# Patent

## Title
Tetradentate metal complexes containing indoloacridine and its analogues

## Abstract

Platinum, palladium, and gold tetradentate metal complexes of Formulas I and II including indoloacridine.




The complexes are suitable for use as phosphorescent or delayed fluorescent and phosphorescent emitters in display and lighting applications.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to U.S. Provisional Patent Application No. 62/170,049 entitled “TETRADENTATE METAL COMPLEXES CONTAINING INDOLOACRIDINE AND ITS ANALOGUES” filed on Jun. 2, 2015, and U.S. Provisional Patent Application No. 62/274,456 entitled “TETRADENTATE METAL COMPLEXES CONTAINING INDOLOACRIDINE AND ITS ANALOGUES” filed on Jan. 4, 2016, which are hereby incorporated by reference in their entirety.


TECHNICAL FIELD
The present disclosure relates to tetradentate metal complexes containing indoloacridine suitable for use as phosphorescent or delayed fluorescent and phosphorescent emitters in display and lighting applications.
BACKGROUND
Compounds capable of absorbing and/or emitting light can be ideally suited for use in a wide variety of optical and electroluminescent devices, including, for example, photo-absorbing devices such as solar- and photo-sensitive devices, organic light emitting diodes (OLEDs), photo-emitting devices, and devices capable of both photo-absorption and emission and as markers for bio-applications. Much research has been devoted to the discovery and optimization of organic and organometallic materials for using in optical and electroluminescent devices. Generally, research in this area aims to accomplish a number of goals, including improvements in absorption and emission efficiency and improvements in the stability of devices, as well as improvements in processing ability.
Despite significant advances in research devoted to optical and electro-optical materials (e.g., red and green phosphorescent organometallic materials are commercially available and have been used as phosphors in organic light emitting diodes (OLEDs), lighting, and advanced displays), many currently available materials exhibit a number of disadvantages, including poor processing ability, inefficient emission or absorption, and less than ideal stability, among others.
Good blue emitters are particularly scarce, with one challenge being the stability of the blue devices. The choice of the host materials has an impact on the stability and the efficiency of the devices. The lowest triplet excited state energy of the blue phosphors is high compared with that of the red and green phosphors, which means that the lowest triplet excited state energy of host materials for the blue devices should be even higher. Thus, one of the problems is that there are limited host materials to be used for the blue devices. Accordingly, a need exists for new materials which exhibit improved performance in optical emitting and absorbing applications.
SUMMARY
Tetradentate cyclometalated complexes containing indoloacridine having tunable emission wavelengths in the visible range are described. These emitters can be used in organic light emitting diodes (OLEDs), displays and lighting applications.
A first general aspect includes complexes of Formula I:




wherein:

M is Pt (II), Pd (II), or Au (III),
each of V, V1, V2, and V3 is independently N, C, P, or Si,
each of X, X1, X2, and X3 is independently present or absent, and each X, X1, X2, and X3 present independently represents a single bond, CR8R9, C═O, SiR8R9, GeR8R9, NR8, PR8, PR8R9, R8P═O, AsR8, R8As═O, O, S, S═O, SO2, Se, Se═O, SeO2, BR8, BR8R9, AlR8, AlR8R9, R8Bi═O, or BiR8,
each of Y, Y1 and Y2 is independently CR10, SiR10, GeR10, N, P, P═O, As, As═O, B, Bi═O, or Bi,
L is a substituted or unsubstituted aryl, heteroaryl, or N-heterocyclic carbene,
each of R1, R2, R3, R4, R5, R6, and R7 is independently absent or present as a single substituent or multiple substituents, valency permitting, and each R1, R2, R3, R4, R5, R6, and R7 present independently represents deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof, and
each of R8, R9, and R10 is independently hydrogen, deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof.
Implementations of the first general aspect include the following.
When M is Pt or Pd and one of X, X1, X2, and X3 is BR8R9 or AlR8R9, then one of V, V1, V2, and V3 is C or Si.
When M is Pt or Pd and two of X, X1, X2, and X3 are independently BR8R9 or AlR8R9, then each of V, V1, V2, and V3 is independently N or P.
When M is Au and one of X, X1, X2, and X3 is BR8R9 or AlR8R9, then two of V, V1, V2, and V3 are independently C or Si.
When M is Au and two of X, X1, X2, and X3 are independently BR8R9 or AlR8R9, then one of V, V1, V2, and V3 is C or Si.
When M is Au and three of X, X1, X2, and X3 are BR8R9 or AlR8R9, then each of V, V1, V2, and V3 is independently N or P.
In some implementations of Formula I, V and V1 are C; V2 and V3 are N; Y, Y1, and Y2 are N; and L is a substituted or unsubstituted pyridyl. In other implementations of Formula I, V and V1 are C; V2 and V3 are N; Y, Y1, and Y2 are N; L is a substituted or unsubstituted pyridyl; X is CR8R9, and X1 is a single bond.
A second general aspect includes complexes of Formula II:




wherein:

M is Pt (II), Pd (II), or Au (III),
each of V, V1, V2, and V3 is independently N, C, P, or Si,
each of X and X1 is independently present or absent, and each X and X1 present independently represents CR7R8, C═O, SiR7R8, GeR7R8, PR7, PR7R8, R7P═O, AsR7, R7As═O, O, S, S═O, SO2, Se, Se═O, SeO2, BR7, BR7R8, R7Bi═O, BiR7, or a single bond,
each of Y and Y1 is independently CR9, SiR9, GeR9, N, P, P═O, As, As═O, B, Bi═O, or Bi,
L is a substituted or unsubstituted aryl, heteroaryl, or N-heterocyclic carbene,
each of R1, R2, R3, R4, R5, and R6 is independently absent or present as a single substituent or multiple substituents, valency permitting, and each R1, R2, R3, R4, R5, and R6 present independently represents deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof, and
each of R7, R8, and R9 is independently hydrogen, deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof.
Implementations of the second general aspect include the following.
When M is Pt or Pd and one of X and X1 is BR7R8 or AlR7R8, then one of V, V1, V2, and V3 is C or Si.
When M is Pt or Pd and both of X and X1 are independently BR7R8 or AlR7R8, then each of V, V1, V2, and V3 is independently N or P.
When M is Au and one of X and X1 is BR7R8 or AlR7R8, then two of V, V1, V2, and V3 are independently C or Si.
When M is Au and both of X and X1 are independently BR7R8 or AlR7R8, then one of V, V1, V2, and V3 is C or Si.
In some implementations of Formula II, V and V2 are C; V1 and V3 are N, Y and Y1 are N; and L is a substituted or unsubstituted pyridyl. In other implementations of Formula II, V and V2 are C; V1 and V3 are N, Y and Y1 are N; L is a substituted or unsubstituted pyridyl; and X is a single bond. In still other implementations of Formula II, V and V2 are C; V1 and V3 are N, Y and Y1 are N; L is a substituted or unsubstituted pyridyl; X is a single bond; and X1 is CR8R9.
The complexes of Formulas I and II are suitable for use as phosphorescent or delayed fluorescent and phosphorescent emitters in display and lighting applications.
A third general aspect includes one or more complexes the first and second general aspects or any combination thereof as an emitter in an organic light emitting device (OLED).
A fourth general aspect includes a lighting device, such as a photovoltaic device, an organic phototransistor, an organic photovoltaic cell, or an organic photodetector, or a luminescent display device, any one of which may include the OLED of the third general aspect.
Thus, particular embodiments have been described. Variations, modifications, and enhancements of the described embodiments and other embodiments can be made based on what is described and illustrated. In addition, one or more features of one or more embodiments may be combined. The details of one or more implementations and various features and aspects are set forth in the accompanying drawings, the description, and the claims below.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 depicts a cross section of an exemplary organic light-emitting diode (OLED).
FIG. 2 shows an emission spectrum of PdN′N3 in CH2Cl2 at room temperature and in 2-methyltetrahydrofuran at 77K.
FIG. 3 shows an emission spectrum of PtN′N3 in CH2Cl2 at room temperature and in 2-methyltetrahydrofuran at 77K.
FIG. 4 shows an emission spectrum of PtN—N′N-t-Bu in CH2Cl2 at room temperature and in 2-methyltetrahydrofuran at 77K.
FIG. 5 shows a room temperature emission spectrum of PtN′—NN in a solution of dichloromethane.



DETAILED DESCRIPTION
Introducing an indoloacridine group to the ligand of metal complexes as described herein increases the stability of the metal complexes. Chemical structures of the emissive luminophores and the ligands may be modified, and the metal interchanged (e.g., platinum, palladium, or gold) to adjust the energy of the singlet states and the triplet states of the metal complexes, thereby allowing selection of desired optical properties of the metal complexes. The present disclosure can be understood more readily by reference to the following detailed description and the Examples included therein.
Before the present compounds, devices, and/or methods are disclosed and described, it is to be understood that they are not limited to specific synthetic methods unless otherwise specified, or to particular reagents unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing, example methods and materials are now described.
As used in the specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component” includes mixtures of two or more components.
As used herein, the terms “optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.
Disclosed are the components to be used to prepare the compositions described herein as well as the compositions themselves to be used within the methods disclosed herein. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these compounds cannot be explicitly disclosed, each is specifically contemplated and described herein. For example, if a particular compound is disclosed and discussed and a number of modifications that can be made to a number of molecules including the compounds are discussed, specifically contemplated is each and every combination and permutation of the compound and the modifications that are possible unless specifically indicated to the contrary. Thus, if a class of molecules A, B, and C are disclosed as well as a class of molecules D, E, and F and an example of a combination molecule, A-D is disclosed, then even if each is not individually recited each is individually and collectively contemplated meaning combinations, A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are considered disclosed. Likewise, any subset or combination of these is also disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E would be considered disclosed. This concept applies to all aspects of this application including, but not limited to, steps in methods of making and using the compositions. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific embodiment or combination of embodiments of the methods.
As referred to herein, a linking atom or group can connect two atoms such as, for example, a N atom and a C atom. A linking atom or group is in one aspect disclosed as X, Y, Y1, Y2, and/or Z herein. The linking atom can optionally, if valency permits, have other chemical moieties attached. For example, in one aspect, an oxygen would not have any other chemical groups attached as the valency is satisfied once it is bonded to two groups (e.g., N and/or C groups). In another aspect, when carbon is the linking atom, two additional chemical moieties can be attached to the carbon. Suitable chemical moieties include amine, amide, thiol, aryl, heteroaryl, cycloalkyl, and heterocyclyl moieties.
The term “cyclic structure” or the like terms used herein refer to any cyclic chemical structure which includes, but is not limited to, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocyclyl, carbene, and N-heterocyclic carbene.
As used herein, the term “substituted” is contemplated to include all permissible substituents of organic compounds. In a broad aspect, the permissible substituents include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, and aromatic and nonaromatic substituents of organic compounds. Illustrative substituents include, for example, those described below. The permissible substituents can be one or more and the same or different for appropriate organic compounds. For purposes of this disclosure, the heteroatoms, such as nitrogen, can have hydrogen substituents and/or any permissible substituents of organic compounds described herein which satisfy the valences of the heteroatoms. This disclosure is not intended to be limited in any manner by the permissible substituents of organic compounds. Also, the terms “substitution” or “substituted with” include the implicit proviso that such substitution is in accordance with permitted valence of the substituted atom and the substituent, and that the substitution results in a stable compound, e.g., a compound that does not spontaneously undergo transformation such as by rearrangement, cyclization, elimination, etc. It is also contemplated that, in certain aspects, unless expressly indicated to the contrary, individual substituents can be further optionally substituted (i.e., further substituted or unsubstituted).
In defining various terms, “A”. “A1”, “A2”, “A3”, “A4” and “A5” are used herein as generic symbols to represent various specific substituents. These symbols can be any substituent, not limited to those disclosed herein, and when they are defined to be certain substituents in one instance, they can, in another instance, be defined as some other substituents.
The term “alkyl” as used herein is a branched or unbranched saturated hydrocarbon group of 1 to 24 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, isopentyl, s-pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, eicosyl, tetracosyl, and the like. The alkyl group can be cyclic or acyclic. The alkyl group can be branched or unbranched. The alkyl group can also be substituted or unsubstituted. For example, the alkyl group can be substituted with one or more groups including, but not limited to, alkyl, cycloalkyl, alkoxy, amino, ether, halide, hydroxy, nitro, silyl, sulfo-oxo, or thiol, as described herein. A “lower alkyl” group is an alkyl group containing from one to six (e.g., from one to four) carbon atoms.
Throughout the specification “alkyl” is generally used to refer to both unsubstituted alkyl groups and substituted alkyl groups; however, substituted alkyl groups are also specifically referred to herein by identifying the specific substituent(s) on the alkyl group. For example, the term “halogenated alkyl” or “haloalkyl” specifically refers to an alkyl group that is substituted with one or more halide, e.g., fluorine, chlorine, bromine, or iodine. The term “alkoxyalkyl” specifically refers to an alkyl group that is substituted with one or more alkoxy groups, as described below. The term “alkylamino” specifically refers to an alkyl group that is substituted with one or more amino groups, as described below, and the like. When “alkyl” is used in one instance and a specific term such as “alkylalcohol” is used in another, it is not meant to imply that the term “alkyl” does not also refer to specific terms such as “alkylalcohol” and the like.
This practice is also used for other groups described herein. That is, while a term such as “cycloalkyl” refers to both unsubstituted and substituted cycloalkyl moieties, the substituted moieties can, in addition, be specifically identified herein; for example, a particular substituted cycloalkyl can be referred to as, e.g., an “alkylcycloalkyl.” Similarly, a substituted alkoxy can be specifically referred to as, e.g., a “halogenated alkoxy,” a particular substituted alkenyl can be, e.g., an “alkenylalcohol,” and the like. Again, the practice of using a general term, such as “cycloalkyl,” and a specific term, such as “alkylcycloalkyl,” is not meant to imply that the general term does not also include the specific term.
The term “cycloalkyl” as used herein is a non-aromatic carbon-based ring composed of at least three carbon atoms. Examples of cycloalkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, norbornyl, and the like. The term “heterocycloalkyl” is a type of cycloalkyl group as defined above, and is included within the meaning of the term “cycloalkyl,” where at least one of the carbon atoms of the ring is replaced with a heteroatom such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorus. The cycloalkyl group and heterocycloalkyl group can be substituted or unsubstituted. The cycloalkyl group and heterocycloalkyl group can be substituted with one or more groups including, but not limited to, alkyl, cycloalkyl, alkoxy, amino, ether, halide, hydroxy, nitro, silyl, sulfo-oxo, or thiol as described herein.
The term “polyalkylene group” as used herein is a group having two or more CH2 groups linked to one another. The polyalkylene group can be represented by the formula —(CH2)a—, where “a” is an integer of from 2 to 500.
The terms “alkoxy” and “alkoxyl” as used herein to refer to an alkyl or cycloalkyl group bonded through an ether linkage; that is, an “alkoxy” group can be defined as —OA1 where A1 is alkyl or cycloalkyl as defined above. “Alkoxy” also includes polymers of alkoxy groups as just described; that is, an alkoxy can be a polyether such as —OA1—OA2 or —OA1-(OA2)a-OA3, where “a” is an integer of from 1 to 200 and A1, A2, and A3 are alkyl and/or cycloalkyl groups.
The term “alkenyl” as used herein is a hydrocarbon group of from 2 to 24 carbon atoms with a structural formula containing at least one carbon-carbon double bond. Asymmetric structures such as (A1A2)C═C(A3A4) are intended to include both the E and Z isomers. This can be presumed in structural formulae herein wherein an asymmetric alkene is present, or it can be explicitly indicated by the bond symbol C═C. The alkenyl group can be substituted with one or more groups including, but not limited to, alkyl, cycloalkyl, alkoxy, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, azide, nitro, silyl, sulfo-oxo, or thiol, as described herein.
The term “cycloalkenyl” as used herein is a non-aromatic carbon-based ring composed of at least three carbon atoms and containing at least one carbon-carbon double bound, i.e., C═C. Examples of cycloalkenyl groups include, but are not limited to, cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclopentadienyl, cyclohexenyl, cyclohexadienyl, norbornenyl, and the like. The term “heterocycloalkenyl” is a type of cycloalkenyl group as defined above, and is included within the meaning of the term “cycloalkenyl,” where at least one of the carbon atoms of the ring is replaced with a heteroatom such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorus. The cycloalkenyl group and heterocycloalkenyl group can be substituted or unsubstituted. The cycloalkenyl group and heterocycloalkenyl group can be substituted with one or more groups including, but not limited to, alkyl, cycloalkyl, alkoxy, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, azide, nitro, silyl, sulfo-oxo, or thiol as described herein.
The term “alkynyl” as used herein is a hydrocarbon group of 2 to 24 carbon atoms with a structural formula containing at least one carbon-carbon triple bond. The alkynyl group can be unsubstituted or substituted with one or more groups including, but not limited to, alkyl, cycloalkyl, alkoxy, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, azide, nitro, silyl, sulfo-oxo, or thiol, as described herein.
The term “cycloalkynyl” as used herein is a non-aromatic carbon-based ring composed of at least seven carbon atoms and containing at least one carbon-carbon triple bound. Examples of cycloalkynyl groups include, but are not limited to, cycloheptynyl, cyclooctynyl, cyclononynyl, and the like. The term “heterocycloalkynyl” is a type of cycloalkenyl group as defined above, and is included within the meaning of the term “cycloalkynyl,” where at least one of the carbon atoms of the ring is replaced with a heteroatom such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorus. The cycloalkynyl group and heterocycloalkynyl group can be substituted or unsubstituted. The cycloalkynyl group and heterocycloalkynyl group can be substituted with one or more groups including, but not limited to, alkyl, cycloalkyl, alkoxy, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, azide, nitro, silyl, sulfo-oxo, or thiol as described herein.
The term “aryl” as used herein is a group that contains any carbon-based aromatic group including, but not limited to, benzene, naphthalene, phenyl, biphenyl, phenoxybenzene, and the like. The term “aryl” also includes “heteroaryl,” which is defined as a group that contains an aromatic group that has at least one heteroatom incorporated within the ring of the aromatic group. Examples of heteroatoms include, but are not limited to, nitrogen, oxygen, sulfur, and phosphorus. Likewise, the term “non-heteroaryl,” which is also included in the term “aryl,” defines a group that contains an aromatic group that does not contain a heteroatom. The aryl group can be substituted or unsubstituted. The aryl group can be substituted with one or more groups including, but not limited to, alkyl, cycloalkyl, alkoxy, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, heteroaryl, aldehyde, amino, carboxylic acid, ester, ether, halide, hydroxy, ketone, azide, nitro, silyl, sulfo-oxo, or thiol as described herein. The term “biaryl” is a specific type of aryl group and is included in the definition of “aryl.” Biaryl refers to two aryl groups that are bound together via a fused ring structure, as in naphthalene, or are attached via one or more carbon-carbon bonds, as in biphenyl.
The term “aldehyde” as used herein is represented by the formula —C(O)H. Throughout this specification “C(O)” is a short hand notation for a carbonyl group, i.e., C═O.
The terms “amine” or “amino” as used herein are represented by the formula —NA1A2, where A1 and A2 can be, independently, hydrogen or alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein.
The term “alkylamino” as used herein is represented by the formula —NH(-alkyl) where alkyl is a described herein. Representative examples include, but are not limited to, methylamino group, ethylamino group, propylamino group, isopropylamino group, butylamino group, isobutylamino group, (sec-butyl)amino group, (tert-butyl)amino group, pentylamino group, isopentylamino group, (tert-pentyl)amino group, hexylamino group, and the like.
The term “dialkylamino” as used herein is represented by the formula —N(-alkyl)2 where alkyl is a described herein. Representative examples include, but are not limited to, dimethylamino group, diethylamino group, dipropylamino group, diisopropylamino group, dibutylamino group, diisobutylamino group, di(sec-butyl)amino group, di(tert-butyl)amino group, dipentylamino group, diisopentylamino group, di(tert-pentyl)amino group, dihexylamino group, N-ethyl-N-methylamino group, N-methyl-N-propyl amino group, N-ethyl-N-propylamino group and the like.
The term “carboxylic acid” as used herein is represented by the formula —C(O)OH.
The term “ester” as used herein is represented by the formula —OC(O)A1 or —C(O)OA1, where A1 can be alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein. The term “polyester” as used herein is represented by the formula -(A1O(O)C-A2-C(O)O)a— or -(A1O(O)C-A2-OC(O))a—, where A1 and A2 can be, independently, an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group described herein and “a” is an integer from 1 to 500. “Polyester” is as the term used to describe a group that is produced by the reaction between a compound having at least two carboxylic acid groups with a compound having at least two hydroxyl groups.
The term “ether” as used herein is represented by the formula A1OA2, where A1 and A2 can be, independently, an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group described herein. The term “polyether” as used herein is represented by the formula -(A1O-A2O)a—, where A1 and A2 can be, independently, an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group described herein and “a” is an integer of from 1 to 500. Examples of polyether groups include polyethylene oxide, polypropylene oxide, and polybutylene oxide.
The term “polymeric” includes polyalkylene, polyether, polyester, and other groups with repeating units, such as, but not limited to —(CH2O)n—CH3, —(CH2CH2O)n—CH3, —[CH2CH(CH3)]n—CH3, —[CH2CH(COOCH3)]n—CH3, —[CH2CH(COO CH2CH3)]n—CH3, and —[CH2CH(COOtBu)]n—CH3, where n is an integer (e.g., n>1 or n>2).
The term “halide” as used herein refers to the halogens fluorine, chlorine, bromine, and iodine.
The term “heterocyclyl,” as used herein refers to single and multi-cyclic non-aromatic ring systems and “heteroaryl as used herein refers to single and multi-cyclic aromatic ring systems: in which at least one of the ring members is other than carbon. The terms includes azetidine, dioxane, furan, imidazole, isothiazole, isoxazole, morpholine, oxazole, oxazole, including, 1,2,3-oxadiazole, 1,2,5-oxadiazole and 1,3,4-oxadiazole, piperazine, piperidine, pyrazine, pyrazole, pyridazine, pyridine, pyrimidine, pyrrole, pyrrolidine, tetrahydrofuran, tetrahydropyran, tetrazine, including 1,2,4,5-tetrazine, tetrazole, including 1,2,3,4-tetrazole and 1,2,4,5-tetrazole, thiadiazole, including, 1,2,3-thiadiazole, 1,2,5-thiadiazole, and 1,3,4-thiadiazole, thiazole, thiophene, triazine, including 1,3,5-triazine and 1,2,4-triazine, triazole, including, 1,2,3-triazole, 1,3,4-triazole, and the like.
The term “hydroxyl” as used herein is represented by the formula —OH.
The term “ketone” as used herein is represented by the formula A1C(O)A2, where A1 and A2 can be, independently, an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein.
The term “azide” as used herein is represented by the formula —N3.
The term “nitro” as used herein is represented by the formula —NO2.
The term “nitrile” as used herein is represented by the formula —CN.
The term “silyl” as used herein is represented by the formula —SiA1A2A3, where A1, A2, and A3 can be, independently, hydrogen or an alkyl, cycloalkyl, alkoxy, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein.
The term “sulfo-oxo” as used herein is represented by the formulas —S(O)A1, —S(O)2A1, —OS(O)2A1, or —OS(O)2OA1, where A1 can be hydrogen or an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein. Throughout this specification “S(O)” is a short hand notation for S═O. The term “sulfonyl” is used herein to refer to the sulfo-oxo group represented by the formula —S(O)2A1, where A1 can be hydrogen or an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein. The term “sulfone” as used herein is represented by the formula A1S(O)2A2, where A1 and A2 can be, independently, an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein. The term “sulfoxide” as used herein is represented by the formula A1S(O)A2, where A1 and A2 can be, independently, an alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, cycloalkynyl, aryl, or heteroaryl group as described herein.
The term “thiol” as used herein is represented by the formula —SH.
“R,” “R1,” “R2,” “R3,” “Rn,” where n is an integer, as used herein can, independently, possess one or more of the groups listed above. For example, if R1 is a straight chain alkyl group, one of the hydrogen atoms of the alkyl group can optionally be substituted with a hydroxyl group, an alkoxy group, an alkyl group, a halide, and the like. Depending upon the groups that are selected, a first group can be incorporated within second group or, alternatively, the first group can be pendant (i.e., attached) to the second group. For example, with the phrase “an alkyl group comprising an amino group,” the amino group can be incorporated within the backbone of the alkyl group. Alternatively, the amino group can be attached to the backbone of the alkyl group. The nature of the group(s) that is (are) selected will determine if the first group is embedded or attached to the second group.
Compounds described herein may contain “optionally substituted” moieties. In general, the term “substituted,” whether preceded by the term “optionally” or not, means that one or more hydrogens of the designated moiety are replaced with a suitable substituent. Unless otherwise indicated, an “optionally substituted” group may have a suitable substituent at each substitutable position of the group, and when more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. Combinations of substituents envisioned by this invention are preferably those that result in the formation of stable or chemically feasible compounds. In is also contemplated that, in certain aspects, unless expressly indicated to the contrary, individual substituents can be further optionally substituted (i.e., further substituted or unsubstituted).
In some aspects, a structure of a compound can be represented by a formula:




which is understood to be equivalent to a formula:





wherein n is typically an integer. That is, Rn is understood to represent five independent substituents, Rn(a), Rn(b), Rn(c), Rn(d), Rn(e). By “independent substituents,” it is meant that each R substituent can be independently defined. For example, if in one instance Rn(a) is halogen, then Rn(b) is not necessarily halogen in that instance.

Several references to R, R1, R2, R3, R4, R5, R6, etc. are made in chemical structures and moieties disclosed and described herein. Any description of R, R1, R2, R3, R4, R5, R6, etc. in the specification is applicable to any structure or moiety reciting R, R1, R2, R3, R4, R5, R6, etc. respectively.
Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.
Tetradentate cyclometalated complexes with 6-membered coordination rings represented by Formula I and Formula II are efficient emitters having tunable emission wavelengths in the visible range. These compounds have a high quantum efficiency of emission, which is proportional to the integral of the wavefunction of the ground state and the excited state, and favors a small difference in equilibrium geometry between the ground state and the excited state.
Complexes of Formula I are represented as shown below.




In Formula I:

M is Pt (II), Pd (II), or Au (III),
each of V, V1, V2, and V3 is independently N, C, P, or Si,
each of X, X1, X2, and X3 is independently present or absent, and each X, X1, X2, and X3 present independently represents CR8R9, C═O, SiR8R9, GeR8R9, NR8, PR8, PR8R9, R8P═O, AsR8, R8As═O, O, S, S═O, SO2, Se, Se═O, SeO2, BR8, BR8R9, AlR8, AlR8R9, R8Bi═O, BiR8, or a single bond,
each of Y, Y1 and Y2 is independently CR10, SiR10, GeR10, N, P, P═O, As, As═O, B, Bi═O, or Bi,
L is a substituted or unsubstituted aryl, heteroaryl, or N-heterocyclic carbene,
each of R1, R2, R3, R4, R5, R6, and R7 is independently absent or present as a single substituent or multiple substituents, valency permitting, and each R1, R2, R3, R4, R5, R6, and R7 present independently represents deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof, and
each of R8, R9, and R10 is independently hydrogen, deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof.
Complexes of Formula I include the following implementations.
When M is Pt or Pd and one of X, X1, X2, and X3 is BR8R9 or AlR8R9, then one of V, V1, V2, and V3 is C or Si.
When M is Pt or Pd and two of X, X1, X2, and X3 are independently BR8R9 or AlR8R9, then each of V, V1, V2, and V3 is independently N or P.
When M is Au and one of X, X2, and X3 is BR8R9 or AlR8R9, then two of V, V1, V2, and V3 are independently C or Si.
When M is Au and two of X, X1, X2, and X3 are independently BR8R9 or AlR8R9, then one of V, V1, V2, and V3 is C or Si.
When M is Au and three of X, X1, X2, and X3 are BR8R9 or AlR8R9, then each of V, V1, V2, and V3 is independently N or P.
In some implementations of Formula I, V and V1 are C; V2 and V3 are N; Y, Y1, and Y2 are N; and L is a substituted or unsubstituted pyridyl. In other implementations of Formula I, V and V1 are C; V2 and V3 are N; Y, Y1, and Y2 are N; L is a substituted or unsubstituted pyridyl; X is CR8R9, and X1 is a single bond.
Additional implementations of Formula I are shown below, in which above:
M is Pt(II), Pd(II), or Au(III),
each U is independently CR8R9, C═O, SiR8R9, GeR8R9, NR8, PR8, PR8R9, R8P═O, AsR8, R8As═O, O, S, S═O, SO2, Se, Se═O, SeO2, BR8, BR8R9, AlR8, AlR8R9, R8Bi═O, or a single bond,
each A is independently BR8R9 or AlR8R9, and




is one of





where R is hydrogen, deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof.
















































































Further implementations of Formula I are shown below, in which M is Pt(II) or Pd(II).































































































































































































































































































































































































































































































































































































































Further implementations of Formula I include the structures below, in which M=Au(III).










































































































































































































Complexes of Formula II are represented as shown below.




In Formula II:

M is Pt (II), Pd (II), or Au (III),
each of V, V1, V2, and V3 is independently N, C, P, or Si,
each of X and X1 is independently present or absent, and each X and X1 present independently represents CR7R8, C═O, SiR7R8, GeR7R8, NR7, PR7, PR7R8, R7P═O, AsR7, R7As═O, O, S, S═O, SO2, Se, Se═O, SeO2, BR7, BR7R8, AlR7R8, R7Bi═O, BiR7, or a single bond,
each of Y and Y1 is independently CR9, SiR9, GeR9, N, P, P═O, As, As═O, B, Bi═O, or Bi,
L is a substituted or unsubstituted aryl, heteroaryl, or N-heterocyclic carbene,
each of R1, R2, R3, R4, R5, and R6 is independently absent or present as a single substituent or multiple substituents, valency permitting, and each R1, R2, R3, R4, R5, and R6 present independently represents deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof, and
each of R7, R8, and R9 is independently hydrogen, deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof.
Complexes of Formula II include the following implementations.
When M is Pt or Pd and one of X and X1 is BR7R8 or AlR7R8, then one of V, V1, V2, and V3 is C or Si.
When M is Pt or Pd and both of X and X1 are independently BR7R8 or AlR7R8, then each of V, V1, V2, and V3 is independently N or P.
When M is Au and one of X and X1 is BR7R8 or AlR7R8, then two of V, V1, V2, and V3 are independently C or Si.
When M is Au and both of X and X1 are independently BR7R8 or AlR7R8, then one of the V, V1, V2, and V3 is C or Si.
In some implementations of Formula II, V and V2 are C; V1 and V3 are N, Y and Y1 are N; and L is a substituted or unsubstituted pyridyl. In other implementations of Formula II, V and V2 are C; V1 and V3 are N, Y and Y1 are N; L is a substituted or unsubstituted pyridyl; and X is a single bond. In still other implementations of Formula II, V and V2 are C; V1 and V3 are N, Y and Y1 are N; L is a substituted or unsubstituted pyridyl; X is a single bond; and X1 is CR8R9.
Further implementations of Formula II include the structures below, in which:
M is Pt(II), Pd(II), or Au(III),
each U is independently CR8R9, C═O, SiR8R9, GeR8R9, NR8, PR8, PR8R9, R8P═O, AsR8, R8As═O, O, S, S═O, SO2, Se, Se═O, SeO2, BR8, BR8R9, AlR8, AlR8R9, R8Bi═O, or a single bond,
each A is independently BR8R9 or AlR8R9, and




is one of











Further implementations of Formula II include the structures below, in which M is Pt(II) or Pt(II).






























































































Compounds described herein can be used in a light emitting device such as an OLED. FIG. 1 depicts a cross-sectional view of an OLED 100. OLED 100 includes substrate 102, anode 104, hole-transporting material(s) (HTL) 106, light processing material 108, electron-transporting material(s) (ETL) 110, and a metal cathode layer 112. Anode 104 is typically a transparent material, such as indium tin oxide. Light processing material 108 may be an emissive material (EML) including an emitter and a host.
In various aspects, any of the one or more layers depicted in FIG. 1 may include indium tin oxide (ITO), poly(3,4-ethylenedioxythiophene) (PEDOT), polystyrene sulfonate (PSS), N,N′-di-1-naphthyl-N,N-diphenyl-1,1′-biphenyl-4,4′ diamine (NPD), 1,1-bis((di-4-tolylamino)phenyl)cyclohexane (TAPC), 2,6-Bis(N-carbazolyl)pyridine (mCpy), 2,8-bis(diphenylphosphoryl)dibenzothiophene (PO15), LiF, Al, or a combination thereof.
Light processing material 108 may include one or more compounds of the present disclosure optionally together with a host material. The host material can be any suitable host material known in the art. The emission color of an OLED is determined by the emission energy (optical energy gap) of the light processing material 108, which can be tuned by tuning the electronic structure of the emitting compounds, the host material, or both. Both the hole-transporting material in the HTL layer 106 and the electron-transporting material(s) in the ETL layer 110 may include any suitable hole-transporter known in the art.
Compounds described herein may exhibit phosphorescence. Phosphorescent OLEDs (i.e., OLEDs with phosphorescent emitters) typically have higher device efficiencies than other OLEDs, such as fluorescent OLEDs. Light emitting devices based on electrophosphorescent emitters are described in more detail in WO2000/070655 to Baldo et al., which is incorporated herein by this reference for its teaching of OLEDs, and in particular phosphorescent OLEDs.
EXAMPLES
The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary and are not intended to be limiting in scope. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in ° C. or is at ambient temperature, and pressure is at or near atmospheric.
Various methods for the preparation method of the compounds described herein are recited in the examples. These methods are provided to illustrate various methods of preparation, but are not intended to limit any of the methods recited herein. Accordingly, one of skill in the art in possession of this disclosure could readily modify a recited method or utilize a different method to prepare one or more of the compounds described herein. The following aspects are only exemplary and are not intended to be limiting in scope. Temperatures, catalysts, concentrations, reactant compositions, and other process conditions can vary, and one of skill in the art, in possession of this disclosure, could readily select appropriate reactants and conditions for a desired complex.
1H spectra were recorded at 400 MHz, 13C NMR spectra were recorded at 100 MHz on Varian Liquid-State NMR instruments in CDCl3 or DMSO-d6 solutions and chemical shifts were referenced to residual protiated solvent. If CDCl3 was used as solvent, 1H NMR spectra were recorded with tetramethylsilane (δ=0.00 ppm) as internal reference; 13C NMR spectra were recorded with CDCl3 (δ=77.00 ppm) as internal reference. If DMSO-d6 was used as solvent, 1H NMR spectra were recorded with residual H2O (δ=3.33 ppm) as internal reference; 13C NMR spectra were recorded with DMSO-d6 (δ=39.52 ppm) as internal reference. The following abbreviations (or combinations thereof) were used to explain 1H NMR multiplicities: s=singlet, d=doublet, t=triplet, q=quartet, p=quintet, m=multiplet, br=broad.
Example 1
Synthesis of PdN′—N3




N-(2-(prop-1-en-2-yl)phenyl)-9-(pyridin-2-yl)-9H-carbazol-2-amine (2): 2-bromo-9-(pyridin-2-yl)-9H-carbazole (1.00 g, 3.0 mmol, 1.00 eq), 2-(prop-1-en-2-yl)benzenamine (0.48 g, 3.6 mmol, 1.20 eq), Pd2(dba)3 (0.14 g, 0.15 mmol, 0.05 eq), and (2-biphenyl)ditert-butylphosphine) (0.09 g, 0.3 mmol, 0.10 eq) was added to a dry pressure tube equipped with a magnetic stir bar. The tube was then taken into a glove box. t-BuONa (0.60 g, 6 mmol. 2.00 eq) and dry toluene (10 mL) were added. The mixture was bubbled with nitrogen for 10 minutes and then the tube was sealed. The tube was taken out of the glove box and heated to 95° C.-105° C. in an oil bath. The reaction was monitored by TLC and about 6 hours later the starting was consumed completely. Then the mixture was cooled to ambient temperature, diluted with ethyl acetate and washed with water. The organic phase was dried over sodium sulfate, then filtered and concentrated under vacuum. The residue was purified by silica gel column chromatography, using a mixture of hexanes and ethyl acetate as an eluent, in a ratio of 1:4 in volume and giving a white solid 0.80 g in yield of 70%. 1H NMR (400 MHz, CDCl3):δ 8.69-8.68 (m, 1H), 8.10-8.07 (m, 1H), 8.02 (d, 1H, J=7.5 Hz), 7.96 (d, 1H, J=8.5 Hz), 7.71-7.67 (m, 1H), 7.58 (s, 1H), 7.46-7.44 (m, 1H), 7.32-7.21 (m, 6H), 7.02-6.99 (m, 1H), 6.95-6.93 (m, 1H), 5.11 (s, 1H), 5.02(s, 1H), 1.98 (s, 3H).




7,13-Dihydro-13,13-dimethyl-7-(pyridin-2-yl)-5H-indolo[3,2-b]acridine (3): N-(2-(prop-1-en-2-yl)phenyl)-9-(pyridin-2-yl)-9H-carbazol-2-amine (2) (1.00 g, 2.80 mmol) was added to a mixture of 98% concentrated sulfuric acid (5 mL) and phosphoric acid (5 mL) at 60° C. The resulting dark solution was stirred for 15 min, then cooled to room temperature and quenched with water. A white precipitate was formed and extracted with ethyl acetate. Then the organic phase was separated and dried over sodium sulfate, then filtered and the filtrate was concentrated under vacuum. The residue was purified by silica gel column chromatography using a mixture of ethyl acetate and hexane as an eluent in a ratio of 1:4 in volume, giving a white solid 0.75 g in a yield of 75%. 1H NMR (CDCl3):δ, 9.12 (s, 1H), 8.76 (d, 1H, J=4.0 Hz), 8.22 (s, 1H), 8.15 (d, 1H J=3.5 Hz), 7.8 (d, 1H, J=9.0 Hz), 7.73 (d, 1H, J=9 Hz), 7.49-7.47 (m, 1H), 7.43-7.41 (m, 1H), 7.31-7.30 (m, 1H), 7.26-7.24 (m, 2H), 7.09-7.06 (m, 1H), 6.85-6.80 (m, 2H), 1.64 (m, 6H).




7,13-Dihydro-13,13-dimethyl-7-(pyridin-2-yl)-5-(3-(pyridin-2-yl)phenyl)-5H-indolo[3,2-b]acridine (4): 7,13-Dihydro-13,13-dimethyl-7-(pyridin-2-yl)-5H-indolo[3,2-b]acridine (3) (0.38 g, 1.00 mmol, 1.0 eq), 2-(3-bromophenyl)pyridine (0.30 g, 1.30 mmol, 1.30 eq), Pd2(dba)3 (0.05 g, 0.05 mmol, 0.05 eq), and (2-biphenyl)ditert-butylphosphine) (0.03 g, 0.10 mmol, 0.10 eq) was added to a dry pressure tube equipped with a magnetic stir bar. The tube was then taken into a glove box. t-BuONa (0.20 g, 2 mmol. 2.00 eq) and dry toluene (5 mL) was added. The mixture was bubbled with nitrogen for minutes and then the tube was sealed. The tube was taken out of the glove box and heated to 95° C.-105° C. in an oil bath. The reaction was monitored by TLC and about 6 hours later the starting was consumed completely. Then the mixture was cooled to ambient temperature, diluted with ethyl acetate and washed with water. The organic phase was dried over sodium sulfate, then filtered and concentrated under vacuum. The residue was purified by silica gel column chromatography, using a mixture of hexanes and ethyl acetate as an eluent, in a ratio of 1:4 in volume and gave the title compound as a white solid 0.30 g in yield of 53%. 1H NMR (400 MHz, CDCl3):δ 8.64-8.63 (m, 1H), 8.33 (s, 1H), 8.30-8.29 (m, 1H), 8.27-8.25 (d, 1H, J=8.0 Hz), 8.15 (d, 1H J=6.8 Hz), 8.10 (s, 1H), 8.04 (d, 1H, J=6.4 Hz), 7.93-7.84 (m, 1H), 7.80-7.66 (m, 2H), 7.56-7.54 (m, 1H), 7.49-7.46 (m, 2H), 7.31-7.19 (m, 4H), 7.00-6.90 (m, 2H), 6.81 (s, 1H), 6.27 (d, 1H), 3.53 (s, 3H), 1.76 (s, 3H).




PdN′—N3:7,13-Dihydro-13,13-dimethyl-7-(pyridin-2-yl)-5-(3-(pyridin-2-yl)phenyl)-5H-indolo[3,2-b]acridine (4) Ligand (50 mg, 0.1 mmol, 1.0 eq), Pd(OAc)2 (22.30 mg, 0.10 mmol, 1.00 eq) and n-Bu4NBr (3.20 mg, 0.01 mmol, 1.00 eq) were added to a dry pressure tube was then taken into a glove box and acetic acid (6 mL) was added. The mixture was bubbled with nitrogen for 30 minutes and then the tube was sealed. The tube was taken out of the glove box and the mixture was stirred at room temperature for 20 hours. Then the mixture was heated to 105° C.-115° C. in an oil bath and stirred at that temperature for 2 days, cooled to ambient temperature and water (30 mL) was added slowly. After stirring at room temperature for 10 minutes, the precipitate was filtered off and washed with water three times. Then the solid was purified through column chromatography on silica gel using dichloromethane as eluent to obtain to obtain the desired product, PdN′—N3 as a yellow solid 47 mg in 65% yield. FIG. 2 shows an emission spectrum of PdN′—N3 in CH2Cl2 at room temperature and in tetrahydro-2-methylfuran at 77K. 1H NMR (400 MHz, d6-DMSO):δ 9.04 (d, 1H, J=5.2 Hz), 8.60 (d, 1H, J=4.4 Hz), 8.24 (d, 1H, J=8.4 Hz), 8.17 (d, 1H, J=7.2 Hz), 7.51-7.39 (m, 4H), 7.25-7.22 (m, 2H), 7.13-7.09 (m, 2H), 7.05-7.02 (m, 1H), 2.00 (s, 3H), 1.23(s, 3H).
Example 2
Synthesis of PtN′—N3




PtN′—N3 7,13-Dihydro-13,13-dimethyl-7-(pyridin-2-yl)-5-(3-(pyridin-2-yl)phenyl)-5H-indolo[3,2-b]acridine (4) Ligand (200 mg, 0.40 mmol, 1.0 eq), K2PtCl4 (167 mg, 0.40 mmol, 1.00 eq) and n-Bu4NBr (13 mg, 0.04 mmol, 1.00 eq) were added to a dry pressure tube was then taken into a glove box and acetic acid (24 mL) was added. The mixture was bubbled with nitrogen for 30 minutes and then the tube was sealed. The tube was taken out of the glove box and the mixture was stirred at room temperature for 20 hours. Then the mixture was heated to 105° C.-115° C. in an oil bath and stirred at that temperature for 2 days, cooled to ambient temperature and water (30 mL) was added slowly. After stirring at room temperature for 10 minutes, the precipitate was filtered off and washed with water three times. Then the solid was purified through column chromatography on silica gel using dichloromethane as eluent to obtain to obtain the desired product, PtN′N3, as a yellow solid 85 mg in 25% yield. The product (60 mg) was further purified by sublimation in a sublimator, giving a red solid 15 mg. FIG. 3 shows an emission spectrum of PtN′—N3 in CH2Cl2 at room temperature and in 2-methyl tetrahydrofuran at 77K. 1H NMR (400 MHz, d6-DMSO):δ 9.04 (d, 1H, J=4.4 Hz), 8.64 (d, 1H, J=5.2 Hz), 8.04 (d, 1H, J=6.6 Hz), 7.94-7.92 (m, 1H), 7.87 (d, 1H, J=8.0 Hz), 7.80-7.73 (m, 3H), 7.69 (s, 1H), 7.44-7.33 (m, 5H), 7.34-7.31 (m, 4H), 7.04-6.93 (m, 4H), 1.96 (s, 3H), 1.42 (s, 9H).
Example 3
Synthesis of PtN—N′N-tBu




5-(9-(4-Tert-butylpyridin-2-yl)-9H-carbazol-2-yl)-7,13-dihydro-13,13-dimethyl-7-(pyridin-2-yl)-5H-indolo[3,2-b]acridine (5):7,13-Dihydro-13,13-dimethyl-7-(pyridin-2-yl)-5H-indolo[3,2-b]acridine (3): (0.30 g, 0.80 mmol, 1.00 eq), 9-(4-tert-butylpyridin-2-yl)-2-bromo-9H-carbazole (0.30 g, 0.80 mmol, 1.0 eq), Pd2(dba)3 (40 mg, 0.004 mmol, 0.05 eq), and (2-biphenyl)ditert-butylphosphine) (24 mg, 0.08 mmol, 0.10 eq) was added to a dry pressure tube equipped with a magnetic stir bar. The tube was then taken into a glove box. t-BuONa (0.20 g, 6 mmol. 2.00 eq) and dry toluene (4 mL) was added. The mixture was bubbled with nitrogen for minutes and then the tube was sealed. The tube was taken out of the glove box and heated to 95° C.-105° C. in an oil bath. The reaction was monitored by TLC and about 6 hours later the starting was consumed completely. Then the mixture was cooled to ambient temperature and diluted with ethyl acetate and washed with water. The organic phase was dried over sodium sulfate, then filtered and concentrated under vacuum. The residue was purified by silica gel column chromatography, using a mixture of hexanes and ethyl acetate as an eluent, in a ratio of 1:4 in volume and gave the title compound as a white solid 0.30 g in yield of 63%. 1H NMR (400 MHz, d6-DMSO):δ 8.56-8.53 (m, 1H), 8.38-8.35 (m, 1H), 8.24-8.18 (m, 1H), 7.83-7.80 (m, 1H), 7.72-7.50 (m, 2H), 7.43-7.36 (m, 2H), 7.15-7.7.12 (m, 1H), 6.96-6.92 (m, 2H), 7.25-7.19 (m, 2H), 6.99-6.92 (m, 2H), 6.84-6.82 (m, 1H), 2.05 (s, 3H), 1.76 (s, 6H), 1.23 (s, 9H).




PtN—N′N-t-Bu: 5-(9-(4-Tert-butylpyridin-2-yl)-9H-carbazol-2-yl)-7,13-dihydro-13,13-dimethyl-7-(pyridin-2-yl)-5H-indolo[3,2-b]acridine (5): Ligand (250 mg, 0.40 mmol, 1.00 eq), K2PtCl4 (167 mg, 0.40 mmol, 1.00 eq) and n-Bu4NBr (13 mg, 0.04 mmol, 1.0 eq) were added to a dry pressure tube. The tube was then taken into a glove box and acetic acid (24 mL) was added. The mixture was bubbled with nitrogen for 30 minutes and then the tube was sealed. The tube was taken out of the glove box and the mixture was stirred at room temperature for 20 hours. Then the mixture was heated to 105° C.-115° C. in an oil bath and stirred at that temperature for 2 days, cooled to ambient temperature and water (30 mL) was added slowly. After stirring at room temperature for 10 minutes, the precipitate was filtered off and washed with water three times. Then the solid was purified through column chromatography on silica gel using dichloromethane as eluent to obtain to obtain the desired product, PtN—N′N-t-Bu, as a yellow solid 80 mg in 25% yield. FIG. 4 shows an emission spectrum of PtN—N′N-t-Bu in CH2Cl2 at room temperature and in tetrahydro-2-methylfuran at 77K. 1H NMR (400 MHz, d6-DMSO):δ 8.90 (d, 1H, J=6.4 Hz), 8.18-8.16 (d, 1H, J=8.0 Hz), 8.14-8.07 (m, 4H), 8.04 (m, 1H), 8.01-7.99 (d, 1H, J=8.0 Hz), 7.90 (s, 1H), 7.53-7.49 (m, 1H), 7.44-7.33 (m, 5H), 7.25-7.19 (m, 2H), 6.99-6.92 (m, 2H), 6.84-6.82 (m, 1H), 2.05 (s, 3H), 1.36 (s, 3H), 1.34 (s, 9H).
Example 4
Synthesis of PtN′—NN




PtN′—NN: To a solution of N′—NN ligand (34 mg, 0.055 mmol) in HOAc (5 mL, 0.011 M) were added K2PtCl4 (25 mg, 0.0605 mmol) and n-Bu4NBr (2 mg, 0.0055 mmol). The mixture was heated to reflux and maintained at this temperature for 2 days. The reaction mixture was cooled to room temperature and filtered through a short pad of silica gel. The filtrate was concentrated under reduced pressure. Purification by column chromatography (hexanes:DCM=1:1 to 1:2) gave the PtN′—NN (18 mg, 0.0222 mmol, yield: 40%) as a yellow solid. 1H NMR (400 MHz, DMSO-d6, δ): 8.99 (d, J=5.9 Hz, 1 H), 8.79 (dd, J=6.1, 1.4 Hz, 1 H), 8.32-8.19 (m, 5 H), 8.16-8.10 (m, 2 H), 8.07 (d, J=8.4 Hz, 1 H), 8.01 (s, 1 H), 7.99-7.94 (m, 1 H), 7.65-7.59 (m, 1 H), 7.57-7.38 (m, 5 H), 7.38-7.32 (m, 1 H), 7.31-7.23 (m, 3 H), 7.18-7.13 (m, 1 H), 2.12 (s, 3 H), 1.40 (s, 3 H). FIG. 5 shows a room temperature emission spectrum of PtN′—NN in a solution of dichloromethane. 1H NMR (400 MHz, DMSO-d6, δ): 8.73-8.68 (m, 1H), 8.43 (d, J=8.2 Hz, 1H), 8.39 (s, 1H), 8.37-8.30 (m, 2H), 8.25 (d, J=7.8 Hz, 1H), 8.14 (td, J=7.8, 1.9 Hz, 1H), 7.90-7.84 (m, 2H), 7.82-7.74 (m, 2 H), 7.60-7.19 (m, 10 H), 7.09-6.98 (m, 2 H), 6.70 (s, 1 H), 6.56-6.49 (m, 1 H), 1.73 (s, 6 H).
Example 5
Synthesis of PtN′—N′N




To a solution of 6 (1.205 g, 3.3 mmol) in toluene (20 mL, 0.165 M) were added methyl 2-aminobenzoate (598 mg, 3.96 mmol), Pd(OAc)2 (74 mg, 0.33 mmol), ligand (122 mg, 0.33 mmol) and t-BuONa (476 mg, 4.95 mmol). The reaction mixture was heated to reflux for 2 days. The mixture was cooled to rt and filtered through a short pad of Celite. The filtrate was concentrated under reduced pressure. Purification by column chromatography (hexanes:EtOAc) gave 7 (1.02 g, yield: 71%) as a light yellow solid. 1H NMR (500 MHz, DMSO-d6, δ): 9.16 (s, 1H), 8.71 (m, 1 H), 8.05 (td, J=7.7, 2.0 Hz, 1H), 7.83 (dd, J=8.0, 1.6 Hz, 1H), 7.51 (dd, J=7.7, 1.6 Hz, 1H), 7.49-7.44 (m, 3 H), 7.33 (m, 1 H), 7.11 (d, J=8.4 Hz, 1 H), 7.07-6.97 (m, 2 H), 6.86 (dd, J=8.4, 2.2 Hz, 1H), 6.75 (m, 1 H), 6.43 (dd, J=8.0, 1.5 Hz, 1 H), 6.32 (d, J=1.9 Hz, 1 H), 3.81 (s, 3 H), 1.61 (s, 6 H).





To a solution of 7 (1.02 g, 2.34 mmol) in THF (20 mL, 0.117 M) was slowly added methylmagnesium bromide (9.4 mL, 1 M in THF) at room temperature. The mixture was then heated to 50° C. and maintained at this temperature for 12 hours. The mixture was cooled to rt and quenched with saturated NH4Cl (aq). The organic layer was then separated and the inorganic phase was extracted with EtOAc for three times. The combined organic phase was then dried over Na2SO4 and filtered through a short pad of silica gel. The filtrate was evaporated under reduced pressure. Purification by column chromatography (hexanes:EtOAc) gave 8 (847 mg, yield: 83%). 1H NMR (500 MHz, DMSO-d6, δ): 8.71-8.66 (m, 1 H), 8.35 (s, 1 H), 8.03 (t, J=7.8 Hz, 1 H), 7.49 (d, J=7.8 Hz, 1 H), 7.46-7.40 (m, 2 H), 7.34 (d, J=8.3 Hz, 1 H), 7.18 (d, J=7.8 Hz, 1 H), 7.08 (d, J=7.8 Hz, 1 H), 7.02 (t, J=8.1 Hz, 2 H), 6.96 (t, J=7.3 Hz, 1 H), 6.75 (t, J=7.6 Hz, 1 H), 6.61 (dd, J=8.3, 1.9 Hz, 1 H), 6.44 (d, J=8.3 Hz, 1 H), 6.15 (d, J=1.9 Hz, 1 H), 5.70 (s, 1 H), 1.58 (s, 6 H), 1.46 (s, 6 H).





A solution of 8 (847 mg, 1.94 mmol) in 10 mL H3PO4 (85%, 0.194 M) was stirred at room temperature. After about 20 mins (monitored by TLC), 20 mL of water was added. The mixture was then slowly quenched with K2CO3. The mixture was extracted with EtOAc for three times. The combined organic phase was then dried over Na2SO4 and filtered through a short pad of silica gel. The filtrate was evaporated under reduced pressure. Purification by column chromatography (hexanes:EtOAc) gave 9 (445 mg, 55% yield). 1H NMR (500 MHz, DMSO-d6, δ): 8.76-8.71 (m, 1 H), 8.59 (s, 1 H), 8.07 (td, J=7.7, 1.5 Hz, 1 H), 7.53-7.45 (m, 2 H), 7.43 (d, J=7.9 Hz, 1 H), 7.40 (s, 1 H), 7.31 (d, J=7.9 Hz, 1 H), 7.02-6.90 (m, 3 H), 6.74 (t, J=7.8 Hz, 1 H), 6.65 (d, J=7.8 Hz, 1 H), 6.37 (d, J=8.3 Hz, 1 H), 5.89 (s, 1 H), 1.60 (s, 6 H), 1.50 (s, 6 H).





To a solution of 9 (84 g, 0.2 mmol) in toluene (10 mL, 0.02 M) were added 2-bromo-9-(pyridin-2-yl)-9H-carbazole (97 mg, 0.3 mmol), Pd2(dba)3 (9 mg, 0.01 mmol), JohnPhos (6 mg, 0.02 mmol) and t-BuONa (29 mg, 0.3 mmol). The reaction mixture was heated to reflux for 2 days. The mixture was cooled to rt and filtered through a short pad of Celite. The filtrate was concentrated under reduced pressure. Purification by column chromatography (hexanes:EtOAc) gave N′—N′N Ligand (89 mg, yield: 67%). 1H NMR (500 MHz, DMSO-d6, δ): 8.74-8.68 (m, 1 H), 8.40-8.33 (m, 2 H), 8.11 (td, J=7.8, 1.5 Hz, 1 H), 7.96-7.90 (m, 2 H), 7.77 (d, J=7.8 Hz, 1 H), 7.59 (t, J=7.7 Hz, 1 H), 7.54-7.36 (m, 7 H), 7.06-6.99 (m, 2 H), 6.95-6.82 (m, 4 H), 6.46-6.39 (m, 1 H), 6.28-6.18 (m, 2 H), 4.95 (s, 1 H), 1.66 (s, 6 H), 1.58 (s, 6 H).





To a solution of N′—N′N ligand (89 mg, 0.055 mmol) in HOAc (5 mL, 0.011 M) were added K2PtCl4 (25 mg, 0.0605 mmol) and n-Bu4NBr (2 mg, 0.0055 mmol). The mixture was heated to reflux and maintained at this temperature for 2 days. The reaction mixture was cooled to room temperature and filtered through a short pad of silica gel. The filtrate was concentrated under reduced pressure. Purification by column chromatography (hexanes:DCM=1:1 to 1:2) gave the PtN′—N′N (32 mg, yield: 28%) as a yellow solid. 1H NMR (500 MHz, DMSO-d6, δ): 9.40 (d, J=5.9 Hz, 1 H), 9.15 (d, J=5.4 Hz, 1 H), 8.38 (d, J=8.7 Hz, 1 H), 8.17 (t, J=7.3 Hz, 1 H), 8.09-8.04 (m, 2 H), 7.92 (t, J=8.1 Hz, 1 H), 7.72 (d, J=7.9 Hz, 1 H), 7.59-7.45 (m, 4 H), 7.41-7.31 (m, 4 H), 7.27-7.15 (m, 4 H), 7.13-7.05 (m, 2 H), 7.01 (d, J=8.3 Hz, 1 H), 1.94 (s, 3 H), 1.90 (s, 3 H), 1.30 (s, 3 H), 1.15 (s, 3 H).

Example 6
Synthesis of PdN′—N′N




To a solution of N′—N′N ligand (1 eq) in HOAc (5 mL, 0.02 M) were added Pd(OAc)2 (1.05 eq) and n-Bu4NBr (0.1 eq). The mixture was heated to reflux and maintained at this temperature for 2 days. The reaction mixture was cooled to room temperature and filtered through a short pad of silica gel. The filtrate was concentrated under reduced pressure. Purification by column chromatography (hexanes:DCM) gave the PdN′—N′N.

Example 7
Synthesis of PtN′—N′3




To a solution of 9 (1 eq) in toluene (0.02 M) were added 2-(3-bromophenyl)pyridine (1.5 eq), Pd2(dba)3 (0.05 eq), JohnPhos (0.1) and t-BuONa (1.5 eq). The reaction mixture was heated to reflux for 2 days. The mixture was cooled to rt and filtered through a short pad of Celite. The filtrate was concentrated under reduced pressure. Purification by column chromatography (hexanes:EtOAc) gave N′—N′3 Ligand.





To a solution of N′—N′3 ligand (1 eq) in HOAc (0.02 M) were added K2PtCl4 (1.05 eq) and n-Bu4NBr (0.1 eq). The mixture was heated to reflux and maintained at this temperature for 2 days. The reaction mixture was cooled to room temperature and filtered through a short pad of silica gel. The filtrate was concentrated under reduced pressure. Purification by column chromatography (hexanes:DCM) gave the PtN′—N′3.

Example 8
Synthesis of PdN′—N′3




To a solution of N′—N′3 ligand (1 eq) in HOAc (0.02 M) were added Pd(OAc)2 (1.05 eq) and n-Bu4NBr (0.1 eq). The mixture was heated to reflux and maintained at this temperature for 2 days. The reaction mixture was cooled to room temperature and filtered through a short pad of silica gel. The filtrate was concentrated under reduced pressure. Purification by column chromatography (hexanes:DCM) gave the PdN′—N′3.

A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of this disclosure. Accordingly, other embodiments are within the scope of the following claims.

## Claims

1. A complex of Formula II:



wherein:
M is Pt (II), Pd (II), or Au (III),
each of V, V1, V2, and V3 is independently N, C, P, or Si,
each of X and X1 is independently present or absent, and each X and X1 present independently represents CR7R8, C═O, SiR7R8, GeR7R8, NR7, PR7, PR7R8, R7P═O, AsR7, R7As═O, O, S, S═O, SO2, Se, Se═O, SeO2, BR7, BR7R8, AlR7, AlR7R8, R7Bi═O, BiR7, or a single bond,
each of Y and Y1 is independently CR9, SiR9, GeR9, N, P, P═O, As, As═O, B, Bi═O, or Bi,
L is a substituted or unsubstituted: 5-membered heteroaryl or 5-membered N-heterocyclic carbene,
each of R1, R2, R3, R4, R5, and R6 is independently absent or present as a single substituent or multiple substituents, valency permitting, and each R1, R2, R3, R4, R5, and R6 present independently represents deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof, and
each of R7, R8, and R9 is independently hydrogen, deuterium, halogen, hydroxyl, thiol, nitro, cyano, nitrile, isonitrile, sulfinyl, mercapto, sulfo, carboxyl, hydrazino; substituted or unsubstituted: aryl, cycloalkyl, cycloalkenyl, heterocyclyl, heteroaryl, alkyl, alkenyl, alkynyl, amino, monoalkylamino, dialkylamino, monoarylamino, diarylamino, alkoxy, aryloxy, haloalkyl, aralkyl, ester, alkoxycarbonyl, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, sulfamoyl, carbamoyl, alkylthio, ureido, phosphoramide, silyl, polymeric; or any conjugate or combination thereof.

2. The complex of claim 1, wherein:
V and V2 are C,
V1 and V3 are N,
Y and Y1 are N, and
L is a substituted or unsubstituted 5-membered heteroaryl.

3. The complex of claim 2, wherein X is a single bond.

4. The complex of claim 3, wherein X1 is CR8R9.

5. The complex of claim 1, wherein M is Pt or Pd; one of X and X1 is BR7R8 or AlR7R8; and one of V, V1, V2, and V3 is C or Si.

6. The complex of claim 1, wherein M is Pt or Pd; both of X and X1 are independently BR7R8 or AlR7R8; and each of V, V1, V2, and V3 is independently N or P.

7. The complex of claim 1, wherein M is Au; one of X and X1 is BR7R8 or AlR7R8; and two of V, V1, V2, and V3 are independently C or Si.

8. The complex of claim 1, wherein M is Au; both of X and X1 are independently BR7R8 or AlR7R8; and one of V, V1, V2, and V3 is C or Si.

9. A light emitting device comprising the complex of claim 1.

10. An OLED device comprising the complex of claim 1.

11. The OLED device of claim 10, wherein the device is a phosphorescent OLED device.

12. A photovoltaic device comprising the complex of claim 1.

13. A luminescent display device comprising the complex of claim 1.

14. The complex of claim 1, wherein X and X1 are both CR8R9.

15. The complex of claim 14, wherein R8 and R9 are both alkyl.

16. The complex of claim 1, wherein M is Pt or Pd; X and X1 are CR8R9; and each of V, V1, V2, and V3 is independently C or N.

17. The complex of claim 1, wherein L is a substituted or unsubstituted 5-membered N-heterocyclic carbene.

18. The complex of claim 1, wherein each of R1, R2, R3,R4, R5, and R6 is hydrogen.

19. The complex of claim 1, wherein:
V and V2 are C,
V1 and V3 are N,
Y and Y1 are N, and
L is a substituted or unsubstituted 5-membered N-heterocyclic carbene.