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X. Zhou et al. / Organic Electronics 25 (2015) 245–253
to remove the unreacted NaBH4. The resulting mixture was
extracted by CH2Cl2 and then the solvent was removed to obtain
the pure product 7. It was no further purified and dissolved in
20 mL of CH2Cl2 for the next step.
(CDCl3, 300 MHz), d (ppm): 10.01 (s, 1H), 8.14 (s, 1H), 7.36–7.31
(m, 3H), 7.26 (s, 1H), 7.15 (s, 1H), 7.11–6.94 (m,10H), 4.35 (t,
2H), 4.25 (t, 2H), 2.33 (s, 6H), 1.90 (m, 4H), 1.57 (m, 4H), 1.37–
1.25 (m, 16H), 0.89 (t, 6H). MS (MALDI-TOF): m/z 772.774 (M+).
2.5.4. (4-(Di-p-tolylamino)benzyl)triphenylphosphonium bromide (8)
PPh3ꢂHBr (1.38 g, 4.0 mmol) was added into the CH2Cl2 solution
of 7 and the mixture refluxed for 4 h. Then the solvent was
removed by rotary evaporation. The product was purified by col-
umn chromatography using CH2Cl2 and CH2Cl2–CH3OH (10:1,
v/v) as eluent continuously. The compound 8 was then obtained
as a solid (2.24 g, yield: 89.1%). 1H NMR (CDCl3, 300 MHz), d
(ppm): 7.74–7.63 (m, 15H), 7.04 (d, 4H), 6.91–6.75 (m, 6H), 6.73
(d, 2H), 5.23 (d, 2H), 2.29 (s, 6H).
2.5.9. 2-Cyano-3-(6-(4-(di-p-tolylamino)styryl)-4,8-bis(octyloxy)-
benzo[1,2-b:4,5-b’]dithiophen-2-yl) acrylic acid (Dye 1)
A 20 mL of acetonitrile solution containing compound 6a
(1.54 g, 2.0 mmol), cyanoacetic acid (171 mg, 2.12 mmol), and
0.20 mL of piperidine were charged sequentially in
a
three-necked flask and heated to reflux overnight under N2 atmo-
sphere. After cooling at room temperature, solvents were removed
by rotary evaporation and the residue was absorbed on silica gel
and purified by column chromatography using CH2Cl2–CH3OH
(10:1, v/v) as eluent to yield Dye 1 as a dark solid (153.6 mg, yield:
46.2%). 1H NMR (CDCl3, 300 MHz), d (ppm): 8.44 (s, 1H), 8.07 (s,
1H), 7.31 (m,2H), 7.12–6.91 (m, 13H), 4.33 (t, 2H), 4.24 (t, 2H),
2.33 (s, 6H), 1.90 (m, 4H), 1.56 (m, 4H), 1.37–1.25 (m, 16H), 0.89
(t, 6H); 13CNMR (CDCl3, 100 MHz), d (ppm): 189.71, 166.39,
161.13, 158.93, 145.99, 144.77, 129.99, 127.82, 127.64, 125.16,
121.58, 99.99, 98.18, 82.67, 75.26, 74.27, 60.55, 56.88, 54.29,
52.84, 52.37, 31.85, 30.49, 29.97, 29.42, 29.30, 26.03, 22.66,
20.85, 20.71, 14.10, 13.72; MS (MALDI-TOF): m/z 839.766
(M+H+); Calcd. For C52H58N2S2O4: C, 74.43%; H, 6.97%; N, 3.34%;
Found: C, 73.96%; H, 6.79%; N, 3.59%.
2.5.5. 9-Octyl-9H-carbazole (9)
Carbazole (1.67 g, 10 mmol), 1-bromo-n-octane (2.41 g,
12.5 mmol) and tetrabutyl ammonium bromide (TBAB, 111.3 mg,
0.3 mmol) were added into a 100 mL flask. Then, 20 mL of 50%
NaOH aqueous solutions and 5 mL of toluene were added into
the flask. The reactants were stirred at 80 °C for 30 min. After cool-
ing to room temperature, the product was extracted by CH2Cl2 for
3 times and yellow solid was obtained by removing the solvent.
Herein, compound 9 was finally obtained as a white crystal
(1.468 g, 52%) by recrystallized in ethanol and used directly in next
step.
2.5.10. 6-(2-(9-Octyl-9H-carbazol-3-yl)vinyl)-4,8-bis(octyloxy)benzo-
[1,2-b:4,5-b0]dithioph-ene-2-carbaldehyde (6b)
2.5.6. 9-Octyl-9H-carbazole-3-carbaldehyde (10)
POCl3 (1.55 g, 9.86 mmol) was slowly added into dry DMF
(1.98 g, 27.0 mmol) under N2 atmosphere at 0 °C. Then the mixture
was allowed to warm at room temperature for 1 h. The dry
1,2-dichloroethane (10 mL) solution of 9 was added dropwise into
the above-mentioned solution at 0 °C. After keeping at 0 °C for 1 h,
the reactants were heated at 90 °C and stirred for 8 h. When the
reaction was over, the product was poured into cold water, and
the pH of the aqueous solution should be adjusted to 9–10. Then,
crude yellow oil was obtained by extracting with CH2Cl2. After
purified it by column chromatography using petroleum ether:
CH2Cl2 (3:2, v/v) as eluent, compound 10 was obtained as a light
yellow oil (1.1 g, yield: 73.3%). 1H NMR (CDCl3, 300 MHz), d
(ppm): 10.10 (s, 1H), 8.62 (s, 1H), 8.16 (d, 1H), 8.00 (d,1H),
7.57–7.30 (m, 4H), 4.34 (t, 2H), 1.87 (t, 2H), 1.35–1.24 (m, 10H),
0.86 (t, 3H).
Product 6b was synthesized according to the procedure of the
synthesis of 6a. The crude compound was purified by column chro-
matography using CH2Cl2–CH3OH (10:1, v/v) as eluent to give red
oil. The resulting product was pure enough to be used in the next
procedure. Therefore, no further characterization was preceded.
2.5.11. 2-Cyano-3-(6-((E)-2-(9-octyl-9H-carbazol-3-yl)vinyl)-4,8-
bis(octyloxy)benzo[1,2-b:4,5-b’]-dithiophen-2-yl)acrylic acid (Dye 2)
Product Dye 2 was synthesized and purified according to the
procedure of Dye 1, giving dark red solid. It is noted that all the
peaks of Dye 2 in 1HNMR spectrum were broaden and no obvious
coupling splits were observed. 1H NMR (d6-DMSO, 300 MHz), d
(ppm): 8.50 (s,1H), 8.40 (s, 1H), 8.32 (s, 1H), 8.13 (s, 1H), 7.72 (s,
1H), 7.63–7.46 (m, 5H), 7.22 (m, 2H), 4.31 (m, 4H), 4.24 (s, 2H),
1.81 (m, 6H), 1.53 (s, 4H), 1.32–1.16 (m, 27H), 0.85–0.81 (m, 9H).
13CNMR (d6-DMSO, 100 MHz), d (ppm): 211.24, 157.97, 143.27,
131.79, 128.55, 127.54, 99.99, 94.52, 88.63, 74.38, 74.09, 56.49,
42.82, 31.73, 31.72, 31.61, 30.42, 29.28, 29.23, 29.14, 29.05,
28.96, 26.91, 25.99, 25.88, 22.57, 22.56, 22.45, 19.01, 14.40,
14.38, 14.32; MS (ESI-MS negative mode): m/z 843.44
([MꢁH+]ꢁ); Calcd. For C52H64N2S2O4: C, 73.89%; H, 7.63%, N,
3.31%; found: C, 73.60%; H, 7.79%; N, 3.59%.
2.5.7. ((9-Octyl-9H-carbazol-3-yl)methyl)triphenylphosphonium
bromide (12)
Herein, compound 11 was obtained as crude product by the
reduction reaction of 10 and NaBH4. Then it was used without fur-
ther purification to synthesize compound 12 according to the pro-
cedure for the synthesis of 8. The compound 12 was obtained as a
yellow solid (1.03 g, yield: 56.58%). 1H NMR (CDCl3, 300 MHz), d
(ppm): 7.79–7.72 (m, 10H), 7.65–7.62 (m, 6H), 7.51–7.35 (m,
4H), 7.18–7.13 (m, 2H).
3. Results and discussion
2.5.8. 6-(4-(Di-p-tolylamino)styryl)-4,8-bis(octyloxy)benzo[1,2-b:4,5-
3.1. Synthesis and characterization
b’]dithiophene-2-carbaldehyde (6a)
Compound
5
(214.3 mg, 0.426 mmol), anhydrous K2CO3
The molecular structures and synthetic routes of the two
organic dyes Dye 1 and Dye 2 are shown in Schemes 1 and 2,
respectively. The two dyes were synthesized by the stepwise syn-
thetic protocol. The main material, compound 5, prepared from
compound 4, was initially obtained by the vilsmeier reaction using
POCl3-DMF system [20]. However, many by-products were found
in the final product which made the purification difficult. Thus,
we employed the BuLi-DMF system, obtaining compound 5 with
a satisfied yield of 66%. We attribute this high yield to the low tem-
perature at which the reaction took place at ꢁ78 °C.
(121.6 mg, 0.881 mmol), and 18-Crown-6 (8.5 mg, 0.032 mmol)
in a three-necked flask were dried in vacuum for 30 min and fol-
lowed by adding 20 mL of dry DMF. After that, the compound 8
(271.2 mg, 0.431 mmol) was dissolved in 5 mL of dry DMF and
added dropwise to the above solution with stirring under N2 atmo-
sphere. The mixture was stirred for another 3 h at ambient temper-
ature and then poured into ice-water (40 mL). The precipitate was
filtered off and purified by silica gel column chromatography with
CH2Cl2-petroleum ether (2:1) as eluent to yield red oil. 1H NMR