Investigation of Tightly Coupled Porphyrin Arrays
J . Org. Chem., Vol. 65, No. 22, 2000 7377
5-(4-Meth ylth iop h en yl)d ip yr r om eth a n e (5). Following
a general procedure,14,15 pyrrole (50.0 mL, 720 mmol) and
4-(methylthio)benzaldehyde (3.83 mL, 28.8 mmol) were added
to a 250 mL flask and degassed with a stream of argon. Then
TFA (0.22 mL, 2.9 mmol) was added, and the mixture was
stirred under argon at room temperature for 5 min and then
quenched with 0.1 M NaOH. Ethyl acetate was then added,
and the organic phase was washed with water and dried (Na2-
SO4). Then the solvent was removed under vacuum to afford
an orange oil. Bulb-to-bulb distillation (200 °C, 0.01 mmHg)
gave a yellow oil. The oil was dissolved in ethanol, and addition
of a small amount of water resulted in white crystals (5.00 g,
CH2Cl2. The organic phase was dried (K2CO3) and the solvent
was removed. The resulting yellow foam and 6 (204 mg, 686
µmol) were dissolved in acetonitrile (275 mL), and stirred at
room temperature. Then TFA (640 µL, 8.3 mmol) was added,
and the solution immediately turned dark blue. After 25 min
DDQ (467 mg, 2.1 mmol) was added because the yield did not
increase any further (checked by oxidizing an aliquot with
DDQ and quantifying with UV/vis spectroscopy). After 1.5 h,
the mixture was filtered through a pad of alumina (CH2Cl2).
The solvent was removed and the residue was purified by
column chromatography on silica (first column: CH2Cl2/
hexanes, 1:4-1:1; second column: CH2Cl2/hexanes, 1:2). Two
brown-purple solids were obtained, yielding the disulfide 9 (14
mg, 3%) and 8 (57 mg, 10%). Data for 9: IR (neat) ν˜ 3316,
1
64.7%): mp 94-95 °C; H NMR δ 2.51 (s, 3H), 5.43 (s, 1H),
5.95 (s, 2H), 6.21 (m, 2H), 6.69 (m, 2H), 7.17, 7.25 (AA′BB′, 2
× 2H), 7.87 (brs, 2H); 13C NMR δ 16.6, 44.1, 108.0, 109.2, 118.1,
127.6, 129.6, 133.1, 137.7, 139.8; EI-MS obsd 268.1033, calcd
exact mass 268.1034. Anal. Calcd for C16H16N2S: C, 71.60; H,
6.01; N, 10.44; S, 11.95. Found: C, 71.60; H, 5.99; N, 10.31; S,
11.81.
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2961, 2924, 2854, 1592, 1466; H NMR δ -2.94 (s, 4H), 1.52
(s, 72H), 7.79 (t, J ) 1.5 Hz, 4H), 8.10, 8.30 (AA′BB′, 2 × 4H),
8.10 (d, J ) 1.5 Hz, 8H), 8.94 (d, J ) 5.1 Hz, 4H), 8.96 (d, J )
5.1 Hz, 4H), 9.07 (d, J ) 5.1 Hz, 4H), 9.34 (d, J ) 4.4 Hz, 4H),
10.22 (s, 2H); LD-MS obsd 1589.4; FAB-MS obsd 1586.87, calcd
exact mass 1586.86 (C108H114N8S2); λabs 417, 511, 544, 586, 642
nm. Data for 8: IR (neat) ν˜ 3307, 2958, 2861, 1708, 1590, 1467;
1H NMR δ -2.95 (s, 2H), 1.55 (s, 36H), 2.60 (s, 3H), 7.81, 8.28
(AA′BB′, 2 × 2H), 7.82 (t, J ) 1.5 Hz, 2H), 8.12 (d, J ) 1.5 Hz,
4H), 8.88 (d, J ) 5.1 Hz, 2H), 8.97 (d, J ) 5.1 Hz, 2H), 9.08 (d,
J ) 5.1 Hz, 2H), 9.35 (d, J ) 4.4 Hz, 2H), 10.2 (s, 1H); LD-MS
obsd 837.2; FAB-MS obsd 836.4503, calcd exact mass 836.4488
(C56H60N4OS); λabs 416, 510, 544, 585, 641 nm.
Zin c(II)-5-[4-(S-Acetylth io)p h en yl]-10,20-bis(3,5-d i-ter t-
bu tylp h en yl)p or p h yr in (Zn -8). A solution of 8 (56 mg, 67
µmol) in CHCl3 (20 mL) was treated with a solution of Zn-
(OAc)2‚2H2O (734 mg, 3.3 mmol) in methanol (5 mL) and the
mixture was stirred for 6.5 h. Purification by column chroma-
tography (silica, CH2Cl2/hexanes, 1:1) afforded a purple solid
(54 mg, 90%): IR (neat) ν˜ 3066, 2956, 1703, 1675, 1590, 1469;
1H NMR δ 1.55 (s, 36H), 2.59 (s, 3H), 7.79, 8.28 (AA′BB′, 2 ×
2H), 7.82 (t, J ) 2.2 Hz, 2H), 8.12 (d, J ) 2.2 Hz, 4H), 8.99 (d,
J ) 4.4 Hz, 2H), 9.06 (d, J ) 4.4 Hz, 2H), 9.17 (d, J ) 4.4 Hz,
2H), 9.43 (d, J ) 4.4 Hz, 2H), 10.29 (s, 1H); LD-MS obsd 900.1;
FAB-MS obsd 898.3617, calcd exact mass 898.3623 (C56H58N4-
OSZn); λabs 420, 545, 583 nm; λem 591, 640 nm.
5-[4-(S-Acetylth io)p h en yl]d ip yr r om eth a n e (6). Follow-
ing a general procedure,14,15 pyrrole (34.0 mL, 489 mmol) and
4-(S-acetylthio)benzaldehyde12 (3.50 g, 19.4 mmol) were added
to a 100 mL flask and degassed with a stream of argon. Then
TFA (0.15 mL, 1.9 mmol) was added, and the mixture was
stirred under argon at room temperature for 5 min and then
quenched with N,N-diisopropylethylamine (0.330 mL, 1.94
mmol). All volatile materials were evaporated under high-
vacuum. The crude mixture was filtered through a pad of silica
to afford a yellow oil, which was dissolved in ethanol and
allowed to stand at -20 °C for 3 days. Yellowish crystals were
isolated by filtration. The filtrate was concentrated, a small
amount of water was added, and the mixture was allowed to
stand at -20 °C for a few days, affording a second crop of
1
crystals giving 3.56 g altogether (62%): mp 100-101 °C; H
NMR δ 2.44 (s, 3H), 5.40 (s, 1H), 5.90 (s, 2H), 6.18 (m, 2H),
6.62 (m, 2H), 7.20, 7.34 (AA′BB′, 2 × 2H), 7.97 (brs, 2H); 13C
NMR δ 31.0, 44.3, 108.2, 108.9, 118.3, 126.8, 130.1, 132.8,
135.3, 144.7, 195.7; EI-MS obsd 296.0996, calcd exact mass
296.0983. Anal. Calcd for C17H16N2OS: C, 68.89; H, 5.44; N,
9.45; S, 10.82. Found: C, 68.69; H, 5.56; N, 9.39; S, 10.91.
1,9-Bis(3,5-d i-ter t-b u t ylb en zoyl)d ip yr r om et h a n e (7).
To a solution of dipyrromethane15 (421 mg, 2.9 mmol) in
toluene (60 mL) stirred under argon and cooled in a water bath
was slowly added a solution of ethylmagnesium bromide (1 M
solution in THF, 14.4 mL, 14.4 mmol). The resulting brown-
orange mixture was stirred for 30 min at ambient temperature.
Zin c(II) Disu lfid e Zn -9. A solution of 9 (14 mg, 8.8 µmol)
in CHCl3 (5 mL) was treated with a solution of Zn(OAc)2‚2H2O
(193 mg, 879 µmol) in methanol (2 mL), and the mixture was
stirred for 7 h. Then additional Zn(OAc)2‚2H2O (194 mg, 879
µmol) was added, and stirring was continued for 15.5 h.
Purification by column chromatography (silica, CH2Cl2/hex-
anes, 1:2) afforded an orange-purple solid (9.0 mg, 60%): IR
[In
a separate reaction, 3,5-di-tert-butylbenzoic acid was
1
refluxed in thionyl chloride in the presence of 1 vol % DMF,
affording a colorless liquid (bp 167 °C; water suction pump)
in 89% yield.] A solution of 3,5-di-tert-butylbenzoyl chloride
(1.82 g, 7.2 mmol) in toluene (8 mL) was added dropwise to
the dipyrromethane-containing mixture. The solution became
darker and was stirred for 2 h after the addition was
completed. Then the reaction was quenched with saturated
aqueous NH4Cl (30 mL). Ethyl acetate was added, and the
organic phase was washed with water, 2 M aqueous NaOH,
water, and brine and then dried (Na2SO4). The solvent was
removed, and the residue was filtered through a pad of silica
(CH2Cl2/ethyl acetate gradient, 6:1-5:3). The solvent was
again removed, and the residue was dissolved in a small
amount of ethyl acetate. Hexanes was added until turbidity
occurred. The mixture was cooled overnight at -20 °C and
filtered, affording a white powder (442 mg, 27%): mp 220 °C;
(neat) ν˜ 3067, 2959, 2923, 2862, 1592, 1468; H NMR δ 1.51
(s, 72H), 7.78 (s, 4H), 8.10, 8.30 (AA′BB′, 2 × 4H), 8.10 (s, 8H),
9.05 (s, 8H), 9.16 (d, J ) 4.4 Hz, 4H), 9.42 (d, J ) 4.4 Hz, 4H),
10.28 (s, 2H); LD-MS obsd 1716.6; FAB-MS obsd 1710.71, calcd
exact mass 1710.69 (C108H110N8S2Zn2); λabs 421, 545, 585 nm;
λem 594, 641 nm.
5,10,15-Tr is(3,5-di-ter t-bu tylph en yl)por ph yr in (10). Fol-
lowing a general procedure,13,22 a solution of 7 (578 mg, 1.0
mmol) in THF/methanol (30 mL, 2:1) under argon was treated
with NaBH4 (1.89 g, 50 mmol) in several portions. The mixture
was stirred for 2 h, then quenched with water and extracted
with CH2Cl2. The organic phase was dried (K2CO3) and the
solvent was removed. The resulting orange oil and 5-(3,5-di-
tert-butylphenyl)dipyrromethane17 (334 mg, 1.0 mmol) were
dissolved in acetonitrile (400 mL) and stirred at room tem-
perature. Then TFA (930 µL, 12.1 mmol) was added, and the
solution immediately turned dark blue. After 25 min DDQ (680
mg, 3.0 mmol) was added because the yield did not increase
any further (checked by oxidizing an aliquot with DDQ and
quantifying with UV/vis spectroscopy). After 75 min, the
solution was filtered through a pad of alumina and eluted with
CH2Cl2. Further purification by column chromatography (silica,
CH2Cl2/hexanes, 1:4-1:2) afforded a purple solid (183 mg,
21%): IR (neat) ν˜ 3305, 3064, 2958, 1588, 1468; 1H NMR δ
-2.91 (s, 2H), 1.51 (s, 18H), 1.55 (s, 36H), 7.79 (t, J ) 1.5 Hz,
1H), 7.81 (t, J ) 2.2 Hz, 2H), 8.0-8.2 (m, 6H), 8.92 (d, J ) 5.1
Hz, 2H), 8.96 (d, J ) 5.1 Hz, 2H), 9.07 (d, J ) 4.4 Hz, 2H),
9.34 (d, J ) 5.1 Hz, 2H), 10.20 (s, 1H); LD-MS obsd 875.7;
1
IR (neat) ν˜ 3263, 2963, 1607, 1582, 1485; H NMR δ 1.32 (s,
36H), 4.27 (s, 2H), 6.17-6.13 (m, 2H), 6.71-6.77 (m, 2H), 7.57
(s, 2H), 7.72 (s, 4H), 11.47 (brs, 2H); 13C NMR (APT): δ 26.8
(+), 31.3 (-), 34.9 (+), 110.0 (-), 121.1 (-), 123.6 (-), 125.6
(-), 131.2 (+), 137.5 (+), 138.0 (+), 150.5 (+), 185.6 (-). Anal.
Calcd for C39H50N2O2: C, 80.93; H, 8.71; N, 4.84; Found: C,
80.69; H, 8.72; N, 4.85.
5-[4-(S-Acet ylt h io)p h en yl]-10,20-b is(3,5-d i-ter t-b u t yl-
p h en yl)p or p h yr in (8). To a solution of 7 (397 mg, 686 µmol)
in THF/methanol (21 mL, 2:1) under argon was added NaBH4
(1.30 g, 34 mmol) in several portions. The mixture was stirred
for 2.5 h, quenched with water (40 mL), and extracted with