X. Qian et al. / Dyes and Pigments 113 (2015) 737e742
739
the organic phase was separated and dried over anhydrous Na2SO4.
After the solvent was removed under vacuum, the crude product
was purified by silica-gel column chromatography using CH2Cl2/
petroleum ether (1:1) as the eluent to afford compound 5 as an
orange solid (Yield: 36.4%). IR (KBr): 3043, 2968, 2929, 1658, 1608,
122.29, 121.71, 121.32, 121.29, 121.22, 120.94, 120.59, 120.19, 120.12,
119.02, 110.80, 110.71, 108.81, 102.57, 102.43, 102.27, 45.04, 41.13,
41.08, 15.25, 15.17, 15.09. HR-MS (ESI): m/z [MꢀH]- calcd for
C
42H33N4O3S2, 705.1994; found, 705.1994.
1564,1435,1331, 1225, 729 cm-1. 1H NMR (400 MHz, CDCl3)
d 9.91 (s,
3. Results and discussion
1H), 8.33 (dd, J ¼ 15.0, 7.9 Hz, 3H), 7.89 (s,1H), 7.77 (t, J ¼ 9.1 Hz,1H),
7.66 (dd, J ¼ 11.6, 4.7 Hz, 3H), 7.56e7.43 (m, 3H), 7.37 (t, J ¼ 7.6 Hz,
2H), 5.12e4.92 (m, 6H), 1.68e1.57 (m, 9H). 13C NMR (101 MHz,
3.1. UVevisible absorption and electrochemical characterization
CDCl3)
d 182.71, 155.81, 141.57, 140.86, 140.73, 140.65, 139.65,
The UVevis absorption spectra of the two dyes in THF solutions
and on TiO2 films are depicted in Fig. 2. Data of absorption, elec-
trochemical properties, and frontier orbital energy levels are
summarized in Table 1. In THF solutions, each of these organic dyes
exhibited two major absorption bands at 300e350 and
400e600 nm. The high-energy absorption bands ranging from 300
139.09, 138.24, 137.81, 127.40, 124.58, 123.41, 123.29, 123.14, 121.76,
121.59, 121.49, 120.11, 120.05, 118.44, 110.44, 110.37, 107.80, 103.53,
103.13, 103.09, 41.71, 41.64, 15.60, 15.57. HR-MS (MALDI): m/z [M]þ
calcd for C35H29N3OS 539.2031; found, 539.2028.
2.3.2. Synthesis of compound 6
to 350 nm correspond to the
pep* transition of the conjugated
The synthesis resembles that of compound
5 using 4-
aromatic rings. The low-energy bands appearing at 400e600 nm
with weaker intensity can be attributed to the intramolecular
charge transfer (ICT) transitions [14]. The peak at 507 nm of JY04 is
red-shifted in comparison to that of JY05 (456 nm) due to the
relatively more electron-rich thiophene unit, which enhanced the
interaction between the donor and acceptor. The molar extinction
coefficients at lmax of JY04 and JY05 are 38355 and
34851 Mꢀ1 cmꢀ1, respectively. These are more than twice as high as
those of conventional polypyridyl Ru(II) complexes dyes, which is
conducive to increase the light harvesting of the cells [15]. As
shown in Fig. 2, when anchoring on mesoporous TiO2 films, both
formylphenylboronic acid instead of 5-formylthiophene-2-boronic
acid. Purification by silica-gel column chromatography with
CH2Cl2/petroleum ether (1:1) as the eluent afforded compound 6 as
a yellow solid (Yield: 48.3%). IR (KBr): 3050, 2972, 2933, 1702, 1600,
1562, 1332, 1227, 730 cm-1. 1H NMR (400 MHz, CDCl3)
d 10.09 (s,
1H), 8.46e8.29 (m, 3H), 8.02 (d, J ¼ 8.2 Hz, 2H), 7.95 (d, J ¼ 8.2 Hz,
2H), 7.88 (s, 1H), 7.76e7.58 (m, 3H), 7.49 (t, J ¼ 7.5 Hz, 2H), 7.38 (t,
J ¼ 7.5 Hz, 2H), 5.19e4.90 (m, 6H), 1.76e1.58 (m, 9H). 13C NMR
(101 MHz, CDCl3)
d 192.03, 147.89, 141.25, 140.78, 140.69, 139.46,
138.96, 138.42, 134.79, 134.13, 130.40, 127.71, 123.83, 123.40, 123.09,
121.84, 121.59, 121.51, 120.04, 120.01, 119.36, 110.44, 110.35, 108.81,
103.46, 103.22, 102.99, 41.73, 41.66, 15.65, 15.61. HR-MS (MALDI):
m/z [M]þ calcd for C37H31N3O, 533.2467; found, 533.2467.
2.3.3. Synthesis of JY04
A mixture of compound 5 (40 mg, 0.074 mmol), ammonium
acetate (28 mg, 0.37 mmol), rhodanine-3-acetic acid (17 mg,
0.09 mmol), and acetic acid (5 mL) was heated at reflux for 3 h
under a nitrogen atmosphere. After cooling to room temperature, it
was precipitated by pouring into water. The resulting solid was
filtered, washed thoroughly with water. Then, the crude product
was purified by silica-gel column chromatography using CH2Cl2/
CH3OH (10:3) as the eluent to afford JY04 as a dark red solid (Yield:
83.5%). IR (KBr): 3057, 2976, 2928, 1707, 1579, 1426, 1332, 1202,
744 cm-1. 1H NMR (400 MHz, DMSO-d6)
d 8.43e8.28 (m, 3H),
8.24e8.16 (m, 1H), 8.15e8.03 (m, 1H), 7.97 (s, 1H), 7.91e7.71 (m,
4H), 7.49 (t, J ¼ 7.6 Hz, 2H), 7.39 (dd, J ¼ 12.2, 7.4 Hz, 2H), 5.26e4.86
(m, 6H), 4.69 (s, 2H), 1.68e1.35 (m, 9H). 13C NMR (101 MHz, DMSO)
d
191.73, 167.22, 165.85, 153.76, 140.34, 140.16, 140.04, 138.72,
138.28, 138.14, 137.27, 135.51, 127.09, 126.88, 125.38, 123.22, 122.30,
122.19, 121.79, 121.30, 121.25, 120.26, 120.15, 118.43, 117.60, 110.83,
110.70, 107.49, 102.66, 102.50, 102.42, 45.00, 41.11, 15.28, 15.24,
15.09. HR-MS (ESI): m/z [MꢀH]- calcd for C40H31N4O3S3, 711.1558;
found, 711.1573.
2.3.4. Synthesis of JY05
The synthesis resembles that of JY04 using intermediate 6
instead of compound 5. The compound was purified by silica-gel
column chromatography using CH2Cl2/CH3OH (10:3) as the eluent
to afford compound JY05 as a red solid (Yield: 82.0%). IR (KBr):
3056, 2969, 2931, 1718, 1586, 1476, 1332, 1203, 728 cm-1. 1H NMR
(400 MHz, DMSO-d6)
d
8.40 (d, J ¼ 8.5 Hz, 1H), 8.35 (t, J ¼ 8.0 Hz,
2H), 8.23 (s, 1H), 8.14 (d, J ¼ 8.2 Hz, 2H), 7.96 (s, 1H), 7.86 (d,
J ¼ 8.1 Hz, 2H), 7.80 (t, J ¼ 8.2 Hz, 3H), 7.49 (t, J ¼ 7.6 Hz, 2H), 7.39 (dt,
J ¼ 10.9, 5.5 Hz, 2H), 5.14 (d, J ¼ 6.9 Hz, 2H), 5.09e4.98 (m, 4H), 4.74
(s, 2H), 1.70e1.35 (m, 9H). 13C NMR (101 MHz, DMSO)
d 192.96,
167.19, 166.33, 143.13, 140.69, 140.15, 140.04, 138.46, 137.94, 137.43,
133.61, 133.26, 131.51, 131.26, 130.70, 127.66, 123.15, 122.58, 122.36,
Fig. 2. UVevis absorption spectra of the dyes (a) in THF solutions and (b) on TiO2 films.