Supporting information

Transcription

1 Supporting information Organic Dyes Incorporating Oligothienylenevinylene for Efficient Dye-sensitized Solar Cells Ana Aljarilla, a Leticia López-Arroyo, a Pilar de la Cruz, a Frederic Oswald, b, * Toby B. Meyer, b and Fernando Langa a, * a Instituto de Nanociencia, Nanotecnología y Materiales Moleculares (INAMOL), Universidad de Castilla-La Mancha, Toledo, Spain b Solaronix SA, Rue de l Ouriette 129, 1170 Aubonne, Switzerland Fernando.Langa@uclm.es, frederic.oswald@solaronix.com Table of contents 1- Experimental conditions S1 2- Synthetic procedures and analytical data S2 3-1 H NMR, 13 C NMR, FT-IR and MALDI-TOF o MS spectra S8 4- UV-Visible and emission spectroscopies S21 5- Square Wave plots of 1a and 1b S24 6- Frontier Orbitals of 1a and 1b S25 7- Tables S1-S5 S26

2 1.- Experimental conditions Synthetic procedures were carried out under inert argon atmosphere, in dry solvent unless otherwise noted. All reagents and solvents were reagent grade and were used without further purification. Chromatographic purifications were performed using silica gel 60 SDS (particle size mm). Analytical thin-layer chromatography was performed using Merck TLC silica gel 60 F H NMR spectra were obtained on Bruker TopSpin AV-400 (400 MHz) spectrometer. Chemical shifts are reported in parts per million (ppm) relative to the solvent residual peak (CDCl 3, 7.27 ppm). 13 C NMR chemical shifts are reported relative to the solvent residual peak (CDCl 3, ppm). UV-Vis measurements were carried out on a Shimadzu UV 3600 spectrophotometer. For extinction coefficient determination, solutions of different concentration were prepared in CH 2 Cl 2, HPLC grade, with absorption between of absorbance using a 1 cm UV cuvette. The emission measurements were carried out on Cary Eclipse fluorescence spectrophotometer. Mass spectra (MALDI-TOF) were recorded on a VOYAGER DE TM STR mass spectrometer using dithranol as matrix. Melting points are uncorrected. The molecular geometries and frontier molecular orbitals of these new dyes have been optimized by density functional theory (DFT) calculations at the B3LYP/6-31G* level. 1 Cyclic voltammetry was performed in o-dichlorobenzene/acetonitrile (4:1) solutions. Tetrabutylammonium perchlorate (0.1 M as supporting electrolyte) were purchased from Acros and used without purification. Solutions were deoxygenated by argon bubbling prior to each experiment which was run under argon atmosphere. Experiments were done in a one-compartment cell equipped with a platinum working microelectrode ( = 2 mm) and a platinum wire counter electrode. An Ag/AgNO 3 (0.01 M in CH 3 CN) electrode was used as reference and checked against the ferrocene/ferrocenium couple (Fc/Fc + ) before and after each experiment. 1 Gaussian 03, Revision D.02, Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery Jr., J. A.; Vreven, T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian, Inc., Wallingford CT, S1

3 2.- Synthetic procedures and analytical data. R N R OH B HO S O H Br K 2 CO 3, PdCl 2 (dppp) Toluene, MeOH reflux, 17 h R R N 1) NaBH 4 CH 2 Cl 2 /MeOH rt, 1 h N S H 2) I 2 /PO(OEt) 3 S O 0 ºC, 15 h 2a; 2b 3a; 3b R R O O P O R R 2TV2CHO ButOK THF rt, 5 h N S S C 6 H 13 C 6 H 13 C 6 H 13 C6 H 13 CN S COOH Cyanoacetic acid Piperidine CHCl 3 reflux 22 h N S C 6 H 13 C6 H 13 S S CHO C 6 H 13 C 6 H 13 R 1a; 1b R 4a; 4b a R = H b R = OC 6 H General procedure for the synthesis of 2a and 2b. To a solution of corresponding bromide (1 mmol) and PdCl 2 (dppf) (0.1 mmol) in dry toluene (8 ml/mmol) was added a solution of 5-formylthiophene-2-yl-2-boronic acid (2 mmol) and K 2 CO 3 (5 mmol) in dry methanol (8 ml/mmol). The mixture was refluxed for 18 h. The reaction was quenched by the addition of water (20 ml) and extracted with CH 2 Cl 2 (3 x 25 ml). The combined organic extract was dried over anhydrous MgSO 4 and filtered. Solvent was removal by rotary evaporation followed. The product was purified by column chromatography (silica gel, Hex/CH 2 Cl 2, 2:3) Synthesis of 5-(4-(diphenylamino)phenyl)thiophene-2-carboxaldehyde (2a): From 1.00 g of 4- bromo-n,n-bis(diphenyl)aniline (Aldrich, 97%) (3.1 mmol) and 966 mg of 5-formylthiophene-2-yl-2-boronic S2

4 acid (6.2 mmol), reacted as the general procedure, giving 846 mg of 2a as yellow solid (77% yield). 1 H NMR (400 MHz, CDCl 3 ) δ/ppm: 10.0 (s, 1H), 7.70 (d, 1H, J = 4.0 Hz), 7.50 (d, 2H, J = 8.7 Hz), 7.30 (d, 1H, J = 4.0 Hz), 7.25 (d, 4H, J = 8.0 Hz), 7.11 (d, 4H, J = 8.0 Hz), 7.06 (t, 2H, J = 7.0 Hz), 7.04 (d, 2H, J = 7.0 Hz). 13 C NMR (100 MHz, CDCl 3 ) δ/ppm: 182.7, 154.6, 149.1, 147.0, 141.3, 137.8, 135.2, 129.5, 127.3, 126.1, 125.2, 125.0, 123.9, 122.9, MS (m/z) (MALDI-TOF): calculated C 23 H 17 NOS: ; found (M+H + ): , , Synthesis of 5-(4-(bis(4-hexyloxy)phenyl)amino)phenyl)thiophene-2-carboxaldehyde (2b): From 1.00 g of 4-bromo-N,N-bis(4-(hexyloxy)phenyl)aniline (1.9 mmol) and 595 mg of 5-formylthiophene-2-yl-2- boronic acid (3.8 mmol) reacted as the general procedure giving 795 mg of 2b as yellow solid (75% yield). 1 H NMR (400 MHz, CDCl 3 ) δ/ppm: 9.84 (s, 1H), 7.70 (d, 1H, J = 4.0 Hz), 7.46 (d, 2H, J = 8.8 Hz), 7.26 (d, 1H, J = 4.0 Hz), 7.09 (d, 4H, J = 8.8 Hz), 6.90 (d, 2H, J = 8.8 Hz), 6.85 (d, 4H, J = 8.8 Hz), 3.95 (t, 4H, J = 6.5 Hz), (m, 4H), (m, 4H), (m, 8H), 0.92 (t, 6H, J = 7.0 Hz). 13 C NMR (100 MHz, CDCl 3 ) δ/ppm: 207.1, 182.5, 156.1, 155.2, 150.0, 140.7, 139.7, 137.9, 127.2, 127.1, 124.0, 122.2, 119.2, 115.4, 68.2, 31.6, 29.3, 25.7, 22.6, MS (m/z) (MALDI-TOF): calculated C 35 H 41 NO 3 S: ; found (M+H + ): , , General procedure for the synthesis of 3a and 3b. In an inert atmosphere, NaBH 4 (1.2 mmol) was added to a solution of corresponding aldehyde (1 mmol) in 25 ml of a mixture of CH 2 Cl 2 \MeOH (1:1) and stirred at room temperature for 1h. The reaction was hydrolyzed with water then the aqueous phase extracted with chloroform. The organic phase was dried over MgSO 4 and concentrated. Without further purification, the alcohol (1 mmol) was added over a mixture of triethylphosphate (5 ml/mmol) and iodine (0.82 mmol), cooled at -20 ºC and stirred for 15 h at under inert atmosphere. After removal of triethyl phosphate at reduced pressure, the crude was purified by column chromatography (silica gel, AcOEt/CH 2 Cl 2, 1:5) Synthesis of diethyl (5-(4-(diphenyl)amino)phenyl)thiophen-2-yl)methylphosphonate (3a): From 600 mg of 2a (1.7 mmol) reacted as the general procedure giving 580 mg of 3a as yellow oil (72% yield). 1 H NMR (400 MHz, CDCl 3 ) δ/ppm: 7.43 (d, 2H, J = 8.4 Hz), 7.27 (t, 2H, J = 7.7 Hz), 7.12 (d, 4H, J = 7.7 Hz), S3

5 7.00 (m, 7H), 6.92 (t, 1H, J = 3.5 Hz), 4.11 (q, 4H, J = 7.2 Hz), 3.37 (d, 2H, J = 21 Hz), 1.31 (t, 6H, J = 7.2 Hz). 13 C NMR (100 MHz, CDCl 3 ) δ/ppm: , , , , , , , , , , , , , , , , , 62.49, 62.42, 28.98, 16.42, IR ν/cm - 1 : 1689, 1491, 1274, 1021, 964, 755, 731, 698. MS (m/z) (MALDI-TOF): calculated C 27 H 28 NO 3 PS: ; found (M+H + ):477.2, 478.2, 479.2, Synthesis of diethyl (5-(4-(bis(4-hexyloxy)phenyl)amino)phenyl) thiophen-2-yl) methylphosphonate (3b): From 500 mg of 2b (0.9 mmol) reacted as the general procedure giving 580 mg of 470 mg 3b as yellow oil (77% yield). 1 H NMR (400 MHz, CDCl 3 ) δ/ppm: 7.35 (d, 2H, J = 8.4 Hz), 7.05 (d, 4H, J = 8.8 Hz), 7.02 (d, 1H, J = 3.5 Hz), 6.91 (d, 1H, J = 3.5 Hz), 6.90 (d, 2H, J = 8.4 Hz), 6.82 (d, 4H, J = 8.8 Hz), 4.10 (q, 4H, J = 7.2 Hz), 3.93 (t, 4H, J = 6.5 Hz), 3.35 (d, 2H, J = 20.7 Hz), 1.76 (dq, 4H, J = 15.2, 7.2 Hz), 1.43 (q, 4H, J = 7.2 Hz), (m, 8H), 1.30 (t, 6H), 0.92 (t, 6H, J = 7.2 Hz). 13 C NMR (100 MHz, CDCl 3 ) δ/ppm: , , , , , , , , , , , , , , , , 68.24, 62.55, 62.48, 31.62, 29.33, 25.78, 22.64, 16.47, 16.41, IR ν/cm -1 : 2953, 2933, 2859, 1505, 1470, 1235, 1053, 1028, 828. MS (m/z) (MALDI-TOF): calculated C 39 H 52 NO 5 PS: ; found (M+H + ): , , General procedure for the synthesis of 4a and 4b. Potassium tert-butoxide (2 mmol) was slowly added to a solution of corresponding phosphonate (1 mmol) and bisformyl oligothienylenevinylene dimer (OHC-2TV-CHO) (2 mmol) in dry THF (120 ml/mmol) under argon atmosphere. The reaction mixture was stirred at room temperature, the reaction was hydrolyzed with water (10 ml) and then extracted with CH 2 Cl 2 (3 x 20 ml). The organic phases were dried with MgSO 4, filtrated and the solvent was removed in vacuo. The product was purified by column chromatography (silica gel, CH 2 Cl 2 /hexane, 1:2) Synthesis of 5-[(E)-2-(3,4-dihexyl-5-[(E)-2-(5-(4-diphenylanimo)phenyl] thiophen-2- yl)vinyl]thiophen-2-yl)vinyl]-3,4-dihexylthiophene-2-carboxaldehyde (4a): From 350 mg of 3a (0.73 mmol), 857 mg of bisformyl oligothienylenevinylene dimer (1.5 mmol) reacted 6 h as the general procedure giving 424 mg of 4a as red oil (64% yield). 1 H NMR (400 MHz, CDCl 3 ) δ/ppm: (s, 1H), 7.50 (d, 2H, J = S4

6 8.7 Hz), 7.29 (d, 2H, J = 7.5 Hz), 7.28 (d, 4H, J = 7.6 Hz), (m, 4H), (m, 6H), 6.99 (d, 1H, J = 3.8 Hz), 6.95 (d, 1H, J = 15.7 Hz), 2.87 (dd, 2H, J = 6.90 Hz), (m, 6H), (m, 8H), (m, 24H), (m, 12H). 13 C NMR (100 MHz, CDCl 3 ) δ/ppm: , , , , , , , , , , , , , , , , , , , , , , , , , 32.26, 31.61, 31.57, 31.52, 31.46, 31.20, 31.12, 29.40, 29.34, 29.31, 27.17, 27.12, 27.00, 26.37, 22.63, UV-Vis (CH 2 Cl 2 ) λ max /nm(log ε): 300 (4.92), 492 (4.76). IR ν/cm -1 : 2953, 2923, 2853, 1648, 1588, 1491, 1277, 695. MS (m/z) (MALDI-TOF): calculated C 59 H 73 NOS 3 : ; found (M+H + ): , , Synthesis of 5-[(E)-2-(3,4-dihexyl-5-[(E)-2-(5-(4-(4-bis(hexyloxy)phenyl)animo) phenyl]thiophen-2- yl)vinyl]thiophen-2-yl)vinyl]-3,4-dihexylthiophene-2-carboxaldehyde (4b): From 400 mg of 3b (0.60 mmol), 700 mg of bisformyl oligothienylenevinylene dimer (1.2 mmol) reacted 6 h as the general procedure giving 399 mg of 4b as red oil (60% yield). 1 H NMR (400 MHz, CDCl 3 ) δ/ppm: 9.98 (s, 1H), 7.40 (d, 2H, J = 8.7 Hz), (m, 2H), 7.07 (d, 1H, J = 15.0 Hz), 7.06 (m, 4H), (m, 2H), 6.94 (d, 1H, J = 15.0 Hz), 6.91 (d, 2H, J = 8.7 Hz), 6.84 (d, 4H, J = 8.9 Hz), 3.90 (t, 4H, J = 6.5 Hz), (m, 2H), (m, 6H), 1.80 (dt, 4H, J = 15.0, 6.5), (m, 44 H), (m, 18 H). 3 C NMR (100 MHz, CDCl 3 ) δ/ppm: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , 68.23, 32.26, 31.68, 31.59, 31.53, 31.50, 31.35, 31.19, 31.12, 29.69, 29.40, 29.30, 27.10, 26.96, 26.55, 26.37, 22.63, 22.61, 22.55, 14.16, , UV-Vis (CH 2 Cl 2 ) λ max /nm (log ε): 301 (4.47); 503 (4.80). IR ν/cm -1 : 2954, 2926, 2856, 1652, 1504, MS (m/z) (MALDI-TOF): calculated C 71 H 97 NO 3 S 3 : ; found (M+H + ): , , , , S5

7 2.4- General procedure for the synthesis of 1a and 1b. To a solution of corresponding aldehyde (1 mmol) in CHCl 3 (30 ml/mmol) under argon were added cyanoacetic acid (1.5 mmol) and piperidine (0.1 mmol). The reaction was stirred at refluxed. After cooling to room temperature, the reaction crude concentrated at reduced pressure and was purified by column chromatography (silica gel, CH 3 Cl 3 /CH 3 OH, 95:5) Synthesis of (E)-2-cyano-3-(5-[(E)-2-(3,4-dihexyl-5-[(E)-2-(5-(4-diphenylani-mo)phenyl]thiophen-2- yl)vinyl]thiophen-2-yl)vinyl]-3,4-dihexylthiophen-2-yl)acrylic acid (1a): From 100 mg of 4a (0.11 mmol) and 14 mg of cyanoacetic acid (0.16 mmol) reacted 7 h as the general procedure giving 76 mg of 1a as a blue solid (71% yield). 1 H NMR (400 MHz, CDCl 3 ) δ/ppm: 8.41 (s broad, 1H), 7.46 (d, 2H, J = 8.5 Hz), (m, 4H), (m, 5H), (m, 4H), 7.00 (s, 2H), (m, 2H), 2.87 (dd, 2H, J = 6.90 Hz), (m, 6H), (m, 8H), (m, 24H), (m, 12H). 13 C NMR (100 MHz, CDCl 3 ) δ/ppm: , , , , , , , , , , , , , , , , , , , , , , , 32.16, 32.03, 31.91, 31.61, 31.56, 31.48, 31.23, 30.98, 29.68, 29.37, 29.24, 27.67, 27.13, 27.00, 26.79, 26.36, 23.42, 22.66, 22.62, UV-Vis (CH 2 Cl 2 ) λ max /nm(log ε): 307 (4.45), 350 (4.25), 429 (4.30), 557 (4.62). IR ν/cm -1 : 2953, 2923, 2853, 1548, 1240, 695. MS (m/z) (MALDI-TOF): calculated C 62 H 74 N 2 O 2 S 3 : ; found (M+H + ): 974.5, 975.5, 976.5, 977.5, Synthesis of (E)-2-cyano-3-(5-[(E)-2-(3,4-dihexyl-5-[(E)-2-(5-(4-(4- bis(hexyloxy)phenyl)animo)phenyl]thiophen-2-yl)vinyl]thiophen-2-yl)vinyl]-3,4-dihexylthiophen-2- yl)acrylic acid (1b): From 100 mg of 4b (0.09 mmol) and 12 mg of cyanoacetic acid (0.14 mmol) reacted 3 h S6

8 as the general procedure giving 90 mg of 1b as a blue solid (85% yield). 1 H NMR (400 MHz, CDCl 3 ) δ/ppm: 8.41 (s broad, 1H), 7.40 (d, 2H, J = 8.8 Hz), 7.29 (d, 2H, J = 14.0 Hz), 7.08 (d, 1H, J = 3.6 Hz), 7.07 (d, 4H, J = 8.8 Hz), 6.98 (m, 3H), 6.97 (d, 1H, J = 3.6 Hz), 6.91 (d, 2H, J = 8.8 Hz), 6.84 (d, 4H, J = 8.8 Hz), 3.94 (t, 4H, J = 6.5 Hz), 2.64 (m, 8H), 1.79 (dq, 4H, J = 8.5, 6.5 Hz), (m, 44H), (m, 18H). 13 C NMR (100 MHz, CDCl 3 ) δ/ppm: , , , , , , , , , , , , , , , , , , , , , , , 93.30, 68.23, 31.59, 31.56, 29.34, 29.32, 29.29, 29.24, 25.74, 22.60, 14.17, 14.13, 14.08, UV-Vis (CH 2 Cl 2 ) λ max /nm (log ε): 308 (4.61), 348 (4.30), 432 (4.43), 564 (4.81). IR ν/cm -1 : 3436, 2953, 2924, 2852, 1551, 1504, 1385, MS (m/z) (MALDI-TOF): calculated C 74 H 98 N 2 O 4 S 3 : ; found (M+H + ): , , , , S7

9 3-1 H NMR, 13 C NMR and IR spectra. Figure S1. 1 H NMR spectrum (400 MHz, CDCl 3 ) of compound 1a. Figure S2. 13 C NMR spectrum (100 MHz, CDCl 3 ) of compound 1a. S8

10 C 6 H 13 O N S C 6 H 13 C 6 H 13 S CN S COOH C 6 H 13 C 6 H 13 C 6 H 13 O 1b Figure S3. 1 H NMR spectrum (400 MHz, CDCl 3 ) of compound 1b. Figure S4. 13 C NMR spectrum (100 MHz, CDCl 3 ) of compound 1b. S9

11 Figure S5. 1 H NMR spectrum (400 MHz, CDCl 3 ) of compound 2a. Figure S6. 13 C NMR spectrum (100 MHz, CDCl 3 ) of compound 2a. S10

12 C 6 H 13 O N S CHO C 6 H 13 O 2b Figure S7. 1 H NMR spectrum (400 MHz, CDCl 3 ) of compound 2b ppm Figure S8. 13 C NMR spectrum (100 MHz, CDCl 3 ) of compound 2b. S11

13 N 3a S O O P O Figure S9. 1 H NMR spectrum (400 MHz, CDCl 3 ) of compound 3a. Figure S C NMR spectrum (100 MHz, CDCl 3 ) of compound 3a. S12

14 Figure S11. 1 H NMR spectrum (400 MHz, CDCl 3 ) of compound 3b ppm Figure S C NMR spectrum (100 MHz, CDCl 3 ) of compound 3b. S13

15 Figure S13. 1 H NMR spectrum (400 MHz, CDCl 3 ) of compound 4a ppm Figure S C NMR spectrum (100 MHz, CDCl 3 ) of compound 4a. S14

16 C 6 H 13 O N S C 6 H 13 C6 H 13 S S CHO C 6 H 13 C 6 H 13 C 6 H 13 O 4b Figure S15. 1 H NMR spectrum (400 MHz, CDCl 3 ) of compound 4b. Figure S C NMR spectrum (100 MHz, CDCl 3 ) of compound 4b. S15

17 Figure S17. MALDI-MS spectrum of compound 1a (Matrix: Ditranol). Voyager Spec #1=>BC=>NR(2.00)=>NR(2.00)=>AdvBC(32,0.5,0.1)=>MC[BP = 227.1, 7071] % Intensity Mass (m/z) Figure S18. MALDI-MS spectrum of compound 1b (Matrix: Ditranol). S16

18 Figure S19. MALDI-MS spectrum of compound 3a (Matrix: Ditranol). Figure S20. MALDI-MS spectrum of compound 3b (Matrix: Ditranol). S17

19 100 Voyager Spec #1=>BC=>AdvBC(32,0.5,0.1)=>NR(1.00)=>NR(1.00)=>NR(1.00)=>MC[BP = 907.6, 1821] % Intensity Mass (m/z) Figure S21. MALDI-MS spectrum of compound 4a (Matrix: Ditranol). Figure S22. MALDI-MS spectrum of compound 4b (Matrix: Ditranol). S18

20 Figure S23. FT-IR spectrum of compound 1a. Figure S24. FT-IR spectrum of compound 1b. S19

21 Figure S25. FT-IR spectrum of compound 4a. Figure S26. FT-IR spectrum of compound 4b. S20

22 4.- UV-Visible and emission spectroscopies A) B) 0,7 0,6 CH 2 Cl 2, 1.32 x 10-5 M 1,2 1,0 CH 2 Cl 2, 1.62 x 10-5 M 0,5 Absorbance / a.u. 0,4 0,3 0,2 Absorbance / a.u. 0,8 0,6 0,4 0,1 0,2 0,0 0, Wavelength / nm Wavelength / nm Figure S27. UV-Vis absorption spectra of compounds 4a (A) and 4b (B) in CH 2 Cl 2. A) B) 1,1 Absorbance / a.u. 1,1 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0-0, Wavelength / nm CH 2 Cl 2 THF EtO 2 Absorbance / a.u. 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0-0, Wavelength / nm CH 2 Cl 2 THF Et 2 O Figure S28. Normalized UV-Vis spectra of compound 1a (A) and 1b (B) in dichloromethane ( ), diethyl ether ( ) and tetrahydrofuran ( ). S21

23 b 1a A Wavelength / nm Figure S29. Energy transitions of the low energy band for dyes 1a (blue) and 1b (red) vs Taft constant of solvents. 1,0 1,0 Absorbance / a.u. 0,8 0,6 0,4 0,8 0,6 0,4 Intensity / % 0,2 0,2 0, Wavelength / nm 0,0 Figure S30. Normalized UV-Vis absorption spectra (solid line) and normalized fluorescence emission spectra (dash line) of 1a in CH 2 Cl 2. S22

24 1,0 1,0 0,8 0,8 Absorbance / a.u. 0,6 0,4 0,6 0,4 Intensity / % 0,2 0,2 0, Wavelength / nm 0,0 Figure S31. Normalized UV-Vis absorption spectra (solid line) and normalized fluorescence emission spectra (dash line) of 1b in CH 2 Cl 2. S23

25 5-. Square Wave plots of 1a and 1b 1,2x10-5 1,0x10-5 8,0x10-6 i / ma 6,0x10-6 4,0x10-6 2,0x10-6 0,0-0,2-0,1 0,0 0,1 0,2 0,3 0,4 0,5 0,6 E / V Figure S32. Square Ware Voltammetry plot (cathodic window) of compound 1a (referred to Fc/Fc + ). 3,0x10-6 2,5x10-6 2,0x10-6 i / ma 1,5x10-6 1,0x10-6 5,0x ,2-0,1 0,0 0,1 0,2 0,3 0,4 0,5 Figure S33. Square Ware Voltametry plot (cathodic window) of compound 1b (referred to Fc/Fc + ). E / V S24

26 6.- Frontier Orbitals of 1a and 1b ev LUMO ev LUMO E / ev -4 E = 1.99 ev ev HOMO ev HOMO -1 Figure S34. Energy levels of frontier Molecular Orbitals of 1a. E / ev -2,0-2,5-3,0-3,5-4,0-4,5-5,0-5,5 E = 1.87 ev ev LUMO ev LUMO ev HOMO ev HOMO -1 Figure S35. Energy levels of frontier Molecular Orbitals of 1b. S25

27 Table S1. UV-Vis data of compound 1a. λ max/ nm A ε log ε Table S2. UV-Vis data of compound 1b. λ max/ nm A ε log ε Table S3. Taft constants (π*) of solvents, absorption maxima and corresponding transition energies (in kcal/mol) of 1a. Solvent λ max /nm E/Kcal*mol -1 π* CH 2 Cl THF Et 2 O Table S4. Taft constants (π*) of solvents, absorption maxima and corresponding transition energies (in kcal/mol) of 1b. Solvent λ max /nm E/Kcal*mol -1 π* CH 2 Cl THF Et 2 O Table S5. E, S values and correlation coefficients for compounds (according to E = E + Sπ*). Compound E (kcal.mol -1 ) S Correlation coefficient 1a b S26