Significant improvement of dye-sensitized solar cell. performance by a slim phenothiazine based dyes

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1 Significant improvement of dye-sensitized solar cell performance by a slim phenothiazine based dyes Yong Hua, a Shuai Chang, b Dandan Huang, c Xuan Zhou, a Xunjin Zhu, *a,d Jianzhang Zhao, c Tao Chen, *b Wai-Yeung Wong, *a,c,d and Wai-Kwok Wong *a,d a Institute of Molecular Functional Materials, Department of Chemistry and Institute of Advanced Materials, Hong Kong Baptist University, Waterloo Road, Kowloon Tong, Hong Kong, P. R. China. Fax: ; Tel: ; xjzhu@hkbu.edu.hk; wkwong@hkbu.edu.hk; rwywong@hkbu.edu.hk. b Department of Physics, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, P. R. China. Fax: ; Tel: ; taochen@phy.cuhk.edu.hk c State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian, , P. R. China d HKBU Institute of Research and Continuing Education, Shenzhen Virtual University Park, Shenzhen, , P. R. China Contents i. Synthesis of intermediates 1a-1d, 2a-2d, and 3a-3d. ii. iii. Figure 1 H NMR, 13 C NMR and HRMS spectra of new compounds

2 General synthetic procedure for 1a-d Phenothiazine (2 g, 10 mmol), NaOH (0.5 g, 13 mmol) and 1-bromoalkane (11 mmol) were dissolved in 100 ml DMSO and the mixture was stirred overnight at room temperature. Then, the reaction mixture was poured into water and extracted with dichloromethane. The organic phase was collected and dried with anhydrous MgSO 4. After removal of the solvent, the residue was purified by column chromatography on silica gel using hexane as the eluent to give the product as a colorless liquid. 10-Ethyl-10H-phenothiazine (1a): 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 7.14 (d, J = 8.0 Hz, 4H), 6.85 (t, J = 8.0 Hz, 4H), 3.84 (t, J = 6.9 Hz, 2H), 1.39 (t, J = 5.1 Hz, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , 43.48, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 14 H 13 NS) ; found, Hexyl-10H-phenothiazine (1b): 2.45 g, 88% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 7.18 (d, J = 8.0 Hz, 4H), 6.87 (t, J = 8.0 Hz, 4H), 3.89 (t, J = 6.9 Hz, 2H), (m, 2H), (m, 6H), 0.88 (t, J = 5.1 Hz, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , 43.89, 31.62, 29.27, 25.79, 22.64, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 18 H 21 NS) ; found, Octyl-10H-phenothiazine (1c): 2.65 g, 79% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 7.43 (d, J = 8.0 Hz, 4H), 6.83 (t, J = 8.0 Hz, 4H), 3.94 (t, J = 6.9 Hz, 2H), (m, 2H), (m, 2H), (m, 8H), (m, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , 48.09, 31.92, 29.17, 29.13, 26.79, 26.53, 22.60, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 20 H 25 NS) ; found, Dodecyl-10H-phenothiazine (1d): 2.09 g, 76% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 7.23 (d, J = 8.0 Hz, 4H), 6.79 (t, J = 8.0 Hz, 4H), 3.90 (t, J = 6.9 Hz, 2H), (m, 4H), (m, 4H), (m, 12H), 0.86 (t, J = 5.1 Hz, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , 43.09, 31.69, 31.45, 29.78, 29.64, 29.54, 29.27, 26.36, 26.18, 25.79, 22.64, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 24 H 33 NS) ; found, General synthetic procedure for 2a-d 1a-d (0.71 g, 2.5 mmol) and dry DMF (0.73g, 10mmol) were dissolved in 1,2-dichloroethane (20 ml), and phosphorus oxychloride (1.54 g, 10 mmol) was added slowly at 0 C in an ice water bath. Then, the mixture was heated to reflux overnight. The reaction mixture was quenched with water and extracted three times with chloroform. The combined organic fractions were washed with brine and dried over MgSO 4. The solvent was removed under reduced pressure and the residue was purified by column chromatography on silica gel using n-hexane/dichloromethane (8/2; v/v) as the eluent to give 2a-d as yellow solids, respectively. 10-Ethyl-10H-phenothiazine-3-carbaldehyde (2a): 0.45 g, 56% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 9.79 (s, 1H), 7.64 (d, J = 8.0 Hz, 1H), 7.58 (d, J = 8.0 Hz, 1H), 7.49 (s, 1H), 7.21 (t, J = 8.0 Hz, 1H), 7.13 (d, J = 8.0 Hz, 1H), 6.85 (d, J = 8.0

3 Hz, 1H), 6.76 (t, J = 8.0 Hz, 1H), 3.85 (t, J = 6.9 Hz, 2H), 1.38 (t, J = 5.1 Hz, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , , , , , , , , 42.58, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 15 H 13 NOS) ; found, Hexyl-10H-phenothiazine-3-carbaldehyde (2b): 0.39 g, 58% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 9.82 (s, 1H), 7.64 (d, J = 8.0 Hz, 1H), 7.43 (s, 1H), 7.13 (t, J = 8.0 Hz, 1H), 7.10 (d, J = 8.0 Hz, 1H), 6.91 (d, J = 8.0 Hz, 2H), 6.85 (t, J = 8.0 Hz, 1H), 3.89 (t, J = 6.4 Hz, 2H), (m, 2H), (m, 6H), 0.86 (t, J = 6.4 Hz, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , , , , , , , , 48.10, 31.43, 26.56, 26.64, 22.36, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 19 H 21 NOS) ; found, (2-Octyl)-10H-phenothiazine-3-carbaldehyde (2c): 0.38 g, 53% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 9.79 (s, 1H), 7.66 (d, J = 8.0 Hz, 1H), 7.58 (d, J = 8.0 Hz, 1H), 7.42 (s, 1H), 7.20 (t, J = 8.0 Hz, 1H), 7.18 (d, J = 8.0 Hz, 1H), 6.90 (d, J = 8.0 Hz, 1H), 6.84 (t, J = 8.0 Hz, 1H), 3.84 (t, J = 6.9 Hz, 2H), (m, 2H), (m, 2H), (m, 8H), (m, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , , , , , , , , 48.12, 31.42, 29.18, 29.13, 26.99, 26.63, 22.61, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 21 H 25 NOS) ; found, (2-Dodecyl)-10H-phenothiazine-3-carbaldehyde (2d): 0.50 g, 49% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 9.80 (s, 1H), 7.64 (d, J = 8.0 Hz, 1H), 7.54 (d, J = 8.0 Hz, 1H), 7.42 (s, 1H), 7.19 (t, J = 8.0 Hz, 1H), 7.16 (d, J = 8.0 Hz, 1H), 6.88 (d, J = 8.0 Hz, 1H), 6.76 (t, J = 8.0 Hz, 1H), 3.85 (t, J = 6.9 Hz, 2H), (m, 2H), (m, 2H), (m, 16H), 0.86 (t, J = 5.1 Hz, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , , , , , , , , 48.01, 31.77, 31.12, 29.48, 29.04, 29.00, 28.28, 26.31, 26.08, 25.39, 22.12, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 25 H 33 NOS) ; found, General synthetic procedure for 3a-d NBS (411 mg, 2.31 mmol) was added in one portion to the solution of 2a-d (510 mg, 2.0 mmol) in THF (50 ml) at 0 C. The mixture was allowed to warm to room temperature and stirring was continued for 1.5 h. Then, the reaction was quenched by addition of water (50 ml), and extracted with dichloromethane. The collected organic layer was evaporated under vacuum and the residue was purified by column chromatography on silica gel with CH 2 Cl 2 as eluent to give 3a-d as yellow solids, respectively. 7-Bromo-10-ethyl-10H-phenothiazine-3-carbaldehyde (3a): 568 mg, 85% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 9.76 (s, 1H), (m, 1H), 7.49 (d, J = 2.0 Hz, 1H), (m, 1H), 7.14 (d, J = 8.4 Hz, 1H), 6.85 (d, J = 8.4 Hz, 1H), 6.67 (d, J = 8.0 Hz, 1H), 3.90 (t, J = 6.4 Hz, 2H), 1.39 (t, J = 6.4 Hz, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , ,

4 128.12, , , , , , 43.56, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 15 H 12 BrNOS) ; found, Bromo-10-hexyl-10H-phenothiazine-3-carbaldehyde (3b): 0.56 g, 89% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 9.80 (s, 1H), 7.64 (d, J = 8.0 Hz, 1H), 7.13 (t, J = 8.0 Hz, 1H), 7.10 (d, J = 8.0 Hz, 1H), 6.91 (d, J = 8.0 Hz, 2H), 6.85 (t, J = 8.0 Hz, 1H), 3.89 (t, J = 6.4 Hz, 2H), (m, 2H), (m, 6H), 0.86 (t, J = 6.4 Hz, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , , , , , , , , 48.10, 31.43, 26.56, 26.64, 22.36, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 19 H 20 BrNOS) ; found, Bromo-10-octyl-10H-phenothiazine-3-carbaldehyde (3c): 0.44 g, 87% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 9.78 (s, 1H), (m, 1H), 7.54 (d, J = 2.0 Hz, 1H), (m, 1H), 7.20 (d, J = 2.0 Hz, 1H), 6.87 (d, J = 8.4 Hz, 1H), 6.68 (d, J = 8.0 Hz, 1H), 3.82 (t, J = 8.8 Hz, 2H), (m, 2H), (m, 2H), (m, 8H), 0.87 (t, J = 8.4 Hz, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , , , , , , , , 48.09, 31.72, 29.18, 29.12, 26.75, 26.62, 22.63, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 21 H 24 BrNOS) ; found, Bromo-10-dodecyl-10H-phenothiazine-3-carbaldehyde (3d): 0.36 g, 82% yield. 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 9.79 (s, 1H), (m, 1H), 7.55 (d, J = 2.0 Hz, 1H), (m, 1H), 7.20 (d, J = 2.0 Hz, 1H), 6.87 (d, J = 8.4 Hz, 1H), 6.69 (d, J = 8.0 Hz, 1H), 3.83 (t, J = 8.8 Hz, 2H), (m, 2H), (m, 2H), (m, 16H), 0.85 (t, J = 8.4 Hz, 3H). 13 C NMR (400 MHz, CDCl 3 ): δ (ppm) , , , , , , , , , , , , , 48.09, 31.72, 29.18, 29.12, 26.75, 26.62, 22.63, HRMS (MALDI-TOF, m/z): [M + ] calcd for (C 25 H 32 BrNOS) ; found, Voltage (V) Time(s) PT-C2 PT-C6 PT-C8 PT-C12 N719 Figure S1 Open-circuit voltage decay profiles of DSSCs based on PT-Cn and N719.

5 iii. 1 H NMR, 13 C NMR and HRMS spectra

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