Syntheses of [60]fullerene and N,N-bis(4-biphenyl)aniline-tethered rotaxane: Photoinduced electron-transfer processes via singlet and triplet states of [60]fullerene

Article abstract of DOI:10.1246/bcsj.78.1008

A rotaxane containing [60]fullerene (C₆₀) and N,N-bis(4-biphenyl)aniline (BBA) moieties was synthesized. In this structure, C₆₀ acting as an electron acceptor, is attached to the crown-ether ring through which the axle with terminal

Full text of DOI:10.1246/bcsj.78.1008

1008 Bull. Chem. Soc. Jpn., 78, 1008–1017 (2005)
ꢀ 2005 The Chemical Society of Japan
Syntheses of [60]Fullerene and N,N-Bis(4-biphenyl)aniline-Tethered
Rotaxane: Photoinduced Electron-Transfer Processes via Singlet
and Triplet States of [60]Fullerene
Atula S. D. Sandanayaka, Kei-ichiro Ikeshita,1 Nobuhiro Watanabe,2 Yasuyuki Araki,
ꢀ;1;2
ꢀ
Yoshio Furusho,1;3 Nobuhiro Kihara,1 Toshikazu Takata,
and Osamu Ito
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University,
Katahira 2-1-1, Aoba-ku, Sendai 980-8577
1Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University,
1-1 Gakuen-cho, Sakai, Osaka 599-8531
2Department of Organic and Polymeric Materials, Tokyo Institute of Technology,
Ookayama, Meguro-ku, Tokyo 152-8552
3Yashima Super-Structured Helix Project, JST, Moriyama-ku, Nagoya 463-0003
Received December 17, 2004; E-mail: ito@tagen.tohoku.ac.jp: ttakata@polymer.titech.ac.jp
A rotaxane containing [60]fullerene (C60) and N,N-bis(4-biphenyl)aniline (BBA) moieties was synthesized. In this
structure, C60 acting as an electron acceptor, is attached to the crown-ether ring through which the axle with terminal
BBA moieties acting as electron donors on both ends is penetrating. This rotaxane had a neutral amide moiety in the
center of the axle in which two BBA moieties act as stoppers. The intra-rotaxane photoinduced electron-transfer proc-
esses of the C60 and BBA moieties were investigated by time-resolved transient absorption and fluorescence measure-
ments while changing solvent polarity and temperature. Time-resolved transient absorption measurements of the
rotaxanes confirmed that the long-lived charge-separated state (C60ꢁꢂ; BBAꢁþ
)
was formed via both the excited
rotaxane
ꢀ
3
ꢀ
singlet and triplet states of C60 (1C60 and C60 , respectively) in polar solvents. The rate constants for charge-separa-
1
ꢀ
3
ꢀ
tion process were evaluated to be in the range of ð3:6{3:7Þ ꢃ 108 sꢂ1 via C60 and ð5:1{5:6Þ ꢃ 107 sꢂ1 via C60 in
the ratio of (0.36–0.38):(0.43–0.51). The rate constants of charge recombination were 2:5 ꢃ 106 sꢂ1 and 4:4 ꢃ 106
s
ꢂ1, corresponding to the lifetimes of the charge-separated states of 400 ns and 230 ns in THF and benzonitrile, respec-
tively. By the temperature dependences, the activation free-energy changes of charge-separation process via 3C60 were
evaluated to be 0.10 eV, while those of the charge-recombination process were estimated to be 0.03 eV in THF
and benzonitrile. These low activation energies are one of the characteristics of through-space electron transfer in the
rotaxanes.
ꢀ
A new, rapidly progressing field on the crossroad between
chemistry and supramolecular chemistry has just emerged as
an interdisciplinary field of science and technology with inter-
esting perspectives.1–3 With the advance of supramolecular
chemistry, efficient synthetic routes of rotaxanes have been
built-up exploiting the ability of assistance from cooperative
noncovalent bonding interactions. [60]Fullerene (C60) deriva-
tives have shown a wide range of physical and chemical prop-
erties that make them attractive for the preparation of supra-
molecular assemblies and new advanced materials for opto-
electronic and molecular electronic devices.4–8 In addition,
the unique geometry of these molecules provides templates
with an enormous scope for a variety of studies including in-
vestigations of energy- and electron-transfer processes within
supramolecular assemblies containing the C60 moieties under
the photoillumination.9–12 Covalent linkages of C60 with spe-
cific electron donors involving the electron-mediating and
hole-transfer reagents have been extensively studied revealing
fast and efficient charge-separation (CS) via the excited singlet
resulting in long lived CS states.13–15 Supramolecules com-
posed of the coordination bonds between the C60–pyridine de-
rivatives and zinc porphyrins have also been studied, showing
fast and efficient CS process via the excited singlet states of
zinc porphyrins and/or the C60 derivatives; in these cases,
the CS states with lifetimes longer than ca. 100 ns were not
observed yet.4,16 The high steady-state concentration of the
CS state is very important for the successful use of these mo-
lecular systems for energy-conversion devices. The strategy
has been developed to investigate the rates of electron-transfer
(ET) process in these supramolecular systems by tuning the
energies of the donor–acceptor pair, and by optimizing the
distance and orientation between the donor–acceptor.
Recently, rotaxanes containing the C60 moiety as electron
acceptors and phthalocyanine and porphyrin as electron donors
were synthesized, of which C60 moiety was spatially placed
with respect to the phthalocyanine and porphyrin moieties.
In these rotaxanes, it has been reported that the CS process
takes place via the excited singlet states of these chromo-
phores.17,18
ꢀ
states of the C60 derivatives (1C60 ) and/or donor molecules,
Published on the web June 6, 2005; DOI 10.1246/bcsj.78.1008

A. S. D. Sandanayaka et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005) 1009
ture and covalently connected dyads with newly synthesized
rotaxane 1, in which the through-space electron transfer would
be anticipated.
O
NH
O
HN
N
N
O
O
S
Experimental
O
O
O
O
S
Syntheses General.
Melting points were measured on a
Yanagimoto micro melting point apparatus. IR spectra were
recorded on a JASCO FT-IR model 230 spectrometer. 1H NMR
measurements were performed with JEOL JNM-GX-270 and
JNM-L-400 spectrometers in CDCl3 with tetramethylsilane as
an internal reference. FAB-MS measurements were performed
with a Finnigan TSQ-70 instrument. For preparative HPLC, a
JAICO LC-908 system using columns JAIGEL 1 (ꢀ 20 mm ꢃ
600 mm) and JAIGEL 2 (ꢀ 20 mm ꢃ 600 mm) was used. Com-
pounds 728 and 818 were prepared according to the methods de-
scribed previously. [60]Fullerene was purchased from Frontier
Carbon Corporation. Other materials used were the commercially
available reagent grade.
1
O
O
O
OCH3
NH
HN
N
N
O
O
S
3
O
O
O
O
S
S
22
O
Synthesis of 6: A mixture of 4-nitroaniline 4 (369 mg, 2.67
mmol), 4-tert-butyl-40-iodobiphenyl 5 (2.37 g, 7.06 mmol), copper
powder (684 mg, 10.8 mmol), potassium carbonate (2.97 g, 21.5
mmol), and 18-crown-6 (144 mg, 0.544 mmol) in 1,2-dichloro-
benzene (8.0 mL) was refluxed for 2 days under argon atmo-
sphere. The reaction mixture was filtered after being cooled to
room temperature. The filtrate was evaporated to dryness. Column
chromatographic separation of the mixture on silica gel (chloro-
form/hexane = 1/1, Rf ¼ 0:30) afforded 6 as an orange solid
(1.37 g, 2.48 mmol, 93%). mp 97–102 ꢄC (dec.). 1H NMR (400
MHz, CDCl3) ꢁ 8.08–8.05 (m, 2H), 7.60–7.16 (m, 12H), 7.27–
7.24 (m, 4H), 7.05–7.02 (m, 2H), 1.37 (s, 18H) ppm. IR (KBr)
Fig. 1. Molecular structures of rotaxanes 1 and 2 and C60-
reference 3.
When the aromatic amines were employed as electron-do-
nors, photoinduced ET processes for C60–amine mixture sys-
tems have gained a great attention,19–23 and a vast variety of
C60–amine dyads, triads, and more complex systems have been
synthesized and investigated.24,25 In most covalently connected
dyad systems of C60 and aromatic amines such as N,N-di-
methylaniline and triphenylamine (TPA), excitation of the
C60 moiety initiates electron transfer from the C60 moiety,
generating the CS states (C60ꢁꢂ–amineꢁþ) with relatively
short lifetimes.25 In our previous paper, however, we reported
that the CS process of rotaxanes of fullerene and TPA
((C60;TPA)rotaxane) predominantly takes place via the excited
triplet state of C60 (3C60 ), and that the CS state
((C60ꢁꢂ;TPAꢁþ
rotaxane) was kept for a relatively long time
(170–300 ns) in rotaxane.26 In the present study, we synthe-
sized C60–[2]rotaxane with N,N-bis(4-biphenyl)aniline
(BBA) moieties as electron donors, as shown in Fig. 1; here,
C60–BBA [2]rotaxane was abbreviated as or
(C60;BBA)rotaxane. In this rotaxane, we chose the BBA moiety
as the amine donor, because it has been reported that the BBA
moiety showed quite a long CS state when the BBA moiety
was covalently connected with C60 (C60–BBA dyad);27 In 1,
BBA moieties are attached to both ends of the axle component,
which penetrates the amide-based macrocycle bearing a C60
unit. [2]Rotaxane without the C60 unit (2) and the 4-me-
thoxy-carbonyl-o-quinodimethane adduct with C60 (3) were
used as reference compounds.
1
ꢀ
3031, 2962, 1587, 1494, 1316 cmꢂ1
.
Synthesis of 7: A suspension of 6 (225 mg, 0.406 mmol) and
5% Pd/C (50.0 mg) in THF (16.0 mL) was stirred at room temper-
ature under H2 atmosphere for 1 day. The catalyst was removed by
filtration and the filtrate was evaporated to dryness to yield 7 (213
mg, 0.406 mmol, quant.) as a yellow solid. mp 87–92 ꢄC. 1H NMR
(270 MHz, CDCl3) ꢁ 7.63–7.52 (m, 12H), 7.23 (d, J ¼ 8:6 Hz,
4H), 7.12 (d, J ¼ 8:4 Hz, 2H), 6.72 (d, J ¼ 8:4 Hz, 2H), 3.63
(s, 2H), 1.47 (s, 18H) ppm. IR (KBr) 3379, 3030, 2959, 1601,
ꢀ
)
a
1495, 1323, 1268 cmꢂ1
.
Synthesis of [2]Rotaxane 2: To a solution of 7 (210 mg,
0.400 mmol) and triethylamine (56.0 mL, 0.401 mmol) in chloro-
form (20.0 mL) was added a mixture of macrolactam 818 (72.3
mg, 0.100 mmol) and isophthaloyl chloride 9 (20.4 mg, 0.100
mmol) in chloroform (20.0 mL) over a period of 1 h at 0 ꢄC. Then,
an additional chloroform solution (10.0 mL) of 9 (20.3 mg, 0.10
mmol) was added over a period of 1 h at 0 ꢄC. After being stirred
1
ꢄ
at 0 C for 1 h and then at room temperature overnight, the mix-
ture was evaporated to dryness. The residue was purified by col-
umn chromatography on silica gel (chloroform, Rf ¼ 0:05) and
preparative HPLC to afford 2 (43.0 mg, 22.6 mmol, 23% yiꢄeld
based on the macrolactam 8) as a yellow solid. mp 173–179 C.
1H NMR (400 MHz, CDCl3) ꢁ 8.89 (s, 1H), 8.33 (s, 2H), 8.27
(s, 2H), 7.99 (s, 1H), 7.87 (d, J ¼ 7:6 Hz, 2H), 7.80 (m, 2H),
7.56–7.53 (m, 16H), 7.46 (d, J ¼ 8:8 Hz, 8H), 7.44 (m, 1H),
7.40 (d, J ¼ 8:8 Hz, 4H), 7.18 (d, J ¼ 8:8 Hz, 8H), 7.11 (d, J ¼
8:8 Hz, 4H), 6.84 (d, J ¼ 8:2 Hz, 4H), 6.45 (d, J ¼ 8:2 Hz, 4H),
4.44 (s, 4H), 3.98 (s, 4H), 3.64 (s, 4H), 3.20 (s, 4H), 1.36 (s, 36H),
1.35 (s, 9H) ppm. IR (KBr) 3365, 2959, 1649, 1601, 1499, 1319,
1272, 1193, 1115, 819 cmꢂ1. FAB-MS (matrix: mNBA) m=z
1901 [M]þ.
For the rotaxane 1, we have investigated the photoinduced
ET processes using the time-resolved transient absorption
and fluorescence measurements with changing solvent
polarity and temperature, expecting longer lifetimes of
(C60ꢁꢂ;BBAꢁþ
)
than those of (C60ꢁꢂ;TPAꢁþ
)
rotaxane. Fur-
thermore, the CS process of C60–BBA dyad efficiently takes
rotaxane
1
ꢀ
place via the C60 moiety. Thus, it would be anticipated that
ꢀ
the contribution of the CS mechanism via the 1C60 moiety in
(C60;BBA)rotaxane may increase. Our aim in this study was to
compare these reported photoinduced ET processes in the mix-

1010 Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
PET of C60: Bis(4-biphenyl)aniline Rotaxane
Synthesis of [2]Rotaxane 1: A mixture of C60 (61.1 mg, 84.9
mmol), 2 (32.2 mg, 16.9 mmol) and hydroquinone (0.800 mg, 7.26
mmol) in 1,2-dichlorobenzene (15.0 mL) was refluxed for 3 h. The
reaction mixture was evaporated to dryness. The residue was chro-
matographed on silica gel (chloroform, Rf ¼ 0:10) and the crude
product was purified by preparative HPLC to afford 1 (23.4 mg,
9.14 mmol, 54%) as a blackish brown solid. mp 277–280 ꢄC
(dec.). 1H NMR (400 MHz, CDCl3, 333 K) ꢁ 8.97 (s, 1H), 8.44
(s, 2H), 8.37 (s, 2H), 8.16 (s, 1H), 7.99 (d, J ¼ 7:2 Hz, 2H),
7.78 (t, J ¼ 4:0 Hz, 2H), 7.52–7.48 (m, 21H), 7.40 (d, J ¼ 8:4
Hz, 8H), 7.18–7.09 (m, 12H), 6.87 (d, J ¼ 8:2 Hz, 4H), 6.52
(d, J ¼ 8:2 Hz, 4H), 4.51 (d, J ¼ 4:0 Hz, 4H), 4.16 (s, 8H),
3.38 (s, 4H), 1.38 (s, 9H), 1.34 (s, 36H) ppm. IR (KBr) 3422,
2958, 1652, 1496 cmꢂ1. FAB-MS (matrix: mNBA) m=z 2560
chromator (Action Research, SpectraPro 150) as an excitation
source and a detector, respectively.
Nanosecond transient absorption measurements were carried
out using SHG (532 nm) of Nd:YAG laser (Spectra-Physics,
Quanta-Ray GCR-130, fwhm 6 ns) as an excitation source. For
transient absorption spectra in the near-IR region (600–1600
nm), monitoring light from a pulsed Xe lamp was detected with
a Ge-avalanche photodiode (Hamamatsu Photonics, B2834).
Details of the transient absorption measurements were described
elsewhere.30,31 All the samples in a quartz cell (1 ꢃ 1 cm2) were
deaerated by bubbling argon through the solution for 15 min.
The temperature dependence of the photoinduced events was
measured by immersing the quartz cell in the controlled media
in a rectangular quartz Dewar-flask.
½M þ Hꢅþ; Anal. Calcd for C180H120N6O8S2 0.25CHCl3: C,
ꢆ
Results and Discussion
83.62; H, 4.68; N, 3.25; S, 2.48%. Found: C, 83.33; H, 4.68; N,
3.36; S, 2.45%.
Design, Preparation, and Characterization of [2]Rotax-
ane 1. [2]Rotaxane 1 was designed to place spatially the
C60 and BBA moieties closely each other. They are capable
of electron-transferring in the excited state, but do not interact
strongly in the ground state. [2]Rotaxane 1 was synthesized by
the hydrogen-bonding-assisted method for sec-amide-based ro-
taxanes. Introduction of the fullerene unit was achieved by the
Diels–Alder reaction of 2 and C60 to afford the fullerene [2]ro-
taxane 1. The synthetic route of 1 is outlined in Scheme 1. The
Ullman-type coupling of 4-nitroaniline 4 and 4-tert-butyl-40-
iodobiphenyl 5 afforded triarylamine 6 in 93% yield. Hydroge-
nation of 6 catalyzed by 5% Pd/C yielded amine 728 quantita-
tively. Condensation of 7 with isophthaloyl chloride 9 in the
presence of macrolactam 818 gave [2]rotaxane (2) bearing a
sulfolene moiety on the macrocyclic component in 23% yield.
The Diels–Alder reaction of 2 and C60 afforded [2]rotaxane (1)
bearing a C60 moiety on the wheel in 54% yield. The structure
Molecular Orbital Calculation.
An optimized structure
and HOMO and LUMO of [2]rotaxane 1 were calculated by the
ꢀ
density function B3LYP/3-21G( ) method.29
Electrochemical Measurements.
The cyclic voltammetry
measurements were performed on a BAS CV-50W electrochemi-
cal analyzer in deaerated benzonitrile solution containing 0.10 M
Bu4NPF6 as a supporting electrolyte at 298 K (100 mV sꢂ1). The
polished glassy carbon and a platinum wire were used as working
electrode and counter electrode, respectively. The measured
potentials were recorded with respect to an Ag/AgCl (saturated
KCl) reference electrode, using ferrocene/ferrocenium (Fc/Fcþ)
as an internal reference.
Spectral Measurements.
Steady-state absorption spectra
in the visible and near-IR regions were measured on a Jasco
V570 DS spectrometer. Fluorescence spectra were measured on
Shimadzu RF-5300PC spectro-fluorophotometer.
Fluorescence lifetimes were measured by a single-photon
counting method using a second harmonic generation (SHG,
410 nm) of a Ti:sapphire laser [Spectra-Physics, Tsunami 3950-
L2S, 1.5 ps full width at half-maximum (fwhm)] and a streak
scope (Hamamatsu Photonics, C4334-01) equipped with a poly-
1
of 1 was confirmed by H NMR, IR, FAB-MS, and elemental
analysis. As C60-reference, 4-methoxycarbonyl-o-quinodi-
methane adduct with C60 (3) was prepared according to the
method described in the literature.32
O
O
O
S
S
NH
O
O
+
O2S
Cl
Cl
I
HN
O
O
O
9
5
H2, Pd-C
8
O2N
NH2
O2N
N
H2N
N
Cu, K2CO3, 18-crown-6
o-DCB, reflux, 2 days
THF, rt, 1 day
quant.
Et3N, CHCl3, rt, overnight
23%
93%
4
6
7
O
O
HN
NH
O
O
O
N
N
HN
NH
O
C60
N
N
N
H
N
H
O
O
O
O
O
hyOdroquinone
N
H
N
o-DCB, reflux, 3 h
O
O
O
O
O
S
S
H
54%
S
S
S
O2
2
1
Scheme 1.

A. S. D. Sandanayaka et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005) 1011
0.8
0.6
(A)
−2
C60
−1
C60
BBA+
0.4
0.2
0.0
−0.2
−0.4
−0.6
−0.8
LUMO, -3.197 eV
0.5 0.0 −0.5 −1.0 −1.5
Voltage / V (vs Fc/Fc+ )
−2
(B)
BBA+
C60
−1
0.6
0.4
C60
HOMO, -4.898 eV
0.2
Fig. 2. An optimized structure and HOMO and LUMO of
[2]rotaxane 1 calculated by density function B3LYP/
3-21G( ) method.
0.0
2
ꢀ
−0.2
−0.4
−0.6
−0.8
−1.0
3
Optimized Structure and Molecular Orbitals. An opti-
mized structure and HOMO and LUMO of [2]rotaxane 1 cal-
ꢀ
culated by the density function B3LYP/3-21G( ) method29 are
shown in Fig. 2; the results indicate that rotaxane 1 is not sym-
metric. One of the two BBA moieties is placed near the C60
moiety, while the other BBA moiety is far from the C60 moie-
ty. The shorter distance between the center of the C60 moiety
and the center of the BBA moiety (RCC) was estimated to be
ꢀ
10.8 A, while the longer distance between the center of C60
ꢀ
and the center of another BBA was estimated to be 14.1 A.
The center-to-center distance between two BBA moieties is
0.5 0.0 −0.5 −1.0 −1.5
Voltage / V (vs Fc/Fc+ )
Fig. 3. Cyclic voltammograms of (A) [2]rotaxane 1 and (B)
references 2 and 3 at 100 mV sꢂ1 in PhCN.
charge-separation (ꢁGCS) were estimated by Eqs. 1 and 2,33
ꢀ
18.8 A. The HOMO was located on the BBA moiety near
the C60 moiety, which corresponds to the radical cation distri-
bution of the CS state, giving the radius of the radical cation
ꢂꢁGCR ¼ Eox ꢂ Ered þ ꢁGs;
ꢂꢁGCS ¼ E0 þ ꢁGCR
ð1Þ
;
ð2Þ
ꢀ
(R ) to be 7.1 A. On the other hand, the LUMO was located
ꢁGs ¼ e2=4ꢂ"0½ð1=2R þ 1=2R ꢂ 1=RCCÞ="s
þ
þ
ꢂ
on the C60 moiety, which corresponds to the radical anion dis-
tribution of the CS state, giving the radius of the radical anion
ꢂ ð1=2R þ 1=2R Þ="Rꢅ;
ð3Þ
þ
ꢂ
in which E0 refers the excitation energy of 1C60 or 3C60 , and
ꢁGs is the correction term which includes the solvent dielec-
tric constants of for photochemistry ("s) and electrochemistry
("R), respectively, in addition to the vacuum permittivity ("0);
the radii of the charged donor (R ) and acceptor (R ) evaluat-
ꢀ
ꢀ
ꢀ
(R ) to be 4.7 A. The HOMO–LUMO gap was evaluated to be
ꢂ
1.7 eV.
Electrochemical Measurements. The cyclic voltammo-
grams of [2]rotaxanes 1 and 2 are shown in Fig. 3. The first
reduction (Ered) and oxidation potentials (Eox) of rotaxane 1
were estimated to be ꢂ1:06 and 0.33 V vs Fc/Fcþ in benzoni-
trile (PhCN). The former negative potential was attributed to
the Ered value of the C60 moiety and the latter positive potential
to the Eox value of the BBA moiety in 1 by comparing with
Ered of the C60 moiety in C60-reference 3 (ꢂ1:05 V vs Fc/
Fcþ) and Eox of the BBA moiety in 2 (þ0:35 V vs Fc/Fcþ)
in PhCN. The electrochemical HOMO–LUMO gap was eval-
uated to be 1.4 eV, which is compatible to the value evaluated
from MO calculations. The electrochemical studies revealed
that there is no appreciable electronic interaction between
the C60 and BBA moieties in the ground states.
þ
ꢂ
ed from HOMO and LUMO were employed.
Steady-State Absorption Measurements.
The steady-
state absorption spectra of [2]rotaxanes 1 and 2 and C60-refer-
ence 3 in toluene are shown in Fig. 4. The absorption peaks at
705 nm and below 350 nm of rotaxane 1 are ascribed to the
C60 moiety. Since the absorption spectrum 1 is almost a super-
imposition of reference compounds, 2 and 3, there is only a
weak interaction between the moieties in the ground state of
rotaxane 1. Similar results were obtained for rotaxane 1 in
THF and PhCN. Thus, laser photolysis was performed with
the 532 nm light, which predominantly excites the C60 moiety.
Steady-State Fluorescence Measurements. Steady-state
fluorescence spectra of [2]rotaxane 1 and C60-reference 3 in
The free-energy changes of charge-recombination (ꢁGCR
of the radical ion-pair states and free-energy changes of
)

1012 Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
PET of C60: Bis(4-biphenyl)aniline Rotaxane
1.0
0.8
0.6
0.4
0.2
0.0
1
2
3
0.8
0.6
0.4
PhCN
toluene
0.2
0.0
1 x 5
400 500 600 700 800 900
Wavelength / nm
0
1
2
3
Time / ns
Fig. 4. Steady-state absorption spectra of [2]rotaxane 1 (0.1
mmol dmꢂ3), reference 2 (0.1 mmol dmꢂ3), and reference
3 (0.1 mmol dmꢂ3) in toluene.
Fig. 6. Fluorescence decay time profiles of [2]rotaxane 1 at
715 nm in PhCN and toluene (ꢃex ¼ 410 nm).
Table 1. Fluorescence Lifetime (ꢄf), Rate Constant (kCSS),a)
Quantum Yield (ꢂCSS),a) and Free-Energy Changes
(ꢁGCSS) of CS of [2]Rotaxane 1 in Toluene, THF, and
PhCN at Room Temperature
1 in toluene
3 in toluene
1 in PhCN
S
kCS /sꢂ1
ꢂCS
ꢂꢁGCSS/eV
S
Solvent
ꢄf/ps
Toluene
THF
PhCN
1560
980
—
3:8 ꢃ 108
—
ꢂ0:05 ꢇ 0:03
0:30 ꢇ 0:01
0:41 ꢇ 0:01
0.38
0.36
1 in THF
1000
3:6 ꢃ 108
a) Calculated from Eqs. 4 and 5. b) Calculated from Eqs. 1–3,
1
ꢀ
in which the E0 value of C60 was set equal to 1.75 eV;34,35
S
the errors of ꢁGCS were estimated when the distances in-
ꢀ
clude estimation error of ꢇ0:5 A.
700
750
800
850
900
which shows almost the same behavior in THF and PhCN. The
fluorescence decay of 1 in PhCN, which was almost the same
as that in THF, was faster than that in toluene. These fluores-
cence decays could be fitted as a single-exponential process,
giving the fluorescence lifetimes (ꢄf) of the C60 moiety in ro-
taxane 1 and reference compound 3 as listed in Table 1. In tol-
uene, the ꢄf value of rotaxane 1 is practically the same as that
of 3 (1550–1560 ps), which is referred to as ðꢄfÞref. In PhCN
and THF, the ꢄf values of rotaxane 1 (ðꢄfÞsample) are slightly
short (980–1000 ps), which is in agreement with the slight
Wavelength / nm
Fig. 5. Steady-state fluorescence spectra of [2]rotaxane 1
and reference 3 (0.1 mmol dmꢂ3) in PhCN, THF, and tol-
uene (ꢃex ¼ 630 nm).
toluene, THF, and PhCN (ꢃex ¼ 600 nm) are shown in Fig. 5.
The C60 moiety of rotaxane 1 and reference 3 shows emission
maxima around 715 nm with a shoulder at 780 nm. No evi-
dence for exciplex emission could be obtained, even by de-
creasing solvent polarity. By comparing the fluorescence peak
with the absorption peak (709 nm), rotaxane 1 showed a small
Stokes shift. The lowest excited singlet energy of C60 was
evaluated to be 1.75 eV (E0ðS1Þ).
1
ꢀ
quenching of the steady-state fluorescence intensity of C60
in polar solvents.
1
ꢀ
From these differences between ðꢄfÞsample and ðꢄfÞref, the
S
S
rate constant kq and the quantum yield ꢂq for fluorescence
quenching were evaluated from Eqs. (4) and (5);
The fluorescence intensity of 1 at 715 nm in toluene was al-
most identical to that of 3. In THF and PhCN, the emission
intensities of 1 are smaller than that in toluene by factor of
ca. 1/2, while the fluorescence intensity of 1 in toluene is
almost the same as those of 3 in PhCN, THF, and toluene.
Further quantitative analyses on the fluorescence properties
were carried out based on the lifetime measurements.
Fluorescence Lifetime Measurements. Figure 6 shows
fluorescence decays of of the C60 moiety in [2]rotaxane 1
in toluene and PhCN obtained by a time-correlated single-pho-
ton-counting apparatus with excitation at 410 nm. The fluores-
cence decay of 1 in toluene was similar to that of 3 in toluene,
S
kq ¼ ð1=ꢄfÞsample ꢂ ð1=ꢄfÞref
;
ð4Þ
S
ꢂq ¼ ðð1=ꢄfÞsample ꢂ ð1=ꢄfÞrefÞ=ð1=ꢄfÞsample
:
ð5Þ
S
S
The kq values are in the range of ð3{4Þ ꢃ 108 sꢂ1 and the ꢂq
values are in the range of 0.30–0.40 as summarized in Table 1.
If one compares these kqS and ꢂqS values with the intersystem-
1
ꢀ
30,34
crossing (ISC) rate constant (kISC ¼ 6:5 ꢃ 108 sꢂ1
)
and
quantum yields (ꢂISC ¼ 0:92{0:96)30,34 of 3, one sees that
1
ꢀ
3
the main process (60–65%) via the C60 moiety in [2]rotax-
ꢀ
ane 1 is the ISC process, producing the C60 moiety even

A. S. D. Sandanayaka et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005) 1013
0.30
0.25
0.20
0.15
0.10
0.05
0.8
0.6
0.4
0.2
0.0
0.20
0.15
0.10
0.05
0.00
0.30
860 nm
700 nm
0.20
1000 nm
0.10
0.00
0.0
0.5
1.0
1.5
Time / µs
0.0
0.5
1.0
1.5
Time / µs
0.00
600
800
1000
1200
400
600
800
1000
1200
Wavelength / nm
Wavelength / nm
Fig. 7. Nanosecond transient absorption spectra of [2]ro-
taxane 1 (0.1 mmol dmꢂ3) observed by 532 nm laser irra-
diation in at 0.1 ms ( ) and 1.0 ms ( ) in toluene. Inset:
Absorption-time profiles at 700 nm in toluene.
Fig. 8. Nanosecond transient absorption spectra of [2]ro-
taxane 1 (0.1 mmol dmꢂ3) observed by 532 nm laser irra-
diation in at 0.1 ms ( ) and 1.0 ms ( ) in PhCN. Inset:
Absorption-time profiles at 860 and 1000 nm in PhCN at
room temperature.
T
Table 2. CS Rate Constant (kCST), CS Minimum Quantum Yield (ꢂCS ,min) and CS Free Energy (ꢂꢁGCST),a) and CR Rate Constant
a)
(kCR) and Lifetime (ꢄRIP) of Radical Ion-Pair and CR Free Energy (ꢂꢁGCR
)
of [2]Rotaxane 1 in THF and PhCN
T
T
kCS
/sꢂ1
ꢂꢁGCS
kCR
/sꢂ1
ꢄRIP
/ns
ꢂꢁGCR
T
T
Solvent
ꢂCS
ꢂCS
,total
,min
/eV
/eV
THF
PhCN
5:1 ꢃ 107
0.69
0.78
0.43
0.51
0.07
0.18
2:5 ꢃ 106
400
230
1.45
1.34
5:6 ꢃ 107
4:4 ꢃ 106
a) Calculated from Eqs. 1–3; the E0 value of 3C60 was set equal to 1.52 eV,34,35 and estimation error was ꢇ0:01 (see footnote under
ꢀ
Table 1).
27
in the polar solvents.
From the sufficiently negative ꢁGCS values in polar sol-
the extinction coefficient (40000 molꢂ1 dm3 cmꢂ1
)
at
S
860 nm of the BBAꢁþ moiety to that of 8500 molꢂ1 dm3 cmꢂ1
at 1000 nm of the C60 moiety,34,35 we could attribute the
transient spectrum in PhCN exclusively to the CS state,
(C60ꢁꢂ;BBAꢁþ
)rotaxane. Similarly, the transient absorption spec-
trum, revealing the formation of (C60ꢁꢂ;BBAꢁþ
)rotaxane, was
obtained in THF for [2]rotaxane 1.
ꢁꢂ
vents (Table 1), one can conclude that the CS process via
1
ꢀ
ble process; thus, the kq and ꢂq values above can be attrib-
the C60 moiety in rotaxane 1 is a thermodynamically possi-
S
S
1
ꢀ
uted to the CS process via the C60 moiety in [2]rotaxane 1.
ꢀ
The CS process can take place in 36–38% of the 1C60 moiety,
which may be characteristic of [2]rotaxane 1 including the
After reaching the maximum at ca. 0.1 ms,
BBA moieties, because this kind of CS process via the C60
(C60ꢁꢂ;BBAꢁþ
)
rotaxane
began to decay during 100–1200 ns as
1
ꢀ
moiety for a similar [2]rotaxane with the TPA moieties is mi-
shown in the inset of Fig. 8. The decays obey first-order kinet-
ics with rate constants in the range of ð2:5{4:4Þ ꢃ 106 sꢂ1 in
polar solvents, which can be assigned to the CR rate constant
(kCR), as summarized in Table 2. From the inverse of the kCR
) of the radical ion-pairs
are evaluated. The longest ꢄRIP value
is 400 ns for rotaxane 1 in THF, which is longer than the
ꢄRIP value (230 ns) for rotaxane 1 in PhCN, suggesting that
the CR process belongs in the inverted region of the Marcus
parabola.36
nor (<20%).26
Time-resolved Transient Absorption Spectra. The time-
resolved transient absorption spectrum of [2]rotaxane 1 in
toluene observed by nanosecond laser photolysis with 532
nm laser excitation (6 ns laser pulse) is shown in Fig. 7; the
values, the lifetimes (ꢄRIP
(C60ꢁꢂ;BBAꢁþ
)
rotaxane
3
ꢀ
spectrum exhibits a peak at 700 nm due to the C60 moiety
in rotaxane 1, because the same absorption was observed for
reference 3 in every solvent under the same experimental
conditions. The time profile at 700 nm showed no appreciable
decay within a few ms as shown in the inset of Fig. 7.
In the time profile at 1ꢁ0ꢂ00 nm on the time scale shorter than
100 ns, a rise of the C60 absorption was observed (Fig. 8.).
From the curve fitting with a single exponential, the CS rates
(kCST) via the C60 moiety were evaluated as listed in
The transient absorption spectra of [2]rotaxane 1 in PhCN
are shown in Fig. 8; in the spectrum observed at 0.1 ms, the
main transient absorption band appeared at 860 nm with a
shoulder at 1000 nm in addition to the band <500 nm. The
absorption bands at 860 nm and <500 nm were attributed to
the BBAꢁþ moiety in roꢁtaꢂxane 1, while the 1000 nm shoulder
was assigned to the C60 moiety. By comparing the ratio of
3
ꢀ
T
Table 2 for rotaxane 1 in polar solvents. The kCS values are
T
in the range of ð5:1{5:6Þ ꢃ 107 sꢂ1. The kCS value in PhCN
is similar to that in THF, which suggests that solvent polarity
does not exert much effect.

1014 Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
PET of C60: Bis(4-biphenyl)aniline Rotaxane
1.0
0.8
0.6
0.4
0.2
0.0
19.0
18.5
18.0
17.5
17.0
16.5
PhCN
THF
(A)
0.0
0.1
0.2
Time / µs
0.3
0.4
3.2
3.6
103 T-1 / K-1
4.0
4.4
Fig. 9. Absorption-time profiles of [2]rotaxane 1 at 700 nm
(green, ꢆ ꢆ ꢆ), 1000 nm (red, ), and subtracted profile from
700 nm (blue, ꢃ) in PhCN.
22
21
20
19
18
17
(B)
PhCN
THF
From the inspection of the time profiles of
(C60ꢁꢂ;BBAꢁþ
)
at 860 and 1000 nm (Fig. 8) at early
rotaxane
times (10–100 ns), one can observe a slow rise after the laser
pulse of ca. 6 ns. One can assume that the radical ion-pair
(C60ꢁꢂ;BBAꢁþ
)
ꢀ
is obtained via the 3C60 moiety as well
rotaxane
ꢀ
as the 1C60 moiety. Figure 9 shows the time profile at 700 nm
in PhCN, in which the rapid decay of the absorption of the
3C60 moiety and the rise of the BBAꢁþ moiety in rotaxane
ꢀ
1 may be overlapped. If one assumes that the riseꢁcꢂurve for
the BBAꢁþ moiety was the same as that of the C60 moiety
at 1000 nm, the observed 700 nm time profile can be curve-
resolved as shown in Fig. 9. The extracted decay rate of the
3.2
3.6
4.0
4.4
ꢀ
103 T-1 / K-1
3C60 moiety (4:8 ꢃ 107 sꢂ1) was almost the same as the rise
ꢁꢂ
rate of the C60 moiety at 1000 nm (5:6 ꢃ 107 sꢂ1), confirm-
Fig. 10. Modified Arrhenius plots of temperature-depend-
ent (A) kCR and (B) kCS for [2]rotaxane 1 in PhCN and
THF.
ꢁꢂ
ing that the C60 moiety and BBAꢁþ moiety are generated via
3
ꢀ
the C60 moiety.
The quantum yields (ꢂCST) of formations of the CS state in
rotaxane 1 via the 3C60 moiety were estimated from the ratio
ꢀ
is slightly larger than the experimental errors included in our
experiments. From a semi-classical Marcus equation, the ET
rate constant kET can be described as follow (Eq. 6):36
ꢁꢂ
of the maximal absorbance at 1000 nm of the C60 moiety to
3
ꢀ
the initial absorbance at 700 nm of the C60 moiety by sub-
stituting each molar extinction coefficient;34,35 one can assume
that the initial absorbance at 700 nm is predominantly due to
lnðkETT1=2Þ ¼ lnf2p3=2jVj =½hðꢃkBÞ ꢅg ꢂ ꢁGz=ðkBTÞ: ð6Þ
2
1=2
3
ꢀ
the C60 moiety as shown in Fig. 9. If the initial absorbance
3
at 700 nm of the C60 may contain the absorption of BBAꢁþ
Here T, h, kB, jVj, ꢃ, and ꢁGz represent absolute temperature,
Planck constant, Boltzmann constant, electron coupling matrix
element, reorganization energy, and Gibbs activation energy in
ꢀ
T
moieties, the ꢂCS values calculated by this method should be
T
,min
minimum values of ꢂCST, which are refered to as ꢂCS
.
values are in the range of 0.60–0.70, respective-
T
T
T
Such ꢂCS
ly, as summarized in Table 2. Compared with ꢂCS less than
the Marcus theory. The plots of lnðkCS ꢃ T1=2Þ and lnðkCR
ꢃ
,min
S
T1=2Þ vs 1=T are shown in Fig. 10. Since the slopes are not
T
0.4, the overall CS process quantum yield via the 3C60 moiety
steep for rotaxane 1, the ꢁGz
0.10–0.11 and 0.03 eV were evaluated, as summarized in
and ꢁGz
values of
CR
ꢀ
CS
1
ꢀ
T
on the basis of the C60 moiety (ꢂCS ,total) can be calculated
T
to be (1 ꢂ ꢂCSS) ꢂCS ,min, which are in the range of 0.43–
Table 3. The ꢁGz values in rotaxanes 1 are smaller than
those for conventional dyad systems such as the retinyl–
CR
3
ꢀ
0.51. Thus, the CS process via C60 in [2]rotaxane 1, result-
ing in formation of (C60ꢁꢂ;BBAꢁþ
C60 (0.16 eV).37 The ꢁGz
values less than 0.03 V imply
T
)
rotaxane, is more effective
CS
1
ꢀ
than that via C60
.
that the CS process occurs without any appreciable energy
barrier.36
Temperature Effect. The charge-separation via 3C60 and
charge-recombination rate constants of rotaxane 1 showed
ꢀ
One reason for the quite small ꢁGz values may be that both
processes are dominated mainly by ‘‘through-space’’ electron-
transfer process between the C60 and BBA chromophores;
thus, there is little contribution from any ‘‘through-bond’’ elec-
tron-transfer process.37–39
T
slight temperature dependences. In PhCN and THF, the kCS
and kCR values decreased with decreasing temperature in each
solvent. For example, the kCR values decrease from 3:2 ꢃ 106
s
ꢂ1 at 30 ꢄC to 2:5 ꢃ 106 sꢂ1 at ꢂ50 ꢄC in THF; this difference

A. S. D. Sandanayaka et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005) 1015
3
ꢀ
Table 3. Activation Free Energy Changes for CS via C60
(ꢁGz T) and CR (ꢁGzCR) for [2]Rotaxane 1 in PhCN
and THF
system. This supports the efficient CS process between the
ꢀ
3C60 and BBA moieties spatially placed near each other
within [2]rotaxane.
Comparison with C60–BBA Dyads. For covalently bond-
CS
Solvent
ꢁGz T/eV
ꢁGzCR/eV
CS
ꢀ
ed C60–BBA, the CS process via the 1C60 moiety exclusively
THF
PhCN
0.11
0.10
0.03
0.03
S
S
takes place in polar solvents, since the kCS and ꢂCS values
were evaluated to be ð3:8{5:0Þ ꢃ 1010 sꢂ1 and 0.98 in THF
and PhCN,27 which are larger than the corresponding values
for [2]rotaxane 1, probably because of the large jVj values
for covalently bonded dyads.38,39 For the CR process of cova-
lently bonded C60–BBA, the major rapid and minor slow proc-
esses were observed;27 the rapid CR process can be also due to
large jVj values. Although the reliable Marcus parameters of
[2]rotaxane 1 were not evaluated in the present study,40 it is
reasonable to consider that the slower ET processes of rotax-
ane 1 may be ascribed to smaller jVj values compared with
those of the covalently connected dyads.
*
(1C60 ;BBA) rotaxane
toluene (1.80 eV)
S
kCS
1.75 eV
kISC
*
(3C60 ;BBA)
1.52 eV
THF (1.45 eV)
PhCN (1.34 eV)
T
kCS
(C60.-;BBA.+
)
rotaxane
hv
(532 nm)
Comparison with Other Rotaxanes. Compared with
(C60:TTP)rotaxane, in which the CS process predominantly takes
ꢀ
ꢀ
place via 3C60 (ca. 70%) compared with via 1C60 (<20%),26
kCR
1
ꢀ
the CS process of (C60:BBA)rotaxane via C60 increases up
3
ꢀ
to 36–38% with decrease in the CS process via C60 to
43–51%. This may be caused by higher donor ability of the
BBA moiety to C60 (kCS ¼ ð3:6{3:8Þ ꢃ 108 sꢂ1) than that
1
ꢀ
S
of TPA (kCS ¼ ð1{2Þ ꢃ 108 sꢂ1), probably because the area
S
( C60;BBA)rotaxane
T
of BBA is larger than that of TPA in [2]rotaxanes. The kCS
Fig. 11. Schematic energy diagram of [2]rotaxane 1.
values in THF and PhCN of (C60:BBA)rotaxane are slightly
smaller than those of (C60:TPA)rotaxane, probably because fluc-
tuation of the distance between the C60 and TPA moieties is
larger than that between the C60 and BBA moieties.26 The
Energy Diagrams. From the ꢁGCR and ꢁGS values in
CS
Tables 1 and 2 in addition to the energy levels of the lowest
excited singlet state, the energy diagram for [2]rotaxane 1 can
be schematically illustrated as shown in Fig. 11. The E0 values
ꢄRIP value of (C60ꢁꢂ;BBAꢁþ
)
in THF is longer than
rotaxane
those of (C60ꢁꢂ;TPAꢁþ
)rotaxane, which may be related to the
1
ꢀ
3
ꢀ
larger size of BBA, in which the radical cation was delocal-
ized.
of C60 and C60 are reported to be 1.75 and 1.52 eV, re-
spectively.31,34,35 The energy levels of (C60ꢁꢂ;BBAꢁþ
depend on the solvent polarity. Therefore, in toluene since
)
rotaxane
Compared with rotaxanes with C60 and porphyrin moieties18
and phthalocyanine moieties,17 in which the CS process takes
place mainly via the excited states of the porphyrin and phtha-
locyanine, we see that the CS process of (C60:amine)rotaxane
takes place via the excited state of the C60 moiety. For the
CS process of rotaxanes composed of the C60 and zinc porphy-
rin moiety, contribution of the CS process via the excited trip-
let state of zinc porphyrin moiety tends to increase with the
length of axle, because of increase in the fluctuation.18b In
the case of rotaxanes composed of Zn porphyrin as an electron
donor and Au porphyrins as an electron acceptor, a super-
exchange mechanism was confirmed.41 However, for rotaxane
1, no clear evidence showing the superexchange mechanism
was obtained, because of the rather smaller ꢂ-system of
BBA moiety.
the CS state of rotaxane 1 is slightly higher than the energy
1
ꢀ
3
ꢀ
level of C60 , no CS process was observed; thus, C60 is
generated via the ISC process as shown in Fig. 7.34 In THF
and PhCN, the CS states of rotaxane 1 are lower than the
1
ꢀ
3
ꢀ
energy levels of C60 and C60 ; thus, the CS process takes
1
ꢀ
in the ratio of (0.36–0.38):(0.43–0.51).
3
ꢀ
place both from the C60 and C60 moieties, producing
(C60ꢁꢂ;BBAꢁþ
)
rotaxane
The CR process is highly exothermic belonging to the inverted
region of the Marcus parabola.36
Comparison with C60–BBA Mixture System. When C60
was photoexcited in the presence of excess BBA in PhCN, it
was reported in our previous paper that intermolecular electron
3
ꢀ
transfer takes place via C60 with the rate constant of 6:5 ꢃ
108 molꢂ1 dm3 sꢂ1, which is one order smaller than the diffu-
sion-controlled limit.27 Thus, when the equimolar BBA to C60
Conclusion
(0.1 mmol dmꢂ3) is present in PhCN, kdecay
and krise
of C60
of C60 and BBAꢁþ can be calculated to be
6:5 ꢃ 108 ꢃ 10ꢂ4 sꢂ1 = 6:5 ꢃ 104 ꢂ1, which is almost the
of C60 in the absence of BBA. This
first-order
3
ꢀ
first-order
ꢁꢂ
For [2]rotaxane 1, the photoinduced CS process takes place
ꢀ ꢀ
both via the 3C60 moiety and via the 1C60 moiety, producing
s
same as kdecay
long-lived CS state (C60ꢁꢂ;BBAꢁþ
)
in polar solvents.
first-order
3
ꢀ
rotaxane
indicates that neither appreciable acceleration of the decay of
ꢀ
This is one of characteristics of the CS process of rotaxanes,
in which through-space electron transfer takes place, although
the contribution changes with the electron-donor abilities
and the fluctuation ability of the C60 and donors moieties in
rotaxanes.
ꢁꢂ
3C60 nor the appearance of C60 and BBAꢁþ was observed
in the mixture system. Inꢁ[ꢂ2]rotaxane 1 in PhCN, on the other
first-order
hand, krise
of C60 and BBAꢁþ was obtained to be
5:6 ꢃ 107 sꢂ1, which is ca. 1000 times larger than the mixture

1016 Bull. Chem. Soc. Jpn., 78, No. 6 (2005)
This lifetime of (C60ꢁꢂ;BBAꢁþ
was longer than
that of the covalently bonded C60–BBA dyad system in
THF. For the [2]rotaxane 1, through-space CS and CR pro-
cesses were also presumed from the low activation free-
energies, as evaluated experimentally by the temperature
dependence of the CS and CR rate constants.
PET of C60: Bis(4-biphenyl)aniline Rotaxane
2626 (1997). b) H. Imahori, K. Tamaki, D. M. Guldi, C. Luo,
M. Fujitsuka, O. Ito, Y. Sakata, and S. Fukuzumi, J. Am. Chem.
Soc., 123, 2607 (2001). c) H. Imahori, Y. Mori, and J. Matano,
J. Photochem. Photobiol., C, 4, 51 (2003). d) T. D. M. Bell,
T. A. Smith, K. P. Ghiggino, M. G. Ranasinghe, M. J. Shephard,
and M. N. Paddon-Row, Chem. Phys. Lett., 268, 223 (1997).
14 T. Da Ros, M. Prato, D. M. Guldi, E. Alessio, M. Ruzzi,
and L. Pasimeni, Chem. Commun., 1999, 635.
)
rotaxane
The present work was supported by Grants-in-Aid for
Scientific Research on Priority Areas (417) from the Ministry
of Education, Culture, Sports, Science and Technology of
Japan.
15 F. Diederich and M. G. Lopez, Chem. Soc. Rev., 28, 263
(1999).
16 P. Piotrowiak, Chem. Soc. Rev., 28, 143 (1999).
17 a) D. M. Guldi, J. Ramey, M. V. Martinez-Diaz, A. de la
Escosura, T. Torres, T. Da Ros, and M. Prato, Chem. Commun.,
2002, 2774. b) K. Li, D. I. Schuster, D. M. Guldi, M. A. Herranz,
and L. Echegoyen, J. Am. Chem. Soc., 126, 3388 (2004).
18 a) N. Watanabe, N. Kihara, Y. Furusho, T. Takata, Y.
Araki, and O. Ito, Angew. Chem., Int. Ed. Engl., 42, 681 (2003).
b) A. S. D. Sandanayaka, N. Watanabe, K. Ikeshita, Y. Araki, N.
Kihara, Y. Furusho, O. Ito, and T. Takata, J. Phys. Chem. B, 109,
2516 (2005).
19 a) J. W. Arbogast, C. S. Foote, and M. Kao, J. Am. Chem.
Soc., 114, 2277 (1992). b) L. Biczok and H. Linschitz, Chem.
Phys. Lett., 195, 339 (1992). c) S. Nonell, J. W. Arbogast, and
C. S. Foote, J. Phys. Chem., 96, 4169 (1992). d) C. A. Steren,
H. von Willigen, L. Biczok, N. Gupta, and H. Linschitz, J. Phys.
Chem., 100, 8920 (1996).
References
1
a) J.-M. Lehn, ‘‘Supramolecular Chemistry-Concepts
and Perspectives,’’ Wiley-VCH, Weinheim (1995). b) F. Vogtle,
¨
‘‘Supramolecular Chemistry,’’ Wiley, New York (1991).
2
K. M. Kadish and R. S. Ruoff, ‘‘Fullerenes,’’ John Wiley &
Sons, New York (2000), p. 225.
a) J.-M. Lehn, Angew. Chem., Int. Ed. Engl., 29, 1304
3
(1990). b) S. Hannessian, J. Am. Chem. Soc., 117, 7630 (1995).
c) K. R. Seddon and B. A. Christer, Chem. Soc. Rev., 22, 397
(1993).
´
D. M. Guldi and N. Martın, ‘‘Fullerene; From Synthesis
4
and Optoelectronic Propertie,’’ Kluver Academic Publisher,
Netherland (2002).
5 D. Gust, T. A. Moore, and A. L. Moore, Acc. Chem. Res.,
26, 198 (1993).
6 N. S. Sacriftci, L. Smilowitz, A. J. Heeger, and F. Wudl,
Science, 258, 1474 (1992).
20 a) O. Ito, Y. Sasaki, Y. Yoshikawa, and A. Watanabe,
J. Phys. Chem., 99, 9838 (1995). b) O. Ito, Res. Chem. Intermed.,
23, 389 (1997). c) Y. Yahata, Y. Sasaki, M. Fujitsuka, and O. Ito,
J. Photosci., 6, 11 (1999).
21 H. N. Ghosh, D. K. Palit, A. V. Sapre, and J. P. Mittal,
Chem. Phys. Lett., 265, 365 (1997).
7
a) T. Da Ros, M. Prato, D. M. Guldi, M. Ruzzi, and L.
Pasimeni, Chem.—Eur. J., 7, 816 (2001). b) D. M. Guldi, C.
Luo, T. Da Ros, M. Prato, E. Dietel, and A. Hirsch, Chem. Com-
mun., 2000, 375. c) D. M. Guldi, C. Luo, A. Swartz, M. Scheloske,
and A. Hirsch, Chem. Commun., 2001, 1066. d) F. Diederich and
G. M. Lopez, Chem. Soc. Rev., 28, 263 (1999). e) P. Piotrowiak,
Chem. Soc. Rev., 28, 143 (1999). f) G. Yin, D. Xu, and Z. Xu,
Chem. Phys. Lett., 365, 232 (2002). g) J. R. Weinkauf, S. W.
Cooper, A. Schweiger, and C. C. Wamser, J. Phys. Chem. A,
107, 3486 (2003). h) D. M. Guldi, H. Imahori, K. Tamaki, Y.
Kashiwagi, H. Yamada, Y. Sakata, and S. Fukuzumi, J. Phys.
Chem. A, 108, 541 (2004).
22 J. Senior, A. Z. Szarka, G. R. Smith, and R. M.
Hochstrasser, Chem. Phys. Lett., 185, 179 (1991).
23 G. E. Lawson, A. Kitaygorodskiy, and S. Ya-Ping, J. Org.
Chem., 64, 5913 (1999).
24 a) R. M. Williams, J. M. Zwier, and J. W. Verhoeven,
J. Am. Chem. Soc., 117, 4093 (1995). b) R. M. Williams, M.
Koeberg, J. M. Lawson, Y.-Z. An, Y. Rubin, M. N. Paddon-
Row, and J. W. Verhoeven, J. Org. Chem., 61, 5055 (1996).
25 H. Luo, M. Fujitsuka, Y. Araki, O. Ito, P. Padmawar, and
L. Y. Chiang, J. Phys. Chem. B, 107, 9312 (2003).
26 A. S. D. Sandanayaka, H. Sasabe, Y. Araki, Y. Furusho,
O. Ito, and T. Takata, J. Phys. Chem. A, 108, 5145 (2004).
27 S. Komamine, M. Fujitsuka, O. Ito, K. Moriwaki, T.
Miyata, and T. Ohno, J. Phys. Chem. A, 104, 11497 (2000).
28 a) Y. Shirota, K. Moriwaki, S. Yoshikawa, T. Ujike, and
H. Nakano, J. Mater. Chem., 8, 2579 (1998). b) S. Gauthier and
J. M. J. Frechet, Synthesis, 1987, 383.
29 M. J. Frich, G. W. Truck, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, V. G. Zakrzewski, J. A.
Montgomery, Jr., R. E. Stratmann, J. C. Burant, S. Dapprich, J.
M. Millam, A. D. Daniels, K. N. Kudin, M. C. Strain, O. Farkas,
J. Tomasi, V. Barone, M. Cossi, R. Cammi, B. Mennucci, C.
Pomelli, C. Adamo, S. Clifford, J. Ochterski, G. A. Petersson,
P. Y. Ayala, Q. Cui, K. Morokuma, D. K. Malick, A. D. Rabuck,
K. Raghavachari, J. B. Foresman, J. Cioslowski, J. V. Ortiz, A. G.
Baboul, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I.
Komaromi, R. Gomperts, R. L. Martin, D. J. Fox, T. Keith, M.
A. Al-Laham, C. Y. Peng, A. Nanayakkara, C. Gonzalez, M.
Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong,
J. L. Andres, C. Gonzalez, M. Head-Gordon, E. S. Replogle, and
8
a) F. D’Souza, G. D. Deviprasad, M. E. El-Khouly, M.
Fujitsuka, and O. Ito, J. Am. Chem. Soc., 123, 5277 (2001). b)
F. D’Souza, G. R. Deviprasad, M. E. Zandler, V. T. Hoang, K.
Arkady, M. Van Stipdonk, A. Perera, M. E. El-Khouly, M.
Fujitsuka, and O. Ito, J. Phys. Chem. A, 106, 3243 (2002). c) F.
D’Souza, G. R. Deviprasad, M. E. Zandler, M. E. El-Khouly,
M. Fujitsuka, and O. Ito, J. Phys. Chem. B, 106, 4952 (2002).
´
R. Ballardini, V. Balzani, M. Clemente-Leon, A. Credi,
9
M. T. Gandolfi, E. Ishow, J. Perkins, J. F. Stoddart, H. R. Tseng,
and S. Wenger, J. Am. Chem. Soc., 124, 12786 (2002).
10 P. Bernier and A. Hirsch, Carbon, 38, 1529 (2000).
11 a) K. Hutchinson, J. Gao, G. Schick, Y. Rubin, and F.
Wudl, J. Am. Chem. Soc., 121, 5611 (1999). b) J. M. Tour, Acc.
Chem. Res., 33, 791 (2000). c) R. M. Metzger, Acc. Chem. Res.,
32, 950 (1999). d) M. A. Fox, Acc. Chem. Res., 32, 201 (1999).
12 D. Gust, T. A. Moore, and A. L. Moore, Res. Chem.
Intermed., 23, 621 (1997).
13 a) H. Imahori, K. Yamada, M. Hasegawa, S. Taniguchi,
T. Okada, and Y. Sakata, Angew. Chem., Int. Ed. Engl., 36,

A. S. D. Sandanayaka et al.
Bull. Chem. Soc. Jpn., 78, No. 6 (2005) 1017
J. A. Pople, ‘‘Gaussian 98, Revision A.7,’’ Gaussian, Inc., Pitts-
burgh, PA (1998).
30 A. Watanabe, O. Ito, M. Watanabe, H. Saito, and M.
Koishi, Chem. Commun., 1996, 117.
31 M. M. Alam, A. Watanabe, and O. Ito, Bull. Chem. Soc.
Jpn., 70, 1833 (1997).
32 P. Belik, A. Gugel, A. Kraus, M. Walter, and K. Mullen,
¨
J. Org. Chem., 60, 3307 (1995).
33 A. Z. Weller, Phys. Chem. Neue Folge, 133, 93 (1982).
34 a) R. J. Senion, C. M. Phillips, A. Z. Szarka, W. J.
Romanow, A. R. McGhie, Jr., J. P. McCauly, A. P. Smith, and
R. M. Hochstrasser, J. Phys. Chem., 95, 6075 (1991). b) T. W.
Ebbesen, K. Tanigaki, and S. Kuroshima, Chem. Phys. Lett.,
181, 501 (1991). c) M. Lee, O.-K. Song, J.-C. Seo, D. Kim, Y.
D. Suh, S. M. Jin, and S. K. Kim, Chem. Phys. Lett., 196, 325
(1992).
35 C. Luo, M. Fujitsuka, A. Watanabe, O. Ito, L. Gan, Y.
Huang, and C.-H. Huang, J. Chem. Soc., Faraday Trans., 94,
527 (1998).
36 a) R. A. Marcus, J. Chem. Phys., 24, 966 (1956). b) R. A.
Marcus, J. Chem. Phys., 43, 679 (1965). c) R. A. Marcus and N.
Sutin, Biochim. Biophys. Acta, 811, 265 (1985).
37 M. Yamazaki, Y. Araki, M. Fujitsuka, and O. Ito, J. Phys.
Chem. A, 105, 8615 (2001).
38 a) C. Luo, D. M. Guldi, H. Imahori, K. Tamaki, and Y.
Sakata, J. Am. Chem. Soc., 122, 6535 (2000). b) S. Fukuzumi,
H. Imahori, H. Yamada, M. E. El-Khouly, M. Fujitsuka, O. Ito,
and D. M. Guldi, J. Am. Chem. Soc., 123, 2571 (2001). c) H.
Imahori, D. M. Guldi, K. Tamaki, Y. Yoshida, Y. C. Luo, Y.
Sakata, and S. Fukuzumi, J. Am. Chem. Soc., 123, 6617 (2001).
d) H. Imahori, K. Tamaki, Y. Araki, Y. Sekiguchi, O. Ito, Y.
Sakata, and S. Fukuzumi, J. Am. Chem. Soc., 124, 5165 (2002).
39 a) P. A. Lindell, D. Kuciauskas, J. P. Sumida, B. Nash, D.
Nguyen, A. L. Moore, T. A. Moore, and D. Gust, J. Am. Chem.
Soc., 119, 1400 (1997). b) D. Carbonera, M. D. Valentin, C.
Corvaja, G. Agostini, G. Giacometti, P. A. Liddell, D. Kuciauskas,
A. L. Moore, T. A. Moore, and D. Gust, J. Am. Chem. Soc., 120,
4398 (1998).
40 We evaluated electron coupling matrix elements in addi-
tion to the reorganization energies; although the coupling matrix
elements are in the region of 0.1 cmꢂ1, the reorganization energies
are also extremely small (ca. 0.1 eV). The strict application of
semi-classical Marcus equation (Eq. 6) can not be performed such
an electron transfer in the inverted region. Thus, we discussed
only on the basis of the activation energies in the present study.
41 A. Andersson, M. Linke, J.-C. Chambron, J. Davidsson, V.
Heitz, J.-P. Sauvage, and L. Hammarstrom, J. Am. Chem. Soc.,
122, 3526 (2000).
¨