Synthesis and photoreaction of a porphyrin-Co(III)-complex linked molecule

Article abstract of DOI:10.1016/S0020-1693(02)01137-4

A dyad molecule composed of a zinc porphyrin and a Co(III) complex that are linked together via a coordination bond underwent intramolecular electron transfer when irradiated with visible light, and subsequent ligand exchange at the Co(II) center led to dissociation of the two moieties.

Full text of DOI:10.1016/S0020-1693(02)01137-4

Inorganica Chimica Acta 342 (2003) 139Á144
/
www.elsevier.com/locate/ica
Synthesis and photoreaction of a porphyrinÁ
/
Co(III)-complex linked
molecule
Toshi Nagata a,b,ꢀ, Yoshihiro Kikuzawa a,b, Atsuhiro Osuka c
a Department of Structural Molecular Science, The Graduate University for Advanced Studies, Myodaiji, Okazaki 444-8585, Japan
b Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan
c Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606, Japan
Received 15 February 2002; accepted 21 May 2002
Abstract
A dyad molecule composed of a zinc porphyrin and a Co(III) complex that are linked together via a coordination bond underwent
intramolecular electron transfer when irradiated with visible light, and subsequent ligand exchange at the Co(II) center led to
dissociation of the two moieties.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Photoreaction; Porphyrin; Cobalt complexes
1. Introduction
generally include intermolecular electron transfer be-
tween photoexcited pigments and electron donorÁac-
/
Covalently-linked porphyrin-acceptor systems have
been actively studied for past 20 years as model systems
for photoinduced electron transfer in photosynthesis [1].
Flash photolysis studies on these systems have provided
information on dynamics of the fast, intramolecular
electron transfer, especially how the rates of electron
transfer are affected by geometrical and energetical
factors [2]. More recently, porphyrin-acceptor systems
linked via non-covalent bonds (such as hydrogen bonds)
have also been studied [3]. On the other hand, one of the
fascinating subjects in photosynthetic model chemistry
is to achieve real chemical changes (i.e. cleavage/forma-
tion of chemical bonds) triggered by photoinduced
electron transfer. There have been reported many
successful systems that undergo redox chemical reac-
tions in the presence of light and ‘sacrificial’ electron
donor (such as tertiary amines [4]) or acceptor (such as
Co(III) complexes [5]) reagents. These systems, however,
ceptor reagents, which introduces complication in
elucidating reaction mechanisms because of the rate-
limiting diffusion process.
In this article, we wish to report synthesis of a dyad
molecule in which a porphyrin and a Co(III) complex
are linked together via a coordination bond. As shown
below, this dyad molecule underwent cleavage of the
porphyrinÁcobalt bond upon irradiation with visible
/
light. Although Co(III) complexes are well-known
electron acceptors that have been used in intramolecular
donor-acceptor systems [6], our dyad is the first example
of a porphyrinÁCo(III) linked molecule in which the
/
Co(III) moiety serves as a sacrificial electron acceptor.
Another interesting feature in our dyad is the use of a
pentadentate ligand [7] that binds the Co(III) center.
Whereas simple Co(III) complexes such as
[Co(NH3)5Cl]2ꢁ often suffer complete solvolysis after
initial photoreduction, the Co(III) moiety in our dyad
retains the pentadentate ligand even after the detach-
ment from the porphyrin moiety. Such a characteristic
may be useful in utilizing the Co(III) complex as an
ꢀ Corresponding author. Tel.: ꢁ
/
81-564-55 7347; fax: ꢁ81-564-54
/
2254
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 1 3 7 - 4

140
T. Nagata et al. / Inorganica Chimica Acta 342 (2003) 139Á144
/
Fig. 1. Cyclic voltammograms of (a) 7, (b) 2, and (c) 1. Conditions:
CH3CN (a) or CH2Cl2 (b and c), 0.1 mol dmꢂ3 Bu4NClO4, Pt working
electrode. The broken line below (c) shows the scan for 1 in the range
ꢂ
/
0.3Á
/
0.3 V, which represents the reversibility of the first oxidation
wave.
1H NMR (500 MHz), ESI-MS, and elemental analysis
(C, H, N).
2.2. Electronic properties of the dyad 1
Scheme 1. Reagents and conditions: (i) CCl3CO2H, CH3CN; (ii)
LiAlH4, Et2O; (iii) SOBr2, CH2Cl2; (iv) sodium imidazolate, THF;
(v) see text.
The cyclic voltammogram of 1 (Fig. 1) in CH2Cl2
revealed two anodic peaks at ꢁ
Fe(C5H5)2Á
[Fe(C5H5)2]ꢁ) and one cathodic peak at
0.95 V. From comparison with the voltammograms
/
0.20 and ꢁ0.47 V (vs.
/
/
ꢂ
/
electron-carrying device in multicomponent redox sys-
tems.
of 2 and 7, the anodic peaks were assigned to the first
and second oxidation of the porphyrin ring, and the
cathodic peak was assigned to the reduction of Co(III)Á
/
Co(II). The cathodic peaks in 2 and 7 showed marked
irreversibility; this can be attributed to the rapid ligand
exchange of the substitutionally-labile Co(II) center.
2. Results and discussion
2.1. Synthesis of the dyad 1
The UVÁ
reference porphyrin compound) in CH2Cl2 (Fig. 2)
showed no significant difference in the range of 350Á
/Vis absorption spectra of 1 and 2 (the
Synthesis of the dyad 1 is shown in Scheme 1. The
imidazole-linked porphyrin 5 was synthesized from a
methoxycarbonyl derivative 2, which was prepared by
cross-condensation of dipyrrolylmethane and corre-
sponding aldehydes followed by chromatographic se-
paration. On the other hand, the pentadentate ligand 6,
first developed by Bernauer et al. [7], was prepared by
/
the reaction of L-proline benzyl ester and 2,6-bis(bro-
momethyl)pyridine, followed by deprotection by hydro-
genolysis. Subsequently, the ligand 6 was treated with
[Co(CH3CN)6](BF4)2 [8] in CH3CN in the presence of 2
equiv. of 2,6-lutidine and precipitated from CH3CNÁ
/
EtOAc to remove 2,6-lutidine×HBF4. The resulting ‘6×
/
/
Co’ material was treated with the imidazole-linked
porphyrin 5 to give the desired dyad molecule 1, which
was obtained as deep red powders after precipitation
Fig. 2. UVÁ
in CH2Cl2 (4.0ꢃ
/
Vis absorption spectra of 1 (solid line) and 2 (broken line)
10ꢂ6 mol dmꢂ3) at room temperature.
from acetoneÁ
/
H2OÁ/NaClO4 and fully characterized by
/

T. Nagata et al. / Inorganica Chimica Acta 342 (2003) 139Á
/
144
141
In summary, our new dyad molecule 1 undergoes
photoinduced electron transfer to give a ‘reactive’ state
of the cobalt center that eventually leads to a cleavage of
the coordination bond. The present system, however, is
still non-productive because the transient Co(II) species
returns to the Co(III) state by fast intermolecular back-
electron transfer. Our next project will be to utilize this
transient reactive species for real chemical transforma-
tion.
3. Experimental
Fig. 3. Steady-state fluorescence spectra of 1 (solid line) and 2 (broken
line) in CH2Cl2 (4.0ꢃ
10ꢂ6 mol dmꢂ3) at room temperature. The
excitation wavelength is 543 nm.
3.1. General
/
All reagents and solvents were of the commercial
reagent grade and were used without further purifica-
tion unless otherwise noted. Dry CH2Cl2 was distilled
from calcium hydride. Dry ether and THF were distilled
from sodium benzophenone ketyl. Acetnitrile and
ethanol were dried over activated molecular sieves 3A.
1H NMR spectra were recorded on a JEOL LAMBDA-
500 (500 MHz) spectrometer, and chemical shifts were
reported in the delta scale relative to Me4Si in ppm.
600 nm. On the other hand, the relative intensity of the
steady-state fluorescence spectrum of 1 was 0.10 com-
pared with that of 2 (Fig. 3). The free energy change
(DG) calculated by the RehmÁ
/
Weller equation [9] was
111 kJ molꢂ1) [10]. The large negative
ꢂ
/
1.15 eV (ꢂ
/
value of DG strongly suggests that the fluorescence of 1
was quenched by the intramolecular electron transfer
from the singlet excited state of the porphyrin to the
Co(III) complex.
UVÁVis absorption spectra were recorded on a Shi-
/
madzu UV-2500PC spectrometer. Steady-state fluores-
cence emission spectra were recorded on a Shimadzu
RF-5300PC spectofluorometer. FAB-MS and ESI-MS
spectra were recorded on a JEOL HX-110 spectrometer
2.3. Photoreaction of the dyad 1
When a solution of 1 in CDCl3ꢁ
/
CD3CN (v/vꢄ1/5)
/
and a PerkinÁElmer SCIEX API 300 spectrometer,
/
was irradiated with a halogen lamp for 3 min, the red
solution turned yellow and red precipitate formed.
1
The H NMR and ESI-MS spectra indicated that the
respectively. Cyclic voltammograms were obtained
with an ALS/CHI Model 660 voltammetric analyzer.
yellow
supernatant
exclusively
contained
[Co(III)(6)(CD3CN)]ꢁ (yield 80%). The red precipitate
3.2. 5-(3,5-Di-t-butylphenyl)-15-(4-
methoxycarbonylphenyl)-2,8,12,18-tetraethyl-3,7,13,17-
tetramethylporphine zinc complex (2)
1
were collected, analyzed by H NMR, and found to be
the compound 5 (isolated yield 70%). This reaction did
not proceed in the absence of light. The reaction is,
therefore, the light-induced ligand exchange of the
Co(III) center, in which the imidazole (linked to the
porphyrin moiety) is replaced by CD3CN. We assume
that the intramolecular electron transfer from the
excited porphyrin to the Co(III) moiety is the first step
in this reaction. The hypothetical reaction mechanism is
as follows:
Bis(3-ethyl-4-methyl-2-pyrrolyl)methane (1.16 g, 5.04
mmol), 3,5-di-t-butylbenzaldehyde (0.548 g, 2.51 mmol)
and methyl 4-formylbenzoate (0.384 g, 2.52 mmol) were
dissolved in 50 ml of dry acetonitrile. Trichloroacetic
acid (0.116 g, 0.710 mmol) was added and the mixture
was stirred under N2 in the dark for 6 h. A suspension of
p-chloranil (1.97 g, 8.01 mmol) in 30 ml of dry THF was
added and the mixture was stirred overnight. After
removal of the solvent, the residual solid was dissolved
in CH2Cl2. The solution was washed with saturated
aqueous NaHCO3 solution and water, and concentrated
in vacuo. The concentrate was treated with a saturated
solution of zinc acetate in MeOH (20 ml). The solution
was washed with water, saturated aqueous NaHCO3,
and water again. The organic layer was dried over
Na2SO4 and evaporated. The resulting product was
separated by column chromatography (silica gel,
Namely, the initial photoinduced electron transfer
generates the Co(II), which is substitutionally labile and
undergoes fast ligand exchange with the solvent
(CD3CN) molecule. Subsequently, the intermolecular
back electron transfer takes place from the Co(II)Á
/
CD3CN complex to the porphyrin cation radical, which
results in the observed final products, a Co(III) complex
and a neutral porphyrin.
CH2Cl2 then CH2Cl2 ꢁ
/
1% MeOH). The second fraction
was further purified by repeated flash column chroma-

142
T. Nagata et al. / Inorganica Chimica Acta 342 (2003) 139Á144
/
tography (silica gel, toluene). Red solid. Yield 0.755 g
(35%). 1H NMR (500 MHz, CDCl3) 10.20 (s, 2H, meso),
8.44 (d, 2H, phenyl), 8.21 (d, 2H, phenyl), 7.93 (d, 2H,
phenyl), 7.82 (t, 1H, phenyl), 4.14 (s, 3H, CO2CH3), 4.01
(m, 8H, CH2CH3), 2.17 (s, 12H, CH3), 1.77 (m, 12H,
CH2CH3), and 1.54 (s, 18H, t-butyl). Anal. Found: C,
75.13; H, 7.05; N, 6.35 %. Calc: C, 75.02; H, 7.23; N,
CH2Cl2, washed with saturated aqueous NaHCO3
solution and water, and evaporated. The residual solid
was purified by column chromatography (silica gel,
CH2Cl2). Reprecipitation from CH2Cl2ÁMeOH gave a
/
purple solid. Yield 104 mg (80 %). 1H NMR (500 MHz,
CDCl3) 10.23 (s, 2H, meso), 8.07 (d, 2H, phenyl), 7.91
(d, 2H, phenyl), 7.81 (s, 1H, phenyl), 7.78 (d, 2H,
phenyl), 4.87 (s, 2H, CH2Br), 4.02 (m, 8H, CH2CH3),
2.51(s, 6H, CH3), 2,46 (s, 6H, CH3), 1.77 (m, 12H,
6.48%. FAB-MS (3-nitrobenzyl alcohol) m/zꢄ
/
862.
3.3. 5-(3,5-Di-t-butylphenyl)-15-(4-
(hydroxymethyl)phenyl)-2,8,12,18-tetraethyl-3,7,13,17-
tetramethylporphine (3)
CH2CH3), 1.51 (s, 18H, t-butyl), and ꢂ
NH).
/
2.43 (br, 2H,
3.5. 5-(3,5-Di-tert-butylphenyl)-2,8,12,18-tetraethyl-15-
(4-(1-imidazolylmethyl)phenyl)-3,7,13,17-
tetramethylporphine zinc complex (5)
The compound 2 (161 mg, 0.186 mmol) was dissolved
in 10 ml of dry ether. A suspension of lithium aluminum
hydride (16 mg, 0.42 mmol) in 5 ml of dry ether was
added in portions to the solution. The mixture was
stirred under nitrogen atmosphere for 40 min in the
dark. Water (5 ml) was carefully added and the mixture
was stirred for 4 h. The organic layer was separated and
the aqueous layer was extracted twice with CH2Cl2. All
of organic layer were combined and dried over anhy-
drous Na2SO4. After removal of the solvent, the
resulting solid was dissolved in 10 ml of CH2Cl2 and a
saturated solution of zinc acetate in MeOH (2 ml) was
added to the solution. The mixture was stirred for 1 h in
the dark. The resulting solution was poured into water
and extracted two times with CH2Cl2. The combined
extracts were washed with saturated aqueous NaHCO3
solution and water, then dried over anhydrous Na2SO4.
The solvent was removed in vacuo, the residual solid
was purified by column chromatography (silica gel,
CH2Cl2). The resulting product was dissolved in
CH2Cl2, treated with 1 N aqueous HCl, and washed
with saturated aqueous NaHCO3 solution and water.
The organic layer was dried over anhydrous Na2SO4
and the solvent was taken off by a rotary evaporator.
The resulting purple solid was dried under reduced
pressure. Yield 142 mg (99%). 1H NMR (500 MHz,
CDCl3) 10.23 (s, 2H, meso), 8.08 (d, 2H, phenyl), 7.92
(d, 2H, phenyl), 7.81 (s, 1H, phenyl), 7.75 (d, 2H,
phenyl), 5.10 (s, 2H, CH2OH), 4.02 (q, 8H, CH2CH3),
2.49 (s, 6H, CH3), 2,46 (s, 6H, CH3), 2.01 (br, 1H, OH),
1.77 (m, 12H, CH2CH3), 1.51 (s, 18H, t-butyl), and
The compound 4 (225 mg, 0.269 mmol) was dissolved
in 15 ml of dry CH2Cl2 under nitroge, and a suspension
of sodium imidazolate (481 mg, 5.46 mmol) was added
to the solution. The mixture was stirred at 50 8C in the
dark until the starting materials were not visible by
TLC. Water (20 ml) was added, and the organic layer
was separated and the aqueous layer was extracted twice
with CH2Cl2. The extracts were combined, washed with
1 N HCl, saturated aqueous NaHCO3 and water. The
solution was dried over Na2SO4, evaporated, and dried
in vacuo. The residual solid was dissolved in 10 ml of
CH2Cl2 and a saturated solution of zinc acetate in
MeOH (2 ml) was added to the solution. The mixture
was stirred overnight in the dark. The resulting solution
was washed with water, saturated aqueous NaHCO3
solution, and water. The extract was dried over Na2SO4,
evaporated, and dried in vacuo. The resulting product
was reprecipitated from CH2Cl2ÁMeOH. Yield 228 mg
/
(96%). 1H NMR (500 MHz, CDCl3) 10.15 (s, 2H, meso),
7.98 (d, 2H, phenyl), 7.80 (t, 2H, phenyl), 7.68 (br, 2H,
phenyl), 6.13 (br, 2H, phenyl), 5.06 (br, 1H, imidazole),
4.03 (m, 8ꢁ2H, benzylic CH2 and CH2CH3), 2.45 (s,
/
6H, CH3), 2.10 (s, 6H, CH3), 1.82 (t, 6H, CH2CH3), 1.72
(t, 6H, CH2CH3), and 1.52 (s, 18H, t-butyl). FAB-MS
(3-nitrobenzyl alcohol) m/zꢄ884.
/
3.6. 2,6-Bis(((2S)-2-benzyloxycarbonylpyrrolidin-1-
yl)methyl)pyridine
ꢂ2.42 (br, 2H, NH).
/
L
-proline benzyl ester hydrochloride [11] (5.04 g, 19.0
3.4. 5-(4-(Bromomethyl)phenyl)-15-(3,5-di-tert-
butylphenyl)-2,8,12,18-tetraethyl-3,7,13,17-
tetramethylporphine (4)
mmol) was suspended in 200 ml of THF under nitrogen
atmosphere. Triethylamine (7.98 g 78.9 mmol) was
added to the solution at 0 8C, and the resulting solution
was stirred for 10 min. Then a solution of 2,6-
bis(bromomethyl)pyridine [12] (2.52 g, 9.50 mmol) in
95 ml of THF was added to the mixture, and the mixture
was stirred for 66 h at r.t. The reaction was monitored
by NMR. When the reaction stopped, the mixture was
poured into 150 ml of water, and extracted with 500 ml
of CH2Cl2. The organic layer was separated and dried
The compound 3 (121 mg, 0.157 mmol) was dissolved
in 3 ml of dry CH2Cl2. Thionyl bromide (69 mg, 0.33
mmol) in 0.20 ml of CH2Cl2 was added to the solution.
The mixture was stirred under nitrogen in the dark at
room temperature (r.t.) overnight. The reaction mixture
was poured into water, extracted four times with

T. Nagata et al. / Inorganica Chimica Acta 342 (2003) 139Á
/
144
143
over anhydrous Na2SO4. The solvent was removed by a
rotary evaporator. The oily residue was separated by
column chromatography (silica gel, diameter 4 cm,
MHz, CD3CN) 8.14 (t, 1H, 4-H-pyridine), 7.83 (s, 1H,
imidazole), 7.65 (d, 2H, 3,5-H-pyridine), 7.33 (s, 1H,
imidazole), 7.16(s, 1H, imidazole), 4.80 (d, 2H, pyridine-
CH2-pyrrolidine), 4.31 (d, 2H, pyridine-CH2-pyrroli-
length 20 cm, CH2Cl2, CH2Cl2ꢁ
/
1% MeOH, CH2Cl2ꢁ
/
1
3% MeOH). Yield 4.33 g (44%). H NMR (500 MHz,
CDCl3) 7.53 (t, 2H, 4-H-pyridine), 7.37Á7.27 (12H, 3,5-
H-pyridine ÃCO2CH2Ph), 5.12 (dd, 4H, ÃCO2CH2Ph),
4.04 (d, 2H, pyridineÃCH2Ãpyrrolidine), 3.79 (d, 2H,
pyridineÃCH2Ãpyrrolidine), 3.46 (dd, 2H, pyrrolidine),
3.07 (m, 2H, pyrrolidine), 2.52 (dd, 2H, pyrrolidine),
2.14 (m, 2H, pyrrolidine), and 2.01Á1.78 (m, 6H,
dine), 3.82 (s, 3H, Ã/CH3), 3.47 (d, 2H, pyrrolidine),
/
3.17 (m, 2H, pyrrolidine), 2.70 (m, 2H, pyrrolidine), 2.13
(m, 2H, pyrrolidine), 1.90 (m, 2H, pyrrolidine), 1.69 (m,
2H, pyrrolidine), and 0.56 (m, 2H, pyrrolidine). ESI-MS
/
/
/
/
/
/
(in MeOH) m/zꢄ
472 ([Me-ImCo(III)L]ꢁ).
/
/
pyrrolidine).
3.9. PorphyrinÁCo(III) complex linked molecule 1
/
3.7. 2,6-Bis(((2S)-2-carboxypyrrolidin-1-
yl)methyl)pyridine (6)
A solution of [Co(CH3CN)6](BF4)2 [8b] (30.7 mg, 63.4
m mol) in 0.5 ml was added to 6 (21.2 mg, 63.5 mmol)
under argon atmosphere. The mixture was stirred for 20
min until the solid was dissolved, then 2,6-lutidine (15
ml, 129 mmol) was added to the solution. The resulting
solution was stirred for 7 h. The solvent was taken off in
vacuo, and the residue was dried in vacuo. The solid was
dissolved in 0.1 ml of acetonitrile, and 1 ml of ethyl
acetate was added to the solution to precipitate. The
precipitate was collected by filtration and washed with 2
ml of ethyl acetate. This procedure of precipitation was
repeated four times, and the pink product was dried in
vacuo at 60 8C for 2.5 h. A solution of 5 (34.8 mg, 39.3
mmol) in 7.5 ml of CHCl3 was added to the solid. The
mixture was stirred at 60 8C in the dark overnight. To
the solution, 1.5 ml of acetonitrile was added and the
mixture was heated with stirring in the dark for 1 h. The
solvent was taken off by a rotary evaporator in the dark.
All of solvents used by the following purification were
distilled. The solid was dissolved in 2 ml of CH2Cl2, and
precipitated with 20 ml of hexane. The red solid was
collected by filtration and washed with 10 ml of hexane.
A solution of the solid in acetone was filtered and the
solvent was removed in vacuo. The residual solid was
dissolved in 1 ml of acetone, and 1 ml of water was
added. To the solution, a solution of anhydrous sodium
perchlorate (405 mg, 3.31 mmol) in 2 ml of water was
added. Red solid formed upon cooling at 0 8C over-
night was collected by filtration and washed with 2 ml of
Palladium on carbon (10%, 0.80 g) was suspended in 5
ml of ethanol and the suspension was purged with
hydrogen. A solution of the dibenzyl ester (see above;
4.08 g, 7.94 mmol) in 20 ml of ethanol was added to the
suspension with stirring. The mixture was stirred
vigorously for 1 week. The catalyst was removed by
filtration and rinsed with ethanol, and the filtrate was
evaporated. A yellow solid thus gained was dried in
vacuo. Yield 2.14 g (81 %). 1H NMR (500 MHz, CDCl3)
7.70 (t, 1H, 4-H-pyridine), 7.30 (d, 2H, 3,5-H-pyridine),
4.44 (d, 2H, pyridine-CH2-pyrrolidine), 4.30 (d, 2H,
pyridine-CH2-pyrrolidine), 3.83 (m, 2H, pyrrolidine),
3.71 (m, 2H, pyrrolidine), 2.99 (m, 2H, pyrrolidine), 2.30
(m, 4H, pyrrolidine), 2.10 (m, 2H, pyrrolidine), and 2.00
(m, 2H, pyrrolidine). FAB-MS (3-nitrobenzyl alcohol)
m/zꢄ
/
334 (Mꢁ
Hꢁ).
/
3.8. Co(III) complex of 6 and 1-methylimidazole (7)
A solution of [Co(CH3CN)6](BF4)2 (152 mg, 0.317
mmol) in 2.5 ml of acetonitrile was added to 6 (106 mg,
0.317 mmol) under argon atmosphere. The mixture was
stirred for 20 min till the solid was dissolved, then 2,6-
lutidine (75 ml, 0.65 mmol) was added to the solution.
The resulting solution was stirred for 7 h. The solvent
was taken off in vacuo, and the residue was dried in
vacuo. The solid was dissolved in 0.5 ml of acetonitrile,
and 5 ml of ethyl acetate was added to the solution. The
precipitate was collected by filtration and washed with
10 ml of ethyl acetate. This procedure of precipitation
was repeated four times, and the pink product was dried
in vacuo at 60 8C for 2.5 h. The product was dissolved
in 5 ml of acetonitrile, and 1-methylimidazole (26 ml,
0.33 mmol) was added to the solution. The mixture was
heated at 60 8C with stirring overnight, then the solvent
was removed under reduced pressure. The residual solid
was dissolved in 0.2 ml of acetonitrile, and precipitated
with 2 ml of ethyl acetate. The pink solid was collected
by filtration and washed with 2 ml of ethyl acetate. Yield
cold water. The product was dried in vacuo. Yield 27.5
1
mg (51%). H NMR (500 MHz, CD3CN:CDCl3ꢄ
/
5:1);
the porphyrin moiety: 10.17 (s, 2H, meso), 8.33 (s, 1H,
imidazole), 8.10 (d, 2H, phenyl), 7.87 (s, 1ꢁ2H,
/
imidazole and phenyl), 7.70 (m, 3H, phenyl), 5.71 (dd,
4H, benzylic CH2), 4.01 (q, 8H, CH2CH3), 2.45 (s, 6H,
CH3), 2.42 (s, 6H, CH3), 1.75 (t, 12H, CH2CH3), 1.50 (s,
18H, t-butyl); the cobalt-complex moiety: 8.20 (t, 1H),
7.70 (m, 2H), 4.92 (d, 2H, benzylic CH2), 4.38 (d, 2H,
benzylic CH2), 3.56 (m, 2H), 3.38 (m, 2H), 2.81, (m, 2H),
2.32 (m, 2H), 0.68 (m, 2H). ESI-MS (in acetone) m/zꢄ
/
1274. Anal. Found: C, 63.50; H, 6.18; N, 8.76%. Calcd
for [C73H85N9O4CoZn](ClO4)(acetone): C, 63.64; H,
6.39; N, 8.79%. Caution! Perchlorate salts containing
1
115 mg (65% as tetrafluoroborate salt). H NMR (500

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T. Nagata et al. / Inorganica Chimica Acta 342 (2003) 139Á144
/
(d) T.D. Ros, M. Prato, D. Guldi, E. Alessio, M. Ruzzi, L.
Pasimeni, Chem. Commun. (1999) 635.
organic components are potentially explosive; they
should be handled with care and in small amounts.
[4] (a) H. Ishida, T. Terada, K. Tanaka, T. Tanaka, Inorg. Chem. 29
(1990) 905;
3.10. Photoreaction of 1
(b) C.S. Christ, Jr., J. Yu, X. Zhao, G.T.R. Palmore, M.S.
Wrighton, Inorg. Chem. 31 (1992) 4439;
(c) I. Willner, R. Kasher, E. Zahavy, N. Lapidot, J. Am. Chem.
Soc. 114 (1992) 10963;
A solution of 1 (2.07 mg, 1.52 mmol) and 1,1,2,2-
tetrachloroethane (1.0 ml, an internal standard) in 0.25
ml of CDCl3 and 1.25 ml of CD3CN was purged with
argon for 20 min in an NMR tube. The solution was
irradiated for 3 min with a Shimadzu AT-100 HG light
source equipped with a halogen lamp. The red-violet
solution became turbid, and red powders precipitated
leaving a clear yellow supernatant. The 1H NMR
spectra were measured before and after irradiation.
The resulting mixture was filtered, and the precipitate
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1
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˚
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The authors thank Professor Yoshihito Watanabe
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/
ꢁ
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