Silicon-phthalocyanine-cored fullerene dendrimers: Synthesis and prolonged charge-separated states with dendrimer generations

Article abstract of DOI:10.1002/chem.200601254

Silicon-phthalocyanine-cored fullerodendrimers with up to eight fullerene substituants (SiPc-n C₆₀; n = 2, 4, and 8) have been synthesized. Photophysical properties of newly synthesized SiPc-n C₆₀ have been investigated by time-resol

Full text of DOI:10.1002/chem.200601254

DOI: 10.1002/chem.200601254
Silicon-Phthalocyanine-Cored Fullerene Dendrimers: Synthesis and
Prolonged Charge-Separated Stateswith Dendrimer Generations
[
a, b]
[c]
[c]
[d]
Mohamed E. El-Khouly,
Eui Su Kang, Kwang-Yol Kay,* Chan Soo Choi,
[a]
[
a]
Yasuyuki Aaraki, and Osamu Ito*
1
Abstract: Silicon-phthalocyanine-cored
fullerodendrimers with up to eight full-
erene substituents (SiPc–nC ; n=2, 4,
and 8) have been synthesized. Photo-
physical properties of newly synthe-
sized SiPc–nC60 have been investigated
by time-resolved fluorescence and tran-
sient absorption analysis with pulsed
laser light. Laser photolysis measure-
ments suggest the occurrence of a
charge-separation process from SiPc*
to the C60 subunits. The nanosecond
transient absorption spectra in the
near-IR region indicate that the life-
times of the formed radical ion pairs
are prolonged on the order of SiPc–
8C >SiPc–4C >SiPc–2C ,
which
60
60
60
may be related to the electron migra-
tion among the C60 subunits. The use-
fulness of SiPc–nC60 as light-harvesting
systems, evaluated as a ratio of the
rates of charge recombination to those
of charge separation, increases marked-
ly with the dendrimer generation.
6
0
Keywords: charge transfer · den-
drimers · photochemistry · phthalo-
cyanines · silicon
[
4]
[5]
Introduction
drimers, or polymers. Phthalocyanines (Pc), structural an-
alogues of porphyrins, with a strong absorption in the visible
region (the Q band; lmax ꢀ700 nm), are highly versatile and
stable chromophores with unique photophysical and photo-
chemical properties that make them, alone or in combina-
tion with many other electro- and photoactive moieties,
ideal building blocks for the construction of molecular mate-
Studies on the energy- and electron-transfer processes in
photosynthetic antenna proteins have undergone an enor-
mous growth in recent years to develop artificial photosyn-
[1]
thetic systems. Various strategies have been employed to
develop molecular electronic devices that use porphyrin
[2]
[3]
[6]
arrays linked by covalent bonds, self-assemblies, den-
rials with special electronic and optical properties. Among
the Pc derivatives, the axially substituted silicon phthalocya-
nines (SiPc) are of great interest because the axial substitu-
tions make it possible to preclude undesirable aggregation
[
a] Dr. M. E. El-Khouly, Dr. Y. Aaraki, Prof. O. Ito
Institute of Multidisciplinary Research for Advanced Materials
Tohoku University, Sendai, 980–8577 (Japan)
Fax : (+81)22-217-5608
[6]
in solution. Furthermore, the axially substituted phthalo-
cyanines with bulky dendritic subunits are known to pro-
[
6–8]
duce glassy solids,
which allow the fabrication of the non-
E-mail: ito@tagen.tohoku.ac.jp
[6,8]
scattering films for practical-device applications.
Howev-
[
b] Dr. M. E. El-Khouly
Department of Chemistry
Faculty of Education, Kafr El-Sheikh
Tanta University (Egypt)
er, despite such advantages, the number of axially substitut-
ed silicon phthalocyanines as multicomponent systems is
still limited. A few elegantly designed dendrimers that incor-
porate a phthalocyanine core have been synthesized so far,
and most photophysical and photochemical studies have
been carried out with either metallic complexes or with a sil-
[
c] E. S. Kang, Prof. Dr. K.-Y. Kay
Department of Molecular Science and Technology
Ajou University, Wonchon-dong
Youngtong-gu, Suwon 443–749 (South Korea)
Fax : (+82)31-219-1615
[7–10]
icon derivative located within the central macrocycle.
E-mail: kykay@ajou.ac.kr
Such dendrimers are known to produce glassy solids, which
could be readily fabricated into nonscattering films for opti-
cal applications.
[
d] Prof. Dr. C. S. Choi
Department of Applied Chemistry
Daejeon University
Daejeon 300–716 (South Korea)
As photosynthetic models, phthalocyanine–fullerene sys-
[11]
tems have been mainly prepared covalently or noncova-
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
[12]
lently and are promising for efficient light harvesting. In
2854
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2854 – 2863

FULL PAPER
[
7]
the light of their particular electronic properties, fullerene
derivatives appear to be superior electron acceptors owing
to the low reorganization energy that results in rapid charge
separation and rather slow charge recombination as a conse-
axial fullerene substituents. This success prompted us to
synthesize phthalocyanine-cored fullerene dendrimers G1–
G3 with up to eight fullerene subunits.
Our synthetic strategy for the dendritic fullerenes G1–G3
consisted of preparing larger dendrimer arms or dendrons
(Gn-OH) and coupling several of these to a phthalocyanine
core convergently. In the present context, the synthesis of
the requisite dendrons was based upon a repetitive cou-
pling/deprotection sequence that utilized silyl-protected phe-
nols and dicarboxylic acids. Every step of the reaction se-
quence proceeded smoothly and efficiently to give a good-
or-moderate yield of the product.
[13]
quence of accessing the Marcus inverted region.
To the
best of our knowledge, a phthalocyanine with more than
two fullerene substituents had not been presented until we
reported the first synthesis of silicon phthalocyanine with
[7]
two axial fullerene substituents. Dendrimers with fullerene
[14]
cores have been widely studied, whereas the synthesis of
fullerene-rich dendrimers has been considered to a lesser
degree, mainly because of the difficulties encountered in
their synthesis, such as low solubility and limited chemical
The compound G1 was synthesized as depicted in
Scheme 2. The starting compound bis(malonate) 1 was pre-
[15]
reactivity.
A
H
R
U
G
In line with these aspects, herein we have for the first
time designed and synthesized a series of silicon-phthalocya-
nine-cored fullerodendrimers bearing up to eight axial full-
erene subunits (SiPc–nC ; n=2 (G1), 4 (G2), and 8 (G3);
see Scheme 1) and exclusively investigated their photophysi-
cal properties by employing steady-state and time-resolved
techniques. The main advantage of such highly soluble den-
drimers is the maintenance of prolonged charge-separated
states between the phthalocyanine-donor and fullerene-ac-
ceptor components, in addition to the harvesting of a wide
range of the solar-light spectrum.
pared in four steps from the commercially available 5-hy-
droxyisophthalic acid according to a method previously re-
ported by us. Reaction of 1 with C60 was based on the
[7]
highly regioselective reaction developed by Diederich and
6
0
[16]
co-workers, which led to a macrocyclic bisadduct of C60
through a macrocyclization reaction of the carbon sphere
with bis(malonate) derivatives in a double Bingel addi-
A
T
E
N
[17]
tion. Treatment of C60 with 1, iodine, and 1,8-diazabicyclo-
[5.4.0]undec-7-ene (DBU) in toluene at room temperature
AHCTREUNG
afforded the bisadduct G1-OH 2 in 34% yield. The final re-
action of bisadduct 2 with silicon phthalocyanine dichloride
went smoothly in the presence of K CO to produce G1 in
2
3
2
7% yield.
The structure of G1 was confirmed by H and C NMR
1
13
Results and Discussion
spectroscopic and MALDI-TOF mass-spectrometric analy-
sis. The H NMR spectrum is particularly informative, be-
1
Synthesis: Since the first reported preparation of the periph-
erally four-fullerene-substituted porphyrin by Nierengarten
cause the strong ring current of the Pc macrocycle helps to
differentiate protons of similar type (see the Supporting In-
[15a]
et al.,
we synthesized a silicon phthalocyanine with two
Scheme 1. Molecular structures of G1–G3.
Chem. Eur. J. 2007, 13, 2854 – 2863ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2855

O. Ito, K.-Y. Kay et al.
nine core in the presence of
K CO to produce the dendri-
2
3
mer G2 with four fullerene
subunits in 62% yield.
1
13
H
and
C NMR spectra
were most useful for the char-
acterization of G2. In spite of
the increase in generation
number, well-resolved reso-
nance signals in the aliphatic
and aromatic regions were
Scheme 2. Synthesis of G1. Reagents and conditions: a) C60, I
phthalocyanine dichloride, K CO , toluene, reflux, 15 h (27%).
2
, DBU, toluene, RT, 24 h (34%); b) silicon
2
3
1
present in both the H and
13
13
formation). The C NMR spectrum showed a set of signals
for the C60 nucleus (d=136.85–149.50 ppm), two carbonyl
carbon atoms (d=162.37 and 162.03 ppm), aromatic carbon
atoms (d=113.91–135.88 ppm), and aliphatic carbon atoms
C NMR spectra of G2, and distinct assignments could be
made for the structure of G2 (see the Supporting Informa-
tion). Analogous to the G1 fragmentation patterns, the
MALDI-TOF mass spectrum also showed a basis peak at
+
(
d=14.33–70.31 ppm). Further confirmation of the hybrid
m/z 3781.10 ([M ÀG2-OH-1). These results gave good evi-
Pc–fullerene structure was obtained from the IR and UV/
Vis spectra, which contain absorption bands that arise from
the Pc and fullerene components. The MALDI-TOF mass
dence for the structure of G2.
The synthesis of dendrimer G3 with eight fullerene sub-
units is described in Scheme 4. Silyl-protected diacid 5 was
A
H
R
U
G
+
spectrum showed peaks at m/z 2086.39 ([M ÀG1-OH-1]) as
coupled with the G2-OH dendron 7 in the presence of
DCC, DMAP, and HOBT to give 8 in 57% yield, and the
silyl-protected phenol group of 8 was then deprotected with
HF to afford the G3-OH dendron 9 with four fullerene sub-
units in 54% yield. This dendron G3-OH (9) was coupled to
the silicon phthalocyanine core to produce the G3 dendri-
mer with eight fullerene subunits in 25% yield.
The largest dendritic fullerophthalocyanine G3 contains
eight fullerene subunits and has a molar mass of 13978. The
purity of G3 was confirmed by thin-layer chromatography,
the basis peak and 1546.3767 (G1-OH-1). These results pro-
vided direct evidence for the structure of G1.
The preparation of G2 is depicted in Scheme 3. According
to the method developed by Corey and Venkateswarlu,
[18]
the hydroxy groups of 5-hydroxyisophthalic acid (3) were
protected by reaction with tert-butyldimethylsilyl chloride to
afford silyl-protected 4 in 94% yield and then selectively de-
[19]
posited by glacial acetic acid/water (3:1)
in 89% yield.
to give diacid 5
1
13
The reaction of 5 with a silyl-protected phenol group was
carried out by a coupling reaction with G1-OH (2) under
standard coupling conditions using dicyclohexylcarbodiimide
H and C NMR spectroscopic, and MALDI-TOF mass-
spectrometric analysis. Despite its macromolecular structure,
the protons of the G3 dendrimer showed clearly separated
resonance signals in the aromatic and aliphatic regions.
Owing to the highly symmetrical structure of G3, the
(
DCC), 4-dimethylaminopyridine (DMAP), and 1-hydroxy-
1
6
H-benzotriazole hydrate (HOBT) to afford silyl-protected
in 47% yield. The silyl-protected phenol group in 6 was
1
3
C NMR spectrum was simple, well resolved, and showed
then deprotected with HF to give G2-OH dendron 7 in
7% yield. Finally, 7 was coupled to the silicon phthalocya-
each set of the signals for the fullerene, carbonyl, aromatic,
and aliphatic carbon atoms in the expected regions.
9
Scheme 3. Synthesis of G2. Reagents and conditions: a) tert-butyldimethylsilyl chloride, imidazole, DMF, 578C, 24 h (94%); b) THF/CH
1:3:1), RT, 3 h (89%); c) G1–OH (2), DCC, DMAP, HOBT, CHCl , RT, 24 h (47%); d) HF, THF, RT, 15 h (97%); e) silicon phthalocyanine dichloride,
CO , [18]crown-6, toluene, reflux, 15 h (62%). DMF=N,N,-dimethylformamide.
3 2 2
CO H/H O
(
3
K
2
3
2856
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2854 – 2863

Synthesis and Photophysical Properties of Silicon Phthalocyanine/Fullerene Dendrimers
FULL PAPER
Scheme 4. Synthesis of G3. Reagents and conditions: a) G2–OH (7), DCC, DMAP, HOBT, CHCl
con phthalocyanine dichloride, K CO , [18]crown-6, toluene, reflux, 15 h (54%).
3
, RT, 24 h (57%); b) HF, THF, RT, 15 h (54%); c) sili-
2
3
MALDI-TOF mass spectrum showed a signal at m/z 7169.67
Cyclic voltammetry studies: The determination of the redox
potentials of SiPc–nC60 is important to evaluate the energet-
ics of the electron-transfer processes. In benzonitrile
+
(
[M ÀG3-OH-1) and a basis peak at m/z 1096.31.
Silicon phthalocyanine (SiPc) 10 was also prepared as a
reference compound in the electrochemical and photophysi-
(PhCN), the first oxidation potentials (E ) of the SiPc moi-
ox
cal characterization of Pc–fullerene dendrimers G1–G3. Bis-
eties of SiPc–nC were located at 650–670 mV versus Ag/
Ag and are almost the same as SiPc (720 mV). The first re-
6
0
+
A
C
H
T
R
E
U
N
G
(malonate) 1 was treated with silicon phthalocyanine di-
chloride under similar conditions as those for G1 to produce
dark blue 10 in 20% yield (Scheme 5).
duction potentials (Ered) of the C60 moieties of SiPc–nC
60
+
were located at around À800 mV versus Ag/Ag . The driv-
ing forces for the charge recombination (ÀDG ) and
CR
charge separation (ÀDG ), calculated from the Rehm–
CS
[20]
Weller equations
charge-separation process via SiPc* to form SiPcC –C C -
(see Table 1) suggest an exothermic
1
+
À
60
A
H
R
U
G
On the other hand, quite small negative
6
0
1
DGCS values were calculated via C * in PhCN but not in
60
toluene.
Steady-state absorption studies: The absorption spectrum of
the SiPc reference compound in toluene shows the B band
at 352 nm, the Q band at 682 nm, and a shoulder at 615 nm
(
Figure 1). The absorption spectrum of SiPc–2C60 shows a
red shift of the Q band at about 2 nm with respect to that of
SiPc. The absorption bands of the C60 subunits were ob-
served at 265 and 340 nm; thus, the absorption in the region
3
00–600 nm is significantly increased with an increasing
number of attached C60 units. Interestingly, the red shift of
the Q band is noted as the generation number of the den-
dritic C60 subunits increases: 684 (G1, SiPc–2C ), 689 (G2,
60
SiPc–4C ), and 690 nm (G3, SiPc–8C ). The surrounding
6
0
60
C60 groups may interact with a SiPc unit in addition to the
nearest C60 groups attached to the axial positions, thus caus-
ing the observed shift. In PhCN, the absorption spectra of
Scheme 5. Synthesis of reference compound SiPc (10). Reagents and con-
ditions: a) silicon phthalocyanine dichloride, K
ene, reflux, 15 h (20%).
2 3
CO , [18]crown-6, tolu-
Chem. Eur. J. 2007, 13, 2854 – 2863ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2857

O. Ito, K.-Y. Kay et al.
creased by 10–20% on changing the solvent from nonpolar
toluene to polar PhCN. From this solvent dependence, we
infer efficient electron-transfer quenching of the excited sin-
1
glet state of the SiPc moiety ( SiPc*) by the surrounding C60
moieties.
Time-resolved studies: Time-resolved fluorescence measure-
ments were performed to monitor the charge-separation
process. Figure 3shows the fluorescence decay–time profiles
Figure 1. Steady-state absorbance spectra of SiPc–nC60 in PhCN. Concen-
À6
trations: 5”10 m.
the dendrimers SiPc–nC60 show almost the same behavior as
in toluene, although an additional red shift of the Q band of
1–2 nm was observed.
Figure 3. Fluorescence decay profiles of SiPc in toluene and G1 in PhCN
and toluene monitored at 690 nm; lex =400 nm.
Steady-state fluorescence studies: The fundamental photo-
physical behavior of SiPc–nC60 was investigated by using
steady-state fluorescence in both toluene and PhCN
(
Figure 2). The peak maxima of the SiPc emission of SiPc–
at 690 nm of SiPc—-2C60 in toluene and PhCN along with
pristine SiPc in toluene. The fluorescence time profile of
pristine SiPc exhibited a single exponential decay with a life-
time (t ) of 5.0 ns. The lifetimes (t ) of the SiPc moiety of
f0
f
SiPc–2C60 were evaluated by curve fitting with single expo-
nential functions of 1.79 and 2.08 ns in PhCN and toluene,
respectively. Substantially similar fluorescence lifetimes of
SiPc–nC60 were observed (Table 1). These observations sug-
1
gest the quenching of SiPc* by the appended C entities.
6
0
The quenching is likely to occur by the charge-separation
1
+
·À
process via SiPc* generating SiPcC ÀC
A
H
R
N
60
1
fluorescence lifetimes of SiPc*, the rate constants (k ) and
CS
quantum yields (F ) of the charge-separation process of
CS
SiPc–nC60 were estimated as listed in Table 1. Although the
1
Figure 2. Steady-state fluorescence spectra of SiPc–nC60 in toluene. Con-
centrations: 5”10 m.
charge separation via C * is energetically feasible, the esti-
6
0
À6
1
mation of both kCS and FCS via C * is difficult as a result
60
of the weak emission of C , which is hidden under the emis-
6
0
sion of SiPc.
nC60 revealed red shifts relative to the SiPc reference: 691
The nanosecond transient studies that aimed to confirm
the charge-separated states and follow the charge-recombi-
nation process were performed by the excitation of both the
SiPc and C60 moieties with 355-nm laser light, at which the
(
G1, SiPc—2C ), 684 (G2, SiPc–4C ), and 697 nm (G3,
60 60
SiPc–8C ), which correspond to the red shifts of the absorp-
60
tion bands. In SiPc–nC , the SiPc emission bands are
6
0
quenched by the fullerene subunits by approximately 83–
6% relative to that of the SiPc reference. It was observed
that the emission quenching for the SiPc–4C60 and SiPc–
C60 was slightly higher relative to that of SiPc–2C . These
observations suggest efficient quenching of the singlet excit-
ed state of the SiPc unit by the appended fullerene moieties,
and such quenching increases with increasing the number of
C60 subunits. It may also be mentioned that the fluorescence
peak of the C60 unit at 720 nm was hidden by the strong
absorption ratio of SiPc/C60 is 80:20 for SiPc–2C ; the parti-
tion of C60 increases with the dendrimer generation. The
60
8
transient spectra of SiPc–nC60 in Ar-saturated PhCN exhib-
·
+
8
ited the absorption bands of the SiPc moiety at 740 and
60
·
À
860 nm and the characteristic band of the C
moiety at
6
0
[22,23]
1020 nm (Figure 4).
The assignment of the absorption
·
+
bands for SiPc at 740 and 860 nm was confirmed by the
transient spectra of a mixture of SiPc and C60 in PhCN (see
the Supporting information) that exhibited a slow growth in
the absorption bands of SiPcC at 740 and 860 nm and C C
accompanied by decays of the absorption
bands of SiPc* and C * at 500 and 760 nm, respectively.
60
+
À
emission that results from the SiPc unit because of the very
60
À4 [21]
[24]
low fluorescence quantum yield of C60 (F =6.0”10 ).
at 1080 nm,
f
3
3
Similar fluorescence spectral changes were observed in
PhCN. The overall fluorescence quenching efficiency was in-
+
À
Judging from the energy level of SiPcC –C C
A
H
R
U
G
in
6
0
60 nÀ1
2858
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2854 – 2863

Synthesis and Photophysical Properties of Silicon Phthalocyanine/Fullerene Dendrimers
FULL PAPER
1
Table 1. Free-energy changes (DGCR and DGCS), fluorescence lifetimes of SiPc* (t
f
), rates (kCS), and quantum yields (FCS) of the charge separation, rate
[
a]
of the charge recombination (kCR), and lifetime of the radical ion pairs (tRIP) of SiPc–nC60 in PhCN and toluene.
Compound
Solvent
ÀDGCR
ÀDGCS
t
f
k
CS
À1
F
CS
k
CR
À1
t
RIP
[
eV]
[eV]
[ns]
A
H
R
U
G
]
A
H
R
U
G
]
[ns]
8
8
8
8
8
8
7
7
6
6
6
6
SiPc–2C60 (G1)
SiPc–4C60 (G2)
SiPc–8C60 (G3)
PhCN
toluene
PhCN
toluene
PhCN
toluene
1.48
1.70
1.46
1.72
1.44
1.74
0.32
0.10
0.34
0.08
0.36
0.06
1.79
2.08
2.18
2.05
2.25
1.96
3.6”10
2.8”10
2.7”10
2.8”10
2.4”10
3.1”10
0.64
0.58
0.58
0.58
0.55
0.60
3.0”10
7.0”10
6.7”10
9.6”10
5.0”10
6.3”10
33
13
149
104
200
160
[
a] The driving forces for DGCR and DGCS were calculated by equations ÀDGCR =e
A
H
R
U
G
S
and ÀDGCS =DE00
À(ÀDGCR), in which DE00 is the
A
T
E
N
1
1
energy of the 0–0 transition (1.80 and 1.76 eV for SiPc* and C60*, respectively) and DG
S
refers to the static energy. Calculation of this energy was car-
2
2
[24]
ried by using ÀDG
and R are radii of the radical cation (7.0 Š) and anion (4.2 Š), respectively; RCC is the center–center distance between C60 and SiPc (6.5 Š), which were
evaluated from the optimized structure (see the Supporting Information); e and e refer to the solvent dielectric constants for the electrochemical and
photophysical measurements, respectively; the kCS and FCS values via SiPc were calculated from the relation kCS =(1/t
which tf0 is the lifetime of the SiPc reference (5.0 ns).
S
=e /(4pe
0
e
R
R
CC) in PhCN and ÀDG
S
=À
A
H
R
N
A
H
R
U
(4pe
0
))((1/
A
H
E
G
+
)+1/
S
À(1/
A
H
R
U
G
+
)+1/
A
H
E
N
À R +
(2R ))/e ) in toluene, in which R
À
R
*
S
1
f
)À
A
H
R
U
G
A
C
H
T
R
E
U
N
G
f
(1/tf0) and FCS =kCS/(1/t ), in
[25]
por-(C CHCOO) ), the pro-
6
0
2
longed lifetimes of the charge-
separate state of SiPc–2C60 in
the present study are notable,
which may reflect the effect of
the SiPc donor ability and the
bond character on increasing
the tRIP value of SiPc–2C60.
Moreover, the tRIP values of
the studied systems are ex-
tremely long relative to the re-
ported axially substituted tita-
Figure 4. Nanosecond transient spectra of SiPc–2C60 (left) and SiPc–8C60 (right) in Ar-saturated PhCN; lex
55 nm. Inset: decay profile at 1020 nm.
=
3
[26]
nium Pc–C .
6
0
In the case of SiPc–2C , as
60
1
+
À
PhCN, the charge-separation processes via SiPc* (and also
one side of the species is SiPcC –C C , electron migration is
60
1
via C *) are possible.
impossible. However, for SiPc–4C and SiPc–8C , these
60
60
+
60
À
+
sides are SiPcC –C C
60
À
À
The characteristic band of the C C moiety was employed
to determine the rate constants of the charge-recombination
A
H
R
U
G
A
H
R
N
(C ) , respective-
6
0
60
60
60 3
À
ly; thus, it is possible for an electron to migrate to C C -
60
+
À
process (kCR) of SiPcC –C C
A
H
R
U
G
A
H
R
U
G
60
60 nÀ1
the absorption in the longest wavelength region may not be
such prolongation of the tRIP values. In separate experi-
3
3
disturbed by the absorption tails of SiPc* and C *. In the
ments, the electron migration among the C moieties of
6
0
60
À
case of SiPc–2C60 (inset of Figure 4a) the decay showed
C C
A
H
R
U
G
,
60
60 nÀ1
major fast decay followed by the minor slow decay; such
slow decay can be attributed to the absorption tails of the
absorption spectra of a solution of SiPc–nC60 in tetrakis(di-
methylamino)ethylene (TDAE), which is a strong electron
3
[27]
triplet states, in which SiPc* may be generated through in-
donor. For SiPc–2C , a new sharp absorption band ap-
6
0
1
tersystem crossing via SiPc* as a fraction of (1ÀF ) and
peared at 990 nm that can be clearly assigned to the isolated
CS
3
À
C * after direct excitation. Thus, the fast decay was well
C C species (see the Supporting Information). This sharp
60
60
fitted by the single-exponential function. Interestingly, in the
case of SiPc–8C60 (inset of Figure 4b), the decay seems to
be fitted with a single exponential. An examination of
Table 1 reveals slower kCR with increasing number of C60
units; that is, kCR(SiPc–2C )>k (SiPc–4C )>kCR(SiPc–
absorption is quite similar to that observed in the transient
absorption in Figure 4a. With an increasing number of C
60
À
subunits, the absorption peak of the C C unit generated by
6
0
reduction with TDAE became broader and more similar to
that in Figure 4b, thus reflecting the electron migration be-
60
CR
60
8
C ) (Table 1). From the k values, the lifetimes (tRIP) of
tween the C60 moieties.
The charge-separation process via C * was confirmed by
60
CR
+
À
1
SiPcC –C C
A
C
H
T
R
E
U
N
G
(C )
are evaluated as 33 (SiPc–2C ), 149
60
60 nÀ1
60
60
(
SiPc–4C ), and 200 ns (SiPc–8C ). From these findings,
observing the nanosecond transient spectra of G1–G3 in
60
60
the tRIP value of SiPc–8C60 is seven times longer than that of
benzonitrile by 532-nm laser light (at which the absorption
SiPc–2C , thus reflecting the role of dendritic C subunits
ratio of C /SiPc is 60:40), which shows that the partition of
60
60
60
+
À
on prolonging the lifetime of SiPcC –C C
A
H
R
U
G
C60 increases with the dendrimer generation. The spectra
show similar characteristic peaks, as recorded by 355-nm
laser light. The tRIP values were evaluated as 55, 111, and
6
0
60 nÀ1
to a previously reported fullerene–tin porphyrin–fullerene
triad linked by the axial coordination of tin porphyrin (Sn
Chem. Eur. J. 2007, 13, 2854 – 2863ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2859

O. Ito, K.-Y. Kay et al.
2
80 ns for G1–G3, respectively. These values are almost the
Conclusion
1
same as those obtained via SiPc*.
The transient absorption spectra in Ar-saturated toluene
Figure 5) show similar characteristic peaks to those in
PhCN. Therefore, the fluorescence quenching can also be
We have explored a novel strategy to prepare silicon-phtha-
locyanine-cored fullerodendrimers with up to eight fullerene
subunits (SiPc–nC ; n=2, 4, and 8). The steady-state and
(
6
0
time-resolved measurements
indicate charge-separation
a
1
process from SiPc* to the full-
erodendrimer moieties in both
benzonitrile and toluene. The
collected data support that the
stabilization of the formed rad-
ical ion pairs is achieved for
multiple C60 subunits on one
side of the SiPc moiety, which
may be related to the electron
migration among the C60 sub-
A
H
R
U
G
combination in SiPc–nC60 are
slower than those of charge
separation by about two orders
of magnitude, thus suggesting
that these SiPc–nC60 dendrim-
Figure 5. Nanosecond transient spectra of SiPc–2C60 (left) and SiPc–8C60 (right) in Ar-saturated toluene; lex
55 nm. Inset: decay profile at 1020 nm.
=
3
1
mainly attributed to charge separation from SiPc* to C .
ers could be useful as components in light-harvesting sys-
tems. Furthermore, such the usefulness of SiPc–nC60 units as
light-harvesting systems, evaluated as a ratio of the rate of
charge recombination to that of charge separation, increases
markedly with the dendrimer generation.
6
0
The kCR and tRIP values were similarly evaluated as listed in
Table 1: 13, 104, and 160 ns (SiPc–2C , SiPc–4C , and
6
0
60
SiPc–8C , respectively). Although this order is the same as
60
that in PhCN, each value is shorter than the corresponding
one in PhCN, which is not in agreement with the prediction
[28]
of the Marcus inverted region.
This behavior suggests
therefore that the direction of the charge recombination in
toluene is not the same as that in PhCN; namely, that it is
possible that charge recombination directs to the triplet
states in toluene but to the ground state in PhCN.
Experimental Section
Materialsand in st ruments : The reagents and solvents were purchased as
reagent grade and used without further purification. All reactions were
performed using dry glassware in a nitrogen atmosphere. Analytical TLC
analysis was carried out on Merck 60 F254 silica gel plates and column
chromatography was performed on Merck 60 silica gel (230—400 mesh).
The melting points were determined on an Electrothemal IA 9000 series
melting-point apparatus and were uncorrected. The NMR spectra were
recorded on a Varian Mercury 400 (400 MHz) spectrometer with trime-
thylsilane as the reference signal. The FT-IR spectra were recorded on a
Nicolet 550 spectrophotometer with KBr disks. MALDI mass spectra
were obtained on a VGAutoSpec spectrometer using ditranol as the
matrix.
Figure 6 shows energy-level diagrams that summarize the
observed photoinduced events in the SiPc–nC60 species in
PhCN and toluene. The fluorescence quenching pathway is
1
mainly through electron transfer from SiPc* to the cova-
lently bonded C60 entity in both solvents. The charge recom-
+
À
bination of SiPcC –C C
A
H
R
U
G
may direct to the ground
6
0
60 nÀ1
state of SiPc–nC60 in PhCN, whereas charge recombination
3
3
may produce SiPc* and C * in toluene.
6
0
[
7]
G1–OH (2): Bis
A
H
E
N
(malonate)
1
(600 mg, 0.72 mmol),
I
2
(228 mg,
1
.80 mmol), and DBU (0.59 mL, 3.93 mmol) were added to a solution of
fullerene (520 mg, 0.72 mmol) in toluene (500 mL). The reaction mixture
was stirred at room temperature for 24 h, and the fullerene starting mate-
rial was eliminated by flash chromatography on silica gel with toluene.
The crude product was subjected to chromatography on silica gel with
MeOH/CHCl
run on silica gel with THF/hexane (2:5) as the eluant. The fraction col-
lected at R =0.2 was evaporated to give G1-OH (0.40 g, 34%) as a red-
dish-brown solid. M.p. 1908C; H NMR (400 MHz, CDCl
3
(1:50) as the eluant followed by a second chromatographic
f
1
3
): d=7.10 (s,
), 4.40 (t, 4H, CH ),
); IR
1
1
(
H, ArH), 6.70–6.80 (s, 2H, ArH), 5.80 (d, 2H, CH
2
2
.70 (m, 4H, CH
2
), 1.30 (m, 60H, CH
2
), 0.90 ppm (t, 6H, CH
3
À1
KBr): n˜ =3412, 2921, 2851, 1748, 1723, 1450, 1237 cm
G1: K CO
45 mL) were stirred under nitrogen for 0.5 h. Silicon phthalocyanine di-
.
2
3
(15 mg, 0.015 mmol) and 2 (144 mg, 10.093mmol) in toluene
(
chloride (28 mg, 0.046 mmol) and 18-crown-6 (4 mg, 0.015 mmol) were
added to this reaction mixture. The reaction mixture was cooled to room
temperature after heating at reflux for 15 h, and the solvent was evapo-
Figure 6. Energy-level diagram of SiPc–nC60 in PhCN and toluene.
2860
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2854 – 2863

Synthesis and Photophysical Properties of Silicon Phthalocyanine/Fullerene Dendrimers
FULL PAPER
rated. The crude product was subjected to chromatography on silica gel
with CH CN/CHCl (1:45) as the eluant. The fraction collected at R =0.9
was evaporated to give G1 (45 mg, 27%) as a green solid. M.p. >3538C
14.29 ppm; IR (KBr): n˜ =2921, 2850, 1749, 1592, 1461, 1336, 1292, 1234,
À1
3
3
f
1195 cm ; UV/Vis (CHCl
3
): lmax =259, 318, 354, 618, 657, 689 nm; MS
+
(MALDI-TOF); m/z: 3781.10 [M ÀG1-OH-1), 2087.63, 765.15, 557.11.
: G2-OH (7) (228 mg, 0.07 mmol), DCC (15 mg, 0.07 mmol), DMAP
9 mg, 0.07 mmol), and HOBT (10 mg, 0.07 mmol) were added to a solu-
tion of 5 (9 mg, 0.03mmol) in CHCl (80 mL). The reaction mixture was
1
(
(
decomp); H NMR (400 MHz, CDCl
m, 8H, SiPc ArH), 5.85 (s, 2H, ArH), 4.50 (d, 4H, CH
), 3.70 (d, 4H, CH ), 2.30 (s, 4H,ArH), 1.10–1.60 (m, 128H, CH
.90 ppm (t, 12H, CH
48.93, 148.27, 147.24, 147.04, 145.78, 145.45, 145.38, 145.35 145.07,
44.92, 144.87, 144.73, 144.31, 144.07, 143.96, 143.90, 143.58, 143.39,
43.31, 142.91, 142.62, 141.84, 140.96, 140.71, 139.46, 136.85, 135.88,
35.17, 135.14, 134.41, 131.32, 123.76, 115.30, 113.91, 70.31, 67.02, 66.72,
5.65, 48.99, 32.05, 29.85, 29.81, 29.75, 29.63, 29.57, 29.51, 29.12, 28.36,
3
): d=9.65 (m, 8H, SiPc ArH), 8.40
), 4.15 (t, 8H,
),
3 3
); C NMR (CDCl ): d=162.37, 162.03, 149.50,
8
(
2
CH
2
2
2
3
1
3
0
1
1
1
1
6
2
1
stirred at room temperature for 24 h and the insoluble residue filtered.
The solvent was evaporated and the crude product was subjected to chro-
matography on silica gel with ethyl acetate/CHCl
The fraction collected at R =0.9 was evaporated to give 8 (116 mg, 57%)
as a black solid. M.p. 94–978C; H NMR (400 MHz, CDCl
H, ArH), 8.70 (s, 1H, ArH), 8.38 (s, 4H, ArH), 7.98 (s, 2H, ArH), 7.50
s, 4H, ArH), 7.21 (s, 8H, ArH), 5.80 (d, 8H, CH ), 5.28 (d, 8H, CH ),
), 1.10 (s, 9H, CH ), 0.90 (t,
); IR (KBr): n˜ =2921, 2850, 1749, 1598,
3
(1:60) as the eluant.
f
1
3
): d=8.98 (s,
2
5.78, 22.85, 14.33 ppm; IR (KBr): n=2921, 2850, 1749, 1596, 1525, 1461,
(
2
2
À1
234 cm ; UV/Vis (CHCl
3
): lmax =260, 330, 352, 615, 656, 684 nm; MS
4
2
1
.40 (t, 16H, CH
2
), 1.20–1.80 (m, 256H, CH
2
3
+
(
MALDI-TOF): m/z 2086.39 [M ÀG1-OH-1), 17485.17, 1546.38 (G1-
4H, CH
3
), 0.30 ppm (s, 6H, CH
3
OH-1), 1284.11, 1096.08.
À1
461, 1292, 1232, 1201 cm
.
Bis(tert-butyldimethylsilyl)-5-(tert-butyldimethylsiloxy)isophthalate (4):
G3-OH (9): An excess of HF (50% solution, 2.2 g) was added to a solu-
tion of 8 (116 mg, 0.017 mmol) in THF (25 mL), and the reaction mixture
was stirred at room temperature for 15 h. The solvent was evaporated
and washed with water to eliminate excess HF. The crude product was
[
19]
This compound was prepared according to reported procedures
in
): d=8.27 (t, 1H,
), 0.99 (s, 9H, CH ), 0.39 (s,
(KBr): n˜ =2956, 2859, 1708, 1598,
1
9
4% yield. M.p. 38–398C; H NMR (400 MHz, CDCl
3
ArH), 7.70 (d, 2H, ArH), 1.03(s, 18H, CH
3
3
1
1
2H, CH
3
), 0.23ppm (s, 6H, CH
3
); IR
ACHTREUNG
subjected to chromatography on silica gel with ethyl acetate/CHCl
1:60) as the eluant, and the fraction collected at R =0.5 was evaporated
to yield (61 mg, 54%) as black solid. M.p. 1208C; H NMR
(400 MHz, CDCl ): d=8.98 (s, 2H, ArH), 8.65 (s, 1H, ArH), 8.39 (s, 4H,
ArH), 8.00 (s, 2H, ArH), 7.55 (s, 4H, ArH), 7.21 (s, 8H, ArH), 5.80 (d,
8H, CH ), 5.25 (d, 8H, CH ), 4.38 (t, 16H, CH ), 1.10–1.80 (m, 256H,
); IR(KBr): n˜ =3434, 2919, 2850, 1747, 1598,
3
À1
255 cm
.
(
f
1
5
-(tert-Butyldimethylsiloxy)isophthalic acid (5): This compound was pre-
9
a
[
19]
pared according to reported procedures in 89% yield. M.p. 44–468C;
3
1
H NMR (400 MHz, CDCl
.61 (d, 2H, ArH), 1.01 (s, 9H, CH
n˜ =3500–2500 (CO
3 2
): d=13.37 (s, 2H, CO H), 8.15 (t, 1H, ArH),
7
3
), 0.27 ppm (s, 6H, CH
3
); IR (KBr):
2
2
2
À1
2
H), 2956, 2859, 1700, 1596, 1282 cm
.
CH
2
), 0.90 ppm (t, 24H, CH
3
ACHTREUNG
À1
1
292, 1232, 1201 cm
.
6
: Compound 2 (295 mg, 0.19 mmol), DCC (40 mg, 0.19 mmol), DMAP
24 mg, 0.19 mmol), and HOBT (26 mg, 0.19 mmol) were added to a so-
lution of 5 (29 mg, 0.10 mmol) in CHCl (70 mL). The reaction mixture
(
G3: K CO
2
3
(4 mg, 0.029 mmol) and 9 (127 mg, 0.019 mmol) in toluene
3
(40 mL) were stirred under nitrogen at room temperature for 0.5 h. Sili-
con phthalocyanine dichloride (4.5 mg, 0.007 mmol) and [18]crown-6
(1 mg, 0.004 mmol) were added to this reaction mixture, which was
cooled to room temperature after reflux for 15 h. The insoluble solids
were filtered, the filtrate was evaporated, and the crude product was sub-
was stirred at room temperature for 24 h and filtered. The filtrate was
evaporated to dryness, and the crude product was subjected to chroma-
tography on silica gel with CH
2 2
Cl as the eluant. The fraction collected at
R
f
=0.9 was evaporated to yield 6 (153mg, 47%). M.p. 114–117 8C;
1
H NMR (400 MHz, CDCl
.50 (s, 2H, ArH), 7.20 (s, 4H, ArH), 5.81 (d, 4H, CH
CH ), 4.30 (t, 8H, CH ), 1.20–1.70 (m, 128H, CH ), 1.10 (s, 9H, CH
); IR (KBr): n˜ =2921, 2850,
3
): d=8.60 (s, 1H, ArH), 7.90 (s, 2H, ArH),
), 5.20 (d, 4H,
),
jected to chromatography on silica gel with CH
eluant. The fraction collected at R =0.9 was evaporated to produce G3
(25 mg, 25%) as a dark green solid. M.p. >4008C (decomp); H NMR
(400 MHz, CDCl ): d=9.65 (m, 8H, SiPc ArH), 8.90 (s, 2H, ArH), 8.35
(m, 8H, SiPc ArH), 7.80 (s, 8H, ArH), 7.55 (s, 8H, ArH), 7.50 (s, 4H,
ArH), 7.30 (s, 16H, ArH), 5.75 (d, 16H, CH ), 5.30 (d, 16H, CH ), 4.35
t, 32H, CH ), 3.60 (s, 4H, ArH), 1.00–1.80 (m, 512H, CH ), 0.90 ppm (t,
): d=162.65, 162.56, 150.25, 149.72, 148.46,
3 3
CN/CHCl (1:45) as the
7
2
f
1
2
2
2
3
0
1
.90 (t, 12H, CH
749, 1598, 1461, 1232, 1197 cm
3
), 0.30 ppm (s, 6H, CH
3
3
À1
.
G2-OH (7): An excess amount of HF (50% solution, 2.2 g) was added to
a solution of 6 (151 mg, 0.045 mmol) in THF (25 mL), and the reaction
mixture was stirred at room temperature for 15 h. The solvent was evapo-
rated and washed with water to eliminate the excess HF. The crude prod-
2
2
(
2
1
2
3
4
1
1
1
8H, CH
3
); C NMR(CDCl
3
A
T
E
N
48.18, 147.37, 147.18, 145.95, 145.79, 145.54, 145.15, 144.94, 144.39,
44.19, 143.98, 143.64, 143.33, 143.16, 142.86, 142.10, 141.12, 140.88,
39.74, 138.61, 137.41, 136.06, 135.71, 135.12, 128.46, 124.12, 119.82, 70.68,
uct was subjected to chromatography on silica gel with CH
eluant, and the fraction collected at R =0.5 was evaporated to afford
G2-OH (142 mg, 97%) as a black solid. M.p. 1078C; H NMR (400 MHz,
CDCl ): d=8.59 (s, 1H, ArH), 7.90 (s, 2H, ArH), 7.50 (s, 2H, ArH), 7.20
s, 4H, ArH), 5.80 (d, 4H, CH ), 5.20 (d, 4H, CH ), 4.30 (t, 8H, CH ),
); IR(KBr): n˜ =3434,
2 2
Cl as the
f
1
67.44, 66.92, 49.33, 45.28, 36.08, 32.03, 30.52, 29.84, 29.73, 29.49, 29.29,
2
1
3
8.63, 26.01, 22.83, 14.30, 6.77, 3.90 ppm; IR (KBr): n˜ =2919, 2848, 1749,
3
À1
598, 1461, 1430, 1292, 1232, 1199 cm ; UV/Vis (CHCl
3
): lmax =259, 319,
r
90Si (M =
(
2
2
2
56, 364, 619, 658, 690 nm; MS (MALDI-TOF) for C960
H
682
N
8
O
1
2
.10–1.70 (m, 128H, CH
921, 2850, 1749, 1598, 1461, 1294, 1232, 1201 cm
2
), 0.90 ppm (t, 12H, CH
3
ACHTREUNG
+
À1
13797.77); m/z: 7169.67 [M ÀG3-OH-1], 3780.33, 2086.78, 1096.31.
SiPc (10): K CO (52 mg, 0.375 mmol) and 1 (290 mg, 0.35 mmol) were
.
G2: K
2
CO
3
(9 mg, 0.061 mmol) and 7 (190 mg, 0.058 mmol) were stirred
2
3
stirred in toluene (45 mL) under nitrogen at room temperature for 0.5 h.
Silicon phthalocyanine dichloride (100 mg, 0.163mmol) and [18]crown-6
in toluene (30 mL) under nitrogen at room temperature for 0.5 h. Silicon
phthalocyanine dichloride (16 mg, 0.026 mmol) and [18]crown-6 (3mg,
(
15 mg, 0.0543mmol) were added to this reaction mixture, which was
0
.011 mmol) were added to this reaction mixture. The reaction mixture
cooled to room temperature after heating to reflux for 15 h. The insolu-
ble solids were removed by filtration, the filtrate was evaporated, and the
crude product was subjected to chromatography on silica gel with
was cooled to room temperature after heating at reflux for 15 h and fil-
tered. The filtrate was evaporated and the resulting residues were isolat-
ed by chromatography on silica gel with CH
3 3
CN/CHCl (1:45) as the
CH
3 3 f
CN/CHCl (1:30) as the eluant. The fraction collected at R =0.45
eluant. The fraction collected at R =0.8 was evaporated to give G2
f
1
was evaporated to afford SiPc (70 mg, 20%) as a deep blue solid.
(
(
7
115 mg, 62%) as a green solid. M.p. >3758C (decomp); H NMR
400 MHz, CDCl ): d=9.70 (m, 8H, SiPc ArH), 8.38 (m, 8H, SiPc ArH),
.50 (s, 4H, ArH), 7.40 (s, 2H, ArH), 6.70 (s, 8H, ArH), 5.80 (d, 8H,
1
M.p. 3208C (decomp); H NMR (400 MHz, CDCl
SiPc ArH), 8.35 (m, 8H, Si–Pc ArH), 5.65 (s, 2H, ArH), 3.95 (t, 8H,
CH ), 3.80 (s, 8H, CH ), 3.00 (s, 8H, CH ), 2.30 (s, 4H, CH ), 1.00–1.50
(m, 128H, CH ), 0.85 ppm (t, 12H, CH ); IR (KBr): n˜ =2917, 2850, 1781,
3
): d=9.60 (m, 8H,
3
CH
2
), 5.20 (d, 8H, CH
2 2
), 4.45 (t, 16H, CH ), 3.50 (s, 4H, ArH), 1.10–1.80
2
2
2
2
1
3
(
m, 256H, CH
2
), 0.90 ppm (t, 24H, CH
3
); C NMR (CDCl
3
): d=162.68,
2
3
À1
1
6
1
731, 1594, 1469, 1336 cm ; UV/Vis (CHCl
83nm; MS (MALDI-TOF) for C 132
370.76 [M À1—1], 869.38, 809.40.
Electrochemical measurements: The redox values were measured by
3
): lmax =356, 613, 653,
1
1
1
1
6
62.56, 149.72, 147.43, 146.07, 145.98, 145.67, 145.66, 145.54, 145.29,
45.13, 145.10 144.95, 144.50, 144.29, 144.19, 144.08, 143.95, 143.73,
43.49, 143.23, 141.24, 140.96, 140.01, 138.02, 137.95, 136.03, 135.75,
35.55, 134.68, 131.95, 128.50, 124.68, 124.02, 120.01, 119.03, 70.99, 67.85,
7.05, 49.79, 32.03, 29.83, 29.78, 29.75, 29.48, 29.34, 26.06, 22.82,
H
186
N
8
O
18Si (M =2201.02); m/z:
r
+
using the differential pulse voltammetry (DPV) technique with a BAS
Chem. Eur. J. 2007, 13, 2854 – 2863ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2861

O. Ito, K.-Y. Kay et al.
CV-50W Voltammetric Analyzer. A platinum disk electrode was used as
the working electrode, a platinum wire as the counter electrode, and an
Ag/AgCl electrode as the reference electrode. All measurements were
Gust, T. A. Moore, A. L. Moore, J. T. M. Kennis, J. Phys. Chem. B
2004, 108, 414–425; e) J. L. Rodriguez-Redondo, A. Sastre-Santos,
F. Fernandez-Lazaro, D. Soares, G. C. Azzellini, B. Elliot, L. Eche-
goyen, Chem. Commun. 2006, 1265–1267.
carried out in different solvents containing 0.1m (nBu)
4
NClO
4
as the sup-
À1
porting electrolyte. Scan rate=0.1 Vs
.
[10] a) M. Brewis, G. J. Clarkson, A. M. Holder, N. B. McKeown, Chem.
Commun. 1998, 969–970; b) D. K. P. Ng, C. R. Chim. 2003, 6, 903–
Steady-state optical measurements: Steady-state fluorescence spectra
were measured on a Shimadzu RF-5300 PC spectrofluorophotometer
equipped with a photomultiplier tube with high sensitivity in the 700–
9
10; c) G. A. Kraus, S. V. Louw, J. Org. Chem. 1998, 63, 7520–7521;
d) M. Kimura, Y. Sugihara, T. Muto, K. Hanabusa, H. Shirai, N. Ko-
bayashi, Chem. Eur. J. 1999, 5, 3495–3500; e) M. Brewis, G. J. Clark-
son, M. Helliwell, A. M. Holder, N. B. McKeown, Chem. Eur. J.
8
00-nm region.
Laser flash photolysis: The picosecond time-resolved fluorescence spectra
were measured by a single-photon counting method using a second har-
monic generation (SHG, 400 nm) of a Ti:sapphire laser (Spectra-Physica;
Tsunami 3950 L2S, 1.5 ps fwhm (fwhm=full width half maximum) and a
streakscope (Hamamatsu Photonics) equipped with a polychromator as
the excitation source and detector, respectively. Lifetimes were evaluated
with software attached to the equipment. The nanosecond transient ab-
sorption measurements in the near-IR region were measured by laser-
flash photolysis, and 355-nm and 532-nm light from a Nd:YAG laser
2
000, 6, 4630–4636; f) X. Li, L. E. Sinks, B. Rybtchinski, M. R. Wa-
sielewski, J. Am. Chem. Soc. 2004, 126, 10810–10811; g) J. Leclaire,
R. Dagiral, S. Fery-Forgues, Y. Coppel, B. Donnadieu, A.-M. Cami-
nade, J.-P. Majoral, J. Am. Chem. Soc. 2005, 127, 15762–15770.
11] a) T. G. Linßen , K. Dꢁrr, M . Hanack, A. Hirsch, J. Chem. Soc.
Chem. Commun. 1995, 103–104; b) K. Dꢁrr, S. Fiedler, T. G.
Linßen, A. Hirsch, M. Hanack, Chem. Ber. Recueil 1997, 130, 1375–
[
1
378; c) A. Sastre, A. Gouloumis, P. Vazquez, T. Torres, V. Doan,
B. J. Schwarz, F. Wudl, L. Echegoyen, J. Rivera, Org. Lett 1999, 1,
807–1810; d) A. Gouloumis, S-G. Liu, A. Sastre, P. Vꢂzquez, L.
(
Spectra-Physics and Quanta-Ray GCR-130; 6-ns fwhm) was used as the
1
excitation source. The monitoring lights from a pulsed Xe lamp were de-
tected through a Ge-avalanche photodiode module. The samples were
held in a quartz cell (1”1 cm) and were deaerated by bubbling argon gas
Echgoyen, T. Torres, Chem. Eur. J. 2000, 6, 3600–3607; e) D. M.
Guldi, A. Gouloumis, P. Vazquez, T. Torres, Chem. Commun. 2002,
2056–2057; f) D. M. Guldi, I. Zilbermann, A. Gouloumis, P. Vaz-
quez, T. Torres, J. Phys. Chem. B 2004, 108, 18485–18494; g) H.
Neugebauer, M. A. Loi, C. Winder, N. S. Sariciftci, G. Cerullo, A.
Gouloumis, P. Vazquez, T. Torres, Solar Energy Mater. Solar Cells
[
29]
through the solution for 20 min.
2
004, 83, 201–209; h) D. M. Guldi, A. Gouloumis, P. Vazquez, T.
Torres, V. Georgakilas, M. Prato, J. Am. Chem. Soc. 2005, 127,
811–5813; i) S. M. Schultes, P. Sullivan, S. Heutz, B. M. Sanderson,
Acknowledgements
5
T. S. Jones, Mater. Sci. Eng. C 2005, 25, 858–865.
This work was supported by a Grant-in-Aid for Scientific Research on
Priory Area (417) from the Ministry of Education, Culture, Sports, Sci-
ence, and Technology of the Japanese Government. M.E.K. thanks the
JSPS fellowship, and K.-Y.K. acknowledges the Brain Korea 21 Program
of the Ministry of Education for financial support.
[
12] a) T. Nojiri, M. M. Alam, H. Konami, A. Watanabe, O. Ito, J. Phys.
Chem. A 1997, 101, 7943–7947; b) D. M. Guldi, J. Ramey, M. V.
Martinez-Diaz, A. de la Escosura, T. Torres, T. D. Ros, M. Prato,
Chem. Commun. 2002, 2774–2775; c) M. V. Martinez-Diaz, N. S.
Fender, M. S. Rodriguez-Morgade, M. Gomez-Lopez, F. Didderich,
L. Echegoyen, J. F. Stoddart, T. Torres, J. Mater. Chem. 2002, 12,
2
1
095–2099; d) F. DꢃSouza, O. Ito, Coord. Chem. Rev. 2005, 249,
410–1422; e) A. de la Escosura, M. V. Martinez-Diaz, D. M. Guldi,
[
1] a) J. Deisenhofer, H. Michel, Angew. Chem. 1989, 101, 872–892;
Angew. Chem. Int. Ed. Engl. 1989, 28, 829–847; b) R. Huber,
Angew. Chem. 1989, 101, 849–871; Angew. Chem. Int. Ed. Engl.
T. Torres, J. Am. Chem. Soc. 2006, 128, 4112- 4118.
[
13] a) N. Martin, L. Sanchez, B. Illescas, I. Perez, Chem. Rev. 1998, 98,
1
989, 28, 848–869; c) The Photosynthetic Reaction Center (Eds.: J.
2
2
527–2547; b) D. Gust, T. A. Moore, A. L. Moore, Acc. Chem. Res.
001, 34, 40–48; c) H. Imahori, H. Yamada, D. M. Guldi, Y. Endo,
Deisenhofer, J. R. Norris), Academic Press , New York, 1993; d) V.
Sundstrçm, T. Pullerits, R. van Grondelle, J. Phys. Chem. B 1999,
A. Shimomura, S. Kundu, K. Yamada, S. Fukuzumi, Angew. Chem.
Int. Ed. 2002, 41, 2344–2347; d) D. M Guldi, Chem. Soc. Rev. 2002,
3
lerenes: From Synthesis to Optoelectronic Properties (Eds.: D. M.
Guldi, N. Martin), Kluwer Academic Publishers, Norwell, MA,
1
03, 2327–2346; e) Molecular Mechanisms of Photosynthesis (Ed.:
R. E. Blankenship), Blackwell Science, 2002.
1, 22–36; e) Electron Transfer in Functionalized Fullerenes. In Ful-
[
[
[
2] a) M. R. Wasielewski, Chem. Rev. 1992, 92, 435–461; b) J. Li, A.
Ambroise, S. I. Yang, J. R. Diers, J. Seth, C. R. Wack, D. F. Bocian,
D. Holten, J. S. Lindsey, J. Am. Chem. Soc. 1999, 121, 8927–8940;
c) D. Gust, T. A. Moore, A. L. Moore, Acc. Chem. Res. 2001, 34,
2
002, pp. 163–212; f) M. Fujutsuka, O. Ito, Photochemistry of Full-
ernes. In Handbook of Photochemistry and Photobiology, vol. 2, Or-
ganic Photochemistry (Ed.: H. S. Nalwa), 2003, pp. 111–145;
g) M. E. El-Khouly, O. Ito, P. M. Smith, F. DꢃSouza, J. Photochem.
Photobiol. C 2004, 5, 79–104.
4
0–48; d) H. Imahori, J. Phys. Chem. B 2004, 108, 6130–6143.
3] a) R. A Haycock, C. A. Hunter, D. A. James, U. Michelson, L. R.
Sutton, Org. Lett. 2000, 2, 2435–2438; b) T. van der Boom, R. T.
Hayes, Y. Zhao, P. J. Bushard, E. A. Weiss, M. R. Wasielewski, J.
Am. Chem. Soc. 2002, 124, 9582–9590; c) R. Takahashi, Y. Kobuke,
J. Am. Chem. Soc. 2003, 125, 2372–2373.
[14] For selected examples, see: a) K. L. Wooley, C. J. Hawker, J. M. J.
Frꢄchet, F. Wudl, G. Srdanov, S. Shi, C. Li, M. Kao, J. Am. Chem.
Soc. 1993, 115, 9836–9837; b) J.-F. Nierengarten, T. Habicher, R.
Kessinger, F. Cardullo, F. Diederich, V. Gramlich, J.-P. Gisselbrecht,
C. Boudon, M. Gross, Helv. Chim. Acta 1997, 80, 2238–2276; c) M.
Brettreich, A. Hirsch, Tetrahedron Lett. 1998, 39, 2731–2734; d) F.
Cardullo, F. Diederich, L. Echegoyen, T. Habicher, N. Jayaraman,
R. M. Leblanc, J. F. Stoddart, S. Wang, Langmuir 1998, 14, 1955–
1959; e) J. L. Segura, R. Gꢅmez, N. Martꢆn, C. P. Luo, A. Swartz,
D. M. Guldi, Chem. Commun. 2001, 707–708; f) F. Langa, M. J.
Gꢅmez-Es-calonilla, E. Dꢆez-Barra, J. C. Garcꢆa-Martꢆnez, A. De la-
Hoz, J. Rodrꢆguez-Lꢅpez, A. Gonzꢂlez-Cortꢄs, V. Lꢅpez-Arza, Tet-
rahedron Lett. 2001, 42, 3435–3438; g) T. Chuard, R. Deschenaux, J.
Mater. Chem. 2002, 12, 1944–1951; h) Y. Murata, M. Ito, K. Komat-
su, J. Mater. Chem. 2002, 12, 2009–2020; i) Y. Rio, G. Accorsi, H.
Nierengarten, C. Bourgogne, J.-M. Strub, A. VanDorsselaer, N. Ar-
maroli, J.-F. Nierengarten, Tetrahedron 2003, 59, 3833–3844; j) M.-S.
4] J. M. J. Fàechet, J. Polym. Sci. Polym. Chem. Ed. J. Polym. Sci., Part
A: Polym. Chem. 2003, 41, 3713–3725.
[
[
5] S. E. Webber, Chem. Rev. 1990, 90, 1469–1482.
6] Phthalocyanine Materials: Synthesis, Structure and Function (Ed.:
N. B. McKeown), Cambridge University Press, Cambridge, 1998.
7] K. N. Kim, C. S. Choi, K.-Y. Kay, Tetrahedron Lett. 2005, 46, 6791–
[
[
[
6
795.
8] a) N. B. McKeown, Adv. Mater. 1999, 11, 67–69; b) B. M. Hassan, H.
Li, N. B. McKeown, J. Mater. Chem. 2000, 10, 39–45.
9] a) J. Silver, J. L. Sosa-Sanchez, C. S. Frampton, Inorg. Chem. 1998,
3
7, 411–417; b) C. Farren, C. A. Christensen, S. FitzGerald, M. R.
Bryce, A. Beeby, J. Org. Chem. 2002, 67, 9130–9139; c) P.-C. Lo, S.
Wang, A. Zeug, M. Meyer, B. Rçder, D. K. P. Ng, Tetrahedron Lett.
2
003, 44, 1967–1970; d) G. Kodis, C. Herrero, R. Palacios, E.
Marino-Ochoa, S. Gould, L. de la Garza, R. van Groundelle, D.
2862
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 2854 – 2863

Synthesis and Photophysical Properties of Silicon Phthalocyanine/Fullerene Dendrimers
FULL PAPER
Cho, T. Aida, H. Luo, Y. Araki, O. Ito, Angew. Chem. Int. Ed. 2003,
2, 2060–4063; k) J.-F. Nierengarten, N. Aramaroli, G. Accorsi, Y.
d) H. Imahori, M. E. El-Khouly, M. Fujitsuka, O. Ito, Y. Sakata, S.
Fukuzumi, J. Phys. Chem. A 2001, 105, 325–332.
4
Rio, J. F. Eckert, Chem. Eur. J. 2003, 9, 37–41.
15] a) J.-F. Nierengarten, C. Schall, J.-F. Nicoud, Angew. Chem. Int. Ed.
[23] a) F. DꢃSouza, G. R. Deviprasad, M. E. El-Khouly, M. Fujitsuka, O.
Ito, J. Am. Chem. Soc. 2001, 123, 5277–5284; b) M. E. El-Khouly, Y.
Araki, O. Ito, S. Gadde, A. L. McCarty, P. A. Karr, M. E. Zandler, F.
DꢃSouza, Phys. Chem. Chem. Phys. 2005, 7, 3163–3171; c) M. E. El-
Khouly, P. Padmawar, Y. Araki, S. Verma, L. Y. Chiang, O. Ito, J.
Phys. Chem. A 2006, 110, 884–891.
[
1
998, 37, 1934–1936; b) J.-F. Nierengarten, D. Felder, J.-F. Nicoud,
Tetrahedron Lett. 1999, 40, 269–272; c) J.-F. Nierengarten, D.
Felder, J.-F. Nicoud, Tetrahedron Lett. 2000, 41, 41–44; d) D. Felder,
H. Nierengarten, J.-P. Gisselbrecht, C. Boudon, E. Leize, J.-F.
Nicoud, M. Gross, A. VanDorsselaer, J.-F. Nierengarten, New J.
Chem. 2000, 24, 687–695; e) J.-F. Nierengarten, Chem. Eur. J. 2000,
[
24] a) J. L. Anderson, Y.-Z. An, Y. Rubin, C. S. Foote, J. Am. Chem.
Soc. 1994, 116, 9763–9764; b) D. M. Guldi, P. Neta, K.-D. Asums, J.
Phys. Chem. 1994, 98, 4617–4621; c) M. M. Alam, A. Watanabe, O.
Ito, Bull. Chem. Soc. Jpn. 1997, 70, 1833–1838; d) M. E. El-Khouly,
S. D.-M. Islam, M. Fujitsuka, O. Ito, J. Porphyrins Phthalocyanines
6
, 3667–3670; f) M. Gutierrez-Nava, G. Accorsi, P. Masson, N. Ar-
maroli, J.-F. Nierengarten, Chem. Eur. J. 2004, 10, 5076–5086; g) M.
Gutierrez-Nava, G. Accorsi, P. Masson, N. Armaroli, J-F. Nieren-
garten, Chem. Eur. J. 2004, 10, 5076–5086; h) U. Hahn, K. Hosomi-
zu, H. Imahori, J.-F. Nierengarten, Eur. J. Org. Chem. 2006, 85–91.
16] J.-F. Nierengarten, V. Gramlich, F. Cardullo, F. Diederich, Angew.
Chem. 1996, 108, 2242–2244; Angew. Chem. Int. Ed. Engl. 1996, 35,
2
000, 4, 713–721.
[
25] a) H. J. Kim, K-M. Park, T. K. Ahn, S. K. Kim, K. S. Kim, D. Kim,
H.-J. Kim, Chem. Commun. 2004, 2594–2595; b) J. Y. Lee, S. J. Lee,
H. J. Kim, H-J. Kim, J. Phys. Chem. B 2006, 110, 5337–5342.
[
[
[
[
26] Y. Chen, M. E. El-Khouly, M. Sasaki, Y. Araki, O. Ito, Org. Lett.
2
101–2103.
2
005, 7, 1613–1616.
27] C. Luo, M. Fujitsuka, C.-H. Huang, O. Ito, J. Phys. Chem. A 1998,
02, 8716–8721.
[
[
17] C. Bingel, Chem. Ber. 1993, 126, 1957–1959.
18] E. J. Corey, A. Venkateswarlu, J. Am. Chem. Soc. 1972, 94, 6190–
1
6
191.
19] T. M. Miller, E. W. Kwock, T. X. Neenan, Macromolecules 1992, 25,
143–3148.
20] a) D. Rehm, A. Weller, Ber. Bunsenges Phys. Chem. 1969, 73, 83 4–
39; b) A. Weller, Phys. Z. 1982, 133, 93–98.
28] R. A. Marcus, J. Chem. Educ. 1968, 45, 356–358; R. A. Marcus,
Angew. Chem. 1993, 105, 1161–1172; Angew. Chem. Int. Ed. Engl.
[
[
3
1
993, 32, 1111–1121.
1
1
3
[
29] The H NMR and C NMR spectra of SiPc–nC60, MO calculations
of SiPc–C60, electrochemistry measurements, and transient spectra
of G2 in PhCN and toluene are available in the Supporting Informa-
tion.
8
[
[
21] C. S. Foote, Top. Curr. Chem. 1994, 169, 347–363.
22] a) D. M. Guldi, Chem. Commun. 2000, 321–327; b) C. A. Reed,
R. D. Bolskar, Chem. Rev. 2000, 100, 1075–1120; c) D. Gust, T. A.
Moore, A. L. Moore, J. Photochem. Photobiol. B 2000, 58, 63 –71;
Received: September 1, 2006
Published online: December 19, 2006
Chem. Eur. J. 2007, 13, 2854 – 2863ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
2863