46/[424]
J. Ahn et al.
the photovoltaic performances for new dyes were also characterized compare to those of
reference N749 DSSC.
Experimental
1-[2-(4-Methoxycarbonylpyridin-2-yl)-2-oxo-ethyl]–pyridinium-iodide (1), Krohnke Re-
agent [2]: Methyl 2-acetylisonicotinate (0.24 g, 1.34 mmol) was added to a warmed a
solution of I2 (0.35 g, 1.38 mmol, 1.03 eq) in anhydrous pyridine (10 ml). The reaction
mixture was refluxed for 3 hr under Ar condition. After cooling to room temperature, a
precipitate was collected by filtration and wash with chloroform and diethyl ether to give 3
as powder (yield: 34%). 1H NMR (400 MHz, DMSO-d6), δppm: 9.10 (1H, d, J = 4.8 Hz),
9.09 (2H, d, J = 5.6 Hz), 9.00 (1H, t, J = 8 Hz), 8.36 (1 H, s), 8.30 (2H, t, J = 6.8 Hz), 8.28
(1H, dd, J = 1.6 Hz, 4.8 Hz), 6.52 (2H, s), 3.95 (3H, s); 13C NMR (100 MHz, DMSO-d6),
δ ppm: 191.20, 164.70, 152.07, 151.49, 146.92, 146.84, 139.21, 128.26, 127.88, 120.77,
67.71, 53.69.
Methyl-2-(3-Thiophen-2-yl-acryloyl)-isonicotinate (2): Piperidine (0.6 mL, 6.19
mmol) and acetic acid (0.35 mL, 6.19 mmol) were dissolved in methanol (10 mL) and
stirred for 5 min at room temperature. At room temperature, methyl-2-acetylisonicotinate
(1 g, 5.58 mmol) were added to solution and stirred for further 5 min. 2-
Thiophenecarboxaldehyde (0.62 g (0.52 mL), 5.58 mmol) were added to solution and
reflux for 5 h. When yellow precipitate was found on the solution, cool to room tempera-
ture. Precipiate was washed with small amount of methanol and no further purification is
needed. 1H NMR (400 MHz, DMSO-d6), δ ppm: 8.90 (1H, dd, J = 0.8 Hz, 4.8 Hz), 8.69
(1H, dd, J = 0.8 Hz, 1.6 Hz), 8.13 (1H, s), 8.09 (2H, m), 7.47 (2H, dd, J = 5.2 Hz, 10.8 Hz),
7.12 (1H, t, J = 3.6 Hz), 4.0 (3H, s); 13C NMR (100 MHz, CDCl3), δ ppm: 188.28, 165.16,
155.15, 149.75, 140.77, 138.69, 137.74, 132. 52, 129.50, 128.37, 125.88, 122.13, 119.47,
52.93.
Methyl-2-(3-thieno[3,2-b]thiophen-2-yl-acryloyl)-isonicotinate (2ꢀ): Piperidine (4.69
mL, 47.99 mmol, 1.1 eq) and acetic acid (2.73 mL, 47.99 mmol, 1.1eq) were added to a
stirred solution of thieno[3,2-b]thiophene-2-carbaldehyde (7.29 g, 43.33 mmol) and methyl-
2-acetylisonicotinate (8.6 g, 47.99 mmol, 1.1 eq) in methanol (50 mL). The mixture was re-
fluxed for 5 h and turned red with precipitation of orange crystals. After cooling to room tem-
perature, the crystals was filtered and washed with methanol. The crude product was chro-
matographed on silica gel, eluting with hexane: Ethyl acetate (5 : 1) and then it was recrystal-
lized with methanol to give 4 as orange crystals (yield: 58%). 1H NMR (400 MHz, DMSO-
d6), δ ppm: 9.03 (1H, d, J = 5.2 Hz), 8.44 (1H, s), 8.18 (1H, d, J = 16 Hz), 8.13 (1H, d,
J = 5.2 Hz), 8.05 (1H, d, J = 35.6 Hz), 7.93 (1H, d, J = 5.6 Hz), 7.53 (1H, d, J = 5.2 Hz),
3.95 (1H, s); 13C NMR (100 MHz, DMSO-d6), δ ppm: 187.48, 165.07, 154.72, 151.10,
142.27, 141.83, 140.10, 139.14, 138.91, 133.18, 127.61, 126.56, 121.35, 120.94, 118.71,
53.52.
4,4ꢀꢀ-Dimethoxycarbonyl-4ꢀ-thieno[3,2-b]thiophenyl-2,2ꢀ:6ꢀ2ꢀꢀ-terpyridine (3): En-
one reagent (2) (0.188 g, 0.69 mmol) and Krohnke’s reagent (1) (0.327 g, 0.85 mmol)
were added to a solution of excess ammonium acetate (2 g, 26 mmol) in methanol (3 mL)
and the resulting solution was heated to reflux for 4 h. After cooling to room temperature, a
precipitate was collected by filtration and triturated successively with methanol (2 × 2 mL)
and then with chloroform (2 × 2 mL). The chloroform extract was freed of solvent, and
then the crude was washed with methanol and then it was recrystallized with chloroform to
give 5 as a brown powder (yield: 27%). 1H NMR (400 MHz, DMSO-d6), δ ppm: 9.16 (2H,
s), 8.90 (2H, d, J = 4 Hz), 8.75 (2H, s), 8.00 (1H, s), 7.94 (2H, d, J = 4 Hz), 7.49 (1H, d, J