Two New Dyes with Carboxypyridinium Regioisomers as Anchoring Groups for Dye-Sensitized Solar Cells

This paper is dedicated to the memory of Prof. Manfred Schlosser

Abstract

Two new organic dye-sensitized solar cell (DSSC) sensitizers bearing regioisomeric carboxyl-N-methylpyridinium moieties were prepared and fully characterized. Based on TD-DFT calculations, they were anticipated to show a significantly red-shifted absorption spectrum compared to normal carboxypyridines and other regioisomeric pyridinium salts. Although this prediction was met, the two regioisomers unexpectedly showed very different stabilities upon adsorption on TiO₂.

Key words

organic dyes - photosensitizer - regioisomers - dye-sensitized solar cells - photostability

• References and Notes

• 1 O’Regan B, Grätzel M. Nature (London, U.K.) 1991; 353: 737
• 2 Hagfeldt A, Boschloo G, Sun L, Kloo L, Pettersson H. Chem. Rev. 2010; 110: 6595
• 3a Ooyama Y, Harima Y. ChemPhysChem 2012; 13: 4032
• 3b Lee C.-P, Lin RY.-Y, Lin L.-Y, Li C.-T, Chu T.-C, Sun S.-S, Lin JT, Ho K.-C. RSC Adv. 2015; 5: 23810
• 4 Kim BG, Chung K, Kim J. Chem. Eur. J. 2013; 19: 5220
• 5 Zhang L, Cole JM. ACS Appl. Mater. Interfaces 2015; 7: 3427
• 6a Ooyama Y, Inoue S, Nagano T, Kushimoto K, Ohshita J, Imae I, Komaguchi K, Harima Y. Angew. Chem. Int. Ed. 2011; 50: 7429
• 6b Delcamp JH, Aswani Y, Nazeeruddin MK, Grätzel M. Chem. Commun. 2012; 48: 2295
• 6c Harima Y, Fujita T, Kano Y, Imae I, Komaguchi K, Ooyama Y, Ohshita J. J. Phys. Chem. C 2013; 117: 16364
• 7 Cecconi B, Mordini A, Reginato G, Zani L, Taddei M, Fabrizi de Biani F, De Angelis F, Marotta G, Salvatori P, Calamante M. Asian J. Org. Chem. 2014; 3: 140
• 8 Franchi D, Calamante M, Reginato G, Zani L, Peruzzini M, Taddei M, Fabrizi de Biani F, Basosi R, Sinicropi A, Colonna D, Di Carlo A, Mordini A. Tetrahedron 2014; 70: 6285
• 9a Cheng M, Yang X, Li J, Chen C, Zhao J, Wang Y, Sun L. Chem. Eur. J. 2012; 18: 16196
• 9b Zhao J, Yang X, Cheng M, Li S, Sun L. ACS Appl. Mater. Interfaces 2013; 5: 5227
• 10 Tian J, Yang X, Zhao J, Wang L, Wang W, Lia J, Sun L. RSC Adv. 2014; 4: 34644
• 11 Complete Gaussian 09 reference: see Supporting Information.
• 12a Becke AD. J. Chem. Phys. 1993; 98: 5648
• 12b Stephens PJ, Devlin FJ, Chabalowski CF, Frisch MJ. J. Phys. Chem. 1994; 9: 11623
• 12c Lee C, Yang W, Parr RG. Phys. Rev. B 1998; 37: 785
• 12d Lynch BJ, Fast PL, Harris M, Truhlar DG. J. Phys. Chem. A 2000; 104: 4811
• 12e Yanai T, Tew D, Handy N. Chem. Phys. Lett. 2004; 393: 51
• 13 Synthesis of Compound DF39ACompound 2a (25 mg, 0.03 mmol, 1.0 equiv) was dissolved in dry THF (0.5 mL), then Pd(PPh₃)₄ (4 mg, 0.003 mmol, 0.1 equiv) and AcOH (30 μL, 0.34 mmol, 10.0 equiv) were added. The solution was stirred at r.t. for 4 h, then the reaction mixture was diluted with Et₂O (1 mL), and washed with H₂O (2 × 10 mL) and brine (10 mL). The organic phase was dried over Na₂SO₄, then the solvent was removed under reduced pressure, and the crude product purified by preparative TLC (CH₂Cl₂–MeOH = 10:1). A red-violet amorphous solid was recovered (15 mg, 0.02 mmol, yield 65%). ¹H NMR(200 MHz, DMSO-d ₆): δ = 9.35 (1 H, s), 8.70 (1 H, d, J = 7.3 Hz) 8.16 (1 H, d, J = 8.8 Hz), 7.80 (1 H, d, J = 3.7 Hz), 7.54–7.31 (3 H, m), 7.29–6.80 (10 H, m), 6.70 (2 H, d, J = 7.7 Hz), 4.40 (3 H, s), 3.91 (4 H, t, J = 6.2 Hz), 1.80–1.51 (16 H, m), 1.48–0.98 (6 H, m) ppm. ¹³C NMR{¹H} (50 MHz, DMSO-d ₆): δ = 155.9, 150.6, 149.2, 148.8, 148.4, 146.2, 144.0, 139.6, 135.7, 131.9, 130.1, 129.9, 129.2, 128.4, 128.3, 127.5, 126.8, 118.6, 117.6, 115.8, 68.0, 48.0, 31.4, 29.1, 25.4, 22.5, 14.3 ppm. IR (KBr): 3681, 3051, 2931, 1724, 1595 cm^–1. HRMS: m/zcalcd for C₄₃H₄₉N₂O₄S: 689.3413; found: 689.3422 [M⁺].
• 14 Synthesis of Compound DF39CEster 1b (73 mg, 0.10 mmol, 1.0 equiv) was dissolved in dry CH₂Cl₂ (1.7 mL), the solution was cooled to 0 °C, then Cs₂CO₃ (150 mg, 0.46 mmol, 4.5 equiv), and trimethyloxonium tetrafluoroborate (Me₃OBF₄, 80 mg, 0.54 mmol, 5.4 equiv) were added. The solution was stirred at 0 °C for 15 min, then warmed to r.t. and left under stirring overnight. The reaction mixture was diluted with CH₂Cl₂ (10 mL), the organic phase was washed with a cold sat. solution of NH₄Cl (10 mL), and the aqueous solution extracted with CH₂Cl₂ (2 × 10 mL). The combined organic phases were dried over Na₂SO₄. The solvent was removed under reduced pressure, and the crude product was purified by preparative TLC (CH₂Cl₂–MeOH = 10:1). A red-violet amorphous solid was recovered (59 mg, 0.08 mmol, yield 65%). ¹H NMR(200 MHz, CDCl₃): δ = 8.56 (1 H, d, J = 6.2 Hz), 8.13 (1 H, d, J = 3.9 Hz), 8.02–7.98 (2 H, m), 7.41 (2 H, d, J = 8.6 Hz), 7.33 (1 H, d, J = 3.7 Hz), 7.27 (1 H, d, J = 16.0 Hz) 7.10 (1 H, d, J = 16.0 Hz), 7.02 (4 H, d, J = 8.9 Hz), 6.90 (4 H, d, J = 8.9 Hz) 6.70 (2 H, d, J = 8.6 Hz), 4.18 (3 H, s), 3.92 (4 H, t, J = 6.5 Hz), 1.77–1.57 (4 H, m), 1.52–1.34 (4 H, m), 1.34–1.25 (8 H, m), 0.86 (6 H, t, J = 6.8 Hz) ppm. ¹³C NMR{¹H} (100 MHz, CDCl₃): δ = 156.0, 149.7, 145.1, 139.8, 138.6, 135.2, 133.4, 133.2, 128.0, 127.9, 127.2, 127.1, 127.0, 126.6, 120.1, 119.2, 117.0, 116.6, 115.6, 115.3, 68.3, 31.6, 31.5, 29.3, 25.7, 22.6, 14.0 ppm. IR (KBr): 3676, 3056, 2978, 1658, 1593 cm^–1. HRMS: m/z calcd for C₄₃H₄₉N₂O₄S: 689.3413; found: 689.3428 [M⁺].
• 15 Chang YJ, Chow TJ. J. Mater. Chem. 2011; 21: 9523
• 16 Hagberg DP, Jiang X, Gabrielsson E, Linder M, Marinado T, Brinck T, Hagfeldt A, Sun L. J. Mater. Chem. 2009; 19: 7232
• 17 Listorti A, O’Regan B, Durrant JR. Chem. Mater. 2011; 23: 3381
• 18a Dyson P, Hammick DL. J. Chem. Soc. 1937; 1724
• 18b Ashworth MR. F, Daffern RP, Hammick DL. J. Chem. Soc. 1939; 809
• 19a Brown BR, Hammick DL. J. Chem. Soc. 1949; 659
• 19b Haake P, Mantecon J. J. Am. Chem. Soc. 1964; 86: 5230
• 20a Kraeutler B, Bard AJ. J. Am. Chem. Soc. 1978; 100: 5985
• 20b Soja GR, Watson DF. Langmuir 2009; 25: 5398