be in a range of about 100 Å to about 1,000 Å, for example, about 200 Å to about 600 Å. While not wishing to be bound by theory, it is understood that when the thickness of the emission layer is within this range, excellent light-emission characteristics may be obtained without a substantial increase in driving voltage. 
     Then, an electron transport region may be located on the emission layer. 
     The electron transport region may include a hole blocking layer, an electron transport layer, an electron injection layer, or any combination thereof. 
     For example, the electron transport region may have a hole blocking layer/electron transport layer/electron injection layer structure or an electron transport layer/electron injection layer structure, but the structure of the electron transport region is not limited thereto. The electron transport layer may have a single-layered structure or a multi-layered structure including two or more different materials. 
     Conditions for forming the hole blocking layer, the electron transport layer, and the electron injection layer which constitute the electron transport region may be understood by referring to the conditions for forming the hole injection layer. 
     When the electron transport region includes a hole blocking layer, the hole blocking layer may include, for example, at least one of BCP, BPhen, and BAlq but embodiments of the present disclosure are not limited thereto. 
     
       
         
         
             
             
         
       
     
     A thickness of the hole blocking layer may be in a range of about 20 Å to about 1,000 Å, for example, about 30 Å to about 300 Å. While not wishing to be bound by theory, it is understood that when the thickness of the hole blocking layer is within these ranges, the hole blocking layer may have excellent hole blocking characteristics without a substantial increase in driving voltage. 
     The electron transport layer may further include at least one selected from BCP, BPhen, Alq 3 , BAlq, TAZ, and NTAZ. 
     
       
         
         
             
             
         
       
     
     In one or more embodiments, the electron transport layer may include at least one of ET1 to ET25, but are not limited thereto: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     A thickness of the electron transport layer may be in a range of about 100 Å to about 1,000 Å, for example, about 150 Å to about 500 Å. While not wishing to be bound by theory, it is understood that when the thickness of the electron transport layer is within the range described above, the electron transport layer may have satisfactory electron transport characteristics without a substantial increase in driving voltage. 
     Also, the electron transport layer may further include, in addition to the materials described above, a metal-containing material. 
     The metal-containing material may include a Li complex. The Li complex may include, for example, Compound ET-D1 (lithium 8-hydroxyquinolate, LiQ) or ET-D2. 
     
       
         
         
             
             
         
       
     
     The electron transport region may include an electron injection layer (EIL) that promotes flow of electrons from the second electrode  19  thereinto. 
     The electron injection layer may include at least one selected from LiF, NaCl, CsF, Li 2 O, and BaO. 
     A thickness of the electron injection layer may be in a range of about 1 Å to about 100 Å, and, for example, about 3 Å to about 90 Å. While not wishing to be bound by theory, it is understood that when the thickness of the electron injection layer is within the range described above, the electron injection layer may have satisfactory electron injection characteristics without a substantial increase in driving voltage. 
     The second electrode  19  is located on the organic layer  15 . The second electrode  19  may be a cathode. A material for forming the second electrode  19  may be metal, an alloy, an electrically conductive compound, or a combination thereof, which have a relatively low work function. For example, lithium (Li), magnesium (Mg), aluminum (AI), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In), or magnesium-silver (Mg—Ag) may be formed as the material for forming the second electrode  19 . To manufacture a top-emission type light-emitting device, a transmissive electrode formed using ITO or IZO may be used as the second electrode  19 . 
     Hereinbefore, the organic light-emitting device has been described with reference to the FIGURE, but embodiments of the present disclosure are not limited thereto. 
     Another aspect provides a diagnostic composition including at least one organometallic compound represented by Formula 1. 
     The organometallic compound represented by Formula 1 provides high luminescent efficiency. Accordingly, a diagnostic composition including the organometallic compound may have high diagnostic efficiency. 
     The diagnostic composition may be used in various applications including a diagnosis kit, a diagnosis reagent, a biosensor, and a biomarker. 
     The term “C 1 -C 60  alkyl group” as used herein refers to a linear or branched saturated aliphatic hydrocarbon monovalent group having 1 to 60 carbon atoms, and non-limiting examples thereof include a methyl group, an ethyl group, a propyl group, an iso-butyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an iso-amyl group, and a hexyl group. The term “C 1 -C 60  alkylene group” as used herein refers to a divalent group having the same structure as that of the C 1 -C 60  alkyl group. 
     The term “C 1 -C 60  alkoxy group” as used herein refers to a monovalent group represented by —OA 101  (wherein A 101  is the C 1 -C 60  alkyl group), and examples thereof include a methoxy group, an ethoxy group, and an iso-propyloxy group. 
     The term “C 2 -C 60  alkenyl group” as used herein refers to a hydrocarbon group formed by including at least one carbon-carbon double bond in the middle or at the terminus of the C 2 -C 60  alkyl group, and examples thereof include an ethenyl group, a propenyl group, and a butenyl group. The term “C 2 -C 60  alkenylene group” as used herein refers to a divalent group having the same structure as that of the C 2 -C 60  alkenyl group. 
     The term “C 2 -C 60  alkynyl group” as used herein refers to a hydrocarbon group formed by including at least one carbon-carbon triple bond in the middle or at the terminus of the C 2 -C 60  alkyl group, and examples thereof include an ethynyl group, and a propynyl group. The term “C 2 -C 60  alkynylene group” as used herein refers to a divalent group having the same structure as that of the C 2 -C 60  alkynyl group. 
     The term “C 3 -C 10  cycloalkyl group” as used herein refers to a monovalent saturated hydrocarbon monocyclic group having 3 to 10 carbon atoms, and examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. The term “C 3 -C 10  cycloalkylene group” as used herein refers to a divalent group having the same structure as that of the C 3 -C 10  cycloalkyl group. 
     The term “C 1 -C 10  heterocycloalkyl group” as used herein refers to a monovalent saturated monocyclic group having at least one heteroatom selected from N, O, P, Si and S as a ring-forming atom and 1 to 10 carbon atoms, and non-limiting examples thereof include a tetrahydrofuranyl group, and a tetrahydrothiophenyl group. The term “C 1 -C 10  heterocycloalkylene group” as used herein refers to a divalent group having the same structure as the C 1 -C 10  heterocycloalkyl group. 
     The term “C 3 -C 10  cycloalkenyl group” as used herein refers to a monovalent monocyclic group that has 3 to 10 carbon atoms and at least one carbon-carbon double bond in the ring thereof and no aromaticity, and non-limiting examples thereof include a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group. The term “C 3 -C 10  cycloalkenylene group” as used herein refers to a divalent group having the same structure as the C 3 -C 10  cycloalkenyl group. 
     The term “C 1 -C 10  heterocycloalkenyl group” as used herein refers to a monovalent monocyclic group that has at least one heteroatom selected from N, O, P, Si, and S as a ring-forming atom, 1 to 10 carbon atoms, and at least one double bond in its ring. Examples of the C 1 -C 10  heterocycloalkenyl group are a 2,3-dihydrofuranyl group, and a 2,3-dihydrothiophenyl group. The term “C 1 -C 10  heterocycloalkenylene group” as used herein refers to a divalent group having the same structure as the C 1 -C 10  heterocycloalkenyl group. 
     The term “C 6 -C 60  aryl group” as used herein refers to a monovalent group having a carbocyclic aromatic system having 6 to 60 carbon atoms, and the term “C 6 -C 60  arylene group” as used herein refers to a divalent group having a carbocyclic aromatic system having 6 to 60 carbon atoms. Non-limiting examples of the C 6 -C 60  aryl group include a phenyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a pyrenyl group, and a chrysenyl group. When the C 6 -C 60  aryl group and the C 6 -C 60  arylene group each include two or more rings, the rings may be fused to each other. The C 7 -C 60  alkylaryl group refers to a C 6 -C 60  aryl group substituted with at least one C 1 -C 60  alkyl group. 
     The term “C 1 -C 60  heteroaryl group” as used herein refers to a monovalent group having a heterocyclic aromatic system that has at least one heteroatom selected from N, O, P, Si, and S as a ring-forming atom, and 1 to 60 carbon atoms. The term “C 1 -C 60  heteroarylene group” as used herein refers to a divalent group having a heterocyclic aromatic system that has at least one heteroatom selected from N, O, P, and S as a ring-forming atom, and 1 to 60 carbon atoms. Examples of the C 1 -C 60  heteroaryl group include a pyridinyl group, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, a triazinyl group, a quinolinyl group, and an isoquinolinyl group. When the C 6 -C 60  heteroaryl group and the C 6 -C 60  heteroarylene group each include two or more rings, the rings may be fused to each other. The C 2 -C 60  alkylheteroaryl group refers to a C 1 -C 60  heteroaryl group substituted with at least one C 1 -C 60  alkyl group. 
     The term “C 6 -C 60  aryloxy group” as used herein indicates —OA 102  (wherein A 102  is the C 6 -C 60  aryl group), the term “C 6 -C 60  arylthio group” as used herein indicates —SA 103  (wherein A 103  is the C 6 -C 60  aryl group), and the term “C 7 -C 60  aryl alkyl group” as used herein indicates —A 104 A 105  (wherein A 106  is the C 6 -C 59  aryl group and A 104  is the C 1 -C 53  alkylene group). 
     The term “C 1 -C 60  heteroaryloxy group” as used herein refers to —OA 106  (wherein A 106  is the C 2 -C 60  heteroaryl group), the term “C 1 -C 60  heteroarylthio group” as used herein indicates —SA 107  (wherein A 107  is the C 1 -C 60  heteroaryl group), and the term “C 2 -C 60  heteroarylalkyl group” as used herein refers to —A 108 A 109  (A 109  is a C 1 -C 59  heteroaryl group, and A 108  is a C 1 -C 59  alkylene group). 
     The term “monovalent non-aromatic condensed polycyclic group” as used herein refers to a monovalent group (for example, having 8 to 60 carbon atoms) having two or more rings condensed to each other, only carbon atoms as ring-forming atoms, and no aromaticity in its entire molecular structure. Examples of the monovalent non-aromatic condensed polycyclic group include a fluorenyl group. The term “divalent non-aromatic condensed polycyclic group” as used herein refers to a divalent group having the same structure as the monovalent non-aromatic condensed polycyclic group. 
     The term “monovalent non-aromatic condensed heteropolycyclic group” as used herein refers to a monovalent group (for example, having 2 to 60 carbon atoms) having two or more rings condensed to each other, a heteroatom selected from N, O, P, Si, and S, other than carbon atoms, as a ring-forming atom, and no aromaticity in its entire molecular structure. Non-limiting examples of the monovalent non-aromatic condensed heteropolycyclic group include a carbazolyl group. The term “divalent non-aromatic condensed heteropolycyclic group” as used herein refers to a divalent group having the same structure as the monovalent non-aromatic condensed heteropolycyclic group. 
     The term “C 5 -C 30  carbocyclic group” as used herein refers to a saturated or unsaturated cyclic group having, as a ring-forming atom, 5 to 30 carbon atoms only. The C 5 -C 30  carbocyclic group may be a monocyclic group or a polycyclic group. 
     The term “C 1 -C 30  heterocyclic group” as used herein refers to a saturated or unsaturated cyclic group having, as a ring-forming atom, at least one heteroatom selected from N, O, Si, P, and S other than 1 to 30 carbon atoms. The C 1 -C 30  heterocyclic group may be a monocyclic group or a polycyclic group. 
     at least one of substituents of the substituted C 5 -C 30  carbocyclic group, substituted C 1 -C 30  heterocyclic group, substituted C 1 -C 60  alkyl group, substituted C 2 -C 60  alkenyl group, substituted C 2 -C 60  alkynyl group, substituted C 1 -C 60  alkoxy group, substituted C 3 -C 10  cycloalkyl group, substituted C 1 -C 10  heterocycloalkyl group, substituted C 3 -C 10  cycloalkenyl group, substituted C 1 -C 10  heterocycloalkenyl group, substituted C 6 -C 60  aryl group, substituted C 7 -C 60  alkylaryl group, substituted C 6 -C 60  aryloxy group, substituted C 6 -C 60  arylthio group, substituted C 7 -C 60  arylalkyl group, substituted C 1 -C 60  heteroaryl group, substituted C 1 -C 60  heteroaryloxy group, substituted C 1 -C 60  heteroarylthio group, substituted C 2 -C 60  heteroarylalkyl group, substituted C 2 -C 60  alkylheteroaryl group, substituted monovalent non-aromatic condensed polycyclic group, and substituted monovalent non-aromatic condensed heteropolycyclic group is selected from: 
     deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, and a C 1 -C 60  alkoxy group; 
     a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, and a C 1 -C 60  alkoxy group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkylaryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, a C 2 -C 60  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 11 )(Q 12 ), —Si(Q 13 )(Q 14 )(Q 15 ), —B(Q 16 )(Q 17 ), and —P(═O)(Q 18 )(Q 19 ); 
     a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycoalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkylaryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -Coo arylalkyl group, a C 1 -C 60  heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, a C 2 -C 60  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group; 
     a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkylaryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 2 -C 60  arylalkyl group, a C 1 -C 60  heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, a C 2 -C 60  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, —CD 3 , —CD 2 H, —CDH 2 , —CF 3 , —CF 2 H, —CFH 2 , a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 7 -C 60  alkylaryl group, a C 2 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, a C 2 -C 60  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q 21 )(Q 22 ), —Si(Q 23 )(Q 24 )(Q 25 ), —B(Q 26 )(Q 27 ), and —P(═O)(Q 28 )(Q 29 ); and 
     —N(Q 31 )(Q 32 ), —Si(Q 33 )(Q 34 )(Q 35 ), —B(Q 36 )(Q 37 ), and —P(═O)(Q 38 )(Q 39 ); 
     wherein Q 1  to Q 9 , Q 11  to Q 19 , Q 21  to Q 29 , and Q 31  to Q 39  may each independently be selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C 1 -C 60  alkyl group, a C 1 -C 60  alkyl group substituted with at least one selected from deuterium, a C 1 -C 60  alkyl group, and a C 6 -C 60  aryl group, a C 2 -C 60  alkenyl group, a C 2 -C 60  alkynyl group, a C 1 -C 60  alkoxy group, a C 3 -C 10  cycloalkyl group, a C 1 -C 10  heterocycloalkyl group, a C 3 -C 10  cycloalkenyl group, a C 1 -C 10  heterocycloalkenyl group, a C 6 -C 60  aryl group, a C 6 -C 60  aryl group substituted with at least one selected from deuterium, a C 1 -C 60  alkyl group, and a C 6 -C 60  aryl group, a C 6 -C 60  aryloxy group, a C 6 -C 60  arylthio group, a C 7 -C 60  arylalkyl group, a C 1 -C 60  heteroaryl group, a C 1 -C 60  heteroaryloxy group, a C 1 -C 60  heteroarylthio group, a C 2 -C 60  heteroarylalkyl group, a C 2 -C 60  alkylheteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group. 
     Hereinafter, a compound and an organic light-emitting device according to embodiments are described in detail with reference to Synthesis Example and Examples. However, the organic light-emitting device is not limited thereto. The wording “B was used instead of A” used in describing Synthesis Examples means that an amount of A used was identical to an amount of B used, in terms of a molar equivalent. 
     EXAMPLES 
     Synthesis Example 1: Synthesis of Compound 3 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 3-C 
     2 grams (g) (6.60 millimoles, mmol) of starting material 3-A, 2.53 g (7.26 mmol, 1.1 equivalents, equiv.) of starting material 3-B, 0.53 g (0.46 mmol, 0.07 equiv.) of tetrakis(triphenylphosphine)palladium (0)), and 2.74 g (19.79 mmol, 3 equiv.) of potassium carbonate were mixed with 48 mL of a mixture including tetrahydrofuran (THF) and H 2 O at a ratio of 3:1, and the resulting mixture was refluxed overnight. The obtained resultant was cooled to room temperature, and the precipitate was removed therefrom to obtain a filtrate. The filtrate was washed with ethylene acetate (EA)/H 2 O, and purified by column chromatography to produce 1.7 g (yield of 78%) of Intermediate 3-C. The obtained compound was identified by LC-MS. 
     LC-MS m/z=444.28 (M+H) +   
     Synthesis of Compound 3 
     1.5 g (3.37 mmol) of Intermediate 3-C and 1.68 g (4.05 mmol, 1.2 equiv.) of K 2 PtCl 4  were mixed with a mixture including 80 mL of AcOH (acetic acid) and 4 mL of H 2 O, and then the resulting mixture was refluxed overnight. The obtained resultant was cooled to room temperature and filtered to obtain the precipitate, which was then mixed with methylene chloride (MC) and washed with H 2 O, and purified by column chromatography to produce 1.1 g (yield 51%) of Compound 3. The obtained compound was identified by LC-MS. 
     LC-MS m/z=637.23 (M+H) +   
     Synthesis Example 2: Synthesis of Compound 17 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 17-C 
     2 g (4.19 mmol) of starting material 17-A, 1.93 g (4.61 mmol, 1.1 equiv.) of starting material 17-B, 0.34 g (0.29 mmol, 0.07 equiv.) of tetrakis(triphenylphosphine)palladium (0), and 1.74 g (12.57 mmol, 3 equiv.) of potassium carbonate were mixed with 30 mL of a mixture including THF and H 2 O at a ratio of 3:1, and the resulting mixture was refluxed overnight. The obtained resultant was cooled to room temperature, and the precipitate was removed therefrom to obtain a filtrate. The filtrate was washed with EA/H 2 O, and purified by column chromatography to produce 1.9 g (yield 66%) of Intermediate 17-C. The obtained compound was identified by LC-MS. 
     LC-MS m/z=688.42 (M+H) +   
     Synthesis of Compound 17 
     1.8 g (2.61 mmol) of Intermediate 17-C and 1.3 g (3.14 mmol, 1.2 equiv.) of K 2 PtCl 4  were mixed with a mixture including 65 mL of AcOH and 3 mL of H 2 O, and the resulting mixture was refluxed overnight. The obtained resultant was cooled to room temperature and filtered to obtain the precipitate, which was then mixed with MC and washed with H 2 O, and purified by column chromatography to produce 1.41 g (yield of 61%) of Compound 17. The obtained compound was identified by LC-MS. 
     LC-MS m/z=881.37 (M+H) +   
     Synthesis Example 3: Synthesis of Compound 24 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 24-C 
     2 g (3.75 mmol) of starting material 24-A, 1.73 g (4.12 mmol, 1.1 equiv.) of starting material 24-B, 0.30 g (0.26 mmol, 0.07 equiv.) of tetrakis(triphenylphosphine)palladium (0), and 1.82 g (11.25 mmol, 3 equiv.) of potassium carbonate were mixed with 27 mL of a mixture including THF and H 2 O at a ratio of 3:1, and the resulting mixture was refluxed overnight. The obtained resultant was cooled to room temperature, and the precipitate was removed therefrom to obtain a filtrate. The filtrate was washed with EA/H 2 O, and purified by column chromatography to produce 1.9 g (yield 68%) of Intermediate 24-C. The obtained compound was identified by LC-MS. 
     LC-MS m/z=744.48 (M+H) +   
     Synthesis of Compound 24 
     1.7 g (2.28 mmol) of Intermediate 24-C and 1.3 g (3.14 mmol, 1.2 equiv.) of K 2 PtCl 4  were mixed with a mixture including 57 mL of AcOH and 3 mL of H 2 O, and the resulting mixture was refluxed overnight. The obtained resultant was cooled to room temperature and filtered to obtain the precipitate, which was then mixed with MC and washed with H 2 O, and purified by column chromatography to produce 1.41 g (yield of 65%) of Compound 24. The obtained compound was identified by LC-MS. 
     LC-MS m/z=937.43 (M+H) +   
     Synthesis Example 4: Synthesis of Compound 27 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 27-C 
     2 g (3.39 mmol) of starting material 27-A, 1.84 g (3.73 mmol, 1.1 equiv.) of starting material 27-B, 0.27 g (0.24 mmol, 0.07 equiv.) of tetrakis(triphenylphosphine)palladium (0), and 1.41 g (10.18 mmol, 3 equiv.) of potassium carbonate were mixed with 27 mL of a mixture including THF and H 2 O at a ratio of 3:1, and the resulting mixture was refluxed overnight. The obtained resultant was cooled to room temperature, and the precipitate was removed therefrom to obtain a filtrate. The filtrate was washed with EA/H 2 O, and purified by column chromatography to produce 2.2 g (yield of 74%) of Intermediate 27-C. The obtained compound was identified by LC-MS. 
     LC-MS m/z=875.57 (M+H) +   
     Synthesis of Compound 27 
     1.5 g (1.71 mmol) of Intermediate 27-C and 0.85 g (3.14 mmol, 1.2 equiv.) of K 2 PtCl 4  were mixed with a mixture including 43 mL of AcOH and 2 mL of H 2 O, and the resulting mixture was refluxed overnight. The obtained resultant was cooled to room temperature and filtered to obtain the precipitate, which was then mixed with MC and washed with H 2 O, and purified by column chromatography to produce 1.1 g (yield of 60%) of Compound 27. The obtained compound was identified by LC-MS. 
     LC-MS m/z=1068.52 (M+H) +   
     Synthesis Example 5: Synthesis of Compound 31 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 31-C 
     2 g (3.58 mmol) of starting material 31-A, 1.65 g (3.73 mmol, 1.1 equiv.) of starting material 31-B, 0.29 g (0.25 mmol, 0.07 equiv.) of tetrakis(triphenylphosphine)palladium (0), and 1.48 g (10.74 mmol, 3 equiv.) of potassium carbonate were mixed with 26 mL of a mixture including THF and H 2 O at a ratio of 3:1, and the resulting mixture was refluxed overnight. The obtained resultant was cooled to room temperature, and the precipitate was removed therefrom to obtain a filtrate. The filtrate was washed with EA/H 2 O, and purified by column chromatography to produce 1.8 g (yield of 65%) of Intermediate 31-C. The obtained compound was identified by LC-MS. 
     LC-MS m/z=769.48 (M+H) +   
     Synthesis of Compound 31 
     1.7 g (2.21 mmol) of Intermediate 31-C and 1.1 g (2.65 mmol, 1.2 equiv.) of K 2 PtCl 4  were mixed with a mixture including 55 mL of AcOH and 3 mL of H 2 O, and the resulting mixture was refluxed overnight. The obtained resultant was cooled to room temperature and filtered to obtain the precipitate, which was then mixed with MC and washed with H 2 O, and purified by column chromatography to produce 1.2 g (yield of 56%) of Compound 31. The obtained compound was identified by LC-MS. 
     LC-MS m/z=962.43 (M+H) +   
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 99-C 
     2 g (3.28 mmol) of starting material 99-A, 1.52 g (3.61 mmol, 1.1 equiv.) of starting material 99-B, 0.27 g (0.23 mmol, 0.07 equiv.) of tetrakis(triphenylphosphine)palladium(0), and 1.36 g (9.84 mmol, 3 equiv.) of potassium carbonate were mixed with 36 mL of a mixture including THF and H 2 O at a ratio of 3:1, and the resultant mixture was refluxed overnight. The obtained result was cooled to room temperature, and then, the precipitate was removed therefrom to obtain a filtrate. The filtrate was washed with EA/H 2 O, and column chromatography was performed thereon to complete the production of 2.1 g (yield of 78%) of Intermediate 99-C. The obtained compound was identified by LC-MS. 
     LC-MS m/z=824.54 (M+H) +   
     Synthesis of Compound 99 
     2 g (2.42 mmol) of Intermediate 99-C and 1.21 g (2.91 mmol, 1.2 equiv.) of K 2 PtCl 4  were mixed with a mixture including 61 mL of AcOH and 3 mL of H 2 O, and the resultant mixture was refluxed overnight. The obtained result was cooled to room temperature and filtered to obtain the precipitate, which was then mixed with MC and washed with H 2 O, and column chromatography was performed thereon to complete the production of 1.3 g (yield of 53%) of Compound 99. The obtained compound was identified by LC-MS. 
     LC-MS m/z=1017.49 (M+H) +   
     Synthesis Example 7: Synthesis of Compound 157 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 157-C 
     2 g (3.5 mmol) of starting material 157-A, 1.64 g (3.85 mmol, 1.1 equiv.) of starting material 157-B, 0.28 g (0.24 mmol, 0.07 equiv.) of tetrakis(triphenylphosphine)palladium(0), and 1.45 g (10.50 mmol, 3 equiv.) of potassium carbonate were mixed with 38 mL of a mixture including THF and H 2 O at a ratio of 3:1, and the resultant mixture was refluxed overnight. The obtained result was cooled to room temperature, and then, the precipitate was removed therefrom to obtain a filtrate. The filtrate was washed with EA/H 2 O, and column chromatography was performed thereon to complete the production of 2.1 g (yield of 76%) of Intermediate 157-C. The obtained compound was identified by LC-MS. 
     LC-MS m/z=791.55 (M+H) +   
     Synthesis of Compound 157 
     2 g (2.52 mmol) of Intermediate 157-C 1.26 g (3.03 mmol, 1.2 equiv.) of K 2 PtCl 4  were mixed with a mixture including 63 mL of AcOH and 3 mL of H 2 O, and the resultant mixture was refluxed overnight. The obtained result was cooled to room temperature and filtered to obtain the precipitate, which was then mixed with MC and washed with H 2 O, and column chromatography was performed thereon to complete the production of 1.2 g (yield of 48%) of Compound 157. The obtained compound was identified by LC-MS. 
     LC-MS m/z=984.50 (M+H) +   
     Synthesis Example 8: Synthesis of Compound 186 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 186-C 
     2 g (3.61 mmol) of starting material 186-A, 1.73 g (3.97 mmol, 1.1 equiv.) of starting material 186-B, 0.29 g (0.25 mmol, 0.07 equiv.) of tetrakis(triphenylphosphine)palladium(0), and 1.50 g (10.84 mmol, 3 equiv.) of potassium carbonate were mixed with a mixture including THF and H 2 O at a ratio of 3:1, and the resultant mixture was refluxed overnight. The obtained result was cooled to room temperature, and then, the precipitate was removed therefrom to obtain a filtrate. The filtrate was washed with EA/H 2 O, and column chromatography was performed thereon to complete the production of 1.8 g (yield of 64%) of Intermediate 186-C. The obtained compound was identified by LC-MS. 
     LC-MS m/z=780.48 (M+H) +   
     Synthesis of Compound 186 
     1.5 g (1.92 mmol) of Intermediate 186-C and 0.96 g (2.3 mmol, 1.2 equiv.) of K 2 PtCl 4  were mixed with a mixture including 48 mL of AcOH and 3 mL of H 2 O, and the resultant mixture was refluxed overnight. The obtained result was cooled to room temperature and filtered to obtain the precipitate, which was then mixed with MC and washed with H 2 O, and column chromatography was performed thereon to complete the production of 0.8 g (yield of 43%) of Compound 186. The obtained compound was identified by LC-MS. 
     LC-MS m/z=973.43 (M+H) +   
     Synthesis Example 9: Synthesis of Compound 448 
     
       
         
         
             
             
         
       
     
     Synthesis of Intermediate 448-C 
     2 g (3.51 mmol) of starting material 448-A, 1.89 g (3.86 mmol, 1.1 equiv.) of starting material 448-B, 0.28 g (0.25 mmol, 0.07 equiv.) of tetrakis(triphenylphosphine)palladium(0), and 1.45 g (10.52 mmol, 3 equiv.) of potassium carbonate were mixed with 38 mL of a mixture including THF and H 2 O at a ratio of 3:1, and the resultant was refluxed overnight. The obtained result was cooled to room temperature, and then, the precipitate was removed therefrom to obtain a filtrate. The filtrate was washed with EA/H 2 O, and column chromatography was performed thereon to complete the production of 2.0 g (yield of 73%) of Intermediate 448-C. The obtained compound was identified by LC-MS. 
     LC-MS m/z=852.48 (M+H) +   
     Synthesis of Compound 448 
     1.8 g (2.11 mmol) of Intermediate 448-C and 1.05 g (2.53 mmol, 1.2 equiv.) of K 2 PtCl 4  were mixed with a mixture including 53 mL of AcOH and 3 mL of H 2 O, and the resultant mixture was refluxed overnight. The obtained result was cooled to room temperature and filtered to obtain the precipitate, which was then mixed with MC and washed with H 2 O, and column chromatography was performed thereon to complete the production of 1.1 g (yield of 50%) of Compound 448. The obtained compound was identified by LC-MS. 
     LC-MS m/z=1045.43 (M+H) +   
     Evaluation Example 1: Evaluation of Photoluminescence Quantum Yields (PLQY) 
     PMMA in CH 2 Cl 2  solution, 5 percent by weight (wt %) of CBP, and Compound 3 were mixed, and the resultant was coated on a quartz substrate by using a spin coater, and then, heat-treated in an oven at a temperature of 80° C., and cooled to room temperature to obtain a film. 
     The PLQY of Compound 3 in film was evaluated by using a Hamamatsu Photonics absolute PL quantum yield measurement system equipped with a xenon light source, a monochromator, a photonic multichannel analyzer, and an integrating sphere, and using PLQY measurement software (Hamamatsu Photonics, Ltd., Shizuoka, Japan), and the same experiment was performed on each of Compounds 17, 24, 27 and 31. Results thereof are shown in Table 2. 
     
       
         
           
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Com- 
                   
               
               
                 pound 
                   
               
               
                 No. 
                 PLQY 
               
               
                   
               
             
            
               
                  3 
                 0.978 
               
               
                  17 
                 0.999 
               
               
                  24 
                 0.998 
               
               
                  27 
                 0.999 
               
               
                  31 
                 0.999 
               
               
                  99 
                 0.993 
               
               
                 157 
                 0.986 
               
               
                 186 
                 0.999 
               
               
                 448 
                 0.985 
               
               
                   
               
            
           
           
               
            
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     From Table 2, it was confirmed that Compounds 3, 17, 24, 27, 31, 99, 157, 186 and 448 had high PLQY (in film). 
     Evaluation Example 2: Decay Time Measurement 
     A quartz substrate washed with chloroform and pure water was prepared, and then, a predetermined material shown in Table 3 was vacuum-(co)deposited at a degree of vacuum of 10 −7  torr to prepare Films 1 to 5 having a thickness of 50 nanometers (nm). 
     
       
         
           
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Film name 
                 Compound used in film production 
               
               
                   
               
             
            
               
                 Film 1 
                 CBP:Compound 3 (weight ratio of 9:1) 
               
               
                 Film 2 
                 CBP:Compound 17 (weight ratio of 9:1) 
               
               
                 Film 3 
                 CBP:Compound 24 (weight ratio of 9:1) 
               
               
                 Film 4 
                 CBP:Compound 27 (weight ratio of 9:1) 
               
               
                 Film 5 
                 CBP:Compound 31 (weight ratio of 9:1) 
               
               
                 Film 6 
                 CBP:Compound 99 (weight ratio of 9:1) 
               
               
                 Film 7 
                 CBP:Compound 157 (weight ratio of 9:1) 
               
               
                 Film 8 
                 CBP:Compound 186 (weight ratio of 9:1) 
               
               
                 Film 9 
                 CBP:Compound 448 (weight ratio of 9:1) 
               
               
                   
               
            
           
         
       
     
     Photoluminescence (PL) spectrum of each of Films 1 to 9 was measured by using FluoTime 300, which is a TRPL measurement system manufactured by PicoQuant Inc. and PLS340 (excitation wavelength=340 nanometers, spectral width=20 nanometers), which is a pumping source of PicoQuant Inc. at room temperature. Then, the main peak of each spectrum was identified, and the number of photons emitted at the wavelength of photon pulse (pulse width=500 picoseconds) applied by PLS340 to each of Films 1 to 9 was repeatedly measured based on time-correlated single photon counting (TCSPC) according to time, thereby obtaining a TRPL curve sufficient for fitting. The obtained result was fitted with two or more exponential decay functions to obtain T decay  (E x ), that is, decay time of each of Films 1 to 9 (decay time). Results obtained therefrom were shown in Table 4. A function for fitting is as shown in Equation 1, and from among T decay  values obtained from each exponential decay function used for fitting, the largest T decay  was obtained as T decay  (E x ). In this regard, the same measurement was performed during the same measurement time as that for obtaining TRPL curve in the dark state (in which pumping signals entering a film are blocked) to obtain a baseline or a background signal curve for use as a baseline for fitting. 
     
       
         
           
             
               
                 
                   
                     f 
                     ⁡ 
                     
                       ( 
                       t 
                       ) 
                     
                   
                   = 
                   
                     
                       ∑ 
                       
                         i 
                         = 
                         1 
                       
                       n 
                     
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     
                       
                         A 
                         i 
                       
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       exp 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       
                         ( 
                         
                           
                             - 
                             t 
                           
                           ⁢ 
                           
                             / 
                           
                           ⁢ 
                           
                             T 
                             
                               decay 
                               , 
                               i 
                             
                           
                         
                         ) 
                       
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
               
             
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE 4 
               
               
                   
               
               
                   
                   
                 Decay time 
               
               
                   
                 Film name 
                 (μs) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 Film 1 (Compound 3) 
                 2.340 
               
               
                   
                 Film 2 (Compound 17) 
                 2.081 
               
               
                   
                 Film 3 (Compound 24) 
                 2.010 
               
               
                   
                 Film 4 (Compound 27) 
                 2.174 
               
               
                   
                 Film 5 (Compound 31) 
                 2.002 
               
               
                   
                 Film 6 (Compound 99) 
                 2.228 
               
               
                   
                 Film 7 (Compound 157) 
                 2.470 
               
               
                   
                 Film 8 (Compound 186) 
                 2.323 
               
               
                   
                 Film 9 (Compound 448) 
                 2.371 
               
               
                   
               
            
           
         
       
     
     From Table 4, it was confirmed that Compounds 3, 17, 24, 27, 31, 99, 157, 186 and 448 had excellent decay time characteristics. 
     Example 1 
     An ITO glass substrate was cut to a size of 50 mm×50 mm×0.5 mm (mm=millimeter) and then, sonicated in acetone iso-propyl alcohol and pure water, each for 15 minutes, and then, washed by exposure to UV ozone for 30 minutes. 
     Then, m-MTDATA was deposited on an ITO electrode (anode) of the glass substrate at a deposition speed of 1 Angstroms per second (Å/sec) to form a hole injection layer having a thickness of 600 Angstroms (Å), and then, α-NPD (NPB) was deposited on the hole injection layer at a deposition speed of 1 Å/sec to form a hole transport layer having a thickness of 250 Å. 
     Compound 3 (dopant) and CBP (host) were co-deposited on the hole transport layer at a deposition speed of 0.1 Å/sec and a deposition speed of 1 Å/sec, respectively, to form an emission layer having a thickness of 400 Å. 
     BAlq was deposited on the emission layer at a deposition speed of 1 Å/sec to form a hole blocking layer having a thickness of 50 Å, and Alq 3  was deposited on the hole blocking layer to form an electron transport layer having a thickness of 300 Å, and then, LiF was deposited on the electron transport layer to form an electron injection layer having a thickness of 10 Å, and then, Al was vacuum deposited on the electron injection layer to form a second electrode (cathode) having a thickness of 1,200 Å, thereby completing manufacturing of an organic light-emitting device having a structure of ITO/m-MTDATA (600 Å)/α-NPD (250 Å)/CBP+Compound 3 (10%) (400 Å)/BAlq (50 Å)/Alq 3 (300 Å)/LiF (10 Å)/Al(1,200 Å). 
     
       
         
         
             
             
         
       
     
     Examples 2 to 9 and Comparative Examples A to C 
     Organic light-emitting devices were manufactured in the same manner as in Example 1, except that in forming an emission layer, for use as a dopant, corresponding compounds shown in Table 5 were used instead of Compound 3. 
     Evaluation Example 3: Evaluation on Characteristics of Organic Light-Emitting Devices 
     The driving voltage, the luminescence quantum efficiency, the roll-off ratio, and the lifespan (T 95 ) of each of the organic light-emitting devices manufactured according to Examples 1 to 9 and Comparative Examples A to C were evaluated. Results thereof are shown in Table 5. This evaluation was performed using a current-voltage meter (Keithley 2400) and a luminescence meter (Minolta Cs-1,000A), and the lifespan (T 95 )(at 6000 nit) was evaluated by measuring the amount of time that elapsed until luminance was reduced to 95% of the initial brightness of 100%. The lifespan (T 95 )(at 6000 nit) was represented as a relative value (%) in Table 5. The roll-off ratio was calculated by the following equation: 
     
       
         
           
             
               
                 
                   
                     Roll 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     off 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     ratio 
                   
                   = 
                   
                     
                       { 
                       
                         1 
                         - 
                         
                           ( 
                           
                             efficiency 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             
                               ( 
                               
                                 at 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 9 
                                 ⁢ 
                                 
                                   , 
                                 
                                 ⁢ 
                                 000 
                                 ⁢ 
                                 
                                     
                                 
                                 ⁢ 
                                 nit 
                               
                               ) 
                             
                             ⁢ 
                             
                               / 
                             
                             ⁢ 
                             maximum 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             luminescent 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             efficiency 
                           
                           ) 
                         
                       
                       } 
                     
                     × 
                     100 
                     ⁢ 
                     % 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   20 
                 
               
             
           
         
       
     
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE 5 
               
               
                   
               
               
                   
                   
                   
                 Luminescent 
                   
                 Lifespan 
               
               
                   
                 Dopant 
                 Driving 
                 quantum 
                 Roll-off 
                 (Relative 
               
               
                   
                 Compound 
                 Voltage 
                 Efficiency 
                 ratio 
                 value, %) 
               
               
                 No. 
                 No. 
                 (V) 
                 (%) 
                 (%) 
                 (T 95 ) 
               
               
                   
               
             
            
               
                 Example 1 
                  3 
                 4.12 
                 19.9 
                 10  
                 15.8% 
               
               
                 Example 2 
                 17 
                 4.08 
                 23.2 
                 9 
                 20.1% 
               
               
                 Example 3 
                 24 
                 4.11 
                 24.7 
                 8 
                 21.5% 
               
               
                 Example 4 
                 27 
                 3.85 
                 23.3 
                 9 
                 32.4% 
               
               
                 Example 5 
                 31 
                 3.97 
                 22.8 
                 8 
                 23.0% 
               
               
                 Example 6 
                 99 
                 4.19 
                 25.0 
                 4 
                 35.3% 
               
               
                 Example 7 
                 157  
                 3.97 
                 26.5 
                 7 
                 38.3% 
               
               
                 Example 8 
                 186  
                 4.08 
                 26.2 
                 8 
                 20.7% 
               
               
                 Example 9 
                 448 
                 3.86 
                 26.5 
                 7 
                 34.9% 
               
               
                 Comparative 
                 A 
                 4.54 
                 17.8 
                 11  
                  4.2% 
               
               
                 Example A 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 B 
                 5.8  
                 14.3 
                 14  
                  7.7% 
               
               
                 Example B 
                   
                   
                   
                   
                   
               
               
                 Comparative 
                 C 
                 5.7  
                 10.2 
                 12  
                  3.0% 
               
               
                 Example C 
                   
                   
                   
                   
                   
               
               
                   
               
            
           
           
               
            
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     From Table 5, it was confirmed that the organic light-emitting devices of Example 1 to 9 have excellent driving voltage characteristics, high luminescence quantum efficiency, low roll-off ratio, and excellent lifespan characteristics compared to the organic light-emitting devices of Comparative Examples A to C. 
     The organometallic compound according to embodiments has excellent electric characteristics and thermal stability. Accordingly, an organic light-emitting device including the organometallic compound may have excellent driving voltage, quantum efficiency, power efficiency, color purity, and lifespan characteristics. Such organometallic compounds have excellent phosphorescent luminescent characteristics, and thus, when used, a diagnostic composition having a high diagnostic efficiency may be provided. 
     It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
     While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present description as defined by the following claims.