Energy Transfer in Dendrimers
FULL PAPER
OCH3), ꢁ2.96 ppm (brs, 2H, NH); MS (MALDI-TOF): m/z: calcd for
0.04 mmol) were dissolved in a mixture of dry DMF (8.0 mL) and dry tol-
uene (16.0 mL). The solution was deoxygenated via bubbling Ar for
10 min and the resulting mixture was heated at 908C for 15 h under Ar.
Allowed to cool, the mixture was quenched with water and extracted
with CH2Cl2. The organic layer was dried over anhydrous MgSO4 and
evaporated. Purification by column chromatography on silica gel, using
THF/petroleum ether 3:7 supplied 8 as a purple crystalline solid (0.096 g,
31%). 1H NMR (300 MHz, CDCl3, 258C): d=9.19 (d, J=4.8 Hz, 2H, b-
pyrrole CH), 8.93 (d, J=4.9 Hz, 2H, b-pyrrole CH), 8.88 (s, 4H, b-pyr-
role CH), 8.14 (d, J=8.2 Hz, 6H, phenyl-H), 7.64 (d, J=7.9 Hz, 1H, aro-
matic CH), 7.29 (d, J=8.8 Hz, 6H, phenyl-H), 7.18 dd, J=6.9 Hz, J=
8.2 Hz, 1H, aromatic CH), 7.05 (d, J=6.5 Hz, 1H, aromatic CH), 6.75 (d,
J=6.6 Hz, 1H, aromatic CH), 6.57 (dd, J=6.7 Hz, J=8.6 Hz, 1H, aro-
matic CH), 6.41 (d, J=8.4 Hz, 1H, aromatic CH), 4.10 (s, 9H, OCH3),
ꢁ2.74 ppm (brs, 2H, NH); MS (MALDI-TOF): m/z: Calcd. for
C41H33N4O3: 629.3; found: 628.9 [M+H]+
C
.
20-Bromo-5,10,15-tris(p-methoxyphenyl)porphyrin (4): Following a stand-
ard procedure,[57] 5,10,15-tris(p-methoxyphenyl)porphyrin (3) (0.571 g,
0.91 mmol) was dissolved in chloroform purged with argon (300.0 mL)
and cooled to 08C. A drop of pyridine (0.40 mL) and NBS (0.194 g,
1.09 mmol) were added, and the reaction stirred at 08C for 30 min. The
reaction mixture was washed with water (3ꢀ100.0 mL). The organic layer
was dried over MgSO4 and concentrated in vacuo. The crude product
was purified by column chromatography (silica gel, CH2Cl2). The frac-
tions containing the product were concentrated to the half volume under
reduced pressure and methanol was added to precipitate the porphyrin
and subsequent filtration gave 4 as a purple solid (0.578 g, 0.82 mmol,
90%). 1H NMR (300 MHz, CDCl3, 258C): d=9.65 (d, J=4.9 Hz, 2H, b-
pyrrole CH), 8.92 (d, J=4.8 Hz, 2H, b-pyrrole CH), 8.82 (s, 4H, b-pyr-
role CH), 8.10 (d, J=8.6 Hz, 4H, phenyl-H), 8.08 (d, J=8.6 Hz, 2H,
phenyl-H), 7.29 (d, J=8.6 Hz, 4H, phenyl-H), 7.27 (d, J=8.4 Hz, 2H,
phenyl-H), 7.28 (d, J=8.5 Hz, 2H, phenyl-H), 4.10 (s, 6H, OCH3), 4.09
(s, 3H, OCH3), ꢁ2.72 ppm (brs, 2H, NH); HRMS (ESI): m/z: calcd for
C53H37BrN4O3: 856.20; found: 856.68 [M]+
C
.
Zinc(II) 5-{8-[zinc(II)-10,15,20-tris(p-methoxyphenyl)porphyrin]-biphe-
nylene-1-yl}-10,15,20-tris(p-methoxyphenyl)porphyrin (9): 5,10,15-Tris(p-
methoxyphenyl)-20-(4,4, 5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)porphi-
natozinc(II) (7) (0.358 g, 0.44 mmol), 1,8-dibromobiphenylene (0.050 g,
C41H32BrN4O3: 707.16523; found: 707.16803 [M+H]+ ; MS (MALDI-
C
TOF): m/z: calcd for C41H33N4O3: 706.16; found: 706.76 [M]+
C
.
0.16 mmol), Cs2CO3 (0.213 g, 0.13 mmol), and [PdACHTNUGTRNEGNU(PPh3)4] (0.062 g,
0.65 mmol) were dissolved in a mixture of dry DMF (9.0 mL) and dry tol-
uene (18.0 mL). The solution was deoxygenated via bubbling Ar for
10 min and the resulting mixture was heated at 908C for 24 h under Ar.
Allowed to cool, the mixture was quenched with water and extracted
with CH2Cl2. The organic layer was dried over anhydrous MgSO4 and
evaporated. Purification by column chromatography on silica gel, using
THF/petroleum ether 3:7 supplied 9 as a brown crystalline solid (0.302 g,
45%). 1H NMR (300 MHz, CDCl3, 258C): d=8.68 (d, J=4.1 Hz, 2H, b-
pyrrole CH), 8.66 (d, J=4.1 Hz, 2H, b-pyrrole CH), 8.52 (d, J=4.7 Hz,
2H, b-pyrrole CH), 8.45 (d, J=4.7 Hz, 2H, b-pyrrole CH), 8.32 (d, J=
7.6 Hz, 1H, aromatic CH), 8.17 (d, J=7.2 Hz, 1H, aromatic CH), 8.06 (d,
J=4.5 Hz, 2H, b-pyrrole CH), 8.05 (d, J=4.5 Hz, 2H, b-pyrrole CH),
7.75 (d, J=7.3 Hz, 1H, aromatic CH), 7.67 (d, J=4.7 Hz, 2H, b-pyrrole
CH), 7.66 (d, J=4.7 Hz, 2H, b-pyrrole CH), 7.62 (d, J=7.3 Hz, 1H, aro-
matic CH), 7.47 (d, J=7.1 Hz, 1H, aromatic CH), 7.30–7.02 (m, 16H,
15H phenyl-H + 1H aromatic CH), 6.93 (m, 6H, phenyl-H), 6.40 (m,
3H, phenyl-H), 4.17 (s, 3H, OCH3), 4.08 ppm (s, 15H, OCH3); MS
(MALDI-TOF): m/z: calcd for C94H64N8O6Zn2: 1528.35; found: 1528.28
20-Bromo-5,10,15-tris(p-methoxyphenyl)porphinatozinc(II) (5): A solu-
tion of porphyrin 4 (0.501 g, 0.80 mmol) in CHCl3 (90.0 mL) was treated
with a saturated solution of zinc acetate in methanol (10.0 mL). The re-
sulting solution was stirred was stirred for 2 h at reflux. After the solvent
was removed, the residue obtained was chromatographed (silica gel,
CH2Cl2/petroleum ether 7:3), to afford 5 as a purple solid (0.620 g,
0.80 mmol, 99%). HRMS (ESI): m/z: calcd forC41H29Br1N4O3ZnNa:
791.06067; found: 791.05951 [M+Na]+ ; MS (MALDI-TOF): m/z: calcd
C
for C41H29BrN4O3Zn768.1; found: 768.1 [M]+
C
.
5,10,15-Tris(p-methoxyphenyl)-20-(4,4,5,5-tetramethyl-1,3,2-dioxaboro-
lan-2-yl)porphyrin (6): Triethylamine (2.7 mL) was added with a syringe
to a solution of 4 (0.425 g, 0.60 mmol), 4,4,5,5-tetramethyl-1,3,2-dioxabor-
olane (0.9 mL, 6.20 mmol) and [PdACHTNUGTRENUNG(PPh3)2Cl2] (0.041 g, 0.06 mmol) in dry
1,2-dichloroethane (74.0 mL) purged with argon (for 15 min) and the sol-
ution was stirred for 2 h at reflux under an argon atmosphere. The reac-
tion was quenched with aqueous NaCl (50.0 mL) and extracted with
CH2Cl2. The organic layer was washed with water (2ꢀ100 mL), dried
over MgSO4 and concentrated in vacuo. The crude product was purified
by column chromatography (silica gel, CH2Cl2/n-heptane 7:3). The
second band was collected, affording a purple solid (0.272 g, 0.36 mmol,
60%). 1H NMR (300 MHz, CDCl3, 258C): d=9.92 (d, J=4.8 Hz, 2H, b-
pyrrole CH), 9.06 (d, J=4.7 Hz, 2H, b-pyrrole CH), 8.92 (d, J=4.7 Hz,
2H, b-pyrrole CH), 8.89 (d, J=4.7 Hz, 2H, b-pyrrole CH), 8.15 (m, 6H,
phenyl-H), 7.30 (m, 6H, phenyl-H), 4.10 (s, 6H, OCH3), 4.07 (s, 3H,
OCH3), 1.88 (s, 12H, CCH3), ꢁ2.67 ppm (brs, 2H, NH); MS (MALDI-
[M]+ ; HRMS (ESI): m/z: Cclcd forC94H64N8O6Zn2: 1528.35263 ; found:
C
1528.35263 [M]+
5-{8-[10,15,20-Tris(p-methoxyphenyl)porphyrin]-biphenylene-1-yl}-
10,15,20-tris(p-methoxyphenyl)porphyrin (10): Compound (0.302 g,
C
.
9
0.20 mmol) was dissolved in dichloromethane (10.0 mL). 6n HCl
(10.0 mL) was added and the resulting mixture was stirred vigorously
during 30 min. The organic layer was separated, washed successively with
saturated, aqueous NaHCO3solution (2ꢀ20.0 mL) and water (2ꢀ
20.0 mL) and then dried over MgSO4. The solvent was removed under re-
duced pressure to afford 10 as a purple solid in quantitative yield
(0.277 mg, 0.20 mmol). 1H NMR (300 MHz, CDCl3, 258C): d=8.65 (d,
J=4.8 Hz, 4H, b-pyrrole CH), 8.44 (d, J=4.7 Hz, 4H, b-pyrrole CH),
8.29 (d, J=8.2 Hz, 2H, aromatic CH), 8.04 (d, J=4.8 Hz, 4H, b-pyrrole
CH), 7.74 (d, J=8.1 Hz, 2H, aromatic CH), 7.65 (d, J=4.8 Hz, 4H, b-
pyrrole CH), 7.42 (d, J=8.3 Hz, 2H, aromatic CH), 7.32–6.98 (m, 16H,
15H phenyl-H + 1H aromatic CH), 6.93 (m, 4H, phenyl-H), 6.39 (m,
4H, phenyl-H), 4.18 (s, 6H, OCH3), 4.08 ppm (s, 12H, OCH3); MS
TOF): m/z: calcd for C47H43BN4O5: 754.33; found: 754.36 [M+H]+
C
.
5,10,15-Tris(p-methoxyphenyl)-20-(4,4,5,5-tetramethyl-1,3,2-dioxaboro-
lan-2-yl)porphinatozinc(II) (7): Triethylamine (3.6 mL) was added with a
syringe to a solution of 5 (0.620 mg, 0.80 mmol), 4,4,5,5-tetramethyl-1,3,2-
dioxaborolane (1.8 mL, 12.41 mmol) and [PdACTHNUGTRNEG(UN PPh3)2Cl2] (0.053 g,
0.08 mmol) in dry 1,2-dichloroethane (48.0 mL) purged with argon (for
15 min) and the solution was stirred for 2 h at reflux under an argon at-
mosphere. The reaction was quenched with aqueous NaCl (50.0 mL) and
extracted with CH2Cl2. The organic layer was washed with water (2ꢀ
100.0 mL), dried over MgSO4 and concentrated in vacuo. The crude
product was purified by column chromatography (silica gel, CH2Cl2/pe-
troleum ether (6:4). The second band was collected, affording a purple
solid (0.358 g, 0.44 mmol, 54%). 1H NMR (300 MHz, CDCl3, 258C): d=
9.92 (d, J=4.8 Hz, 2H, b-pyrrole CH), 9.12 (d, J=4.7 Hz, 2H, b-pyrrole
CH), 8.99 (d, J=4.7 Hz, 2H, b-pyrrole CH), 8.97 (d, J=4.7 Hz, 2H, b-
pyrrole CH), 8.13 (d, J=8.6 Hz, 4H, phenyl-H), 8.11 (d, J=8.6 Hz, 2H,
phenyl-H), 7.23 (m, 6H, phenyl-H), 4.05 (s, 6H, OCH3), 4.02 (s, 3H,
OCH3), 1.88 ppm (s, 12H, CCH3); MS (MALDI-TOF): m/z: calcd for
(MALDI-TOF): m/z: calcd for C94H68N8O6: 1404.53; found: 1404.51 [M]+
C
.
5-{8-[10,15,20-Tris(p-hydroxyphenyl)porphyrin]-biphenylene-1-yl}-
10,15,20-tris(p-hydroxyphenyl)porphyrin
(11):
Boron
tribromide
(0.067 mL, 0.004 mmol) was added to a stirred solution of compound 10
(0.014 mg, 0.01 mmol) in dry dichloromethane (5.0 mL) under Ar. The
resulting mixture was stirred for 18 h at room temperature under Ar,
then cooled to 08C, and treated with H2O (0.5 mL). The reaction mixture
was allowed to return to room temperature and was stirred for a further
1 h. The solvent was removed under vacuum, the residue dissolved in a
mixture of CH2Cl2/Et3N 9:1 (20.0 mL), the solution washed with water
(3ꢀ30.0 mL), dried over MgSO4and evaporated. The crude material was
purified by column chromatography on silica gel, using CH2Cl2/MeOH
C47H41BN4O5Zn: 816.25; found: 816.14 [M]+
C
.
5-(8-Bromobiphenylene-1-yl)-10,15,20-tris(p-methoxyphenyl)porphyrin
(8): Porphyrin 6 (0.347 g, 0.36 mmol), 1,8-dibromobiphenylene (0.201 g,
0.69 mmol), Cs2CO3 (0.200 g, 0.61 mmol), and [PdACHTNUGTRNEGNU(PPh3)4] (0.042 g,
Chem. Eur. J. 2013, 19, 4352 – 4368
ꢂ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4365