Photoinduced electron transfer in a distyryl BODIPY-fullerene dyad

Article abstract of DOI:10.1002/asia.201000537

A novel distyryl BODIPY-fullerene dyad is prepared. Upon excitation at the distyryl BODIPY moiety, the dyad undergoes photoinduced electron transfer to give a charge-separated state with lifetimes of 476ps and 730ps in polar (benzonitrile) and nonpolar (t

Full text of DOI:10.1002/asia.201000537

FULL PAPERS
DOI: 10.1002/asia.201000537
Photoinduced Electron Transfer in a Distyryl BODIPY–Fullerene Dyad
Jian-Yong Liu,[a] Mohamed E. El-Khouly,[b, c] Shunichi Fukuzumi,*[b, d] and
Dennis K.P. Ng*[a]
Abstract: A novel distyryl BODIPY–fullerene dyad is prepared. Upon excitation
at the distyryl BODIPY moiety, the dyad undergoes photoinduced electron trans-
fer to give a charge-separated state with lifetimes of 476 ps and 730 ps in polar
(benzonitrile) and nonpolar (toluene) solvents, respectively. Transient absorption
measurements show the formation of the triplet excited state of distyryl BODIPY
in the dyad, which is populated from charge-recombination processes in both sol-
vents.
Keywords: boron dipyrromethenes ·
donor–acceptor systems · electron
transfer · fullerenes · photophysics
Introduction
stability and favorable photophysical and electrochemical
properties, which can be tuned readily through chemical
modification of the BODIPY core.[4] Generally, they have
large molar absorptivities, high fluorescence quantum yields,
and relatively long singlet excited state lifetimes. As a
result, they have frequently been used as energy-absorbing
and -transferring antenna molecules in photosynthetic an-
tenna–reaction center mimics.[5] In some cases, BODIPYs
can also act as electron-donor or -acceptor entities.[6] In ad-
dition to these applications, BODIPY dyes have also been
used for protein and RNA labeling.[7] However, one of the
drawbacks of these dyes is their relatively short-wavelength
absorption and emission (<600 nm). This can be addressed
by introducing two styryl groups at the 3- and 5-positions of
the BODIPY core. The resulting distyryl BODIPYs, with a
more extended p-conjugated system, can absorb and emit at
longer wavelengths (ca. 650 nm).[4]
Fullerene derivatives have also been widely studied in ar-
tificial photosynthetic models.[5] Owing to their remarkable
electron-accepting properties and low reorganization energy,
fullerenes are excellent electron acceptors. The resulting
fullerene-based electron donor–acceptor ensembles general-
ly exhibit rapid photoinduced charge separation and slow
charge recombination.[8] Hence, we reasoned that a combi-
nation of BODIPYs and fullerenes may result in even more
efficient charge separation by PET and the formation of a
long-lived charge-separated state, which is crucial for the re-
alization of artificial photosynthesis. While a large number
of conjugates of these functional dyes with other photo- and
redox-active units have been studied extensively, to the best
of our knowledge, only a few covalent BODIPY–fullerene
heteroarrays have yet been reported.[6] We report herein the
Development of bioinspired electron donor–acceptor en-
sembles that can undergo efficient photoinduced electron
transfer (PET) is attracting much current interest.[1] These
systems can mimic the functions of the photosynthetic reac-
tion center and are useful for the photochemical conversion
of solar energy into fuels[2] and for the development of vari-
ous molecular optoelectronic devices.[3] Boron dipyrrome-
thenes (BODIPYs) are versatile functional dyes with high
[a] Dr. J.-Y. Liu, Prof. D. K.P. Ng
Department of Chemistry and Center of Novel Functional Molecules
The Chinese University of Hong Kong
Shatin, N. T., Hong Kong (China)
Fax : (+852)2603-5057
E-mail: dkpn@cuhk.edu.hk
[b] Dr. M. E. El-Khouly, Prof. S. Fukuzumi
Department of Material and Life Science
Graduate School of Engineering
Osaka University
Suita, Osaka 565-0871 (Japan)
Fax : (+81)6-6879-7370
E-mail: fukuzumi@chem.eng.osaka-u.ac.jp
[c] Dr. M. E. El-Khouly
Department of Chemistry
Faculty of Science
Kafr El-Sheikh University
Kafr El-Sheikh 33516 (Egypt)
[d] Prof. S. Fukuzumi
Department of Bioinspired Science
Ewha Womans University
Seoul 120-750 (Korea)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201000537.
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Chem. Asian J. 2011, 6, 174 – 179

Scheme 1. Synthesis of DSBDP–C60 dyad 6.
preparation and photoinduced intramolecular processes of a
novel distyryl BODIPY–C60 dyad.
Results and Discussion
Scheme 1 shows the synthetic route used to prepare this
compound. Condensation of BODIPY 1[9] and benzaldehyde
2 in the presence of piperidine gave distyryl BODIPY
(DSBDP) 3 in 30% yield. This compound was then treated
with 1,3-dibromopropane and 4-hydroxybenzaldehyde suc-
cessively in the presence of K2CO3 to afford the aldehyde 5
via bromide 4. Fulleropyrrolidine 6 was prepared by treating
5 with C60 and sarcosine according to the Prato procedure.[10]
This reaction was essentially complete in 8 h in moderate
yield (53%). All new compounds have been fully character-
ized by various spectroscopic methods.
Figure 1a shows the electronic absorption spectra of the
dyad 6 in toluene (TN) and benzonitrile (PhCN) and the
reference compound 5 in TN. The absorption spectrum of 5
exhibited a strong S0–S1 transition at 648 nm (log e=5.14)
and a higher-energy S0–S2 transition at 375 nm (log e=4.95).
It should be noted that the DSBDP absorbs longer-wave-
length light compared with other substituted BODIPYs,[11]
which suggests its usefulness in light-harvesting systems.
Conjugation to C60 in dyad 6 gave virtually the same spec-
trum, which suggests a negligible ground-state interaction
between the DSBDP and C60 entities. The weak band at
432 nm can be ascribed to the fulleropyrrolidine unit. The
Figure 1. a) Steady-state absorption and b) fluorescence emission spectra
of 5 and 6 in TN and PhCN (lex =385 nm).
absorption spectrum of 6 showed similar features in TN and
in PhCN, with a small shift of around 2 nm.
To estimate the driving forces for the electron transfer,
the electrochemical properties of 5 and 6 were studied by
cyclic voltammetry in deaerated PhCN (Figure 2). Com-
pound 5 underwent two quasireversible oxidations at 800
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175

S. Fukuzumi, D. K.P. Ng et al.
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measurements by using a 412 nm laser source. The time-re-
solved spectra in polar PhCN (Figure 3) clearly show the
characteristic absorption band for the C60 radical anion in
Figure 2. Cyclic voltammograms of 5 and 6 in deaerated PhCN with 0.1m
[NBu4]ACHTUNGTRENNUNG .
[ClO4] at a scan rate of 100 mVsÀ1
Figure 3. Femtosecond transient spectra of dyad 6 in deaerated PhCN
(lex =412 nm).
and 1056 mV, and a quasireversible reduction at À976 mV
[all versus saturated calomel electrode (SCE)]. For the dyad
6, in addition to the couples owing to the DSBDP moiety
(792, 1048, and À976 mV), an additional couple appeared at
À572 mV, which can be attributed to the first reduction of
the C60 unit. Based on the first oxidation of DSBDP and the
first reduction of C60, the driving force for the charge-recom-
bination process (ÀDGCR) of the radical-ion pair (DSBDP·+
–C60·À) was determined to be 1.42 eV in PhCN. Similarly, the
ÀDGCR value in TN was estimated to be 1.70 eV. Based on
the ÀDGCR values and the energy of the singlet excited state
of DSBDP (2.10 eV, as described below), the driving forces
for the charge-separation process (ÀDGCS) of dyad 6 were
determined to be 0.68 (in PhCN) and 0.40 eV (in TN),
which indicates that the photoinduced electron transfer
from DSBDP to the C60 moiety is an exothermic process in
both PhCN and TN.[12]
Upon excitation at 385 nm, the fluorescence spectrum of
5 in TN showed two emission bands at 592 and 662 nm. The
fluorescence intensities of dyad 6 in TN and PhCN were
much lower than that of 5 (Figure 1b), which indicates the
presence of intramolecular quenching events. The fluores-
cence quantum yield of 6 was found to be 0.04, which is
much smaller than that of 5 (0.56). The quenching process
may involve electron-transfer and/or energy-transfer pro-
cesses. However, energy transfer can be excluded because
the emission band of the singlet C60 is not seen alongside
the decrease of DSBDP emission. The negative DGCS values
(À0.68 eV in PhCN and À0.40 eV in TN) support the pres-
ence of electron transfer from the singlet excited state of
the electron-donating DSBDP to the electron-accepting C60
the near-IR region at around 1000 nm,[8] in addition to an
absorption band at 767 nm, which can be ascribed to the
radical cation of DSBDP. The latter assignment was con-
firmed by comparing the spectrum with that obtained by
one-electron oxidation of 5 with [RuACTHNUTRGNEUNG
(bpy)3]3+ (bpy=2,2’-bi-
pyrdine) (see Figure S1 in the Supporting Information). The
characteristic absorption band of the C60 radical anion in the
near-IR region was employed as a reliable probe to deter-
mine the rate constants for both charge-separation and
charge-recombination processes. From the rise profile, the
rate constant of charge separation (kCS) was found to be
3.1ꢁ1010 sÀ1, which indicates a fast charge-separation pro-
cess. The rate constant of charge recombination (kCR) was
determined to be 2.1ꢁ109 sÀ1 from the decay profile. Based
on the kCR value, the lifetime of the charge-separated state
(tCS) was determined to be 476 ps in PhCN. The femtosec-
ond measurements in TN exhibited the same features as
those in PhCN (see Figure S2 in the Supporting Informa-
tion) except that the charge-separated state in TN had a
longer lifetime (730 ps) compared to that in PhCN. This can
be understood if the charge-recombination occurs in the
Marcus inverted region.
The complementary nanosecond transient measurements
of 6 in PhCN and TN with 590 nm laser excitation, which se-
lectively excited the DSBDP moiety, exhibited absorption
bands in the visible region with maxima at around 750, 700,
500, and 410 nm (Figure 4 and Figure S3 in the Supporting
Information). These absorption bands can be assigned to the
triplet excited state of DSBDP. To confirm this assignment,
we recorded the transient spectra of DSBDP 5 in both sol-
vents. Upon excitation at 590 nm, the transient absorption
spectra showed no absorption bands in the region of 400–
1200 nm, which shows that the triplet formation of DSBDP
5 is inefficient (see Figures S4 and S5 in the Supporting In-
entity, which results in the formation of the charge-separat-
·À
ed species DSBDP·+–C60
.
Spectroscopic evidence for the radical–ion pair formation
in 6 was obtained from femtosecond transient absorption
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Chem. Asian J. 2011, 6, 174 – 179

Photoinduced Electron Transfer in a Distyryl BODIPY–Fullerene Dyad
Figure 4. Nanosecond transient spectra of dyad 6 in PhCN (lex =590 nm).
Inset: Decay-time profiles of the triplet excited state of DSBDP at
750 nm in argon and oxygen-saturated solutions.
Figure 5. Energy-level diagram showing the various photochemical events
of dyad 6 in PhCN and TN.
formation).[6,11] By utilizing high laser power at 355 nm, we
were able to detect weak signals for the triplet excited state
of DSBDP at around 750, 700, and 490 nm in PhCN (see
Figure S6 in the Supporting Information). These observa-
tions indicate that the triplet excited state of DSBDP in
dyad 6 was populated through charge-recombination of
DSBDP·+–C60·À, but not through direct excitation. This is in
agreement with the lower energy of the triplet excited state
of DSBDP (1.15 eV)[13] compared with the charge-separated
state. The decay rate constant of 3DSBDP*–C60 in PhCN
was found to be 2.1ꢁ103 sÀ1, which is close to that observed
in TN (2.9ꢁ103 sÀ1). The formation of 3DSBDP*–C60 was
lifetimes of 476 and 730 ps in PhCN and TN, respectively.
Transient absorption measurements showed the formation
of the triplet excited state of DSBDP in 6, but not in 5,
which indicates that the triplet excited state of DSBDP is
populated from the charge-recombination processes in both
solvents.
Experimental Section
General
3
All reactions were performed under an atmosphere of nitrogen. Tetrahy-
drofuran (THF), TN, and N,N-dimethylformamide (DMF) were distilled
from sodium benzophenone ketyl, sodium, and barium oxide, respective-
ly. Chromatographic purifications were performed on silica gel (Macher-
ey–Nagel, 70–230 mesh) columns with the eluents indicated. All other
solvents and reagents were of reagent grade and were used as received.
Compounds 1[9] and 2[14] were prepared as described.
1H and 13C{1H} NMR spectra were recorded on a Bruker AVANCE II
400 spectrometer (1H, 400 MHz; 13C, 100.6 MHz) in CDCl3. Spectra were
referenced internally using the residual solvent (1H: d=7.26) or solvent
resonances relative to SiMe4 (13C: d=77.0). Electrospray ionization
(ESI) mass spectra were measured on a Thermo Finnigan MAT 95 XL
mass spectrometer.
confirmed by the oxygen effect: the decay of DSBDP*–C60
was significantly accelerated by the addition of oxygen (k=
8.9ꢁ104 sÀ1), which suggests energy transfer from
3DSBDP*–C60 to triplet oxygen. By utilizing 355 and 430 nm
laser excitation, similar absorption features could be ob-
served for 6 in PhCN (see Figure S7 and S8 in the Support-
ing Information).
Figure 5 shows an energy-level diagram that summarizes
the photoinduced intramolecular events of dyad 6 in PhCN
and TN. Excitation of the DSBDP unit of the dyad results
in transfer of an electron from the DSBDP moiety to the
C60 unit, which generates the charge-separated state
DSBDP·+–C60·À. The decay of the charge-separated state of
6 in both solvents affords 3DSBDP*–C60, as confirmed by
nanosecond laser measurements. Finally, 3DSBDP*–C60
Cyclic voltammograms were measured on a BAS CV-50W voltammetric
analyzer. A platinum-disk electrode was used as the working electrode,
while a platinum wire served as the counter electrode. SCE was used as
the reference electrode. All measurements were carried out in deaerated
benzonitrile with 0.1m [NBu4]
ACHTUNGRTEN[NUNG ClO4] as the supporting electrolyte at a
scan rate of 100 mVsÀ1
.
decays slowly to the ground state.
Time-Resolved Transient Absorption Measurements
Femtosecond laser flash photolysis was conducted using a Clark-MXR
2010 laser system and an optical detection system provided by Ultrafast
Systems (Helios). The sources for the pump and probe pulses were de-
rived from the fundamental output of the Clark laser system (775 nm,
1 mJpulseÀ1, full width at half maximum (fwhm)=150 fs) at a repetition
rate of 1 kHz. A second harmonic generator introduced in the path of
the laser beam provided 412 nm laser pulses for excitation. 95% of the
fundamental output of the laser was used to generate the second harmon-
ic, while 5% of the deflected output was used for white-light generation.
Prior to generating the probe continuum, the laser pulse was fed to a
Conclusions
We have reported the preparation and photoinduced elec-
tron-transfer processes of a novel distyryl BODIPY–C60
dyad in both polar (PhCN) and nonpolar (TN) solvents.
Upon excitation of the DSBDP moiety, the dyad undergoes
rapid electron transfer from the singlet excited state of
DSBDP to C60 to generate a charge-separated state with
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177

S. Fukuzumi, D. K.P. Ng et al.
FULL PAPERS
delay line that provided an experimental time window of 1.6 ns with a
maximum step resolution of 7 fs. The pump beam was attenuated at
5 mJpulseÀ1 with a spot size of 2 mm diameter at the sample cell, where it
was merged with the white probe pulse at a close angle (<108). The
probe beam, after passing through the 2 mm sample cell, was focused on
a 200 mm fiber optic cable that was connected to a charge-coupled device
(CCD) spectrograph (Ocean Optics S2000-UV/Vis for visible region and
Horiba CP-140 for NIR region) for recording time-resolved spectra
(450–800 and 800–1400 nm). Typically, 5000 excitation pulses were aver-
aged to obtain the transient spectrum at a set delay time. Kinetic traces
at appropriate wavelengths were assembled from the time-resolved spec-
tral data.
mixed with water (50 mL) and the mixture was extracted with CHCl3
(50 mLꢁ3). The combined organic fractions were dried over anhydrous
MgSO4 and concentrated to dryness by rotary evaporation. The crude
product was purified by column chromatography using ethyl acetate/di-
chloromethane (1:20 v/v) as the eluent. The product was obtained as a
blue solid (0.34 g, 81%). 1H NMR: d=9.89 (s, 1H, CHO), 7.85 (d, J=
8.8 Hz, 2H, ArH), 7.60 (d, J=16.4 Hz, 2H, CH=CH), 7.56 (d, J=8.8 Hz,
4H, ArH), 7.20 (d, J=8.8 Hz, 2H, ArH), 7.19 (d, J=16.4 Hz, 2H, CH=
CH), 7.05 (d, J=8.8 Hz, 2H, ArH), 7.02 (d, J=8.8 Hz, 2H, ArH), 6.94
(d, J=8.8 Hz, 4H, ArH), 6.60 (s, 2H, pyrrole-H), 4.30 (t, J=6.0 Hz, 2H,
CH2), 4.23 (t, J=6.0 Hz, 2H, CH2), 4.18 (virtual t, J=4.8 Hz, 4H, CH2),
3.88 (virtual t, J=4.8 Hz, 4H, CH2), 3.74–3.78 (m, 4H, CH2), 3.65–3.71
(m, 8H, CH2), 3.55–3.58 (m, 4H, CH2), 3.39 (s, 6H, OCH3), 2.35 (quintet,
J=6.4 Hz, 2H, CH2), 1.47 ppm (s, 6H, CH3); 13C{1H} NMR: d=190.8,
163.9, 159.6, 159.2, 152.6, 141.7, 138.0, 135.6, 133.5, 132.0, 130.0, 129.8,
129.7, 129.0, 127.5, 117.4, 117.2, 114.9, 114.8, 71.9, 70.8, 70.6, 70.5, 69.7,
67.5, 64.8, 64.2, 59.0, 29.1, 14.8 ppm; MS (ESI): isotopic clusters peaking
at m/z 1025 {100%, [M+Na]+} and 983 {42%, [MÀF]+}; HRMS (ESI):
m/z calcd for C57H65BF2N2NaO11 [M+Na]+: 1025.4551; found 1025.4575.
Nanosecond time-resolved transient absorption measurements were car-
ried out using the laser system provided by UNISOKU Co., Ltd. Meas-
urements of nanosecond transient absorption spectra were performed ac-
cording to the following procedure: A deaerated solution containing the
dyad was excited by a Panther OPO pumped by a Nd:YAG laser (Con-
tinuum SLII-10, 4–6 ns fwhm) at l=590 nm. The photodynamics were
monitored by continuous exposure to a xenon lamp (150 W) as a probe
light with a photomultiplier tube (Hamamatsu 2949) as a detector. Tran-
sient spectra were recorded using fresh solutions for each laser excitation.
The solution was deoxygenated by argon purging for 15 min prior to
measurements.
DSBDP-C60 dyad 6: Aldehyde
5 (0.09 g, 0.09 mmol) and sarcosine
(0.08 g, 0.90 mmol) were added to a solution of C60 (0.2 g, 0.28 mmol) in
TN (50 mL). The mixture was heated under reflux for 8 h, then cooled
slowly to ambient temperature. The solvent was then removed under re-
duced pressure. The residue was purified by chromatography using TN
and then ethyl acetate/dichloromethane (1:10 v/v) as the eluents. The
dyad 6 was obtained as a dark blue solid (84 mg, 53%). 1H NMR: d=
7.73 (brs, 2H, ArH), 7.59 (d, J=16.0 Hz, 2H, CH=CH), 7.56 (d, J=
8.8 Hz, 4H, ArH), 7.19 (d, J=16.0 Hz, 2H, CH=CH), 7.19 (d, J=8.8 Hz,
2H, ArH), 6.98–7.02 (m, 4H, ArH), 6.94 (d, J=8.8 Hz, 4H, ArH), 6.59
(s, 2H, pyrrole-H), 4.98 (d, J=9.2 Hz, 1H, pyrrolidine-H), 4.89 (s, 1H,
pyrrolidine-H), 4.21–4.26 (m, 5H, CH2 and pyrrolidine-H), 4.18 (virtual t,
J=4.8 Hz, 4H, CH2), 3.89 (virtual t, J=4.8 Hz, 4H, CH2), 3.75–3.78 (m,
4H, CH2), 3.66–3.72 (m, 8H, CH2), 3.55–3.58 (m, 4H, CH2), 3.39 (s, 6H,
OCH3), 2.79 (s, 3H, NCH3), 2.32 (quintet, J=6.4 Hz, 2H, CH2), 1.47 ppm
(s, 6H, CH3); MS (ESI): isotopic clusters peaking at m/z 1774 {100%,
[M+Na]+}, 1751 {82%, [M]+}, and 1732 {97%, [MÀF]+}; HRMS (ESI):
m/z calcd for C119H70BF2N3NaO10 [M+Na]+: 1773.5048; found 1773.5049.
DSBDP 3: A mixture of the phenol-containing BODIPY 1 (0.34 g,
1.0 mmol), benzaldehyde 2 (0.67 g, 2.5 mmol), glacial acetic acid (2.0 mL,
34.9 mmol), piperidine (2.4 mL, 24.3 mmol), and a small amount of Mg-
ACHTUNGTRENNUNG(ClO4)2 in TN (60 mL) was refluxed for 24 h. The water formed during
the reaction was removed azeotropically with a Dean–Stark apparatus.
The mixture was concentrated under reduced pressure, and the residue
was then purified by column chromatography using ethyl acetate/di-
chloromethane (1:4 v/v) as the eluent. The blue band that developed was
collected and concentrated by rotary evaporation to yield the desired
product 3 (0.25 g, 30%). 1H NMR: d=7.57 (d, J=16.0 Hz, 2H, CH=
CH), 7.51 (d, J=8.8 Hz, 4H, ArH), 7.15 (d, J=16.0 Hz, 2H, CH=CH),
7.04 (d, J=8.8 Hz, 2H, ArH), 6.94 (d, J=8.8 Hz, 2H, ArH), 6.90 (d, J=
8.8 Hz, 4H, ArH), 6.71 (brs, 1H, OH), 6.57 (s, 2H, pyrrole-H), 4.15 (vir-
tual t, J=4.8 Hz, 4H, CH2), 3.87 (virtual t, J=4.8 Hz, 4H, CH2), 3.74–
3.77 (m, 4H, CH2), 3.65–3.72 (m, 8H, CH2), 3.55–3.58 (m, 4H, CH2), 3.38
(s, 6H, OCH3), 1.44 ppm (s, 6H, CH3); 13C{1H} NMR: d=159.4, 156.8,
152.4, 141.8, 138.4, 135.5, 133.5, 129.7, 128.9, 126.8, 117.4, 117.2, 116.0,
114.8, 71.9, 70.8, 70.6, 70.5, 69.7, 67.4, 59.0, 14.8 ppm; MS (ESI): an iso-
topic cluster peaking at m/z 863 {100%, [M+Na]+}; HRMS (ESI): m/z
calcd for C47H55BF2N2NaO9 [M+Na]+: 863.3869; found 863.3894.
The Supporting Information for this article includes absorption spectra of
5 in the absence and presence of [Ru
ond transient spectra of 5 and 6 in TN and PhCN at various excitation
wavelengths, phosphorescence spectrum of
in PhCN, and 1H and
13C{1H} NMR spectra of all the new compounds.
(bpy)3]3+, femtosecond and nanosec-
ACHTUNGTRENNUNG
5
DSBDP 4: Anhydrous K2CO3 (2.76 g, 20.0 mmol) was added to a solu-
tion of 3 (0.84 g, 1.0 mmol) and 1,3-dibromopropane (4.0 g, 19.8 mmol) in
acetone (60 mL). The mixture was heated at reflux overnight, and the
volatiles were then removed in vacuo. The residue was mixed with water
(60 mL) and the mixture was extracted with CHCl3 (60 mLꢁ3). The com-
bined organic fractions were dried over anhydrous MgSO4, and then
evaporated to dryness under reduced pressure. The crude product was
purified by column chromatography using ethyl acetate/dichloromethane
(1:50 v/v) as the eluent. The product was obtained as a blue solid (0.85 g,
89%). 1H NMR: d=7.60 (d, J=16.8 Hz, 2H, CH=CH), 7.56 (d, J=
8.8 Hz, 4H, ArH), 7.20 (d, J=8.8 Hz, 2H, ArH), 7.19 (d, J=16.8 Hz, 2H,
CH=CH), 7.01 (d, J=8.8 Hz, 2H, ArH), 6.94 (d, J=8.8 Hz, 4H, ArH),
6.60 (s, 2H, pyrrole-H), 4.14–4.19 (m, 6H, CH2), 3.88 (virtual t, J=
4.8 Hz, 4H, CH2), 3.74–3.77 (m, 4H, CH2), 3.62–3.71 (m, 10H, CH2),
3.54–3.57 (m, 4H, CH2), 3.39 (s, 6H, OCH3), 2.37 (quintet, J=6.0 Hz,
2H, CH2), 1.48 ppm (s, 6H, CH3); 13C{1H} NMR: d=159.5, 159.2, 152.5,
141.8, 138.1, 135.6, 133.5, 129.7, 129.6, 129.0, 127.6, 117.4, 117.2, 114.9,
114.8, 71.9, 70.8, 70.6, 70.5, 69.7, 67.4, 65.4, 59.0, 32.3, 29.9, 14.8 ppm; MS
(ESI): an isotopic cluster peaking at m/z 985 {100%, [M+Na]+}; HRMS
(ESI): m/z calcd for C50H60BBrF2N2NaO9 [M+Na]+: 983.3444; found
983.3462.
Acknowledgements
This work was financially supported by a strategic investments scheme
administrated by The Chinese University of Hong Kong, a Grant-in-Aid
(Nos. 20108010), a Global COE program “the Global Education and Re-
search Center for Bio-Environmental Chemistry” from the Japan Society
of Promotion of Science (JSPS), and KOSEF/MEST through the WCU
project (R31-2008-000-10010-0).
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Chem. Asian J. 2011, 6, 174 – 179

Photoinduced Electron Transfer in a Distyryl BODIPY–Fullerene Dyad
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Received: August 5, 2010
Published online: October 19, 2010
Chem. Asian J. 2011, 6, 174 – 179
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