536
C. Kaiser et al. / Reactive & Functional Polymers 72 (2012) 533–541
31.0, 30.7, 29.1, 28.9, 21.3, 15.0, 14.9, 14.8, 12.4, 10.3; UV/vis
(kmax, CHCl3): 330 nm.
2.4.3. Diethyl 5,50-(5,50-(N-butyl-pyrrole-2,5-diyl)bis(thiophene-5,2-
diyl)bis(3,4-diethylpyrrole-2-carboxylate) 18
Stille-coupling of N-butyl-2,5-bis(5-(tributylstannyl)thiophen-
2-yl) pyrrole 15 (2.68 g, 3.1 mmol) and ethyl 3,4-diethyl-5-iodo-
1H-pyrrole-2-carboxylate 12 (2.04 g, 2.05 eq, 6.4 mmol). Heptane
(20 mL) was added to the orange/brown reaction mixture at room
temperature. The precipitate was washed twice with heptane
(20 mL) and the residue was further purified by column chromatog-
raphy (methylene chloride, Rf: 0.14) to yield 1.13 g (54%) 18 as an or-
ange solid: mp. 188 °C; 1H NMR (500 MHz, CDCl3, 25 °C): d 8.94 (bs,
2H, NH), 7.14 (d, J = 4 Hz, 2H, ThAH), 7.04 (d, J = 4 Hz, 2H, ThAH),
6.40 (s, 2H, PyrAH), 4.36 (q, J = 7 Hz, 4H, OCH2), 4.24–4.21 (m, 2H,
NACH2), 2.79 (q, J = 7.5 Hz, 4H, PyrACH2), 2.68 (q, J = 7.5 Hz, 4H,
PyrACH2), 1.67–1.60 (m, 2H, NCH2CH2CH2CH3), 1.38 (t, J = 7.5 Hz,
6H, COOCH2ACH3), 1.24–1.19 (m, 14H, NCH2CH2CH2CH3,
PyrACH2ACH3), 0.82 (t, 3H, J = 7.5 Hz, NCH2CH2CH2CH3); 13C NMR
(125 MHz, CDCl3, 25 °C): d 161.4, 134.2, 134.1, 133.7, 128.4, 126.3,
126.0, 124.7, 124.1, 118.4, 111.1, 60.1, 45.2, 33.4, 19.7, 18.3, 17.7,
15.9, 15.8, 14.5, 13.6; HRMS (3.8 kV, 25 °C): m/z = 673.3025 (calcd
673.3003 for [C38H47N3O4S2]+); Anal. C: 67.37 H: 7.06 N: 6.34 S
2.4. General Stille coupling procedure
In a 25 mL round-bottomed flask N-butyl-2,5-bis(5-(tributyl-
stannyl)thiophen-2-yl)pyrrole 15 and the monomers 6, 10, 12
(2.05 eq) respectively were dissolved in toluene (20 mL per mmol
iodopyrrol), the mixture deaerated and an argon atmosphere was
set up. Tetrakis (triphenylphosphine) palladium (0) (6 mol%) was
added and the mixture heated under reflux for 4 days. The solvent
was removed under low pressure and the crude product purified
by column chromatography.
2.4.1. Diethyl 5,50- (5,50-(N-butyl-pyrrole-2,5-diyl)bis(thiophene-5,2-
diyl)bis(N-ethyl-3,4-ethylenedioxypyrrole-2-carboxylate) 16
Stille-coupling of N-butyl-2,5-bis(5-(tributylstannyl)thiophen-
2-yl)pyrrole 15 (0.65 g, 0.75 mmol) and 2-ethyl N-ethyl-3,4-
ethylenedioxy-5-iodopyrrole-2-carboxylate
6
(0.52 g, 2.05 eq,
9.49 (calcd for C38H47N3O4S2 C: 67.72 H: 7.03 N: 6.24 S: 9.52); IR
3315 (NH), 1657 (C@O) cmꢁ1; UV/vis (kmax, CHCl3): 378 nm (log
= 4.60), 303 nm (log = 4.24).
m
1.54 mmol). The yellow crude product was purified by column chro-
matography (ethyl acetate/hexane 1:1 Rf: 0.35) and recrystallized
from heptane to yield 0.29 g (52%) 16 as a yellow solid: mp. 146–
147 °C; 1H NMR (500 MHz, CDCl3, 25 °C): d 7.21 (d, J = 4 Hz, 2H,
ThAH), 7.07 (d, J = 4 Hz, 2H, ThAH), 6.39 (s, 2H, PyrAH), 4.46 (q,
J = 7 Hz, 4H, NACH2CH3), 4.36 (q, J = 7 Hz, 4H, OACH2), 4.36–4.34/
4.28–4.26 (m, 8H, OACH2CH2AO), 4.24–4.21 (m, 2H,
NACH2CH2CH2CH3), 1.65 (pent, J = 7.5 Hz, 2H, NACH2CH2CH2CH3),
1.39 (t, 6H, J = 7 Hz, CH3), 1.31 (t, 6H, J = 7 Hz, CH3), 1.22 (sex,
J = 7.5 Hz, 2H, NACH2CH2CH2CH3), 0.82 (t, 3H, J = 7.5 Hz,
NACH2CH2CH2CH3); 13C NMR (125 MHz, CDCl3, 25 °C): d 160.6,
137.7, 135.8, 129.8, 129.1, 128.4, 128.1, 125.6, 116.1, 111.2, 105.3,
66.1, 65.4, 59.9, 45.2, 40.8, 33.4, 19.7, 16.9, 14.6, 13.6; HRMS
(3.8 kV, 25 °C): m/z = 733.2453, 734.2484, 735.2505 (calcd
733.2468, 734.2517, 735.2501 for [C38H43N3O8S2]+), m/z = (calcd
for [C38H43N3O8S2]+); Anal. C: 61.97 H: 5.85 N: 5.78 S: 8.65
e
e
2.4.4. Diethyl 5,50- (5,50-(N-butylpyrrole-2,5-diyl)bis(thiophene-5,2-
diyl)bis(N-ethyl-3,4-diethylpyrrole-2-carboxylate) 19
Sodium hydride (0.05 g, 10 eq, 2.2 mmol) was slowly added to a
solution of diethyl 5,50-(5,50-(N-butylpyrrole-2,5-diyl)bis(thio-
phene-5,2-diyl)bis(3,4-diethylpyrrole-2-carboxylate) 18 (0.15 g,
0.22 mmol) in dry dimethyl formamide (5 mL) at 0 °C. After stirring
for 15 min at 0 °C iodoethan (0.15 g, 4.2 eq, 0.93 mmol) was added
to the orange/brown suspension via a syringe, the mixture was stir-
red at room temperature over night and finally 4 h at 50 °C to com-
plete reaction. By pouring in saturated aqueous NH4Cl at 0 °C the
reaction was quenched, the solvent was removed at low pressure,
and the obtained yellow crude product was purified by column
chromatography (ethyl acetate/hexane 3:2 Rf: 0.45) to yield 0.13 g
(78%) 19 as a pale yellow solid: mp. 59–60 °C; 1H NMR (500 MHz,
CDCl3, 25 °C): d 7.09 (d, J = 3.5 Hz, 2H, ThAH), 7.00 (d, J = 3.5 Hz,
2H, ThAH), 6.42 (s, 2H, PyrAH), 4.35 (q, J = 7 Hz, 4H, OCH2), 4.29
(q, J = 7 Hz, 4H, NACH2CH3), 4.26–4.23 (m, 2H, NACH2CH2CH2CH3),
2.78 (q, J = 7.5 Hz, 4H, PyrACH2), 2.42 (q, J = 7.5 Hz, 4H, PyrACH2),
1.68–1.62 (m, 2H, NACH2CH2CH2CH3), 1.40 (t, J = 7 Hz, 6H,
COOCH2ACH3), 1.29 (t, 6H, J = 7 Hz, PyrACH2ACH3), 1.20 (t, 6H,
J = 7.5 Hz, PyrACH2ACH3), 1.29–1.20 (m, 2H, NACH2CH2CH2CH3),
1.06 (t, 6H, J = 7.5 Hz, NACH2CH3), 0.81 (t, 3H, J = 7.5 Hz,
NACH2CH2CH2CH3); 13C NMR (125 MHz, CDCl3, 25 °C): d 161.7,
136.7, 133.8, 132.1, 129.7, 128.5, 128.3, 126.0, 125.7, 118.9, 110.9,
59.6, 45.1, 41.3, 33.4, 19.7, 19.2, 17.7, 17.4, 16.6, 16.1, 14.3, 13.5;
HRMS (3.8 kV, 25 °C): m/z = 730.3701 (calcd 730.3712 for
[C42H55N3O4S2 + H]+), m/z = 752.3530 (calcd 752.35317 for
(calcd for C38H43N3O8S2 C: 62.19 H: 5.91 N: 5.73 S: 8.74); IR
(C@O) cmꢁ1; UV/vis (kmax, CHCl3): 291 nm (log
= 4.35), 379 nm
(log = 4.62).
m 1682
e
e
2.4.2. Dimethyl 5,50- (5,50-(N-butylpyrrole-2,5-diyl)bis(thiophene-5,2-
diyl)bis(N-ethyl-3,4-diethoxypyrrole-2-carboxylate) 17
Stille-coupling of N-butyl-2,5-bis(5-(tributylstannyl)thiophen-
2-yl)-1H-pyrrole 15 (0.44 g, 0.50 mmol) and methyl N-ethyl-2-
iodo-3,4-diethoxypyrrole-5-carboxylate 10 (0.38 g, 2.05 eq,
1.0 mmol). The orange crude product was purified by column chro-
matography (ethyl acetate/hexane 1:4 Rf: 0.28) and recrystallized
from heptane to yield 0.225 g (59%) 17 as a bright yellow solid:
mp. 77–78 °C; 1H NMR (500 MHz, CDCl3, 25 °C):
d 7.13 (d,
J = 3.5 Hz, 2H, ThAH), 7.07 (d, J = 3.5 Hz, 2H, ThAH), 6.41 (s, 2H,
PyrAH), 4.39 (q, J = 7 Hz, 4H, NACH2CH3), 4.26–4.23 (m, 2H,
NACH2CH2CH2CH3), 4.15 (q, J = 7 Hz, 4H, OACH2), 4.00 (q, J = 7 Hz,
4H, OACH2), 3.87 (s, 6H, OCH3), 1.65–1.56 (pent (br), J = 7.5 Hz,
2H, NACH2CH2CH2CH3), 1.39 (t, 6H, J = 7 Hz, CH3), 1.32 (t, 6H,
J = 7 Hz, CH3), 1.26 (t, 6H, J = 7 Hz, CH3), 1.21 (sex, J = 7.5 Hz, 2H,
NACH2CH2CH2CH3), 0.79 (t, 3H, J = 7.5 Hz, NACH2CH2CH2CH3); 13C
NMR (125 MHz, CDCl3, 25 °C): d 161.2, 143.3, 136.3, 135.9, 129.5,
128.4, 125.6, 121.7, 111.1, 110.1, 70.2, 69.8, 51.0, 45.2, 41.1, 33.3,
19.7, 17.0, 15.6, 15.5, 13.6; HRMS (3.8 kV, 25 °C): m/z = 766.3205
(calcd 766.3196 for [C40H51N3O4S2 + H]+), m/z = 788.3033
(calcd 788.3015 for [C40H51N3O4S2 + Na]+), m/z = 1553.6178 (calcd
1553.6133 for [2 x C40H51N3O4S2 + Na]+), m/z = 804.2791 (calcd
804.2755 for [C40H51N3O4S2 + K]+); Anal. C: 62.48 H: 6.60 N: 5.49
S: 8.20 (calcd for C40H51N3O4S2 C: 62.72 H: 6.71 N: 5.49 S: 8.37);
[C42H55N3O4S2 + Na]+); IR
341 nm (log = 4.40), 285 nm (log
m
1693 (C@O); UV/vis (kmax, CHCl3):
= 4.35).
e
e
3. Results and discussion
The general synthetic route to the pyrrole monomers is illus-
trated in Scheme 1. Compound 12 is an already known pyrrole sub-
strate that is frequently used in the porphyrinoid synthesis [30]
and in the Suzuki cross coupling [21]. 12 could be easily obtained
in good yield by iodination of the commercially available pyrrole
ester 11. The ether substituted new iodo monomers 6, 10 were pre-
pared according to procedures described in Refs. [49,50] and were
isolated in 15.5% (5 steps) and 20.5% (3 steps) overall yield,
respectively.
IR
m e = 4.54).
1689 (C@O) cmꢁ1; UV/vis (kmax, CHCl3): 364 nm (log