Supporting Information

Metallated conjugation in small-sized-moleculardonors for solution-processed organic solar cells

Chaohua Cui1*,Yunye Zhang2, Wallace C. H.Choy2*, Hua Li1,3Wai-Yeung Wong1,4 *

1Institute of Molecular Functional Materials, Department of Chemistry and Institute of Advanced Materials, Hong KongBaptistUniversity, Waterloo Road, Hong Kong, China

2Department of Electrical and Electronic Engineering, TheUniversity of Hong Kong, Pokfulam Road, Hong Kong, China

3College of Life and Environmental Sciences & Beijing Engineering Research Center of Food Environment and Public Health, Minzu University of China, Beijing100081, China

4HKBU Institute of Research and Continuing Education, Shenzhen Virtual University Park, Shenzhen518057,China

Received October 9, 2014; accepted October 23, 2014

*Corresponding authors (email: ; ; )

3,4'-Dihexyl-5'-((trimethylsilyl)ethynyl)-(2,2'-bithiophene)-5-carbaldehyde (2)

To a solution of compound 1 (2 g, 4.5 mmol) in a mixture of NEt3 and CH2Cl2 (50 mL, 1:1, v/v) was added a catalytic amount of CuI and Pd(PPh3)4 (0.2 g) under nitrogen. After stirring for 30 min at room temperature (RT), trimethylsilylacetylene (TMSA, 1.76 g, 18 mmol) was added and left overnight at 60 oC with constant stirring. The reaction mixture was dried and the crude product was purified by column chromatography on silica gel using hexane and dichloromethane (1:1, v/v) as eluent to give compound 2(1.5 g, yield: 78%) as a yellow oil.

1HNMR (400MHz, CDCl3), δ(ppm): 9.81 (s, 1H, CHO), 7.56 (s,1H, Ar), 7.01 (s, 1H, Ar), 2.79–2.75 (t, J=16 Hz, 2H, alkyl), 2.70–2.66 (m, 4H, alkyl), 1.42–1.26 (m, 12H, alkyl), 0.91–0.86 (m, 6H, alkyl), 0. 26 (s, 9H, alkyl).13C NMR (100 MHz, CDCl3), δ (ppm): 182.48 (H, alkyl), CHO), 149.65, 140.89, 140.53, 140.44, 138.88, 134.96, 128.17, 119.01 (Ar), 85.38, 76.07 (C≡C), 31.60, 30.26, 30.09, 29.46, 29.43, 29.15, 28.93, 22.69, 22.61, 14.15, 14.11, 14.08, 3.40 (alkyl). MALDI-TOF: m/z 458.2 [M]+.

5'-Ethynyl-3,4'-dihexyl-(2,2'-bithiophene)-5-carbaldehyde (3)

Compound 2 (1.5 g, 3.4 mmol) and K2CO3 (0.5 g, 3.7 mmol) were dissolved in MeOH and CH2Cl2 (1:1, v/v) solvent mixture. The mixture was stirred for 6 h at RT. The reaction mixture was poured into water and extracted with CH2Cl2. The organic layer was washed with water three times and dried over Na2SO4. After the removal of solvent, the crude product was purified by column chromatography on silica gel using hexane and dichloromethane (1:1, v/v) as eluent to afford compound 3 (0.78 g, yield: 60%) as a yellow oil.

1HNMR (400MHz, CDCl3), δ(ppm): 9.82 (s, 1H, CHO), 7.57 (s,1H, Ar), 7.03 (s, 1H, Ar), 3.56 (s, 1H, C≡CH), 2.79–2.75 (t, J= 16 Hz,2H, alkyl), 2.72–2.68 (t, J= 16 Hz, 2H, alkyl), 1.69–1.60 (m, 4H, alkyl), 1.42–1.26 (m, 12H, alkyl), 0.91–0.86 (m, 6H, alkyl). 13C NMR (100 MHz, CDCl3), δ (ppm): 182.48 (CHO), 149.65, 140.89, 140.53, 140.44, 138.88, 134.96, 128.17, 119.01 (Ar), 85.38, 76.07 (C≡C). 31.71, 31.55, 30.21, 29.48, 29.13, 28.70, 22.67, 22.62, 14.16, 14.12 (alkyl), MALDI-TOF: m/z 386.1 [M]+.

Synthesis of compound 5

Compounds3(0.84 g, 0.22 mmol) and 4(0.067 g, 0.1 mmol) were added into a flask with 40 mL of THF/NEt3 (1:1, v/v), and the solution was flushed with nitrogen for 10 min. Then, 5.77 mg of Pd(PPh3)4 (0.005 mmol) and 0.8 mg CuI (0.01 mmol) were added. The solution was flushed again for 10 min. After being stirred at room temperature for 24 h under nitrogen, the reaction mixture was poured into water (100 mL) and extracted with CH2Cl2. The organic layer was washed with water and dried over Na2SO4. After the removal of solvent, the crude product was purified by column chromatography on silica gel using a mixture of hexane and dichloromethane (1:2, v/v) as the eluent to afford compound 5 as a red solid (79 mg, yield: 58%).

1HNMR (400MHz, CDCl3), δ(ppm): 9.78 (s, 2H, CHO), 7.54 (s, 2H, Ar), 7.02 (s, 2H, Ar), 2.80–2.76 (t, J=16 Hz, 4H, alkyl), 2.67–2.63 (t, J=16 Hz, 4H, alkyl), 1.68–1.25 (m, 68H, alkyl), 0.96–0.86 (m, 30H, alkyl). 13C NMR (100 MHz, CHCl3): δ(ppm): 182.76 (–C=O), 150.32 (C≡C), 144.65, 139.75, 135.34, 131.21, 130.94, 123.45, 121.56 (Ar), 114.78 (C≡C),75.49 (C≡C), 31.84, 31.68, 30.53, 30.13, 29.43, 29.32, 29.31, 28.16, 26.40, 24.71, 24.52, 24.37, 24.24, 22.63, 22.45, 14.42, 14.09, 13.89 (alkyl).31P (161.9 MHz, CDCl3), δ (ppm): 3.54 (JP-Pt=2315 Hz). MALDI-TOF: m/z 1370.67 [M]+.

3,4'-Dihexyl-[2,2':5',2''-terthiophene]-5-carbaldehyde (6)

Compound 1 (2.5 g, 5.7 mmol) and thiophen-2-ylboronic acid (1.1g, 8.6 mmol) were charged into a flask with 50 mL THF and 6 mL K2CO3 (2 mol L1) solution. The system was flushed with nitrogen for 10 min, to which 200 mg of Pd(PPh3)4 was added. The solution was flushed again for 10 min. After being stirred at 80 oC for 24 h under nitrogen, the reaction mixture was poured into water (100 mL) and extracted with ethyl acetate. The organic layer washed with water was dried over Na2SO4. After the removal of solvent, the crude product was purified by column chromatography on silica gel using a mixture of hexane and dichloromethane (10:1) as the eluent to afford compound 6 (1.7g, yield: 68%) as a yellow oil.

1HNMR (400MHz, CDCl3), δ(ppm): 9.82 (s, 1H, CHO), 7.59 (s,1H, Ar), 7.36–7.35 (d, J=4 Hz, 1H, Ar), 7.18–7.16 (d, J=8 Hz, 1H, Ar), 7.12 (s,1H, Ar), 7.10–7.08 (d, 1H, J=8 Hz, Ar), 2.84–2.74 (m, 4H, alkyl), 1.68–1.66 (m, 4H, alkyl), 1.41–1.26 (m, 12H, alkyl), 0.91–0.87 (m, 6H, alkyl).13C NMR (100 MHz, CDCl3), δ (ppm): 182.58 (CHO), 144.28, 140.28, 140.26, 139.11, 135.25, 132.93, 132.68, 130.31, 127.58, 126.39, 126.01 (Ar), 31.64, 31.62, 30.55, 30.28, 29.42, 20.20, 29.16, 22.68, 22.62, 22.61, 14.15, 14.09 (alkyl). MALDI-TOF: m/z 444.16 [M]+.

5''-Bromo-3,4'-dihexyl-[2,2':5',2''-terthiophene]-5-carbaldehyde (7)

A solution of compound 6 (1.7 g 3.8 mmol) in CH2Cl2and acetic acid (100 mL, 1:1, v/v) was stirred at 0 oC andN-bromosuccinimide (NBS, 7.3 g, 4.1 mmol) was added in small portions intermittently. After being stirred for 12 h at room temperature, the reaction mixture was poured into water and extracted with CH2Cl2. The organic layer was washed with water three times and dried over Na2SO4. After the removal of solvent, the crude product was purified by column chromatography on silica gel using hexane as the eluent to afford compound7 (1.7 g, yield: 84%) as a yellow oil.

1HNMR (400MHz, CDCl3), δ(ppm): 9.82 (s, 1H, CHO), 7.58 (s,1H, Ar), 7.10 (s, 1H, Ar), 7.05–7.04 (d, J=4 Hz, 2H, Ar), 6.91–6.90 (d, J=4 Hz, 2H, Ar), 2.82–2.70 (m, 4H, alkyl), 1.68–1.26 (m, 16H, alkyl), 0.91–0.87 (m, 6H, alkyl). 13C NMR (100 MHz, CDCl3), δ (ppm): 182.53 (CHO), 140.73, 140.46, 140.25, 139.05, 136.75, 133.19, 133.00, 131.80, 130.39, 130.19, 126.54, 112,63 (Ar), 31.64, 30.55, 30.42, 30.30, 30.27, 29.44, 29.18, 22.70, 22.64, 22.61, 14.18, 14.12 (alkyl). MALDI-TOF: m/z 524.07 [M+1]+.

3,4'-Dihexyl-5''-((trimethylsilyl)ethynyl)-(2,2':5',2''-terthiophene)-5-carbaldehyde (8)

To a solution of compound 7 (2.3 g, 4.5 mmol) in a mixture of NEt3 and CH2Cl2 (50 mL, 1:1, v/v) was added a catalytic amount of CuI and Pd(PPh3)4 (0.2g) under nitrogen. After stirring for 30 min at RT, trimethylsilylacetylene (1.76 g, 18 mmol) was added and left overnight at 60 oC with constant stirring. The reaction mixture was dried and the crude product was purified by column chromatography on silica gel using hexane and dichloromethane (1:1, v/v) as the eluent to give compound 8(1.6 g, yield: 67%) as a yellow oil.

1HNMR (400MHz, CDCl3), δ(ppm): 9.82 (s, 1H, CHO), 7.58 (s,1H, Ar), 7.19 (s, 1H, Ar), 7.19–7.18 (d, J=4 Hz, 1H, Ar), 7.11 (s,1H, Ar), 7.01–7.00 (d, J=4 Hz, 1H, Ar), 2.82–2.74 (m, 4H, alkyl), 1.70–1.52 (m, 4H, alkyl), 1.42–1.26 (m, 12H, alkyl), 0.91–0.86 (m, 6H, alkyl), 0.26 (s, 9H, alkyl). 13C NMR (100 MHz, CDCl3), δ (ppm): 182.78 (CHO), 149.15, 144.57, 141.29, 140.43, 140.11, 139.18, 134.96, 128.17, 127.12, 124.43, 121.12, 119.01 (Ar), 85.38, 76.07 (C≡C), 31.60, 30.26, 30.09, 29.47, 29.43, 29.15, 28.93, 22.79, 22.63, 14.15, 14.11, 14.04, 3.40 (alkyl). MALDI-TOF: m/z 540.20 [M]+.

5''-Ethynyl-3,4'-dihexyl-(2,2':5',2''-terthiophene)-5-carbaldehyde (9)

Compound 8 (1.6 g, 3 mmol) and K2CO3 (0.44 g, 3.3 mmol) were dissolved in MeOH and CH2Cl2 (1:1, v/v) solvent mixture. The mixture was stirred for 6 h at RT. The reaction mixture was poured into water and extracted with CH2Cl2. The organic layer was washed thrice with water before drying over Na2SO4. After the removal of solvent, the crude product was purified by column chromatography on silica gel using hexane and dichloromethane (1:1, v/v) as eluent to afford compound9(0.8 g, yield: 57%) as an orange oil.

1HNMR (400MHz, CDCl3), δ(ppm): 9.83 (s, 1H, CHO), 7.59 (s,1H, Ar), 7.25–7.24 (d, J=4 Hz, 1H, Ar), 7.11 (s,1H, Ar), 7.03–7.02 (d, J=4 Hz, 1H, Ar), 3.44 (s, 1H, C≡CH), 2.81–2.76 (m, 4H, alkyl), 1.68–1.26 (m, 16H, alkyl), 0.91–0.87 (m, 6H, alkyl). 13C NMR (100 MHz, CDCl3), δ (ppm): 182.28 (CHO), 149.65, 146.12, 142.31, 140.89, 140.53, 140.44, 138.88, 134.96, 130.12, 128.17, 124.56, 119.12 (Ar), 85.38, 76.07 (C≡C). 31.81, 31.45, 30.11, 29.38, 29.13, 28.71, 22.67, 22.52, 14.26, 14.22 (alkyl), MALDI-TOF: m/z 468.16 [M]+.

Synthesis of compound 10

Compounds9(0.94 g, 0.22 mmol) and 4(0.067 g, 0.1 mmol) were added to a flask with 40 mL of THF/NEt3 (1:1, v/v), and the solution was flushed with nitrogen for 10 min. Then, 5.77 mg of Pd(PPh3)4 (0.005 mmol) and 0.8 mg CuI (0.01 mmol) were added and the solution was flushed again for 10 min. After being stirred at RT for 24 h under nitrogen, the reaction mixture was poured into water (100 mL) and extracted with CH2Cl2. The organic layer was washed with water and dried over Na2SO4. After the removal of solvent, the crude product was purified by column chromatography on silica gel using a mixture of hexane and dichloromethane (1:2, v/v) as the eluent to afford compound 10 as a red solid (155 mg, yield: 47%).

1HNMR (400MHz, CDCl3), δ (ppm): 9.81 (s, 2H, CHO), 7.57 (s, 2H, Ar), 7.09 (s, 2H, Ar), 6.96–6.95 (d, J=4 Hz, 2H, Ar), 6.80–6.79 (d, J=4 Hz, 2H, Ar), 2.83–2.74 (m, 8H, alkyl), 2.14–2.09 (m, 12H, alkyl), 1.68–1.24 (m, 66H, alkyl), 0.97–0.86 (m, 30H, alkyl). 13C NMR (100 MHz, CHCl3): δ(ppm): 182.41 (–C=O), 149.84 (C≡C), 144.40, 139.84, 135.45, 131.75, 131.57, 130.94, 130.86, 127.80, 123.45, 121.56, 114.56 (Ar), 113.62 (C≡C),75.43 (C≡C), 31.67, 31.58, 30.51, 30.13, 29.42, 29.32, 29.30, 28.16, 26.40, 24.71, 24.54, 24.37, 24.14, 22.63, 22.45, 14.42, 14.09, 13.89 (alkyl).31P NMR (161.9 MHz, CDCl3), δ (ppm): 3.15 (JP-Pt=2334 Hz). MALDI-TOF: m/z 1505.61 [M]+.