Abstract:
The present invention is related to oligothiophene derivatives of the formula I or II: wherein X═H or CH 3 , Y═H or CH 3 , n=1 or 2, and R=carbon chain, branched or not, saturated or not, with 6 to 15 carbon atoms.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to new bridged oligothiophene derivatives and to their use in a liquid crystal medium for electronic devices, in particular for semiconductors. 
       TECHNICAL BACKGROUND OF THE INVENTION AND PRIOR ART 
       [0002]    The transport of electric charges in a field effect transistor occurs in the first molecular layers of the interlayer situated between the dielectric layer and the semi-conductive layer. When said first molecular layers are interrupted by some defects, the conductivity of those layer decreases. These defects are one of the reasons for the poor reproducibility of the threshold voltage of those transistors. 
         [0003]    In the past, this problem was handled via the highest possible flatness of the dielectric layer; but on a microscopic scale, surfaces are never perfectly flat. 
         [0004]    Recently, this problem was approached by self-aligning molecules. This self alignment can again be perturbed by surface irregularities at molecular scale. 
         [0005]    The approach of the present invention is to provide molecules that are able to transport charges in three dimensions instead of two dimensions where two conjugated segments are connected by a a-bond bridge. The latter promotes charge transport that is less sensitive to surface defects. 
         [0006]      FIG. 4  of the present invention shows the principle of the improvement reached by a bridged molecule compared to a non-bridged molecule. 
         [0007]    The bridged molecules of the present invention are oligothiophene derivatives. 
         [0008]    Bridged oligothiophene derivatives have been disclosed by A. Berlin et al, “Anodic coupling of oligothiophenes bridged by ethylene groups” in  Synthetic Metals,  55-57 (1993), 4796-4801. Similar structures were also disclosed by Tadatake Sato and al., “Synthesis and photophysical properties of 1,3-Di(oligothienyl)propane” in  Tetrahedron Letters , Vol. 38, N o  34, pp. 6039-6042, 1997. 
         [0009]    Nevertheless, the molecules disclosed in the above-cited references are different from those of the present invention and are synthesised for other purposes. 
       AIMS OF THE INVENTION 
       [0010]    The present invention aims to provide new molecular structures based on bridged oligothiophene derivatives that are able to overcome the drawbacks of the prior art and able to reduce impact of the surface defects due to irregular surfaces on which the semi-conductive layer is applied. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention discloses an oligothiophene derivative of the formula I or II: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    wherein X═H or CH 3 ,
       Y═H or CH 3 ,   n=1 or 2, and   R=carbon chain, branched or not, saturated or not, with 6 to 15 carbon atoms.       
 
         [0015]    Preferred embodiments of the present invention are:
       the oligothiophene derivatives of the formula I or II wherein R is a, b, or c with:
 
a:
       
 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    b: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0000]    c: 
         [0000]    
       
                 
         
             
             
         
       
       
         
           
             the oligothiophene derivative of the formula I, wherein X═Y═H and wherein R is a and n=1. 
             the oligothiophene derivative of the formula I, wherein X═Y═H and wherein R is b and n=1. 
             the oligothiophene derivative of the formula I, wherein X═Y═H and wherein R is c and n=1. 
             the oligothiophene derivative of the formula I, wherein X═Y═CH3 and wherein R is a and n=1. 
             the oligothiophene derivative of the formula I, wherein X═Y═CH3 and wherein R is b and n=1. 
             the oligothiophene derivative of the formula I, wherein X═Y═CH3 and wherein R is c and n=1. 
             the oligothiophene derivative of the formula I, wherein X═H and Y═CH3 and R is a and n=1. 
             the oligothiophene derivative of the formula I, wherein X═H and Y═CH3 and R is b and n=1. 
             the oligothiophene derivative of the formula I, wherein X═H and Y═CH3 and R is c and n=1. 
             the oligothiophene derivative of the formula I, wherein X═Y═H and wherein R is a and n=2. 
             the oligothiophene derivative of the formula I, wherein X═Y═H and wherein R is b and n=2. 
             the oligothiophene derivative of the formula I, wherein X═Y═H and wherein R is c and n=2. 
             the oligothiophene derivative of the formula I, wherein X═Y═CH 3  and wherein R is a and n=2. 
             the oligothiophene derivative of the formula I, wherein X═Y═CH 3  and wherein R is b and n=2. 
             the oligothiophene derivative of the formula I, wherein X═Y═CH 3  and wherein R is c and n=2. 
             the oligothiophene derivative of the formula I, wherein X═H and Y═CH 3  and R is a and n=2. 
             the oligothiophene derivative of the formula I, wherein X═H and Y═CH 3  and R is b and n=2. 
             the oligothiophene derivative of the formula I, wherein X═H and Y═CH 3  and R is c and n=2. 
             the oligothiophene derivative of formula II, wherein R is a and n=2. 
             the oligothiophene derivative of formula II, wherein R is b and n=2. 
             the oligothiophene derivative of formula II, wherein R is c and n=2. 
             the oligothiophene derivative of formula II, wherein R is a and n=1. 
             the oligothiophene derivative of formula II, wherein R is b and n=1. 
             the oligothiophene derivative of formula II, wherein R is c and n=1. 
           
         
       
     
         [0041]    The present invention further discloses the use of the oligothiophene derivative of claim  1  in a liquid crystal medium. 
         [0042]    The present invention additionally discloses the use of the oligothiophene derivative of claim  1  as semiconductor. 
         [0043]    The present invention finally discloses an electronic device element comprising the oligothiophene derivative of claim  1 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]      FIG. 1  represents a photograph of the optical texture of 1,2-di-(5-hexyl-2-terthiophene)ethane 10a at 193° C. under polarized light. 
           [0045]      FIG. 2  schematically represents the synthesis of the oligothiophene derivatives of the formula II. 
           [0046]      FIG. 3  schematically represents the synthesis of the oligothiophene derivatives of the structure I. 
           [0047]      FIG. 4  schematically represents the advantage of a bridged molecule compared to a non-bridged molecule. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0048]    In the different synthetic steps used for the molecules of the present invention, all chemicals were purchased from Aldrich or Acros and used without further purification unless stated otherwise. THF was refluxed over sodium and benzophenone until blue-violet color persisted and directly distilled into a reaction flask. Commercially available solution of BuLi in hexane was titrated with Ph 2 CHCOOH immediately before use. t-BuOK was used as solution in THF (1M). 
         [0049]    For the identification of the chemical structure,  1 H-NMR (300 MHz) and  13 C-NMR (75 MHz) spectra were recorded in CDCl 3  on Brucker Avance 300 spectrometer; chemical shifts (δ) are given in ppm relative to TMS (internal standard); coupling constants (J) are given in Hz. EI-MS (70 eV) spectra were recorded on a VG Micromass 7070F instrument. 
         [0050]    Concerning the liquid crystal properties, phase transition temperatures were measured by differential scanning calorimetry (Mettler Toledo DSC 821), optical textures were observed with polarizing microscopy (Nikon Eclipse 80i). 1,2-Di-(5-bromo-2-thienyl)ethane [1], 5 -hexylterthiophene [2] , 5-(3,7-dimethyloctyl)bithiophene [3]  and 5-mercapto-5′-hexylterthiophene [4]  were prepared as described in the literature. 
         [0051]    In the following description, the underlined numbers refer to the intermediate molecules shown in  FIGS. 2 and 3  and the notation a, b and c to the type of R groups as described in claim  2 . 
       General Procedure 1 for Boronic Ester Derivative 
       [0052]    A solution of 1.3 mmol of monoalkylated oligothiophene in THF is cooled down to −78° C., 2 eq of BuLi is added dropwise. The mixture is stirred during 15 min. at −78° C. Then 1.6 mmol of 2-isopropoxy-4,4-tertramethyl-1,2,3-dioxaborolane is added to the mixture. This solution is stirred during 30 min. at −78° C. and slowly heated to room temperature for 3 hours. The reaction mixture is poured into ether (50 ml) and then into water mixed with 2.5 ml of 1M HCl solution. The organic phase is extracted, dried over MgSO 4  and evaporated. The product is then used for the next reaction without other purification. 
       5-(3,7-dimethyloctyl)-5′-(4,4,5,5-tetramethyl-1,2,3-dioxaborolane-2-yl)-2,2′-bithiophene 8b 
       [0053]    Prepared according to the procedure 1 from 1.3 mmol (0.4 mg) of 5-(3,7-dimethyloctyl)bithiophene 6b and 0.3 ml of 2-isopropoxy-4,4-tertramethyl-1,2,3-dioxaborolane. 
         [0054]    A transparent liquid is obtained. Yield: 98%. 
         [0055]      1 H NMR (300 MHz, CDCl 3 , 25° C.): δ=7.50 (d, 1H, J=3.7 Hz); 7.15 (d, 1H, J=3.7 Hz); 7.03 (d, 1H, J=3.7 Hz); 6.68 (d, 1H, J=3.7 Hz); 2.80 (t, 2H, J=7.7 Hz), 1.71-1.10 (m, 23H), 0.91 (d, 3H, J=6.3 Hz), 0.86 (d, 6H, J=6.7 Hz) ppm. 
       5-(3,7,11-trimethyldodecyl-2,6,10-triene)-5′-(4,4,5,5-tetramethyl-1,2,3-dioxaborolane-2-yl)-2,2′-bithiophene 8c 
       [0056]    Prepared according to the procedure 1 from 1.8 mmol (670 mg) of 5-(3,7,11-trimethyldodecyl-2,6,10-triene)bithiophene and 0.5 ml of 2-isopropoxy-4,4-tertramethyl-1,2,3-dioxaborolane. 
         [0057]    A green liquid is obtained. Yield: 98%. 
         [0058]      1 H NMR (300 MHz, CDCl 3 , 25° C.): δ=7.50 (d, 1H, J=3.7 Hz); 7.15 (d, 1H, J=3.7 Hz); 7.03 (d, 1H, J=3.7 Hz); 6.68 (d, 1H, J=3.7 Hz); 5.4 (t, J=8.8 Hz, 1H), 5.11-5.07 (m, 4H), 3.5 (d, 7.2 Hz, 2H), 1.74-0.8 (m, 30H) ppm. 
       5-hexyl-5″-(4,4,5,5-tetramethyl-1,2,3-dioxaborolane-2-yl)-2,2″-terthiophene 9a 
       [0059]    Prepared according to the procedure 1 from 1.3 mmol (440 mg) of 5-hexylterthiophene 7a and 1.6 mmol (0.4 ml) 2-isopropoxy-4,4-tertramethyl-1,2,3-dioxaborolane. 
         [0060]    A green solid is obtained. Yield: 96%. 
         [0061]      1 H NMR (300 MHz, CDCl 3 , 25° C.): δ=7.51 (d, 1H, J=3.7 Hz), 7.21 (d, 1H, J=3.7 Hz), 7.00-6.97 (m, 3H), 6.68 (d, 1H, J=3.7 Hz), 2.79 (t, 2H, J=7.3 Hz), 1.68 (quint, 4H, J=7.7 Hz), 1.41-1.24 (m, 15H), 0.89 (t, 3H, J=6.6 Hz) ppm. 
       General Procedure 2 for the Suzuki Coupling 
       [0062]    0.7 mmol of 1,2-di-(5-bromo-2-thienyl)ethane 4 and 95 mg of Pd cat in solution with toluene (10 ml) is heated to 75° C., a solution of boron ester (3 eq) in EtOH (6 ml) and a solution of K 2 CO 3  (18 eq) in water (6 ml) are added dropwise. After 24 h of stirring at 75° C., the mixture is cooled down and filtered. The solid is cristallised from toluene. 
       1,2-di-(5-hexylterthiophene)ethane 10a 
       [0063]    Prepared according to the general procedure 2 from 300 mg of 1,2-di-(5-bromo-2-thienyl)ethane 4 and 905 mg of 5-hexyl-5′-(4,4,5,5-tetramethyl-1,2,3-dioxaborolane-2-yl)-2,2′-bithiophene 8a. 
         [0064]    An orange solid is obtained after cristallisation from toluene. Yield: 67%. 
         [0065]      1 H NMR (300 MHz, CDCl 3 , 25° C.): δ=6.99-6.96 (m, 4H), 6.70 (d, 1H, J=3.7 Hz), 6.67 (d, 1H, J=3.7 Hz), 3.17 (s, 4H), 2.79 (t, 4H, J=7.3 Hz), 1.68 (quint, 4H, J=7.3 Hz), 1.30-1.33 (m, 12H), 0.89 (t, 6H, J=6.9 Hz) ppm. DSC: K 113° C. LC1 175° C. LC2 213° C. I. 
       1,2-di-(5-(3,7-dimethyloctyl)terthiophene)ethane. 10b 
       [0066]    Prepared according to the general procedure 1 from 0.2 mmol (74 mg) of 1,2-di-(5-bromo-2-thienyl)ethane 4 and 0.6 mmol (250 mg) 5-(3,7-dimethyloctyl)-5′-(4,4,5,5-tetramethyl-1,2,3-dioxaborolane-2-yl)-2,2′-bithiophene 9b. 
         [0067]    An orange solid is obtained after cristallisation from toluene. Yield: 71%. 
         [0068]      1 H NMR (300 MHz, CDCl 3 , 25° C.): δ=6.99-6.96 (m, 4H), 6.71 (d, 1H, J=3.7 Hz); 6.68 (d, 1H, J=3.7 Hz), 3.17 (s, 4H), 2.79 (t, 4H, J=7.5 Hz), 1.68 (quint, 4H, J=7.5 Hz), 1.71-1.10 (m, 16H), 0.91 (d, 6H, J=6.3 Hz), 0.86 (d, 12H, J=6.7 Hz) ppm. DSC: K 126° C. LC 157° C. I. 
       1,2-di-(5-hexylquaterthiophene)ethane 11a 
       [0069]    Prepared according to the general procedure 1 from 0.4 mmol (147 mg) of 1,2-di-(5-bromo-2-thienyl)ethane 4 and 1.2 mmol (552 mg) 5-hexyl-5″-(4,4,5,5-tetramethyl-1,2,3-dioxaborolane-2-yl)-2,2″-terthiophene 9a. 
         [0070]    A red solid is soxhlet in methanol. Yield: 65%. 
         [0071]      1 H NMR (300 MHz, CDCl 3 , 25° C.): δ=7.06-6.90 (m, 6H), 6.68 (d, 1H, J=3.3 Hz), 6.64 (d, 1H, J=3.3 Hz), 3.19 (s, 4H), 2.80 (t, 4H, J=7.7 Hz), 1.70 (quint, 4H, J=7.3 Hz), 1.36-1.24 (m, 12H), 0.93 (t, 6H, J=6.6 Hz) ppm. Mp: 261° C. 
       1,2-di-(5-(3,7,11-trimethyldodecyl-2,6,10-triene)terthiophene)ethane 10c 
       [0072]    Prepared according to the general procedure 1 from 0.2 mmol (74 mg) of 1,2-di-(5-bromo-2-thienyl)ethane 4 and 0.2 mmol (100 mg) 5-(3,7,11-trimethyldodecyl-2,6,10-triene)-5′-(4,4,5,5-tetramethyl-1,2,3-dioxaborolane-2-yl)-2,2′-bithiophene 9b. 
         [0073]    A yellow solid is obtained after cristallisation from toluene. Yield: 20%. 
         [0074]      1 H NMR (300 MHz, CDCl 3 , 25° C.): δ=6.99-6.96 (m, 4H), 6.70 (d, 1H, J=3.7 Hz), 6.67 (d, 1H, J=3.7 Hz), 3.17 (s, 4H), 5.4 (t, J=6.6 Hz, 2H), 5.11-5.09 (m, 8H), 3.5 (d, J=6.3 Hz, 4H), 2.33-1.94 (m, 8H), 1.61 (s, 6H), 1.59 (s, 6H), 1.45-1.33 (m, 4H), 1.08 (s, 6H), 1.06 (s, 6H) ppm. 
       1,2-di-(5-(3,7-dimethyloctyl)-5-terthiophene)disulfide 14a 
       [0075]    0.04 ml of SO 2 Cl 2  in 4 ml of dichloromethane were added dropwise to 0.8 mmol (300 mg) of 5-mercapto-5′-hexylterthiophene 13a in solution in 2 ml of dichloromethane at room temperature. The solution is stirred for 1 hour at room temperature. After completion of the reaction, the solvent is evaporated in vacuum. 
         [0076]    A yellow solid is obtained. Yield: 85%. 
         [0077]      1 H NMR (300 MHz, CDCl 3 , 25° C.): δ=7.09 (t, 2H, J=4.0 Hz), 7.04-6.99 (m, 3H), 6.68 (d, 1H, J=3.7 Hz), 2.80 (t, 2H, J=7.3 Hz), 1.68 (quint, 4H, J=7.3 Hz), 1.41-1.25 (m, 28H), 0.89 (t, 6H, J=6.6 Hz)ppm. Decomposition&gt;250° C.