Synthesis and structural characterization of some new porphyrin-fullerene dyads and their application in photoinduced H2 evolution

Article abstract of DOI:10.1021/ic201713x

The [3 + 2] cycloaddition reaction of C₆₀ with ethyl isonicotinoylacetate in the presence of piperidine in PhCl at room temperature or in the presence of Mn(OAc)₃ in refluxing PhCl gave the pyridyl-containing dihydrofuran-fused C

Full text of DOI:10.1021/ic201713x

ARTICLE
pubs.acs.org/IC
Synthesis and Structural Characterization of Some New
Porphyrin-Fullerene Dyads and Their Application in
Photoinduced H2 Evolution
Li-Cheng Song,* Xu-Feng Liu, Zhao-Jun Xie, Fei-Xian Luo, and Hai-Bin Song
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
S Supporting Information
b
ABSTRACT: The [3 + 2] cycloaddition reaction of C60 with ethyl
isonicotinoylacetate in the presence of piperidine in PhCl at room
temperature or in the presence of Mn(OAc)3 in refluxing PhCl
gave the pyridyl-containing dihydrofuran-fused C60 derivative (4-
C5H4N)C(O)dC(C60)CO2Et (1), whereas the phenyl-contain-
ing C60 derivative PhC(O)dC(C60)CO2Et (2) was similarly
prepared by [3 + 2] cycloaddition reaction of C60 with ethyl
benzoylacetate in the presence of piperidine or Mn(OAc)3. More
interestingly, one of the new porphyrin-fullerene dyads, i.e., [4-
C5H4NC(O)dC(C60)CO2Et] ZnTPPH (3, ZnTPPH = tetra-
3
phenylporphyrinozinc), could be prepared by coordination reac-
tion of the pyridyl-containing C60 derivative 1 with equimolar
ZnTPPH in CS2/hexane at room temperature. In addition, the β-
keto ester-substituted porphyrin derivative H2TPPC(O)CH2CO2Et (4) was prepared by a sequential reaction of HO2CCH2CO2Et
with n-BuLi in 1:2 molar ratio followed by treatment with H2TPPC(O)Cl in the presence of Et3N and then hydrolysis with diluted
HCl, whereas the porphyrinozinc derivative ZnTPPC(O)CH2CO2Et (5) could be prepared by coordination reaction of 4 with
Zn(OAc)2 in refluxing CHCl3/MeOH. Particularly interesting is that the second new porphyrin-fullerene dyad H2TPPC(O)d
C(C60)CO2Et (6) could be prepared by [3 + 2] cycloaddition reaction of 4 with C60 in the presence of piperidine in PhCl at room
temperature. In addition, treatment of 6 with Zn(OAc)2 in refluxing CHCl3/MeOH afforded the third new dyad ZnTPPC-
(O)dC(C60)CO2Et (7). All the new compounds 1ꢀ7 were characterized by elemental analysis and various spectroscopic methods
and particularly for 2, 3, and 5 by X-ray crystallography. The five-component system consisting of an electron donor EDTA, dyad 3,
an electron mediator methylviologen (MV2+), the catalyst colloidal Pt, and a proton source HOAc was proved to be effective for
photoinduced H2 evolution. A possible pathway for such a type of H2 evolution was proposed.
’ INTRODUCTION
photosensitizer and a [FeFe]hydrogenase model as catalyst.12
Particularly interesting is that both catalytic systems have been
proved to give molecular H2, although their H2-producing
efficiency is low.11,12 To improve the photoinduced H2-produ-
cing efficiency, we continued to study such photoinduced H2
production using a new type of five-component system, which
involves ethylenediamine tetraacetic disodium salt (EDTA) as an
electron donor, colloidal Pt as catalyst, methylviologen (MV2+)
as an electron mediator, and a new type of dyad in which either a
pyridyl-containing dihydrofuran-fused C60 derivative is coordi-
natively linked to Zn atom of the photosensitizer tetraphenyl-
porphyrinozinc (ZnTPPH) or a dihydrofuran-fused C60 moiety
is covalently linked to a phenyl group of the photosensitizer
tetraphenylporphine (H2TPPH). In principle, such five-compo-
nent systems may have two advantages compared to our
previously reported three-component systems:11,12 (i) the
Photoinduced catalytic H2 evolution has attracted great
attention in recent years, largely because of molecular H2 being
considered as a promising energy source to solve the current
energy shortage and environmental problems.1ꢀ6 Generally, the
photoinduced catalytic system for H2 evolution consists of five
separate components, namely, an electron donor, a photosensi-
tizer, an electron mediator, a catalyst, and a proton source.7ꢀ9
-
However, except such a five-component system, some other
systems involving less components were also previously reported
for H2 evolution, such as the four-component system in which a
dyad assembly replaces the corresponding two components such
as photosensitizer and catalyst4,5 or photosensitizer and electron
mediator.8,10We are interested in photoinduced H2 evolution
and have recently reported two examples using the three-
component system without a mediator but involving two kinds
of dyads: one kind of dyad consists of a porphyrin moiety as
photosensitizer and a [FeFe]hydrogenase model as catalyst11
and another kind of dyad includes a fullerene moiety as
Received: August 6, 2011
Published: October 14, 2011
r
2011 American Chemical Society
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Inorganic Chemistry
ARTICLE
Scheme 1
Scheme 2
Figure 1. Partial 1H NMR spectra of 1 and 3 (/: CHCl3).
catalyst colloidal Pt has been proved to have high catalytic activity
for such photoinduced H2 evolution,13ꢀ15 and (ii) porphyrin-
fullerene dyads are well-known donorꢀacceptor systems for
electron transfer and charge separation required for such photo-
induced H2-producing processes.16ꢀ22 It is worth pointing out
that, although numerous porphyrin-fullerene dyads are
known,23ꢀ30 there is no report regarding their application in
the study of photoinduced H2 production. Herein, we report the
synthesis and structural characterization of three new porphyrin-
fullerene dyads and their first application in photoinduced H2
evolution. In addition, the synthesis and characterization of
another four new functionalized porphyrin and C60 derivatives
closely related to the three new porphyrin-fullerene dyads are
also described.
Figure 2. (a) Original 13C NMR spectrum of 1. (b) Expanded partial
13C NMR spectrum of 1.
derivative 1 with an equimolar amount of ZnTPPH in CS2/
hexane at room temperature in 97% yield (Scheme 2).
’ RESULTS AND DISCUSSION
Compounds 1ꢀ3 are airꢀstable solids, which were character-
ized by elemental analysis and various spectroscopic methods.
For example, the IR spectra of 1ꢀ3 displayed one strong
absorption band in the range 1714ꢀ1701 cmꢀ1 for their ester
carbonyls and four absorption bands in the range of
1437ꢀ527 cmꢀ1 attributed to the CꢀC stretching frequencies
for their C60 spheres,33 whereas dyad 3 showed three additional
absorption bands at 1522, 1484, and 1338 cmꢀ1 attributed to the
skeletal vibrations of pyrrole rings in its porphyrin moiety.34 The
1H NMR spectrum of the pyridyl-containing C60 derivative 1 as a
free ligand displayed two doublets at δ = 8.89 and 8.01 ppm for
the two α and two β-protons in its pyridyl group, a quartet at
δ = 4.30 ppm for its CH2 group, and a triplet at δ = 1.22 ppm
Synthesis and Characterization of Dihydrofuran-Fused
C60 Derivatives RC(O)dC(C60)CO2Et (1, R = 4-C5H4N; 2, R =
Ph) and Coordinatively Bonded Porphyrin-Fullerene Dyad
[4-C5H4NC(O)dC(C60)CO2Et] ZnTPPH (3). The new pyridyl
3
group-containing dihydrofuran-fused C60 derivative 1 was found
to be prepared by the base-catalyzed [3 + 2] cycloaddition
reaction31 of ethyl isonicotinoylacetate with C60 in the pre-
sence of piperidine in chlorobenzene at room temperature in
91% yield or by single-electron oxidant Mn(OAc)3-mediated
[3 + 2] cycloaddition reaction32 of ethyl isonicotinoylacetate
with C60 in refluxing chlorobenzene in 59% yield (Scheme 1).
Similarly, the phenyl-containing C60 derivative 2 (a known
analogue of 1)32 could be prepared by the piperidine-catalyzed
cycloaddition reaction of ethyl benzoylacetate with C60 in
chlorobenzene at room temperature in 70% yield or by the
Mn(OAc)3-mediated cycloaddition reaction of ethyl benzoyl-
acetate with C60 in chlorobenzene at reflux in 33% yield
(Scheme 1). More interestingly, it was further found that the
new coordinatively bonded porphyrin-fullerene dyad 3, simi-
lar to the known coordinatively bonded porphyrin-fullerene
dyads,25b,26a could be prepared by solvent diffusion method
and coordination reaction of the pyridyl-containing C60
1
for its CH3 group. However, the H NMR spectrum of the
pyridyl-containing C60 derivative 1 as a coordinated ligand in
dyad 3 exhibited a broad singlet for its two α-pyridyl protons
that is shifted upfield by 5.49 ppm relative to that of free
ligand 1, a doublet for its two β-pyridyl protons shifted
upfield by 1.58 ppm, a quartet for its CH2 group upfield
shifted by 0.43 ppm, and a triplet for its CH3 group upfield
shifted by 0.49 ppm (see Figure 1). Apparently, these upfield
shifts should be attributed to the shielding effect caused
by the macrocycle of ZnTPPH.25b,26a,35,36 In addition, the
13C NMR spectrum of free ligand 1 showed two signals at δ = 72.83
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ꢀ
Table 1. Bond Lengths [Å] and Angles [deg] for 2, 3, and 5
2
C(1)ꢀO(1)
1.470(4)
1.527(4)
1.368(4)
1.466(5)
105.8(2)
109.0(2)
113.9(3)
120.4(3)
C(1)ꢀC(2)
1.598(4)
1.346(5)
1.467(5)
1.210(4)
100.3(2)
110.7(3)
128.8(3)
132.6(3)
C(2)ꢀC(61)
C(61)ꢀC(62)
C(62)ꢀO(1)
C(62)ꢀC(66)
O(1)ꢀC(1)ꢀC(2)
C(62)ꢀO(1)ꢀC(1)
C(61)ꢀC(62)ꢀO(1)
C(63)ꢀC(61)ꢀC(2)
C(61)ꢀC(63)
C(63)ꢀO(2)
C(61)ꢀC(2)ꢀC(1)
C(62)ꢀC(61)ꢀC(2)
C(62)ꢀC(61)ꢀC(63)
C(61)ꢀC(62)ꢀC(66)
3
Figure 3. ORTEP view of 2 with 30% thermal ellipsoids.
Zn(1)ꢀN(1)
O(1)ꢀC(1)
C(61)ꢀC(62)
C(2)ꢀC(61)
O(1)ꢀC(1)ꢀC(2)
C(62)ꢀC(61)ꢀC(2) 109.6(6)
C(63)ꢀC(61)ꢀC(2) 123.8(6)
C(62)ꢀO(1)ꢀC(1)
2.137(3)
1.459(9)
O(1)ꢀC(62)
C(1)ꢀC(2)
1.382(9)
1.587(10)
1.464(10)
1.489(8)
101.2(7)
1.355(11) C(61)ꢀC(63)
1.552(9)
105.2(6)
C(62)ꢀC(66)
C(61)ꢀC(2)ꢀC(1)
C(62)ꢀC(61)ꢀC(63) 126.7(7)
C(61)ꢀC(62)ꢀO(1)
113.0(6)
110.7(6)
C(61)ꢀC(62)ꢀC(66) 137.2(7)
5
Zn(1)ꢀN(1)
2.076(4)
2.117(4)
1.377(5)
1.221(6)
88.89(13)
88.37(13)
88.03(13)
126.7(3)
O(3)ꢀC(47)
1.220(6)
1.329(7)
1.362(5)
1.378(6)
126.1(3)
119.7(4)
119.2(5)
120.5(5)
Zn(1)ꢀO(1)
O(4)ꢀC(47)
N(1)ꢀC(1)
O(2)ꢀC(45)
N(3)ꢀZn(1)ꢀN(2)
N(1)ꢀZn(1)ꢀN(2)
N(1)ꢀZn(1)ꢀN(4)
C(1)ꢀN(1)ꢀZn(1)
N(2)ꢀC(12)
N(3)ꢀC(26)
C(4)ꢀN(1)ꢀZn(1)
C(50)ꢀO(1)ꢀZn(1)
C(42)ꢀC(45)ꢀC(46)
O(2)ꢀC(45)ꢀC(42)
Figure 4. ORTEP view of 3 with 30% thermal ellipsoids.
and 102.59 ppm for its two sp3-C atoms and 30 signals at δ =
135.48ꢀ147.96 ppm for its 58 sp2-C atoms in C60 sphere,37,38
whereas the coordinated ligand 1 in dyad 3 displayed two signals at
δ = 72.14 and 101.91 ppm for the corresponding two sp3-C atoms
and 29 signals at δ = 134.82ꢀ147.23 ppm for the corresponding 58
sp2-C atoms.37,38 It is worth pointing out that, in the 13C NMR
spectrum of dyad 3, the intensity of the signal at δ = 142.72 ppm is
much stronger than other signals because it represents two sp2-C
atoms of C60 moiety and one γ-pyridyl C atom (see Figure 2).
The molecular structures of 2 and 3 have been unequivocally
confirmed by X-ray crystal diffraction techniques. Their ORTEP
plots are depicted in Figures 3 and 4, and selected bond lengths
and angles are given in Table 1. As shown in Figures 3 and 4, both
2 and 3 contain the same ethoxycarbonyl-substituted dihydro-
furan-fused C60 moiety, in which the five atoms C1, C2, C61,
C62, and O1 in the five-membered dihydrofuran ring are nearly
coplanar with a mean deviation of 0.003 Å for 2 and 0.018 Å for 3,
respectively. The C1ꢀC2 single bond length is 1.598 Å for 2 and
1.587 Å for 3, whereas the C61ꢀC62 double bond lengths is
1.346 Å for 2 and 1.355 Å for 3, respectively. Such single and
double bond lengths are very close to those reported in other
dihydrofuran-fused C60 derivatives.39,40 In addition, as can be
seen in Figures 3 and 4, while 2 contains a benzene ring attached
to C62 of the dihydrofuran-fused C60 moiety, dyad 3 has a
pyridine ring whose N1 atom is axially coordinated to Zn1 atom
of the ZnTPPH moiety. The N1ꢀZn1 bond length is 2.137 Å
which compares with those reported for other noncovalently
linked porphyrin-fullerene dyads.25a,b The distance from por-
phyrin center to the center of C60 is found to be 12.225 Å,
whereas the edge-to-edge distance (the closest distance between
the porphyrin β-pyrrole carbon atom and the C60 carbon atom)
is 9.208 Å. The porphyrin ring is slightly ruffled with 0.3033 Å
out-of-plane displacement of the central Zn atom due to its axial
coordination with N1 atom of the pyridine ring.
Synthesis and Characterization of β-Keto Ester-Substi-
tuted Porphyrin Derivatives H2TPPC(O)CH2CO2Et (4)/
ZnTPPC(O)CH2CO2Et (5) and Covalently Bonded Porphyr-
in-Fullerene Dyads H2TPPC(O)dC(C60)CO2Et (6)/ZnTPPC-
(O)dC(C60)CO2Et (7). In order to prepare the covalently
linked porphyrin-fullerene dyads 6 and 7, we first prepared the
β-keto ester-substituted porphyrin 441 and its porphyrinozinc
derivative 5 via the synthetic route shown in Scheme 3. That is,
when monoethyl malonate reacted with n-BuLi in 1:2 molar ratio
followed by treatment with H2TPPCOCl in the presence of
Et3N, the corresponding intermediate lithium salt H2TPP-
COCH(CO2Li)CO2Et (M) was generated. Then, after in situ
hydrolysis of lithium salt M with diluted hydrochloric acid, the
expected β-keto ester-substituted porphyrin 4 was obtained in
81% yield. Further treatment of porphyrin derivative 4 with
excess Zn(OAc)2 in refluxing CHCl3/MeOH resulted in forma-
tion of the porphyrinozinc derivative 5 in 90% yield. Particularly
interesting is that the new covalently bonded porphyrin-fullerene
dyad 6 could be prepared by [3 + 2] cycloaddition reaction of
C60 with porphyrin derivative 4 in the presence of piperidine in
chlorobenzene at room temperature in 77% yield, whereas
further treatment of 6 with excess Zn(OAc)2 in CHCl3/MeOH
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Scheme 3
Scheme 4
NMR determination, the singlet at δ = 12.86 ppm for OH group
in its enol form as well as the singlet at δ = ꢀ2.75 ppm for NH
groups in its keto and enol forms completely disappeared due to
D/H exchanges. According to the integrated values of the
1
corresponding H NMR signals, the molar ratio between the
keto and enol forms was calculated to be 9:1. More interestingly,
in contrast to 4, the 1H NMR spectrum of 5 displayed only one
singlet at δ = 4.27 ppm, which implies that 5 existed only in the
keto form.
The 13C NMR spectra of 4 and 5 also demonstrated that 4 was
a mixture of the keto and enol forms, while 5 was present only in
its keto form. This is because the 13C NMR spectrum of 4
displayed three singlets at δ = 46.33, 88.38, and 173.70 ppm,
assigned respectively to the carbon atom in CH2 group between
two carbonyls in its keto form and those carbon atoms in dCH
and COH groups in its enol form; in addition, 5 showed only one
singlet at δ = 45.94 ppm, assigned to the carbon in CH2 group
between two carbonyls in its keto form without observing any
13C NMR signal for groups dCH and COH in its enol form.
The IR spectra of dyads 6 and 7 showed one absorption band
at ca. 1695 cmꢀ1 for their ester carbonyls, three bands in the
region of 1558ꢀ1368 cmꢀ1 for the skeletal vibrations of pyrrole
rings in their porphyrin moieties,34 and three to four bands in the
range of 1442ꢀ526 cmꢀ1 ascribed to the CꢀC stretching
1
frequencies for their C60 spheres.33 In addition, the H NMR
at room temperature afforded another new covalently bonded
porphyrinozinc-fullerene dyad 7 in 89% yield (Scheme 4).
Compounds 4ꢀ7 are airꢀstable solids and were characterized
by elemental analysis and various spectroscopic techniques. For
example, the IR spectrum of 4 displayed one absorption band at
3316 cmꢀ1 assigned to its NH groups, one band at 1742 cmꢀ1 for
its ketone carbonyl, and one band at 1687 cmꢀ1 for its ester
carbonyl, whereas 5 exhibited one absorption band at 1740 cmꢀ1
for its ketone carbonyl, and one band at 1685 cmꢀ1 for its ester
carbonyl, respectively. In addition, the IR spectra of 4 and 5
displayed three absorption bands in the range of
1558ꢀ1338 cmꢀ1 for the skeletal vibrations of pyrrole rings in
their porphyrin moieties.34
spectrum of 6 showed a singlet at δ = ꢀ2.82 ppm for its NH
groups, which disappeared in 7 since the two H atoms attached to
N atoms in 6 were replaced by Zn atom. Particularly noteworthy
is that the 13C NMR spectra of 6 and 7 also indicated the
presence of both the C60 sphere and the porphyrin moiety. For
example, the 13C NMR spectrum of 6 showed one signal at δ =
73.96 ppm for its two sp3-C atoms and 28 signals in the range of
134.97ꢀ147.71 ppm for the 58 sp2-C atoms in its C60
sphere.37,38 In addition, 6 also displayed two signals at δ =
141.93 and 131.32 ppm for α-C and β-C atoms in its pyrrole
rings, respectively. The two signals at δ = 118.62 and 120.17
ppm can be attributed to meso-C atoms in the porphyrin
macrocycle.
1
It is interesting to note that the H NMR spectrum of 4
displayed three singlets at δ = 4.25, 6.00, and 12.86 ppm. This
implies that in solution 4 is a mixture of the keto form with its
enol form (Scheme 5). The three singlets could be assigned to
the CH2 group between the two carbonyls in its keto form, and to
the both dCH and OH groups in its enol form, respectively.42
However, when excess D2O was added to solution of 4 during 1H
The molecular structure of porphyrin derivative 5 was un-
ambiguously confirmed by X-ray crystallography. The ORTEP
drawing of 5 is presented in Figure 5, whereas Table 1 lists its
selected bond lengths and angles. It can be seen intuitively from
Figure 5 that complex 5 indeed includes a tetraphenylporphyrin
macrocycle in which Zn1 atom is coordinated to N1, N2, N3, and
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Scheme 5
314 nm in the UV region, which are due to the absorption of C60
moiety.12,46ꢀ48The fluorescence emission spectrum of dyad 3
along with that of a 1:1 mixture of ZnTPPH and 2 are shown in
Figure 7. As can be seen in Figure 7, the fluorescence emission
spectrum of dyad 3 showed a 71% decrease of the intensity
relative to that of the 1:1 mixture of ZnTPPH with 2. Apparently,
such a large decrease can be attributed to the existence of a strong
intramolecular electron transfer from the photoexcited ZnTPPH
moiety to the axially coordinated C60 moiety.12,25b,26a,49,50
Interestingly, our experiments indicated that molecular H2 was
indeed produced when a 350 W Xe lamp with a Pyrexꢀglass filter
(λ > 400 nm) was used to irradiate an aqueous solution of the
five-component system consisting of an electron donor EDTA,
dyad 3, an electron mediator methylviologen (MV2+), a catalyst
colloidal Pt (stabilized by sodium polyacrylate51), and a proton
source HOAc in the presence of surfactant Triton X-100. The
control experiments showed that all five components were
essential for H2 production. That is, omission of any of the five
components afforded unobservable to trace amounts of hydro-
gen (see entries 2ꢀ5 in Table 2). In addition, no H2 could be
detected when the reaction involving the five-component system
was carried out in the dark (see entry 6 in Table 2). The highest
turnover number of H2 evolution is 73 under the optimized
conditions during 4 h irradiation (see entry 1 in Table 2).
Actually, this photoinduced H2 evolution with 73 turnovers is
comparable with those previously reported for photoinduced
hydrogen evolution. For example, the system involving chromo-
phore platinum terpyridyl acetylide and colloidal Pt reported by
Eisenberg gave 84 turnovers during 10 h irradiation,52 and that
system involving a cobaloxime-based photocatalyst reported by
Artero gave 103 turnovers during 15 h irradiation.5a
Figure 5. ORTEP view of 5 with 30% thermal ellipsoids.
N4 atoms as well as to O1 atom of the solvent EtOH used in the
single-crystal growing process. The four ZnꢀN bond lengths
(2.059ꢀ2.093 Å) and Zn1ꢀO1 bond length (2.117 Å) of 5 are
very close to those reported for ZnTPPH(MeOH),43 ZnTPPH-
(H2O),44 and [(μꢀSCH2)2NFe2(CO)6]ZnTPP(MeOH).11 In
addition, the four benzene rings around the metalloporphyrin
moiety are twisted relative to the porphyrin plane with a dihedral
angle (84.9°ꢀ95.1°) in order to avoid the strong steric repul-
sions between the proximal H atoms of the benzene and pyrrole
rings in the metalloporphyrin macrocycle.
Investigation on Photoinduced H2 Evolution Under the
Action of a Five-Component System Including Dyad 3. In
order to study such a photoinduced H2 evolution process, it was
necessary first to study the UVꢀvis absorption and fluorescence
emission spectra of dyad 3 and some related compounds. From
such a study, we could select a suitable light wavelength to cause
the electron excitation of the photosensitizer porphyrin moiety in
dyad 3; in addition, we would know if the photoexcited electron
of the porphyrin moiety can be intramolecularly transferred to
the electron acceptor C60 moiety (note that such an electron
transfer (ET) process is one of the important steps required for
proton reduction to H2). The UVꢀvis absorption spectra of
dyad 3 and ZnTPPH are shown in Figure 6. As can be seen in
Figure 6, dyad 3 displayed a Soret band at 418 nm in the near-UV
region and two Q bands at 547 and 585 nm in the visible region,
which are virtually the same as those displayed by ZnTPPH.45 In
addition, dyad 3 also displayed three bands at 227, 254, and
The influences of pH values, the catalyst (colloidal Pt)
concentration, and irradiation time are shown in Figures 8, 9,
and 10, respectively. As shown in Figures 8ꢀ10, the amount of
H2 evolved increases as the pH values decrease, reaching a
maximum at pH = 3.99, whereas the evolved H2 amount is
increased with an increase of either the catalyst concentration or
the irradiation time. It should be noted that only 0.23 μmol H2
with 2.3 turnovers were produced after 4 h irradiation when dyad
3 was replaced by photosensitizer ZnTPPH. This shows that the
C60 moiety plays an important role in the photoinduced hydro-
gen production process (see entry 7 in Table 2).
According to these observations and the previously reported
similar cases,11,12,53 a possible pathway could be proposed for the
photoinduced H2 production catalyzed by colloidal Pt in the
presence of dyad 3 (Scheme 6). Upon irradiation, dyad 3
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Figure 6. UVꢀvis spectra of 3 and ZnTPPH in CH2Cl2 (5 ꢁ 10ꢀ6 M). The Soret band absorptions have been normalized, and the spectra have been
amplified 10-fold in the Q-band region.
Figure 7. Fluorescence emission spectra (λex = 440 nm) of 3 and an equimolar mixture of 2 with ZnTPPH in PhCl (1 ꢁ 10ꢀ4 M).
Table 2. Photoinduced H2 Evolution Catalyzed by Colloidal Pt in Aqueous Solutions
entry
photosensitizer
electron donor
electron mediator
proton source
irradiation time
TONa
1
2
3
4
5
6
7
dyad 3
dyad 3
dyad 3
dyad 3
EDTA
EDTA
MV2+
MV2+
MV2+
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
HOAc
4 h
4 h
4 h
73
<1
<1
<1
<1
0
EDTA
EDTA
EDTA
EDTA
MV2+
MV2+
MV2+
4 h
4 h
dyad 3
ZnTPP
2.3
a TON are calculated on the basis of dyad 3.
ZnTPPH+ C60 via the electron transfer from the excited
ꢀ
consisting of a photosensitizer ZnTPPH moiety and an elec-
tron acceptor C60 moiety turns to a chargeꢀseparated state
3 3 3
state of the ZnTPPH* moiety to the electron acceptor C60
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Inorganic Chemistry
ARTICLE
Figure 8. The pH dependence of photoinduced H2 evolution from an
aqueous solution (10 mL) of colloidal Pt (50 μM) containing EDTA
(15 mM), 3 (20 μM), MV2+ (0.27 mM), and Triton X-100 (0.3 mL) in
the presence of HOAc (0.085 M)/NaOAc (0.015 M) at pH = 3.99;
HOAc (0.036 M)/NaOAc (0.064 M) at pH = 4.95; HOAc (0.005 M)/
Figure 10. The time dependence of photoinduced H2 evolution from
an aqueous solution (10 mL) of colloidal Pt (0.10 mM) containing
EDTA (15 mM), 3 (20 μM), MV2+ (0.41 mM), and Triton X-100
(0.3 mL) in the presence of HOAc (0.10 M) during 4 h irradiation.
NaOAc (0.095 M) at pH = 5.62; NaH2PO4 2H2O (0.085 M)/
with ZnTPPH. Also, we have found that the β-keto ester-
functionalized porphyrin derivatives 4 and 5 can be prepared
by the sequential reaction involving lithiation of the starting
material HO2CCH2CO2Et and subsequent acylation, decarbox-
ylation, and coordination steps, whereas the covalently bonded
porphyrin-fullerene dyads 6 and 7 can be prepared by the base-
catalyzed cycloaddition reaction of C60 with porphyrin derivative
4 and subsequent coordination reaction of 6 with Zn(OAc)2 in
77% and 89% yields, respectively. Particularly interesting is that
photoinduced H2 evolutions using a multicomponent system
involving a porphyrin-fullerene dyad. This multicomponent
system is a five-component system (consisting of electron donor
EDTA, dyad 3, electron mediator MV2+, catalyst colloidal Pt, and
proton source HOAc), which gives H2 with a high turnover
number of 73. On the basis of similar cases and some related
studies, a possible pathway for this photoinduced H2 evolution is
suggested. All the prepared compounds 1ꢀ7 have been char-
acterized by elemental analysis and spectroscopy and particularly
for 2, 3, and 5 by X-ray crystallography. Further studies on the
multicomponent catalytic systems involving dyad 6, 7, and other
porphyrin-fullerene dyads are in progress in this laboratory.
3
Na2HPO4 12H2O (0.058 M) at pH = 6.30 during 4 h irradiation.
3
Figure 9. The colloidal Pt concentration dependence of photoinduced
H2 evolution from an aqueous solution (10 mL) of colloidal Pt
containing EDTA (15 mM), 3 (20 μM), MV2+ (0.27 mM), and Triton
X-100 (0.3 mL) in the presence of HOAc (0.036 M)/NaOAc (0.064 M)
during 4 h irradiation.
’ EXPERIMENTAL SECTION
moiety. The electron mediator MV2+ is then reduced by the
General Comments. All reactions were carried out under an
atmosphere of highly purified nitrogen using standard Schlenk or
vacuum-line techniques. Chlorobenzene was distilled from CaH2;
THF was distilled from Na/benzophenone ketyl, and piperidine was
redistilled under nitrogen prior to use. Ethyl isonicotinoylacetate,54
negatively charged C60ꢀ in the charge-separated state ZnTPPH+
3
C60 to give MV•+ and ZnTPPH+ C60. While reductive
ꢀ
3 3
3 3 3
quenching of the charge-separated species ZnTPPH+ C60 by
EDTA leads to the ground state of dyad 3, the electron transfer
from MV•+ to proton under the action of colloidal Pt gives
hydrogen, completing the catalytic cycle.
3 3 3
ZnTPPH,55monoethyl malonate,56 H2TPPCO2H,57 H2TPPCOCl,58
-
and colloidal Pt51 were prepared according to literature methods.
Ethyl benzoylacetate, C60, Mn(OAc)3 2H2O, ethylenediamine
3
tetraacetic disodium salt (EDTA), N,N0-dimethyl-4,40-bipyridium
(methylviologen, MV2+), Triton X-100, and other chemicals were of
commercial origin and used as received. 1H and 13C NMR spectra were
recorded on a Bruker Avance 300 or a Bruker Avance 400 NMR
spectrometer. IR spectra were taken on a Bio-Rad FTS 135 spectro-
photometer. Elemental analysis was performed on an Elementar Vario
EL analyzer. UVꢀvis spectra and fluorescence emission spectra were
carried out, respectively, on a Varian CARY 100 Bio spectrophotometer
and on a Varian CARY Eclipe spectrophotometer. Melting points were
’ CONCLUSIONS
We have found that the pyridyl and phenyl-containing dihy-
drofuran-fused C60 derivatives 1 and 2 can be prepared by the
base-catalyzed or Mn(OAc)3-mediated [3 + 2] cycloaddition
reactions of C60 with the corresponding β-keto esters in 70ꢀ91%
yields, whereas the designed coordinatively bonded porphyrin-
fullerene dyad 3 can be prepared in a nearly quantitative yield by
coordination reaction of the pyridyl-containing C60 derivative 1
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Inorganic Chemistry
ARTICLE
Scheme 6
determined on a Yanaco MP-500 melting point apparatus and are
uncorrected.
143.10 (2C), 143.36 (2C), 144.56 (2C), 144.72 (2C), 144.83 (2C),
145.12 (2C), 145.34 (2C), 145.48 (2C), 145.76 (2C), 145.97 (2C),
146.27 (2C), 146.34 (2C), 146.49 (2C), 146.55 (2C), 146.77 (2C),
147.64 (1C), 147.71 (2C), 148.35 (1C), 148.64 (2C) ppm. UVꢀvis
(CH2Cl2, 5 ꢁ 10ꢀ6 M): λmax (log ε) = 228 (4.99), 255 (5.11), 315 nm
(4.67).
Preparation of (4-C5H4N)C(O)dC(C60)CO2Et (1). Method (i):
A 100 mL two-necked flask fitted with a magnetic stir-bar, a rubber
septum, and a N2 inlet tube was charged with C60 (72 mg, 0.1 mmol),
ethyl isonicotinoylacetate (39 mg, 0.2 mmol), piperidine (30 μL, 0.3
mmol), and PhCl (20 mL). The mixture was stirred at room temperature
for 36 h to give a red-brown solution. After volatiles were removed at
reduced pressure, the residue was subjected to column chromatography
(silica gel). Elution with toluene developed a purple band, from which
unreacted C60 (20 mg) was recovered. Elution with toluene/ethyl
acetate (v/v 1:1) developed a brown band, from which 1 (60 mg, 91%
yield based on the consumed C60) was obtained as a brown-black solid.
Mp: >300 °C. Anal. Calcd. for C70H9NO3: C, 92.21; H, 0.99; N, 1.54.
Found: C, 91.93; H, 1.09; N, 1.57. IR (KBr disk): νOCdO 1714 (vs),
νCdC 1636 (m), νC60 1436 (m), 1180 (m), 575 (w), 527 (s) cmꢀ1. 1H
NMR (300 MHz, CS2:CDCl3 = 1:1): 1.22 (t, J = 7.2 Hz, 3H, CH3), 4.30
(q, J = 7.2 Hz, 2H, CH2), 8.01 (d, J = 6 Hz, 2β-H in C5H4N), 8.89 (d, J =
6 Hz, 2α-H in C5H4N) ppm. 13C NMR (100.6 MHz, CS2:CDCl3 = 1:1):
13.84 (CH3), 61.05 (CH2), 107.05 (CdCꢀO), 123.65 (2β-C in
C5H4N), 149.67 (2α-C in C5H4N), 163.05, 163.53 (CdCO/CO2);
C60 72.83, 102.59 (2C of sp3-C), 135.48 (2C), 137.08 (2C), 137.43
(2C), 137.40 (2C), 139.89 (2C), 141.32 (2C), 141.50 (2C), 142.20
(2C), 142.26 (2C), 142.33 (2C), 142.35 (2C), 142.64 (2C), 142.72 (3C,
including one γ-C in C5H4N), 143.64 (2C), 144.11 (2C), 144.36 (2C),
144.50 (2C), 144.97 (2C), 145.10 (2C), 145.41 (2C), 145.47 (2C),
145.90 (2C), 145.95 (2C), 146.13 (2C), 146.20 (2C), 146.38 (2C),
147.09 (2C), 147.26 (1C), 147.48 (2C), 147.96 (1C) ppm. UVꢀvis
(CH2Cl2, 5 ꢁ 10ꢀ6 M): λmax (log ε) = 228 (4.99), 255 (5.11), 314 nm
(4.67).
Preparation of (4-C5H4N)C(O)dC(C60)CO2Et ZnTPPH (3).
3
A 25 mL Schlenk tube was charged with fullerene derivative 1 (9.1 mg,
0.01 mmol), ZnTPPH (6.8 mg, 0.01 mmol), and CS2 (1.5 mL). To the
top of the resulting CS2 solution was carefully added hexane (1 mL), and
then, the system was allowed to diffuse its hexane into the CS2 solution.
After 2 days of slow diffusion at room temperature, a black precipitate
was formed, which was collected by filitration, washed with hexane, and
finally dried under vacuum to afford 3 (15.5 mg, 97%) as a black solid.
Mp: 290ꢀ292 °C. Anal. Calcd. for C114H37N5O3Zn 3C6H5Cl: C,
3
82.25; H, 2.72; N, 3.63. Found: C, 82.09; H, 2.74; N, 3.58. IR (KBr
disk): νOCdO 1706 (s), νOCdC 1598 (s), νCdC 1522 (m, pyrrole CdC),
νCdN 1484 (m, pyrrole CdN), νCꢀN 1338 (m, pyrrole CꢀN), νC60
1400 (m), 1175 (m), 575 (w), 527 (s) cmꢀ1. 1H NMR (300 MHz, CS2:
CDCl3 = 1:1): 0.73 (t, J = 7.2 Hz, 3H, CH3), 3.40 (br s, 2α-H in
C5H4N), 3.87 (q, J = 7.2 Hz, 2H, CH2), 6.42 (d, J = 6.0 Hz, 2β-H in
C5H4N), 7.70ꢀ7.72 (m, 8m-H/4p-H in 4C6H5), 8.18ꢀ8.21 (m, 8o-H in
4C6H5), 8.86 (s, 8H in 4 pyrrole rings) ppm. 13C NMR (75.4 MHz, CS2:
CDCl3 = 1:1): 13.64 (CH3), 60.84 (CH2), 107.25 (CdCꢀO), 120.82
(4meso-C attached to phenyl groups), 122.63 (2β-C in C5H4N),
126.45, 127.23 (8m-C/4p-C in 4C6H5), 131.86 (8β-C in pyrrole rings),
134.74 (8o-C in 4C6H5), 143.47 (4ipso-C in 4C6H5), 150.12 (2α-C in
C5H4N/8α-C in pyrrole rings), 161.44, 162.22 (CdCO/CO2); C60:
72.14, 101.91 (2sp3-C), 136.46 (2C), 136.98 (2C), 138.81 (2C), 139.06
(2C), 140.31 (2C), 140.94 (2C), 141.41 (4C), 141.55 (2C), 141.69
(2C), 141.83 (2C), 141.89 (2C), 142.09 (2C), 142.52 (2C), 143.23
(2C), 143.60 (2C), 143.94 (3C, including one γ-C in C5H4N), 144.22
(2C), 144.39 (2C), 144.50 (2C), 144.72 (2C), 145.16 (2C), 145.25
(4C), 145.42 (2C), 145.52 (2C), 146.46 (2C), 146.48 (2C), 146.57
(1C), 147.23 (1C) ppm. UVꢀvis (CH2Cl2, 5 ꢁ 10ꢀ6 M): λmax (log ε) =
227 (5.03), 254 (5.13), 314 (4.77), 418 (5.68), 547 (4.24), 585 nm
(2.93).
Method (ii): A 100 mL two-necked flask equipped with a magnetic
stir-bar, a serum cap, and a reflux condenser topped with a N2 inlet tube
was charged with C60 (36 mg, 0.05 mmol), ethyl isonicotinoylacetate
(19 mg, 0.10 mmol), Mn(OAc)3 2H2O (40 mg, 0.15 mmol), and PhCl
3
(10 mL). While stirring, the mixture was heated at reflux for 15 min and
then was cooled to room temperature. The same workup as that used in
Method (i) afforded unreacted C60 (8 mg) and 1 (21 mg, 59% yield
based on the consumed C60).
Preparation of H2TPPC(O)CH2CO2Et (4). A 100 mL two-
necked flask fitted with a magnetic stir-bar, a rubber septum, and a N2
inlet tube was sequentially charged with THF (20 mL), monoethyl
malonate (0.86 mL, 7.3 mmol), and several milligrams of 2,20-dipyridyl
as an indicator. The mixture was cooled to ꢀ65 °C, and then, n-BuLi
(1.6 M in hexane, 9 mL, 14.6 mmol) was slowly added to allow the low
temperature to raise to ca. ꢀ5 °C. While the pink indicator persisted at
ꢀ5 °C, the mixture was recooled to ꢀ65 °C. To this mixture were added
H2TPPCOCl (494 mg, 0.73 mmol) (prepared from H2TPPCO2H and
oxalyl chloride), Et3N (0.4 mL, 2.87 mmol), and THF (15 mL). The
new mixture was stirred at this temperature for 20 min and at room
temperature for 1 h and then was poured into a mixture of CH2Cl2
(100 mL) and 1 N HCl (20 mL). The organic layer was washed with the
NaHCO3-saturated aqueous solution of (2 ꢁ 30 mL), dried over
Na2SO4, and evaporated to dryness at reduced pressure. The residue
was subjected to column chromatography (silica gel). Elution with
CH2Cl2/petroleum ether (v/v 3:1) developed a purple band, from
which 4 (430 mg, 81%) was obtained as a purple solid. Mp: 84 °C (dec).
Preparation of PhC(O)dC(C60)CO2Et (2). The same proce-
dures were utilized as described for preparation of 1 except that ethyl
benzoylacetate (35 μL, 0.2 mmol) was employed instead of ethyl
isonicotinoylacetate. Using Method (i), unreacted C60 (30 mg) and 2
(37 mg, 70% yield based on the consumed C60) as a brown-black solid
were obtained. Using Method (ii), unreacted C60 (12 mg) and 2 (10 mg,
33% yield based on the consumed C60) were obtained. Mp: >300 °C.
Anal. Calcd. for C71H10O3: C, 93.62; H, 1.11. Found: C, 93.41; H, 1.19.
IR (KBr disk): νOCdO 1701 (vs), νCdC 1618 (m), νC60 1437 (m), 1182
(m), 576 (w), 527 (s) cmꢀ1. 1H NMR (300 MHz, CS2:CDCl3 = 1:1):
1.20 (t, J = 7.2 Hz, 3H, CH3), 4.28 (q, J = 7.2 Hz, 2H, CH2), 7.60ꢀ7.63
(m, two m-H/one p-H in C6H5), 8.11ꢀ8.14 (m, two o-H in C6H5) ppm.
13C NMR (100.6 MHz, CS2:CDCl3 = 1:1): 14.39 (CH3), 60.98 (CH2),
109.99 (CdCO), 128.23, 129.81, 130.35, 131.42 (C6H5), 163.31,
163.55 (CdCO/CO2); C60: 72.43, 105.03 (2 sp3-C), 135.82 (2C),
137.86 (2C), 139.73 (2C), 140.24 (2C), 141.83 (2C), 141.91 (2C),
142.61 (2C), 142.65 (2C), 142.78 (2C), 142.84 (2C), 143.01 (2C),
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Inorganic Chemistry
ARTICLE
Anal. Calcd. for C49H36N4O3: C, 80.75; H, 4.98; N, 7.69. Found: C,
80.56; H, 4.90; N, 7.67. IR (KBr disk): νNꢀH 3316 (m), νCdO 1742 (s),
νOCdO 1687 (s), νCdC 1558 (m, pyrrole CdC), νCdN 1472 (s, pyrrole
MHz, CS2:CDCl3 = 2:1): ꢀ2.82 (s, 2H, 2NH), 1.38 (t, J = 7.2 Hz, 3H,
CH3), 4.43 (q, J = 7.2 Hz, 2H, CH2), 7.79 (s, 6m-H/3p-H in 3C6H5),
8.22 (d, J = 4.8 Hz, 6o-H in 3C6H5), 8.51, 8.53, 8.58, 8.60 (ABq, J = 8.0
Hz, 4H, C6H4), 8.83, 8.91, 8.96 (3s, 8H in 4 pyrrole rings) ppm. 13C
NMR (100.6 MHz, CS2:CDCl3 = 1:1): 14.15 (CH3), 60.79 (CH2),
104.89 (CdCO), 118.62, 120.17 (4meso-C attached to phenyl), 131.32
(8β-C in pyrrole rings), 126.62, 127.58, 128.42, 134.04, 134.44 (C6H5/
C6H4), 141.93 (8α-C in pyrrole rings), 163.57, 166.03 (CdCO/CO2);
C60: 73.96 (2 sp3-C), 134.97 (2C), 136.74 (2C), 138.91 (2C), 139.06
(2C), 140.52 (2C), 141.17 (2C), 141.51 (2C), 141.57 (2C), 141.83
(2C), 142.02 (2C), 142.05 (2C), 142.31 (2C), 143.43 (2C), 143.55
(2C), 143.85 (2C), 143.94 (2C), 144.48 (2C), 144.68 (2C), 144.83
(4C), 145.27 (4C), 145.41 (2C), 145.54 (2C), 145.60 (2C), 145.70
(2C), 146.86 (1C), 146.96 (2C), 147.54 (1C), 147.71 (2C) ppm.
UVꢀvis (CH2Cl2, 5 ꢁ 10ꢀ6 M): λmax (log ε) = 254 (5.04), 314
(4.66), 418 (5.58), 514 (4.09), 551 (3.70), 590 (3.36), 645 nm (3.24).
Preparation of ZnTPPC(O)dC(C60)CO2Et (7). To the same
equipped flask as that used for preparation of 4 were added dyad 6
(17.6 mg, 0.012 mmol) and CHCl3 (10 mL). While stirring, to the
resulting solution was added a MeOH (10 mL) solution of
1
CdN), νCꢀN 1349 (m, pyrrole CꢀN) cmꢀ1. H NMR (400 MHz,
CDCl3): ꢀ2.75 (s, 2H, 2NH), 1.40 (t, J = 7.2 Hz, 3H, CH3), 4.25, (s, 2H
in COCH2CO2 of keto form), 4.37 (q, J = 7.2 Hz, 2H, OCH2CH3), 6.00
(s, 1H in CdCH of enol form), 7.78 (s, 6m-H/3p-H in 3C6H5), 8.24 (s,
8o-H in 3C6H5/C6H4), 8.35 (s, 2m-H in C6H4), 8.79ꢀ8.90 (m, 8H in 4
pyrrole rings), 12.86 (s, 1H in HOCdC of enol form) ppm. 13C NMR
(100.6 MHz, CDCl3) for keto form: 14.63 (CH3), 46.33 (COCH2CO2),
61.95 (OCH2CH3), 118.52, 120.97 (4meso-C attached to phenyl
groups), 127.12 (8m-C in C6H5/C6H4), 128.19 (3p-C in C6H5),
131.78 (8β-C in pyrrole rings), 134.94 (6o-C in C6H5), 135.17 (2o-C
in C6H4), 142.38 (4ipso-C in 3C6H5/C6H4), 148.16 (8α-C in pyrrole
rings), 167.90 (CO2), 192.96 (CdO) ppm; for enol form: 14.55 (CH3),
60.88 (OCH2CH3), 88.38 (CHdCOH), 119.25, 121.24 (4meso-C
attached to phenyl groups), 124.77 (8m-C in 3C6H5/C6H4), 128.15
(3p-C in 3C6H5), 133.17 (8β-C in pyrrole rings), 135.10 (6o-C in
3C6H5), 135.46 (2o-C in C6H4), 145.63 (4ipso-C in 3C6H5/C6H4),
152.51 (8α-C in pyrrole rings), 171.65 (OCdO), 173.70 (CHdCOH)
ppm. UVꢀvis (CH2Cl2, 5 ꢁ 10ꢀ6 M): λmax (log ε) = 418 (5.62), 514
(4.15), 551 (3.65), 590 (3.38), 645 nm (3.30).
Zn(OAc)2 2H2O (10 mg, 0.046 mmol), and then, the new mixture
3
continued to be stirred at room temperature for 0.5 h. The reaction
mixture was washed with water (3 ꢁ 10 mL) and dried over Na2SO4.
After removal of solvents under vacuum, 7 (15.6 mg, 89%) was obtained
as a brown-black solid. Mp: >300 °C (dec). Anal. Calcd. for
C109H32N4O3Zn: C, 86.65; H, 2.13; N, 3.71. Found: C, 86.79; H, 2.19;
N, 3.69. IR (KBr disk): νOCdO 1693 (m); νOCdC 1632 (m), νCdC 1550
(w, pyrrole CdC), νCdN 1439 (w, pyrrole CdN), νCꢀN 1368 (w, pyrrole
CꢀN); νC60 1439 (w), 563 (w), 526 (m) cmꢀ1. 1H NMR (400 MHz,
CDCl3): 1.37 (t, J = 7.2 Hz, 3H, CH3), 4.45 (q, J = 7.2 Hz, 2H, CH2),
8.40 (s, 6m-H/3p-H in 3C6H5), 8.43 (s, 6o-H in 3C6H5), 8.45ꢀ8.60
(m, 4H, C6H4), 8.95ꢀ9.08 (m, 8H in pyrrole rings) ppm. 13C NMR
(100.6 MHz, CS2:CDCl3 = 1:1): 13.24 (CH3), 59.95 (CH2), 103.91
(CdCO), 118.81, 120.32 (4meso-C attached to phenyl), 125.51, 125.60,
126.51, 127.43, 130.78, 131.11, 131.17, 131.35, 133.02, 133.41, 141.72,
141.78 (C6H5/C6H4), 162.90, 165.35 (CdCO/CO2); C60: 72.02, 100.85
(2sp3-C), 134.05 (2C), 134.57 (2C), 135.85 (2C), 138.00 (2C), 138.05
(2C), 139.40 (2C), 140.27 (2C), 140.50 (2C), 140.58 (2C), 140.88 (2C),
141.11 (4C), 141.40 (2C), 142.45 (2C), 142.69 (2C), 142.98 (2C),
143.04 (2C), 143.55 (2C), 143.75 (2C), 143.95 (2C), 144.31 (2C),
144.49 (2C), 144.62 (2C), 144.69 (2C), 144.79 (2C), 145.14 (2C),
145.93 (1C), 146.06 (2C), 146.66 (1C), 146.88 (2C) ppm. UVꢀvis
(CH2Cl2, 5 ꢁ 10ꢀ6 M):λmax (log ε) = 228 (5.27), 257 (5.33), 314 (4.94),
419 (5.79), 548 (4.46), 587 nm (3.87).
X-ray Structure Determinations of 2 and 3 and 5. The single
crystals of 2 suitable for X-ray diffraction analysis were grown by slow
evaporation of its CS2/hexane solution at rt, those of 3 obtained by slow
evaporation of its CS2/PhCl solution at rt, and those of 5 obtained by
slow evaporation of its CH2Cl2/EtOH solution at rt. A single crystal of 2,
3, or 5 was mounted on a Rigaku MM-007 (rotating anode) diffract-
ometer equipped with Saturn 70CCD. Data were collected at 113 K
using a confocal monochromator with Mo Kα radiation (0.71070 Å) in
the ωꢀϕ scanning mode. Data collection and reduction and absorp-
tion correction were performed by CRYSTALCLEAR program.59
All the structures were solved by direct methods using the SHELXS-
97 program60 and refined by full-matrix least-squares techniques
(SHELXL-97)61 on F2. Hydrogen atoms were located using the geo-
metric method. Crystal data and structural refinment details for 2, 3, and
5 are summarized in Table 3 (see Supporting Information).
Preparation of ZnTPPC(O)CH2CO2Et (5). To the same
equipped flask as that described for preparation of 4 were added
porphyrin derivative 4 (50 mg, 0.069 mmol) and CHCl3 (10 mL). To
the stirred solution was added a MeOH (10 mL) solution of Zn-
(OAc)2 2H2O (50 mg, 0.23 mmol), and then, the new mixture was
3
heated at reflux for 1 h. After cooling to room temperature, it was washed
with water (3 ꢁ 10 mL) and the separated organic layer was dried over
Na2SO4 and evaporated to dryness at reduced pressure. The residue was
subjected to column chromatography (silica gel). Elution with CH2Cl2/
petroleum ether (v/v 2:1) developed a purple-red band, from which 5
(49 mg, 90%) was obtained as a purple-red solid. Mp: 214 °C (dec).
Anal. Calcd. for C49H34N4O3Zn: C, 74.29; H, 4.33; N, 7.07. Found: C,
74.09; H, 4.50; N, 7.09. IR (KBr disk): νCdO 1741(s), νOCdO 1685 (s),
νCdC 1558 (w, pyrrole CdC), νCdN 1487 (m, pyrrole CdN), νCꢀN
1338 (s, pyrrole CꢀN) cmꢀ1. 1H NMR (300 MHz, CDCl3): 1.38 (t, J =
7.2 Hz, 3H, CH3), 4.27 (s, 2H, COCH2CO2), 4.35 (q, J = 7.2 Hz, 2H,
OCH2CH3), 7.77 (s, 6m-H/3p-H in 3C6H5), 8.21ꢀ8.23 (m, 6o-H in
3C6H5), 8.35 (s, 4H, C6H4), 8.87ꢀ8.96 (m, 8H in 4 pyrrole rings) ppm.
13C NMR (75.4 MHz, CDCl3): 14.13 (CH3) 45.94 (COCH2CO2),
61.55 (OCH2CH3), 119.06, 121.45 (4meso-C attached to phenyl
groups), 126.60 (8m-C in 3C6H5/C6H4), 127.58 (3p-C in 3C6H5),
131.38 (one p-C in C6H4), 132.18, 132.43 (8β-C in pyrrole rings),
134.48 (6o-C in 3C6H5), 134.82 (2o-C in C6H4), 142.79 (4ipso-C in
3C6H5/C6H4), 148.79, 149.46, 150.27, 150.48 (8α-C in pyrrole rings),
167.50 (CO2), 192.52 (CdO) ppm. UVꢀvis (CH2Cl2, 5 ꢁ 10ꢀ6 M):
λmax (log ε) = 419 (5.73), 548 (4.37), 587 nm (3.67).
Preparation of H2TPPC(O)dC(C60)CO2Et (6). To the same
equipped flask as that used for preparation of 4 were added porphyrin
derivative 4 (109 mg, 0.15 mmol), C60 (72 mg, 0.1 mmol), and
chlorobenzene (20 mL). To the stirred solution was added piperidine
(30 μL, 0.3 mmol), and then, the new mixture continued to be stirred at
room temperature for 36 h under the dark. After volatiles were removed
at reduced pressure, the residue was subjected to column chromatog-
raphy (silica gel). Elution with toluene/petroleum ether (v/v 1:1)
developed a purple band, from which unreacted C60 (28 mg) was
recovered. Elution with toluene developed a brown band, from which 6
(68 mg, 77% based on the consumed C60) was obtained as a brown-
black solid. Mp: >300 °C (dec). Anal. Calcd. for C109H34N4O3: C,
90.45; H, 2.37; N, 3.87. Found: C, 90.57; H, 2.32; N, 3.62. IR (KBr disk):
νNꢀH 3315 (m), νOCdO 1700 (s), νOCdC 1601 (w), νCdC 1558 (m,
pyrrole CdC), νCdN 1460 (s, pyrrole CdN), νCꢀN 1372 (m, pyrrole
CꢀN); νC60 1442 (m), 1180 (s), 576 (w), 527 (s) cmꢀ1. 1H NMR (400
Photoinduced H2 Evolution. A 30 mL Schlenk flask fitted with a
N2 inlet tube, a rubber septum, a magnetic stir-bar, and a water-cooling
jacket was charged with EDTA (55.83 mg, 0.15 mmol), dyad 3 (0.32 mg,
2 ꢁ 10ꢀ4 mmol), colloidal Pt (10 mL of 0.1 mM, 1 ꢁ 10ꢀ3 mmol), MV2
+ (1.76 mg, 4 ꢁ 10ꢀ3 mmol), HOAc (57 μL, 1 mmol), and Triton X-100
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Inorganic Chemistry
ARTICLE
(0.3 mL). While stirring, the resulting solution was thoroughly deox-
ygenated by bubbling with nitrogen and then was irradiated through a
Pyrex-glass filter (λ > 400 nm) using a 350 W Xe lamp at about 25 °C
(controlled by the cooling jacket). During the photoinduced catalysis,
the evolved H2 was withdrawn periodically using a gastight syringe,
which was analyzed by gas chromatography on a Shimadzu GC-9A
instrument with a thermal conductivity detector and a carbon molecular
sieve column (3 mm ꢁ 2.0 m) and N2 as the carrier gas.
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S
Supporting Information. Full tables of crystal data,
b
atomic coordinates, thermal parameters, and bond lengths and
angles for 2, 3, and 5 as CIF files and Table 3 summarizing the
crystal data and structural refinment details for 2, 3, and 5. This
material is available free of charge via the Internet at http://pubs.
acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: lcsong@nankai.edu.cn.
’ ACKNOWLEDGMENT
We are grateful to 973 (2011CB935902), the National Natural
Science Foundation of China (20772059, 20972073), and the
Tianjin Natural Science Foundation (09JCZDJC27900) for fina-
ncial support.
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