SUPPORTING INFORMATION
Thiophene-bithiazole based metal-free dye as DSSC sensitizer:
Effect of co-adsorbents on photovoltaic efficiency
JAYANTHY S PANICKERa,b, BIJITHA BALAN*,a, SURAJ SOMAN*,a, TANWISTHA
GHOSHa,b and VIJAYAKUMAR C NAIRa,b
a
Photosciences and Photonics Group, Chemical Sciences and Technology Division, CSIRNational Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum 695
019, India
b
Academy of Scientific and Innovative Research (AcSIR), Trivandrum 695 019, India
e-mail: bijithab1@gmail.com; suraj@niist.res.in
Table of contents
SI No.
1.
2.
3.
4.
5.
6.
7.
1
Content
Synthetic procedures of TP1
Synthetic procedures of TP2
Characterization data of all the new molecules
Film state absorption of BT1 on TiO2
Absorption and emission spectra of BT1 with increasing
percentage of water
Absorption and emission spectra of TP1 and TP2
Photovoltaic parameters of BT1
Page No.
2-3
4-6
7-31
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32,33
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Synthesis of TP1
Synthesis of 81 and 92 reported in literature.
Figure S1. Synthetic scheme of TP1.
Synthesis of 2-bromo-3-hexyl-5-formylthiophene (8): A vilsmeier reagent was prepared using
POCl3 (2.22 mL, 24.27 mmol, 2 eq.) and dimethylformamide (8.45 mL, 109.21 mmol, 9 eq.) and
it was added to solution of 2-bromo-3-hexylthiophene (3 g, 12.13 mmol, 1 eq.) in dichloroethane
at 0 C under argon. After being stirred for 12 h at 60 C, the mixture was poured into ice water,
neutralised with Na2CO3 and then extracted with CH2Cl2 and dried over Na2SO4. It was purified
by column chromatography (15% Ethyl acetate-hexane). Pure product was obtained as a light
yellow liquid (Yield - 85%). 1H NMR (500 MHz, CDCl3)  9.74 (s, 1H), 7.46 (s, 1H), 2.57 (t,
2H), 1.63-1.57 (m, 2H), 1.36-1.30 (m, 6H), 0.90-0.87 (t, 3H); HRMS: m/z = 274 (M+).
Synthesis of 4-hexyl-5-phenylthiophene-2-carbaldehyde (9): 2-bromo-3-hexyl-5-formylthiophene (547 mg, 1.99 mmol, 1 eq.), 4,4,5,5-tetramethyl-2-phenyl-1,3,2-dioxaborolane (486
mg, 2.39 mmol, 1.2 eq.) and K2CO3 (2.74 g, 19.87 mmol, 10 eq.) were dissolved in THF - H2O
mixture (9:1). Air was removed out of the set up and replaced by nitrogen, three times by using a
freeze-thaw-pump method, then Pd(PPh3)4 was added under nitrogen-counter flow. The reaction
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mixture was heated and stirred under nitrogen for two days, then poured into water and extracted
with CH2Cl2. After washing the combined organic layer with brine and water, it was dried over
Na2SO4 and the solvent evaporated purified by column chromatography (1:1 CHCl3-hexane).
Yield: 89%. 1H NMR (500 MHz, CDCl3)  9.86 (s, 1H), 7.66 (s, 1H), 7.46-7.40 (m, 5H), 2.66 (t,
J 7.75, 2H), 1.64-1.60 (m, 2H), 1.32-1.22 (m, 6H), 0.85 (t, J 6.75, 3H). HRMS: m/z = 295.11
(M+ + Na).
Synthesis of (Z)-2-cyano-3-(4-hexyl-5-phenylthiophen-2-yl) acrylic acid (TP1)
To a mixture of 4-hexyl-5-phenylthiophene-2-carbaldehyde (100 mg, 0.367 mmol, 1 eq.) and
cyanoacetic acid (62.43 mg, 0.367 mmol, 2 eq.) were added acetonitrile (10 mL) and piperidine
(0.04 mL, 0.44 mmol, 1.2 eq.) at room temperature. The solution was refluxed overnight. After
cooling to room temperature, the organic phase was separated and the aqueous layer extracted
with CH2Cl2. The combined organic phases were washed with brine, dried with MgSO4, and
concentrated in vacuo. The crude residue was purified by column chromatography (DCM:
MeOH = 9: 1) to give adduct as a yellow liquid. Yield: 70%. 1H NMR (500 MHz, CDCl3)  8.30
(s, 1H), 7.70 (s, 1H), 7.46-7.43 (m, 5H), 2.69-2.63 (m, 2H), 1.63-1.57 (m, 2H), 1.29-1.25 (m,
6H), 0.85 (t, J 4.5, 3H). 13C NMR (125 MHz, CDCl3)  148.90, 146.61, 139.86, 139.67, 132.72,
132.00, 128.11, 127.87, 127.76, 115.02, 30.44, 29.61, 28.67, 28.00, 27.35, 21.51, 13.00. HRMS:
m/z = 362.11 (M+ + Na).
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Synthesis of TP2
Synthesis of 103 and 114 reported in the literature.
Figure S2. Synthetic scheme of TP2.
Synthesis of 3, 3’,-dihexyl-2, 2’-bithiophene-5-carbaldehyde (10) :
2-bromo-3-hexyl-5-formylthiophene (3.45 g, 12.54 mmol, 1 eq.) and 3-hexylthiophene-2boronic acid pinacolester (4 g, 13.78 mmol, 1.1 eq.) were weighed in a two necked RB flask and
dissolved in anaerobic THF- H2O mixture (2:1). K2CO3 (17 g, 125 mmol, 10 eq.) was added to
the mixture and the flask was connected to a reflux condenser equipped with a septum. Air was
pumped out of the set up and replaced by nitrogen using freeze-thaw-pump method, then
Pd(PPh3)4 was added under Ar-counter flow. The reaction mixture was refluxed for two days
under nitrogen atmosphere then poured in to water and extracted with CH2Cl2. After washing the
combined organic layer with brine and water, it was dried over Na2SO4 and the solvent
evaporated under reduced pressure and purified by column chromatography (1:1 CHCl3-hexane).
Yield: 85%. 1H NMR (500 MHz, CDCl3)  9.87 (s, 1H),7.66 (s, 1H), 7.36 (d, J 5, 1H), 6.99 (d, J
4
5, 1H), 2.57-2.52 (m, 4H), 1.60-1.52 (m, 4H), 1.27-1.25 (m, 12H), 0.85 (t, 6H); HRMS: m/z =
362.17 (M+).
Synthesis of 5-bromo-3,3’,-dihexyl-2,2’-bithiophene-5-carbaldehyde (11):
N-bromosuccinnimide (71 mg, 0.4 mmol, 1.1 eq.) was added in small portions to solution of
3,3’-dihexyl-2,2’-bithiophene-5-carbaldehyde (132 mg, 0.36 mmol, 1 eq.) in chloroform and
acetic acid (1:1) at 0 °C. After being stirred for 6hr at room temperature, the reaction mixture
was poured into water and extracted with dichloromethane. The organic layer was thoroughly
washed with water, aqueous Na2CO3, brine and again with water and dried over Na2SO4 and the
solvent evaporated and purified by column chromatography (1:1 CHCl3-hexane). Pure product
was obtained as a light yellow liquid. Yield: 95%. 1H NMR (500 MHz, CDCl3)  9.87 (s, 1H),
7.64 (s, 1H), 6.97 (s,1H), 2.55 (t,2H), 2.47 (t, 2H), 1.58 - 1.50 (m, 4H), 1.30 - 1.21 (m, 12H),
0.87 (t, 3H), 0 .85 (t, 3H); HRMS: m/z = 442.08 (M+).
Synthesis of 5-phenyl-3, 3’-dihexyl-2,2’-bithiophene-5-carbaldehyde (12):
5-bromo-3,3’-dihexyl-2,2’-bithiophene-5-carbaldehyde (1 g, 2.26 mmol, 1 eq.) and phenyl-2boronic acid pinacol ester (508 mg, 2.49 mmol, 1.1 eq.) were weighed in a two necked RB flask
and dissolved in anaerobic THF - H2O mixture (2:1). K2CO3 (3.08 g, 22.65 mmol, 10 eq.) was
added to the mixture and the flask was connected to a reflux condenser equipped with a septum.
Air was pumped out of the set up and replaced by Ar, three times by using a freeze-thaw-pump
method, then Pd(PPh3)4 (130 mg, 0.11 mmol, 0.05 eq.) was added under Ar-counter flow. The
reaction mixture was refluxed for two days, then poured in to water and extracted with CH2Cl2.
After washing the combined organic layer with brine and water, it was dried over Na2SO4 and
the solvent evaporated and purified by column chromatography (1:1 CHCl3-hexane). 1H NMR
(500 MHz, CDCl3)  9.87 (s, 1H), 7.65 (s, 1H), 7.60 (d, J 7.5, 2H), 7.39 (t, J 7.5, 2H), 7.29 (t, J
7.25, 1H), 7.21 (s, 1H), 2.61 (t, J 7.75, 2H), 2.55 (t, J 7.75, 2H), 1.59 - 1.58 (m, 4H), 1.26 (t, J
5.5, 12H), 0.86 (t, J 6.5, 6H).
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C NMR (125 MHz, CDCl3)  182.86, 144.95, 144.22, 143.65,
142.39, 139.89, 137.73, 133.80, 128.96, 127.93, 127.90, 127.85, 126.54, 125.68, 125.03, 31.62,
31.58, 30.70, 30.51, 29.20, 29.10, 28.99, 28.87, 22.58, 22.56, 14.08, 14.06. HRMS: m/z = 461.19
(M+ + Na).
Synthesis of TP2:
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To a mixture of 5-phenyl -3, 3’,-dihexyl-2, 2’-bithiophene -5-carbaldehyde (180 mg, 0.410 mmol,
1 eq.) and cyanoacetic acid (69.80 mg, 2.50 mmol, 2 eq.) were added acetonitrile (10 mL) and
few drops of piperidine added at room temperature. The solution was refluxed overnight. After
cooling to room temperature, the organic phase was separated and the aqueous layer extracted
with CH2Cl2. The combined organic phases were washed with brine, dried with MgSO4, and
concentrated in vacuo. The crude residue was purified by column chromatography (DCM:
MeOH = 9: 1) to give adduct as a yellow orange liquid. 1H NMR (500 MHz, CDCl3)  8.28 (s,
1H), 7.73 (s, 1H), 7.60 (d, J 8, 2H), 7.39 (t, J 7.5, 2H), 7.31 (t, J 7.25, 1H), 7.21 (s, 1H), 2.62 (t, J
7.75, 2H), 2.57 (t, J 7.75, 2H), 1.59-1.58 (m, 4H), 1.28-1.26 (m, 12H), 0.85 (t, J 4.75, 6H).
13
C
NMR (125 MHz, CDCl3)  146.18, 144.24, 143.45, 142.99, 140.18, 138.34, 133.94, 132.71,
128.23, 127.93, 127.52, 126.90, 125.17, 124.66, 124.09, 115.01, 30.57, 30.50, 29.64, 29.45,
28.67, 28.30, 28.06, 27.99, 27.70, 21.53, 13.05, 13.01. HRMS: m/z = 528.20 (M+ + Na).
6
Figure S3. 1H NMR of 5.
7
Figure S4. 13C NMR of 5.
8
Figure S5. HRMS of 5.
9
Figure S6. 1H NMR of 6.
10
Figure S7. 13C NMR of 6.
11
Figure S8. HRMS of 6.
12
Figure S9. 1H NMR of 7.
13
Figure S10. 13C NMR of 7.
14
Figure S11. HRMS of 7.
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Figure S12. 1H NMR of BT1.
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Figure S13. 13C NMR of BT1.
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Figure S14. HRMS of BT1.
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Figure S15. 1H NMR of 9.
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Figure S16. 13C NMR of 9.
20
Figure S17. HRMS of 9.
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Figure S18. 1H NMR of TP1.
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Figure S19. 13C NMR of TP1.
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Figure S20. 1H NMR of 10.
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Figure S21. 1H NMR of 11.
25
Figure S22. 1H NMR of 12.
26
Figure S23. 13C NMR of 12.
27
Figure S24. HRMS of 12.
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Figure S25. 1H NMR of TP2.
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Figure S26. 13C NMR of TP2.
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Figure S27. HRMS of TP2.
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Photophysical Properties
Figure S28. Film state absorption of BT1 on TiO2.
Figure S29. Absorption spectra of BT1 with increasing percentage of water.
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Figure S30. Emission spectra of BT1 with increasing percentage of water.
Figure S31. (a) Absorption and (b) emission spectra of TP1 and TP2 in THF.
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Table S1. Photovoltaic performance parameters of BT1 in the presence of different coadsorbents
Composition of electrolyte:
from dyesol
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[a]
0.6 M BMII, 0.1 M LiI, 0.05 M I2, 0.5 M TBP.
[b]
Commercial electrolyte
7. References
[1]
Zhang J, Wu G, He C, Dengab D and Li Y 2011 J. Mater. Chem. 21 3768.
[2]
Li W, Maddux T and Yu L 1996 Macromolecules 29 7329.
[3]
Guo Y, Su J, An Z, Chen X and Chen P 2015 J. Mol. Struc. 1094 195.
[4]
Hayashi N, Nishihara T, Matsukihira T, Nakashima H, Miyabayashi K, Miyake M and Higuchi
H 2007 Bull. Chem. Soc. Jpn. 80 371.
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