ARTICLE
5-(4-Bromophenyl)-2H-tetrazole (1)
then water again (1 ꢃ 200 mL). After extraction with EtOAc,
the organic layer was dried (MgSO4) and concentrated to
yield the monomer M2 (2.64 g, 92%).
A mixture of 4-bromobenzonitrile (5.00 g, 27.6 mmol), so-
dium azide (5.35 g, 82.3 mmol), NH4Cl (4.40 g, 82.2 mmol),
and DMF (15 mL) was heated for 4 h underꢂ N2 in an oil
bath maintained at a bath temperature of 150 C. After cool-
ing to room temperature, the solution was poured into 1 N
HCl (150 mL) and stirred for 30 min. After filtering, the solid
product was washed with water (3 ꢃ 300 mL) and dried to
yield 1 (5.30 g, 85%).
1H NMR (300 MHz, DMSO-d6, ppm): 7.20 (d, J ¼ 8.7 Hz, 2H),
7.04 (d, J ¼ 8.7 Hz, 2H). 13C NMR (75 MHz, DMSO-d6, ppm):
155.9, 133.2, 129.6, 125.6, 123.9. HRMS-EI (m/z): [Mþ]
Calcd. for C7H5BrN4, 223.9698; Found, 223.9692.
1H NMR (300 MHz, CDCl3, ppm): 8.18 (d, J ¼ 8.7 Hz, 2H),
8.06 (d, J ¼ 8.7 Hz, 2H), 7.67 (d, J ¼ 8.4 Hz, 2H), 7.55 (d, J
¼ 8.4 Hz, 2H), 7.07 (s, 1H), 1.37 (s, 9H). 13C NMR (75 MHz,
CDCl3, ppm): 164.8, 163.9, 155.4, 140.8, 137.1, 131.3, 129.1,
127.0, 126.8, 126.0, 123.5, 121.0, 111.8, 108.7, 35.1, 31.1.
HRMS-EI (m/z): [Mþ] Calcd. for C22H18Br2N2OS, 517.9507;
Found, 517.9457.
Preparation of Polythiophene Derivatives
All polymers were synthesized through Grignard metathesis
polymerization in THF according to procedures similar to
those described in the literature.37–39 The Grignard metathe-
sis polymerizations of M1 and M2 are presented in Scheme 2.
2-(4-Bromophenyl)-5-(4-tert-butylphenyl)-
1,3,4-oxadiazole (2)
4-tert-Butylbenzoyl chloride (3.25 g, 16.5 mmol) was added
dropwise to a solution of 1 (2.50 g, 11.1 mmol) in pyridine
(30 mL) and then the mixture was heated for 6 h under N2
in an oil bath maintained at 130 ꢂC. After cooling to room
temperature, the solution was poured into water (300 mL).
The solid product was filtered off, washed with water (5 ꢃ
300 mL), and dried to yield 2 (3.25 g, 82%).
1H NMR (300 MHz, CDCl3, ppm): 8.04 (d, J ¼ 8.7 Hz, 2H),
7.99 (d, J ¼ 8.4 Hz, 2H), 7.66 (d, J ¼ 8.7 Hz, 2H), 7.54 (d, J
¼ 8.4, 2H), 1.34 (s, 9H). 13C NMR (75 MHz, CDCl3, ppm):
164.2, 163.2, 155.1, 132.5, 128.6, 126.6, 126.3, 125.6, 122.6,
120.5, 34.9, 30.8. HRMS-EI (m/z): [Mþ] Calcd. for
Poly(3-hexylthiophene)
CH3MgBr (1.50 mL, 4.50 mmol) was added via syringe to a
stirred solution of 2,5-dibromo-3-hexylthiophene (1.60 g,
4.50 mmol) in freshly distilled THF (80 mL) in a three-neck
100-mL round-bottom flask. The solution was heated under
reflux for 2 h and then Ni(dppp)Cl2 (1ꢂ2 mg, 0.02 mmol) was
added. The mixture was stirred at 95 C for 2.5 h before the
reaction was quenched through the addition of MeOH. The
solid polymer was washed with MeOH and hexane within a
Soxhlet extractor; it was then dissolved through Soxhlet
extraction with CHCl3, the solvent was evaporated, and the
residue dried under vacuum to yield P3HT (0.51 g, 61%).
The weight-average molecular weights (Mw) and polydisper-
sity index (PDI) are 15.9 kg molꢁ1and 1.26, respectively.
C18H17BrN2O, 356.0524; Found, 356.0527.
2-(4-tert-Butylphenyl)-5-[4-(thiophen-3-yl)phenyl]-
1,3,4-oxadiazole (3)
1H NMR (300 MHz, CDCl3, ppm): 6.96 (s, 1H), 2.79 (t, 2H);
0.89–0.81, 1.43–1.15, and 1.72–1.45 (m, 11H). 13C NMR (75
MHz, CDCl3, ppm): 139.8, 133.7, 130.4, 128.5, 31.9, 30.6,
29.6, 29.4, 22.7, 14.2. Anal. Calcd: C, 72.23; H, 8.49. Found:
C, 72.10; H, 8.30.
A total of 2 M aqueous potassium carbonate (11 mL) was
added via syringe to a solution of 2 (3.00 g, 8.40 mmol),
4,4,5,5-tetramethyl-2-(thiophen-3-yl)-1,3,2-dioxaborolane (1.80 g,
8.53 mmol), and tetrakis(triphenylphosphine)palladium (2
mol %) in toluene (22 mL) in a 50-mL two-neck flask. The
mixture was then stirred overnight at 90 ꢂC under N2. After
cooling to room temperature, the solution was washed with
water and back-extracted with EtOAc. The organic layer was
dried (MgSO4) and concentrated to yield 3 (2.70 g, 90%).
P05
CH3MgBr (0.820 mL, 2.46 mmol) was added via syringe to a
stirred solution of 2,5-dibromo-3-hexylthiophene (760 mg,
2.33 mmol), M2 (63.5 mg, 0.122 mmol), and freshly distilled
THF (40 mL) in a three-neck 100-mL round-bottom flask.
The solution was heated under reflux for 2 h and then
Ni(dppp)Cl2 (6 mg, 0.01 mmol) was added. The mixture was
stirred at 95 ꢂC for 2.5 h and then the reaction was
quenched through the addition of MeOH. The solid polymer
was washed with MeOH and hexane within a Soxhlet extrac-
tor; it was then dissolved through Soxhlet extraction with
CHCl3, the solvent was evaporated, and the residue dried
under vacuum to yield P05 (202 mg, 46%). The Mw and PDI
are 25.7 kg molꢁ1and 1.36, respectively.
1H NMR (300 MHz, CDCl3, ppm): 8.17 (d, J ¼ 8.1 Hz, 2H),
8.08 (d, J ¼ 8.1 Hz, 2H), 7.77 (d, J ¼ 8.1 Hz, 2H), 7.61–7.59
(m, 1H), 7.56 (d, J ¼ 8.4 Hz, 2H), 7.48–7.43 (m, 2H), 1.38 (s,
9H). 13C NMR (75 MHz, CDCl3, ppm): 164.6, 164.2, 155.3,
141.0, 138.8, 127.4, 126.8, 126.7, 126.2, 126.0, 124.3, 122.5,
121.7, 121.1, 35.1, 31.1. HRMS-EI (m/z): [Mþ] Calcd. for
C22H20N2OS, 360.1296; Found, 360.1287.
2-(4-tert-Butylphenyl)-5-[4-(2,5-dibromothiophen-
3-yl)phenyl]-1,3,4-oxadiazole (M2)
N-Bromosuccinimide (NBS, 2.00 g, 11.2 mmol) was added
portionwise to a solution of 3 (2.00 g, 5.55 mmol) in THF
(20 mL) and acetic acid (20 mL) and then the mixture was
stirred and heated at 80 ꢂC for 6 h. After cooling to room
temperature, the solution was washed sequentially with
water (2 ꢃ 200 mL), saturated NaHCO3 (1 ꢃ 200 mL), and
1H NMR (300 MHz, CDCl3, ppm): 8.3–7.9 (br, 0.25H), 7.7–7.4
(m, 0.25H), 6.96 (s, 1.09H), 2.78 (br, 2.12H), 1.66–1.36 (m,
7.31H), 0.88 (s, 2.98H). 13C NMR (75 MHz, CDCl3, ppm):
140.1, 133.9, 130.7, 129.3, 128.8, 128.5, 127.3, 127.0, 126.3,
31.9, 31.4, 30.7, 29.7, 29.5, 22.9, 14.4. Anal. Calcd: C, 72.30;
H, 8.32; N, 0.39. Found: C, 70.15; H, 7.83; N, 0.39.
DONOR–ACCEPTOR POLY(3-HEXYLTHIOPHENE) COPOLYMERS, WANG, SU, AND WEI
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