Hexameric Wheel of Porphyrins
J. Am. Chem. Soc., Vol. 121, No. 38, 1999 8939
5,15-Dimesityl-10,20-bis(4-ethynylphenyl)porphyrin (Fb-3). A
sample of Zn-3 (210 mg, 0.26 mmol) was dissolved in CH2Cl2 (50
mL) and treated with TFA (0.30 mL). The demetalation was complete
after 30 min as evidenced by TLC and fluorescence excitation
spectroscopy. The reaction mixture was washed with NaHCO3 (10%,
2 × 50 mL), further neutralized with triethylamine (0.6 mL), washed
again with NaHCO3 (50 mL) and once with water, dried (Na2SO4),
filtered, and rotary evaporated to give a purple solid (192 mg, 99%):
1H NMR δ -2.66 (s, 2 H, NH), 1.83 (s, 12 H, ArCH3), 2.63 (s, 6 H,
ArCH3), 7.28 (s, 6 H, ArH), 7.87 (d, J ) 8.1 Hz, 4 H, ArH), 8.17 (d,
J ) 8.1 Hz, 4 H, ArH), 8.69 (d, J ) 4.8 Hz, 4 H, â-pyrrole), 8.76 (d,
J ) 4.8 Hz, 4 H, â-pyrrole); LD-MS obsd 748.8; HRMS (FAB) obsd
747.3524, calcd 747.3488 (C54H42N4); λabs (toluene) 421, 515, 549, 592
nm.
Magnesium 5,15-dimesityl-10,20-bis(4-ethynylphenyl)porphyrin
(Mg-3). To a sample of Fb-3 (90 mg, 0.12 mmol) in CH2Cl2 (15 mL)
was added N,N-diisopropylethylamine (1.00 mL, 4.78 mmol) and MgI2
(334 mg, 1.2 mmol).57 The reaction mixture was stirred at room
temperature. After 30 min the reaction was judged to be complete by
TLC and fluorescence excitation spectroscopy. The reaction mixture
was diluted with CH2Cl2 (30 mL), washed with NaHCO3 (10%, 3 ×
50 mL), dried (Na2SO4), filtered, concentrated, and chromatographed
(alumina, grade V,5e toluene/ethyl acetate 10:1) affording a purple solid
(84 mg, 90%): 1H NMR δ 1.82 (s, 12 H, ArCH3), 2.63 (s, 6 H, ArCH3),
3.30 (s, 2 H, CC-H), 7.27 (s, 6 H, ArH), 7.84 (d, J ) 8.1 Hz, 4 H,
ArH), 8.18 (d, J ) 8.1 Hz, 4 H, ArH), 8.68 (d, J ) 4.2 Hz, 4 H,
â-pyrrole), 8.76 (d, J ) 4.2 Hz, 4 H, â-pyrrole); LD-MS obsd 769.7;
HRMS (FAB) obsd 768.3101, calcd 768.3103 (C54H40N4Mg); λabs
(toluene) 429, 565, 608 nm.
5,15-Dimesityl-10,20-bis(3-iodophenyl)porphyrin (Fb-4). 5-mesi-
tyldipyrromethane56 (2.64 g, 10.0 mmol) and 3-iodobenzaldehyde (2.32
g, 10.0 mmol) were reacted in CH2Cl2 (1000 mL) with TFA catalysis
(1.37 mL, 17.8 mmol). After 30 min DDQ (2.27 g, 10.0 mmol) was
added, and the reaction mixture was stirred at room temperature for a
further 1 h. Workup using a pad of alumina and CH2Cl2 as eluant gave
a purple solid (1.46 g, 31%): 1H NMR δ -2.70 (s, 2H, NH), 1.83 (m,
12H, ArCH3), 2.64 (s, 6H, ArCH3), 7.29 (s, 4H, ArH), 7.47 (t, J ) 7.5
Hz, 2H, ArH), 8.10, 8.13(m, 2H, ArH), 8.17 (d, J ) 7.5 Hz, ArH),
8.58 (t, J ) 1.5 Hz, 2H, ArH), 8.70 (d, J ) 4.5 Hz, â pyrrole), 8.76 (d,
J ) 4.5 Hz, â pyrrole); LD-MS obsd 952.6; HRMS (FAB) obsd
950.1319, calcd 950.1343 (C50H40N4I2); λabs (toluene) 424, 515, 590
nm.
Zinc 5,15-dimesityl-10,20-bis(3-iodophenyl) porphyrin (Zn-4). To
a sample of Fb-4 (80 mg, 0.084 mmol) in CHCl3 (25 mL) was added
a solution of Zn(OAc)2‚2H2O (40 mg, 0.18 mmol) in methanol (5 mL).
The reaction mixture was stirred at room-temperature overnight, and
the metalation was finished as evidenced by TLC and fluorescence
excitation spectroscopy. The reaction mixture was then washed with
NaHCO3 (10%, 3 × 30 mL), H2O (30 mL), dried (Na2SO4), filtered,
and concentrated affording a purple solid (85 mg, 100%): 1H NMR δ
1.82 (m, 12 H, ArCH3), 2.64 (s, 6 H, ArCH3), 7.29 (s, 6 H, ArH), 7.47
(t, J ) 8.1 Hz, 2H, ArH), 8.10 (d, J ) 8.1 Hz, 2H, ArH), 8.19 (d, J )
8.1 Hz, 2 H, ArH), 8.60 (t, J ) 1.5 Hz, 2 H, ArH), 8.78 (d, J ) 5.1
Hz, 4 H, â-pyrrole), 8.85 (d, J ) 5.1 Hz, 4 H, â-pyrrole); LD-MS
obsd 1015.4; HRMS (FAB) obsd 1012.0486, calcd 1012.0477 (C50H38N4-
ZnI2); λabs (toluene) 423, 550, 589 nm.
cyclo-Zn3Fb3U-p/m. Samples of Fb-4 (237.5 mg, 0.25 mmol), Zn-3
(202.5 mg, 0.25 mmol), Pd2(dba)3 (35.5 mg, 0.039 mmol), AsPh3 (110.4
mg, 0.36 mmol), and template 1 (156.0 mg, 0.25 mmol) were added to
a 200 mL Schlenk flask. The flask was pump-purged three times, and
100 mL of deaerated toluene/triethylamine (5:1) was added by syringe.
The flask was immersed in an oil bath at 35 °C and stirred under argon
overnight. The reaction was complete as indicated by analytical SEC.
The solvent was removed in vacuo. The crude reaction mixture was
dissolved in CHCl3 and loaded onto a silica gel column (5.5 × 25
cm). Eluting with CHCl3 afforded porphyrin oligomers as well as some
high-molecular weight material as the first band, which was collected
and concentrated to dryness. The porphyrin mixture obtained was then
dissolved in a minimum of THF (∼30 mL), and half of the solution
was loaded onto a preparative SEC column (4 cm × 60 cm), and eluted
with THF. The other half of the solution was treated likewise. In each
case the desired hexamer eluted as the second band contaminated with
some high-molecular weight material from the first band (heptamer,
pentamer, and tetramer). The respective second bands from the two
columns were combined, loaded onto the same SEC column, and eluted
with THF. The first band was collected in small fractions and examined
by analytical SEC. The fractions containing hexamer were combined
and concentrated to dryness. The crude product obtained was then
dissolved in 5 mL of CHCl3 and precipitated by the addition of an
equal volume of hexanes. The resulting mixture was stored at -20 °C
overnight. The precipitate formed was isolated by filtration and washed
with hexanes/CHCl3 (7:3) until the washings were free from the
impurity (∼50 mL), affording 18.6 mg of a purple solid. The mother
solution as well as the filtrate were then combined, concentrated to
dryness, redissolved in THF, and loaded on the same SEC column.
The fractions containing the hexamer were then combined, and further
purified by the similar procedure, affording another 5.2 mg of purple
solid. The 18.6 mg and 5.2 mg samples were combined, dissolved in
CHCl3, and loaded on a silica gel column (2.5 × 15 cm) packed with
the same solvent. Eluting with CHCl3 afforded the main first band
containing the pure hexamer, which was collected, affording a purple
solid (20.1 mg, 5.3%): 1H NMR δ -2.60 (s, 6H, NH), 1.71 (s, 36 H,
ArCH3), 1.87, 1.88 (m, 36 H, ArCH3), 2.58, 2.64 (m, 36 H, ArCH3),
7.22-7.30 (m, 24 H, ArH), 7.83 (t, J ) 7.5 Hz, 6H, ArH), 7.91 (d, J
) 7.5 Hz, 6H, ArH, 8.07 (d, J ) 7.5 Hz, 6 H, ArH), 8.28-8.33 (m, 6
H, ArH), 8.50 (bs, 6H, ArH), 8.73-8.77 (m, 24 H, â pyrrole), 8.83 (d,
J ) 4.5 Hz, 12 H, â pyrrole), 8.87 (d, J ) 4.5 Hz, 12 H, â pyrrole);
LD-MS obsd 4511.7, calcd av mass 4515.5 (C312H234N24Zn3); λabs in
toluene (log ꢀ) 428 (6.40, fwhm ) 19 nm), 515 (4.95), 550 (5.06), 592
(4.62), 648 (4.11) nm; λem (λexc ) 550 nm, in toluene) 649, 718 nm
(Φf ) 0.11).
cyclo-Zn6U-p/m. A sample of cyclo-Zn3Fb3U-p/m (5.0 mg, 1.37
µmol) was dissolved in CHCl3 (7.0 mL), and then a solution of Zn-
(OAc)2‚2H2O (2.5 mg, 4.6 µmol) in methanol (1.5 mL) was added.
The reaction mixture was stirred at room-temperature overnight, and
the metalation was finished as judged by fluorescence excitation
spectroscopy. The reaction mixture was then washed with NaHCO3
(10%), H2O, dried (Na2SO4), filtered, and concentrated, affording a
purple solid (4.86 mg, 94%): 1H NMR δ 1.78, 1.86 (m, 72 H, ArCH3),
2.57, 2.65 (m, 36 H, ArCH3), 7.22 (s, 12 H, ArH), 7.28 (s, 12 H, ArH),
7.82 (t, J ) 8.1 Hz, 6 H, ArH), 7.89 (d, J ) 7.8 Hz, 12 H, ArH), 8.07
(d, J ) 8.1 Hz, 6 H, ArH), 8.16 (d, J ) 7.8 Hz, 12 H, ArH), 8.31 (d,
J ) 8.1 Hz, 6 H, ArH), 8.52 (s, 6 H, ArH), 8.72 (d, J ) 5.1 Hz, 12 H,
â-pyrrole), 8.30, 8.47 (m, 24 H, â-pyrrole), 8.96 (d, J ) 5.1 Hz, 12 H,
â-pyrrole); LD-MS obsd 4711.2, calcd av mass 4705.7 (C312H228N24-
Zn6); λabs in toluene (log ꢀ) 429 (6.43, fwhm ) 18 nm), 550 (5.28),
592 (4.67) nm; λem (λexc ) 550 nm, in toluene) 599, 646 nm (Φf )
0.039).
Magnesium 5,15-dimesityl-10,20-bis(3-iodophenyl) porphyrin
(Mg-4). To a sample of Fb-4 (80 mg, 0.084 mmol) in CH2Cl2 (12
mL) was added N,N-diisopropylethylamine (0.80 mL, 3.8 mmol) and
MgI2 (234 mg, 0.84 mmol).57 The reaction mixture was stirred at room
temperature, and after 30 min was judged to be complete by TLC and
fluorescence excitation spectroscopy. The reaction mixture was diluted
with CH2Cl2 (20 mL), washed with NaHCO3 (10%, 3 × 30 mL), dried
(Na2SO4), filtered, concentrated, and chromatographed (alumina, grade
V,5e toluene/ethyl acetate 10:1) affording a purple solid (75 mg, 92%):
1H NMR δ 1.82 (m, 12 H, ArCH3), 2.64 (s, 6 H, ArCH3), 7.28 (s, 6 H,
ArH), 7.44 (t, J ) 8.1 Hz, 2 H, ArH), 8.07 (d, J ) 8.1 Hz, 2 H, ArH),
8.18 (d, J ) 8.1 Hz, 2 H, ArH), 8.60 (m, 2 H, ArH), 8.69 (d, J ) 4.8
Hz, 4 H, â-pyrrole), 8.75 (d, J ) 4.8 Hz, 4 H, â-pyrrole); LD-MS
obsd 975.2; HRMS (FAB) obsd 972.1100, calcd 972.1036 (C50H38N4-
MgI2); λabs (toluene) 428, 565, 607 nm.
Zinc(II)-5,10,15-trimesityl-20-(3-iodophenyl)porphyrin. 3-iodo-
benzaldehye (617 mg, 2.66 mmol), mesitaldehyde (1.18 mL, 7.98
mmol) and pyrrole (0.738 mL, 10.64 mmol) were dissolved in 1.04 L
CHCl3.69 The resulting mixture was stirred under argon for 15 min at
room temperature, then BF3‚Et2O (3.19 mmol, 1.28 mL of 2.5 M) was
added. After 1 h 1.82 g (8.0 mmol) of DDQ was added, and the reaction
mixture was stirred for another 1 h. The solvent was removed by rotary
(69) Lindsey, J. S.; Wagner, R. W. J. Org. Chem. 1989, 54, 828-836.