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BSTV Figure 1 Synthesis of (E)-Bis-1,2-(5,5´´-Dimethyl-(2,2´:3´,2´´-terthiophene)vinylene To a solution of 1g of [10] in 13 mL of anhydrous THF is added 1 mL of titanium tetrachloride at -18ºC under Argon atmosphere. The mixture is stirred for half an hour at -18ºC. To this solution was added 1.19 g of Zinc powder in small portions for 10-15 min. The mixture was stirred for 40 min. at -18ºC and was then gradually warmed to room temperature and then heated at reflux overnight. Then, the mixture was cooled in an ice-water bath and 50 mL of aqueous solution of sodium carbonate 10 % were added. The aqueous layer was extracted with chloroform (3x50 mL). The combined organic layers were filtered and washed with water until neutral pH. The organic layer was dried over anhydrous MgSO4. The product was purified by column chromatography on silica gel using hexane as the eluent, yielding a yellow orange solid. (0.81 g; 86% yield. 1H-NMR (CDCl3, 300 MHz) δ (ppm) 7.02 (2H, s), 6.97 (2H, d, J=3.5 Hz), 6.92 (2H, s), 6.89 (2H, d, J=3.5 Hz), 6.67 (4H, m), 2.49 (12H, m). 13C-NMR (CDCl3, 75 MHz) δ (ppm) 141.5, 140.2, 139.8, 134.8, 132.8, 132.0, 130.9, 129.3, 127.6, 126.7, 125.5, 125.3, 121.3, 15.47, 15.43, HRMS (ESI-TOF; CHCl3/MeOH 10:15); m/z 576.0210. [M+H]+( calcd for C30H24S6+ 576.9071). Synthesis and characterization of (E)-Bis-1,2-(5,5´´-Dimethyl-(2,2´:3´,2´´:3’,2’’’tetrathiophene)vinylene (BOTV). The figure 2 shows the scheme synthesis of BOTV

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BOTV Figure 2 Synthesis of (E)-Bis-1,2-(5,5´´-Dimethyl-(2,2´:3´,2´´:3’,2’’’-tetrathiophene) vinylene (BOTV) This compound was synthesized through the McMurry reaction in a similar manner as described above for BSTV, this time the starting compound was 5,5´´´-dimethyl-2,2´:5´,2´´:3´,2´´´tetrathiophene-5´´-carbaldehyde. The product was purified by column chromatography on silica gel using hexane as the eluent, yielding a red solid (0.42 g; 55% yield). 1

H-NMR (CDCl3, 300 MHz) δ (ppm) 7,26 (s, 2H), 7.19-7.00 (m, 3H), 7.01-6.81 (m,7H), 6.67 (dd, J=3.4, 1.8Hz, 4H), 2.55-2.39 (m, 12H). 13C-NMR (CDCl3, 75MHz) δ (ppm) 141.60, 141.57, 140.34, 135.56, 135.07, 134.69, 132.35, 130.76, 127.74, 127.43, 126.80, 126.28, 125.52, 125.37, 124.42, 121.35, 100.01, 15.47, 15.43. HRMS (ESI-TOF; CHCl3/MeOH 10:15); m/z 739.9706 [M+H]+ (calcd. for C38H28S8 739.9986). As concerning the film formation of branched thiophene oligomer compounds blended with typical solar cell constituents, several solutions of blended poly(3-hexylthiophene) (P3HT), [6,6]phenyl C61-butyric acid methylester (PCBM), and BSTV, BOTV were prepared for spin-coating. The preferred solvent was dichlorobenzene (DCB). Each constituent of the blend was first dissolved in a separate tube, and stirred at 50 oC overnight. The solutions were subsequently combined, stirred at 70 οC for 4 h, and overnight at 50 oC. Immediately before the film preparation, the solutions were sonicated for at least 30 min. The “P3HT: PC