Rod-like pyrene-perylene bisimide molecular triads: Synthesis and photophysical properties

Article abstract of DOI:10.1016/j.jphotochem.2010.02.006

Two rod-like pyrene-perylene bisimide triads with different linkers were synthesized and characterized. Their photophysical properties were investigated by UV-vis absorption, both steady-state and time-resolved emission. According to fluorescence excitati

Full text of DOI:10.1016/j.jphotochem.2010.02.006

Journal of Photochemistry and Photobiology A: Chemistry 211 (2010) 115–122
Contents lists available at ScienceDirect
Journal of Photochemistry and Photobiology A:
Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
Rod-like pyrene–perylene bisimide molecular triads: Synthesis and
photophysical properties
Jun-Hua Wana, Zhun Mab, Feng Liub, Zheng Xua, Hong-Yu Wangb, Hong-Ji Jiangc, Wei Huangc,∗
a Key Laboratory of Organosilicon Chemistry and Material Technology of Ministry of Education, Hangzhou Normal University, Hangzhou 310012, China
b Institute of Advanced Materials, Fudan University, Shanghai 200433, China
c Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications (NUPT), 66 XinMoFan Road, Nanjing 210003, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Two rod-like pyrene–perylene bisimide triads with different linkers were synthesized and character-
ized. Their photophysical properties were investigated by UV–vis absorption, both steady-state and
time-resolved emission. According to fluorescence excitation and time-resolved emission spectroscopic
studies, efficient intramolecular resonance energy transfer was observed in both triads. Furthermore, the
influence of the molecular structure on the energy transfer rates was also studied and discussed. To gain
insights into the intramolecular interactions and the electronic structures, the electronic structures of
both triads were investigated through theoretical calculation.
Received 1 November 2009
Received in revised form 21 January 2010
Accepted 12 February 2010
Available online 21 February 2010
Keywords:
Pyrene
Perylene bisimide
Energy transfer
Molecular triad
Linker
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
pyrene–perylene bisimide-based bichromophoric systems were
synthesized [26–27]. Furthermore, effective energy and electron
Design and synthesis of multicomponent molecules have
attracted much attention in the last two decades because of their
applications in artificial photosynthesis systems [1–2], molecular
machines [3–4], and optoelectronic devices [5–6]. One of the inter-
esting photophysical properties of the multicomponent molecules
is the highly efficient electron/energy transfer processes produced
by hybridization of different photoactive or redox-active chro-
mophores [7–10]. The induced intramolecular energy transfer
process can be adopted to extend the “virtual” Stokes’ shift for
fluorescent sensing and biochemical applications [11–13], whilst
the electron transfer process is crucial to create long-lived charge-
separated states for photovoltaic application [14–16].
transfer processes were observed in these systems. These observa-
tions open the door to investigations on pyrene–perylene bisimide
systems for the realization of corresponding optoelectronic devices
(such as photovoltaic cells). The rod-like pyrene–perylene bisimide
systems, however, have not received much attention [28–30]. The
fixed donor–acceptor distance and orientation in rod-like systems
would be expected to produce an obvious influence on photo-
induced processes [31–32]. Additionally, a highly rigid molecule
with a donor–acceptor structure would be useful in studying inter-
molecular interactions by self-assembly [33].
In this paper we describe the synthesis and photophysical
properties of
a bichromophoric system containing the bay-
During the past few years, perylene bisimide (Per) dyes have
been investigated widely as building blocks for photoactive sys-
tems, owing to their good thermal and photochemical stability,
high electron affinity, and fluorescence quantum yield of almost
unity [17–20]. Pyrene (Py) is another widely studied fluorophore
as a building block due to its durable electronic properties and long
excited singlet lifetimes [21–25]. Recently, several flexibly linked
functionalized perylene bisimide moiety as the acceptor and two
pyrene moieties as donors. Two pyrene moieties are linked to the
perylene bisimide core via phenylene linkers to form a triad struc-
ture (Py-Per-Py) (see Scheme 1). This rigid structure compared to
the flexibly linked pyrene–perylene bisimide system could pro-
duce a distinct effect on photophysical behavior and photo-induced
reactions. In another pyrene–perylene bisimide system (Py-e-Per-
e-Py), pyrene moieties are connected with the perylene bisimide
core by way of phenylethyne linkers. For this triad, the pyrene
moieties are expected to rotate freely around the ethylene bond.
Introduction of the ethylene bond produced interesting differences
in the photophysical and photo-induced processes between the
two different triads. The monolayer assembly and electronic states
∗
Corresponding author. Tel.: +86 025 85866396/85866360;
fax: +86 025 85866396.
E-mail addresses: wei-huang@njupt.edu.cn,
iamdirector@fudan.edu.cn (W. Huang).
1010-6030/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jphotochem.2010.02.006

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J.-H. Wan et al. / Journal of Photochemistry and Photobiology A: Chemistry 211 (2010) 115–122
Scheme 1. Structures of triads.
for the two triads have also been investigated by scanning tun-
neling microscopy and spectroscopy (STM/STS) at the liquid/solid
interface [34].
pound 1 [35] and 2 [36–37] were synthesized according to the
literature.
1H and 13C NMR spectra were collected on 400 MHz and
100 MHz spectrometers, respectively, with tetramethylsilane as
the internal standard. Matrix-assisted laser desorption ionization-
time-of-flight (MALDI-TOF) mass spectrometry experiments were
carried out using a Shimadzu AXIMA–CFRTM Plus time-of-flight
mass spectrometer (Kratos Analytical, Manchester, UK). UV–vis
spectra were recorded on a Shimadzu 3150 PC spectrophotometer.
Steady-state emission experiments were carried out on a Shimadzu
RF-5301 PC spectrophotometer with a xenon lamp as a light source.
2. Experimental
2.1. Materials and equipment
All of the chemicals and reagents were purchased from a com-
mercial supplier and used without further purification. The solvents
(THF and CH2Cl2) were dried according to standard methods. Com-
Scheme 2. Reaction conditions: (i) Pd(PPh3)4, 1 M Na2CO3/THF, 50 ◦C; (ii) Pd(PPh3)4/CuI, Et3N/THF, 80 ◦C.

J.-H. Wan et al. / Journal of Photochemistry and Photobiology A: Chemistry 211 (2010) 115–122
117
Fig. 1. 1HNMR spectra in the aromatic range for the two triads.
Time-resolved emission studies were performed with an Edinburgh
FL 920 photon counting system with a hydrogen-filled lamp as the
excitation source. The data were analyzed by iterative convolution
of the luminescence decay profile with the instrument response
function, using a software package provided by Edinburgh Instru-
ments.
MASS (MALDI-TOF, dithranol): 1535.1 (calcd. for C102H82N2O8:
1535.8).
2.3.2. Py-e-Per-e-Py
A mixture of compound 1 (138 mg, 0.1 mmol), Pd(PPh3)4 (15 mg,
0.013 mmol) and CuI (3 mg, 0.016 mmol) was placed in a two-
necked, round-bottom flask fitted with a condenser. The entire
setup was degassed and back-filled with a gaseous mixture of
argon. To the reaction flask was added previously degassed 5 mL of
THF and TEA (10 ml) using syringes. The 1-ethylenepyrene (68 mg,
0.3 mmol) was dissolved in 5 mL of THF and added to the reaction
mixture at about 60 ◦C (bath temperature). The reaction mixture
was then stirred at reflux overnight under the atmosphere of the gas
mixture. The solvents were evaporated and the residue was puri-
fied by column chromatography using dichloromethane/petroleum
ether (1:1) as eluent to give the product as a purple solid (73 mg).
Isolated yield: 46%. 1H NMR (400 MHz, CDCl3) ı 8.67–8.64 (d, 2H),
8.28 (s, 4H), 8.40–8.03 (m, 16H), 7.84–7.82 (d, 4H), 7.34–7.32 (d,
4H), 7.25–7.24 (d, 8H), 6.88–6.85 (m, 8H), 1.25 (s, 36H). 13C NMR
(100 MHz, CDCl3) ı 163.7, 156.3, 153.0, 147.7, 139.5, 137.2, 133.4,
132.7, 132.2, 131.6, 129.9, 129.0, 128.6, 127.5, 126.9, 126.5, 125.9,
124.7, 122.6, 121.0, 120.4, 119.5, 117.9, 94.5, 89.8, 34.6, 31.2, 29.9.
MASS (MALDI-TOF, dithranol): 1583.1 (calcd. for C112H82N2O8:
1583.8).
2.2. Molecular orbital calculations
All geometries were initially optimized with MM2 method com-
bined in ChemBioOffice 2008 with default set, and then by the
semi-empirical AM1 method. The obtained optimized geometries
were finally re-optimized with ab initio HF method at 3–21 g level.
The frontier orbitals were depicted with 0.01 isocontour based on
HF/3–21 g level. All the calculation is done using Gaussian 03 soft-
ware package.[38]
2.3. Synthesis
2.3.1. Py-Per-Py
A mixture of 1-pyrene boronic ester (97 mg, 0.3 mmol), com-
pound 1 (138 mg, 0.1 mmol), and Pd(PPh3)4 (15 mg, 0.013 mmol)
catalyst in 5 mL of 1 M aqueous K2CO3 solution and THF (v/v, 1:1)
was placed in a two-necked, round-bottom flask fitted with a
condenser. The entire setup was degassed and back-filled with a
gaseous mixture of argon. Then the reaction mixture was heated
to reflux for 24 h. After being cooled to room temperature, the
mixture was extracted with 10 mL of CHCl3 three times. The com-
bined organic phase was washed with brine, dried over MgSO4,
and concentrated. The residue was purified by column chromatog-
raphy using a mixture of dichloromethane/petroleum ether (1:1)
as eluent to give the product as a deep red solid (87 mg). Isolated
yield: 57%. 1H NMR (400 MHz, CDCl3) ı 8.32 (s, 4H), 8.24–8.15 (m,
8H), 8.10 (s, 4H), 8.04–8.01 (m, 6H), 7.76–7.74 (d, 4H), 7.45–7.43
(d, 4H), 7.28–7.25 (d, 8H), 6.92–6.90 (d, 8H), 1.25 (s, 36H). 13C
NMR (100 MHz, CDCl3) ı 164.0, 156.4, 153.0, 147.7, 141.8, 136.9,
134.5, 133.2, 131.6, 131.2, 131.0, 128.7, 127.8, 126.9, 126.2, 125.4,
125.1, 125.0, 124.8, 122.7, 121.0, 120.4, 119.6, 53.6, 34.6, 31.0.
3. Result and discussion
3.1. Synthesis
Scheme 2 shows the synthetic routes of both triads. The
approach to the synthesis of the target molecules Py-Per-Py
and Py-e-Per-e-Py involves palladium-catalyzed coupling reac-
tions. N,Nꢀ-i-4-iodiobenzene-1,6,7,12-tetrakis(4-t-butyl-pheoxy)-
3,4:9,10-tetracarboxdiimide (1) was selected as the perylene
building block due to its good solubility and ease of synthe-
sis. After precipitating from methanol, Py-Per-Py was obtained
with 57% yield by coupling compound 1 with 1-pyreneboronic
acid ester by the Suzuki coupling reaction. Py-e-Per-e-Py was

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J.-H. Wan et al. / Journal of Photochemistry and Photobiology A: Chemistry 211 (2010) 115–122
Fig. 2. The absorption spectra for the two triads, compound 2, pyrene and pyrene-
like monomer (1-trimethylsilylacetylenepyrene) in CH2Cl2 (1 × 10−5 M).
prepared through the Sonogashira coupling reaction. In the first
step, the 1-ethynylpyrene building block was synthesized from
1-bromopyrene by a Sonogashira coupling with trimethylsily-
lacetylene [39]. Our initial attempt to synthesize Py-e-Per-e-Py
through cross-coupling of 1-ethynylpyrene with compound 1
under the Sonogashira reaction conditions led to self-coupling of
1-ethynylpyrene to give the corresponding dimer in unacceptable
yield [40]. It is well-known that self-coupling of terminal alkynes
usually occurs as a side-reaction alongside cross-coupling [41–42].
The ethyne-linked pyrene dimer was not easy to remove by column
chromatography due to its low solubility in common solvents. To
reduce the self-coupling reaction, the procedure of reagent addition
was also changed. The solution of 1-ethylenepyrene in anhydrous
THF was added slowly to the reaction mixture at refluxing temper-
ature by a syringe. Following this improved method, Py-e-Per-e-Py
was obtained by coupling 1-ethynylpyrene with I-Per-I, in the pres-
ence of Pd(PPh3)4/CuI in THF/Et3N (v/v = 1:1), with isolated yields
of 46%.
Fig. 3. The emission spectra for the two triads in toluene and CH2Cl2. (1 × 10−5 M)
(a) for Py-Per-Py and (b) for Py-e-Per-e-Py.
The structure and purity of the two triads were verified by 1H
and 13C NMR, MALDI-TOF MS. The fingerprint of these molecules
was given by the 1HNMR spectra. In particular, for Py-e-Per-e-Py a
doublet was found at 8.67 ppm, corresponding to the proton located
at the 2-position of the two pyrene moieties. Both triads exhib-
ited a characteristic single signal at around 8.30 ppm (8.32 ppm
for Py-Per-Py and 8.28 ppm for Py-e-Per-e-Py). In both cases, the
singlet can be attributed to the perylene moiety. The multiple sig-
nals between 8.4 to 8.0 ppm were assigned to the other protons of
pyrene moieties for both triads (see Fig. 1). It is noteworthy that
the quaternary ethynyl carbon that resonates at 94.5 and 89.8 ppm
for Py-e-Per-e-Py in 13C NMR spectra was identified.
3.2. Optical properties
3.2.1. Steady-state spectroscopy
Spectroscopic properties of the two triads were investigated
with UV–vis absorption, excitation and fluorescence emission. The
absorption spectra of two triads and corresponding monomers in
CH2Cl2 solutions are depicted in Fig. 2, and the absorption data
are summarized in Table 1. Both triads exhited several absorption
bands. For Py-Per-Py, the absorption bands in the longer wave-
length range (above 400 nm) came from the perylene bisimide
moiety [43–44]: 447 nm (belonging to the S0–S2 electronic tran-
Table 1
The photophysical properties for two triads.
Compound
Solvents
Absorption (nm)a
Emissionb
c
c
ꢀ (nm)
ꢀ (nm)
ꢁPy (ns)
ꢁPer (ns)
Toluene
DCM
344, 445, 534, 578
346, 447, 540, 582
400
400
602
610
3.25
1.13
4.07
1.19
Py-Per-Py
Py-e-Per-
e-Py
Toluene
DCM
366, 390, 447, 537, 578
366, 386, 452, 541, 582
602
610
3.50
1.13
7.58
1.06
400
2
DCM
448, 537, 573
610
6.53d
a
Measured in solution (1 × 10−5 M).
b
c
The excitation wavelengths are 344 (toluene) and 346 (DCM) nm for Py-Per-Py, 366 nm for Py-e-Per-e-Py.
The excitation wavelength is 370 nm.
Cited from Ref. [35].
d

J.-H. Wan et al. / Journal of Photochemistry and Photobiology A: Chemistry 211 (2010) 115–122
119
Fig. 4. UV/Vis absorption (green line) and fluorescence excitation spectra (blue line, ꢀex = 602 nm in toluene and 610 nm in CH2Cl2, respectively), (a) and (b) for Py-Per-Py
in toluene and CH2Cl2 solution, respectively; (c) and (d) for Py-e-Per-e-Py in toluene and CH2Cl2 solution, respectively.
sition), 540 and 582 nm (belonging to S0–S1 electronic transition).
The other absorption band (346 nm) came from the ␲–␲ transi-
tion of the pyrene moieties. Surprisingly, the absorption of the
pyrene moiety in this triad was obviously different from that of
the pyrene monomer, and exhibited no fine structure besides the
minor bathochromic shift of 9 nm for the absorption of the pery-
lene moiety. The vibration fine structure in Py-Per-Py system is
destroyed by swinging for aromatic ring around the C(Py)-C(pheny)
bond. Py-e-Per-e-Py had almost the same absorption spectrum
for the perylene moiety as Py-Per-Py; but the absorption spec-
trum for the pyrene moiety in Py-e-Per-e-Py exhibited distinct
fine structures. The fine structures come from different conformers
populating in solution. The conformation with pyrene and benzene
rings in phenylethynylpyrene are perpendicular to each other is
most stable (see Section 3.4). The other is a transition state for the
rotation of an aromatic ring around C–C triple bond due to very low
barrier. The absorption bands for both triads in toluene showed no
remarkable differences compared with those in CH2Cl2.
The emission spectra of the two triads in toluene solutions at
room temperature were recorded upon excitation at 344 nm for
Py-Per-Py, and 366 nm for Py-e-Per-e-Py, where the correspond-
ing pyrene-like units had a strong absorption (see Fig. 3). Both triads
had an emission maximum around 602 nm, typical of the pery-
lene moiety. However, no emissions from pyrene moieties between
360 to 500 nm were detected for both triads. This result indicates
that effective energy transfer from Py* to Per* occurred. At the
same time, the emission spectra of the two triads were also inves-
tigated in weakly polar solvent CH2Cl2. The emission maximum
was slightly red-shifted (10 nm) in comparison with that in the
nonpolar solvent toluene. The local excited state of Per would be
relatively polar than the ground state. Hence, the small red shift
of the emission may be ascribed to the stabilization of Per* by the
polar solvent.
The energy transfer process could also be confirmed by the flu-
orescence excitation spectrum (Fig. 4). Although energy transfer
was not quite complete in this system, the spectral profiles were
closely comparable for them in both polar and nonpolar solvents. In
the region of perylene bisimide absorption bands between 400 and
600 nm, the fluorescence excitation spectra exhibited a good match
with the corresponding UV/Vis absorption spectrum, whereas a sig-
nificantly reduced intensity was observed for the pyrene bands.
These results indicate that another photo-induced reaction may be
occur besides the energy transfer process. It is worth noting that,
based on the integrated intensities from 320 to 380 nm for Py-Per-
Py and 320 to 410 nm for Py-e-Per-e-Py, the energy transfer from
Py* to Per* was more efficient in toluene than that in CH2Cl2, espe-
cially for Py-e-Per-e-Py. Generally, the energy transfer process is
independent of the polarity of the solvent. The difference might
arise from the existence of electron transfer (from Py* to CS–charge
separation states, which is more stabilized by the polar solvent). It
is expected that efficient electron transfer reactions can occur in a
covalently linked donor-acceptor system, especially for the rod-like
donor-acceptor-donor triads [45–47]. The emissions in different
polar solvents can indirectly show the existence of this process.
The emission spectra of the perylene bisimide moieties are more
strongly quenched in CH2Cl2 compared to those in toluene for both
triads upon excitation at the same wavelength (344 and 578 nm for
Py-Per-Py, 366 and 578 nm for Py-e-Per-e-Py).

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J.-H. Wan et al. / Journal of Photochemistry and Photobiology A: Chemistry 211 (2010) 115–122
Fig. 5. Time-resolved emission of the triads in toluene and dichloromethane (ꢀex = 370 nm). (a) decaying lifetime of the pyrene moiety of Py-Per-Py measured at 400 nm;
(b) decaying lifetime of the pyrene-like moiety of Py-e-Per-e-Py measured at 408 nm; (c) and (d) decaying lifetime of the perylene bisimide moiety of two triads measured
at 602 nm in toluene and 610 nm in CH2Cl2, respectively.
3.2.2. Time-resolved emission
transfer processes may be in existence for the two triads besides
energy transfer.
The fluorescence lifetimes for Py-Per-Py and Py-e-Per-e-Py at
room temperature were recorded upon excitation at 370 nm. Fig. 5
shows the fluorescence kinetic curves of the two triads in both
toluene and dichloromethane solutions (Table 1). All fluorescence
lifetimes measured followed monoexponential decay. The fluores-
cent states associated with the pyrene moiety have remarkably
shorter lifetimes than that of the pyrene monomer. On this basis,
it appears that photons collected by the appended pyrene poly-
cycles are transferred mostly to the perylene bisimide moiety. The
lifetimes for the pyrene moieties, recorded at 400 nm, change in sol-
vents of different polarity and are remarkably shorter (about 3-fold)
in CH2Cl2 than in toluene. In the same way, the lifetimes for Per* of
the two triads, recorded at 610 nm in CH2Cl2, are also much shorter
in comparison with that of perylene bisimide monomer (compound
2, 6.53 ns)[35]. This observation further suggests that the electron
3.3. Förster energy transfer
According to the steady-state and time-resolved spectroscopic
studies, there is energy transfer from Py* to the Per* in Py-Per-Py
and Py-e-Per-e-Py triads. The following observations support this
conclusion. (1) Both triads exhibit only one maximum emission,
and this emission maximum is clearly independent of the excita-
tion wavelength. (2) The fluorescence excitation spectra match the
corresponding UV/Vis absorption spectrum in the area of the pery-
lene bisimide absorption bands between 400 and 600 nm, in spite
of a significantly reduced intensity for the pyrene bands. (3) The Py*
lifetimes for both triads (1.13 ns in CH2Cl2) are much shorter than
the lifetimes for the corresponding reference monomers (pyrene
and 1-trimethylsilylacetylenepyrene, ꢁF = 650 and 55 ns, respec-
tively) [22,26].
For the two triads, the pyrene polycyclics are attached at two end
positions of the perylene core, which are the nodes of the electronic
energy level (HOMO/LUMO). The ethynylene connector in Py-e-
Per-e-Py could not act as an effective conduit for through-bond
interactions due to the node [48–49]. The dominating mechanism
is intramolecular energy transfer via the through-space exchange
mechanism (Förster-type energy transfer, TS). In general, the rate
of energy transfer depends on the extent of spectral overlap of the
emission spectrum of the donor with the absorption spectrum of
the acceptor, the quantum yield of the donor, the relative orienta-
tion of the donor and acceptor transition dipoles, and the distance
between the donor and acceptor molecules [50]. The rate constant
(kF) for Förster-type energy transfer can be expressed in terms of
Table 2
Parameters used to calculate the rate constants for Förster-type energy transfer in
the two triads.
Parameter
Py-Per-Pya
Py-e-Per-e-Pya
b
ФF
0.65
650
13.0
1.53
0.86
55
14.5
1.95
ꢁF (ns)b
RCC (Å)c
JF (1014 M−1 cm−1 nm4)
R0 (Å)
33.5
44.6
KF (s−1
)
4.5 × 109
4.5 × 1010
a
Refers to singlet energy transfer from the pyrene monomer to the S2 state
localized on the perylene bisimide.
b
Fluorescence quantum yield and lifetime for pyrene and 1-
trimethylsilylacetylenepyrene.
c
Average center-to-center separation distance derived from the optimized struc-
tures at AM1 level.

J.-H. Wan et al. / Journal of Photochemistry and Photobiology A: Chemistry 211 (2010) 115–122
121
Fig. 6. Energy minimized structure calculated showing the distribution, for Py-Per-Py: HOMO (top left), LUMO (top right); for Py-e-Per-e-Py: HOMO (bottom left) and LUMO
(bottom right).
Eq. (1):
where K, n, ˚F, JF are the same as those above-mentioned. Thus,
Förster distances were calculated as 33.5 and 44.6 Å for Py-Per-Py
and Py-e-Per-e-Py, respectively.
(8.8 × 10−25)ꢂFK2
kF
=
JF
(1)
n4ꢁFRC6C
3.4. Optimized molecular structures
where
ꢀ
To gain insights into the intramolecular interactions and the
electronicstructures, theoretical calculations have beenperformed.
The optimized structures are shown in Fig. 6. The highest-occupied
molecular orbital (HOMO) and the lowest-unoccupied molecular
orbital (LUMO) for the triads obtained by using the same method
are also shown in Fig. 6. The HOMO was found to be entirely located
on the pyrene-like moieties, while the LUMO was found to be
entirely located on the perylene bisimide moieties for both triads.
These findings suggest that in the charge-separated state the radi-
cal cation is localized on the pyrene moiety, while the radical anion
is localized on the perylene bisimide moiety. Moreover, the absence
of HOMOs on perylene bisimide and LUMOs on the pyrene-like moi-
ety suggests weak charge-transfer-type interactions between the
donor and acceptor entities of the triad in the ground state. It is
noted that the HOMO of Py-e-Per-e-Py involve the ethynyl group
and the phenylene ring. We can safely conclude, therefore, that the
pyrene with the ethynyl group and the phenylene ring act coop-
eratively as a single chromophore and that the corresponding S1
state is delocalized over the entire substituent moiety. It is con-
ceivable that introducing the ethynylene bond into the rod-like
pyrene–perylene bisimide system produced a remarkable influ-
ence on the photophysical properties.
∞ FD(ꢃ) ∈ A(ꢃ)ꢃ−4 dꢃ
0
JF
=
ꢀ
∞ FD(ꢃ) dꢃ
0
and
n
is the refractive index of the surrounding solvent
(nDCM = 1.4240), ˚F refers to the quantum yield of the donor in the
absence of acceptor (pyrene and 1-trimethylsilylacetylenepyrene,
˚F = 0.65 and 0.86, respectively), ꢁF is the lifetime of the donor
in the absence of acceptor, RCC is the center-to-center separa-
tion distance between the donor and acceptor (13 Å for Py-Per-Py
and 14.5 Å for Py-e-Per-e-Py, obtained from calculations), K2 is
their mutual orientation factor, and generally assumed as 2/3 in
calculations, and JF is the spectral overlap integral of the donor
emission and the acceptor absorption (1.53 × 1014
M
−1 cm−1 nm4
for Py-Per-Py and 1.95 × 1014 M−1 cm−1 nm4 for Py-e-Per-e-Py).
The parameters used to calculate the Förster-type energy trans-
fer rates are collected in Table 2. According to Eq. (1), the
energy transfer rates for both triads can be obtained, 4.5 × 109 s−1
for Py-Per-Py and 4.5 × 1010 s−1 for Py-e-Per-e-Py in CH2Cl2.
The former is 10-fold smaller than the latter. Therefore, the
energy transfer in Py-e-Per-e-Py is much quicker than that in
Py-Per-Py.
Generally, for Förster-type energy transfer, the distance
between the donor (D) and acceptor (A) plays an important role.
The distance at which energy transfer is 50% efficient, called the
Förster distance, is typically in the range of 20–60 Å. The Förster
distance can be obtained from Eq. (2):
4. Conclusion
The rod-like pyrene–perylene bisimide triads were synthesized
and characterized. The steady-state and time-resolved emission
spectroscopy studies gave clear proof that there is energy transfer
from Py* to the Per* in Py-Per-Py and Py-e-Per-e-Py triads. More-
R0 = 0.211[K2n−4˚FJF]1/6
(2)

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J.-H. Wan et al. / Journal of Photochemistry and Photobiology A: Chemistry 211 (2010) 115–122
over, the energy transfer process for the latter is 10-fold faster than
that of the former. The pyrene moieties can rotate freely around
the connecting ethynylene bond in the Py-e-Per-e-Py triad, but
only swing in Py-Per-Py triad, resulting in differences in the pho-
tophysical properties.
[26] B.K. Kaletas, R. Dobrawa, A. Sautter, F. Würthner, M. Zimine, L.D. Cola, R.M.
Williams, J. Phys. Chem. A 108 (2004) 1900.
[27] Y.J. Li, H. Li, Y.L. Li, H.B. Liu, S. Wang, X.R. He, N. Wang, D.B. Zhu, Org. Lett. 7
(2005) 4835.
[28] W. Wolfgang, Ger. Offen. DE. 2237539 19740214, February 14, 1974.
[29] R. Setsu, S. Hirota, S. Mitsuru, Jpn Kokai Tokkyo Koho. JP. 62005672 A 19870112
Showa, January 12, 1987.
[30] J.A. Mikroyannidis, M.M. Stylianakis, M.S. Roy, P. Suresh, G.D. Sharma, J. Power
Sources 194 (2009) 1171.
[31] B. Paulson, K. Hamod, P. Eaton, G. Closs, J.R. Miller, J. Phys. Chem. 97 (1993)
13042.
[32] D.I. Schuster, P. Cheng, S.R. Wilson, V. Prokhorenko, M. Katterle, A.R. Holzwarth,
S.E. Braslavsky, G. Klihm, R.M. Williams, C.P. Luo, J. Am. Chem. Soc. 121 (1999)
11599.
Acknowledgement
The authors wish to thank Prof. M. Kira (Tohoku University,
Japan) for his helpful discussion.
[33] P. Samori, A. Fechtenkotter, E. Reauther, M.D. Waston, N. Severin, K. Müllen, J.P.
Rabe, Adv. Mater. 18 (2006) 1317.
References
[34] Y.B. Li, J.H. Wan, G.C. Qi, K. Deng, Y.L. Yang, Q.D. Zeng, W. Huang, C. Wang, Chem.
Phys. Lett. 474 (2009) 132.
[35] H.Y. Wang, K.Y. Pu, S. Wang, F. Liu, B. Peng, W. Wei, React. Funct. Polym. 69
(2009) 117.
[36] C. Atienza, B. Insuasty, C. Seoane, N. Martín, J. Ramey, G.M.A. Rahmand, D.M.
Guldi, J. Mater. Chem. 15 (2005) 124.
[1] C.-C. Chu, D.M. Bassani, Photochem. Photobiol. Sci. 7 (2008) 521.
[2] A.C. Benniston, A. Harriman, Mater. Today 11 (2008) 26.
[3] H. Tian, Q.-C. Wang, Chem. Soc. Rev. 35 (2006) 361.
[4] V. Balzani, A. Credi, M. Venturi, Molecular Devices and Machines—Concepts and
Perspectives for the Nanoworld, Wiley-VCH, Weinheim, 2008.
[5] J.L. Segura, N. Martín, D.M. Guldi, Chem. Soc. Rev. 34 (2005) 31.
[6] S.-C. Lo, P.L. Burn, Chem. Rev. 107 (2007) 1097.
[37] D. Dotcheva, M. Klapper, K. Müllen, Macromol. Chem. Phys. 195 (1994) 1905.
[38] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheese-
man, J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S.
Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox, H.P.
Hratchian, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Strat-
mann, O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K.
Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich,
A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K. Raghavachari,
J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford, J. Cioslowski, B.B. Ste-
fanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith,
M.A. Al-Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill, B. John-
son, W. Chen, M.W. Wong, C. Gonzalez, J.A. Pople, Gaussian 03, Revision D.01,
Gaussian Inc., Wallingford, CT, 2004.
[7] M.R. Wasielewski, Chem. Rev 92 (1992) 435.
[8] F. Vogtle, J.F. Stoddart, M. Shibasaki, Electron and energy transfer, in: M.N.
Paddon-Row (Ed.), Stimulating Concepts in Chemistry, Wiley-VCH, New York,
2000, pp. 267–291.
[9] D. Gust, T.A. Moore, A.L. Moore, Acc. Chem. Res. 34 (2001) 40.
[10] D.M. Guldi, Chem. Soc. Rev. 31 (2002) 22.
[11] H.C. Kang, R.P. Haugland, U.S. Patent 5451663, September 19, 1995.
[12] C. Goze, G. Ulrich, L. Charbonnie‘re, M. Cesario, T. Prange, R. Ziessel, Chem. Eur.
J. 9 (2003) 3748.
[13] G.S. Jiao, L.H. Thoresen, K. Burgess, J. Am. Chem. Soc. 125 (2003) 14668.
[14] M.A. Loi, P. Denk, H. Hoppe, H. Neugebauer, C. Winder, D. Meissner, C. Brabec,
N.S. Sariciftci, A. Gouloumis, P. Vázquezb, T. Torres, J. Mater. Chem. 13 (2003)
700.
[15] J.E. Mose, Nat. Mater. 4 (2005) 723.
[16] Y. Eichen, G. Nakhmanovich, O. Epshtein, E. Ehrenfreund, J. Phys. Chem. B 104
(2000) 770.
[39] M. Hissler, A. Harriman, A. Khatyr, R. Ziessel, Chem. Eur. J. 5 (1999) 3366.
[40] A.C. Benniston, A. Harriman, D.J. Lawrie, S.A. Rostron, Eur. J. Org. Chem. 10
(2004) 2272.
[17] R. Dobrawa, F. Würthner, Chem. Commun. 17 (2002) 1878.
[18] A. Sautter, B.K. Kaletas, D.G. Schmid, R. Dobrawa, M. Zimine, G. Jung, H.M. Ivo,
van. Stokkum, L.D. Cola, R.M. Williams, F. Würthner, J. Am. Chem. Soc. 125
(2005) 6719.
[19] A. Herrmann, T. Weil, V. Sinigersky, U.M. Wiesler, T. Vosch, J. Hofkens, F.C. De.
Schryver, K. Müllen, Chem. Eur. J. 7 (2001) 4844.
[20] Y. Zhang, Z. Xu, L.Z. Cai, G.Q. Lai, H.X. Qiu, Y.J. Shen, J. Photochem. Photobiol. A
200 (2008) 334.
[21] J.Y. Li, M.L. Peng, L.P. Zhang, L.Z. Wu, B.J. Wang, C.H. Tung, J. Photochem. Pho-
tobiol. A 150 (2002) 101.
[41] K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett. 16 (1975) 4467.
[42] C.S. Wang, L.O. Palsson, A.S. Batsanov, M.R. Bryce, J. Am. Chem. Soc. 128 (2006)
3789.
[43] R. Gvishi, R. Reisfeld, Z. Burshtein, Chem. Phys. Lett. 213 (1993) 338.
[44] D. Liu, S. De Feyter, M. Cotlet, A. Stefan, U.M. Wiesler, A. Herrmann, D.
Grebel-Koehler, J. Qu, K. Mullen, F.C. De Schryver, Macromolecules 36 (2003)
5918.
[45] M.P. O’Neil, M.P. Niemczyk, W.A. Svec, D. Gosztola, G.L. Gaines, M.R.
Wasielewski, Science 257 (1992) 63.
[46] D. Gosztola, M.P. Niemczyk, M.R. Wasielewski, J. Am. Chem. Soc. 120 (1998)
5118.
[22] A. Harriman, G. Izzet, R. Ziessel, J. Am. Chem. Soc. 128 (2006) 10868.
[23] S. Bernhardt, M. Kastler, V. Enkelmann, M. Baumgarten, K. Müllen, Chem. Eur.
J. 12 (2006) 6117.
[47] S. Prathapan, S. Ik Yang, J. Seth, M.A. Miller, D.F. Bocian, D. Holten, J.S. Lindsey,
J. Phys. Chem. B 105 (2001) 8237.
[24] S.W. Yang, A. Elangovan, K.C. Hwang, T.I. Ho, J. Phys. Chem. B 109 (2005) 16628.
[25] A.S.D. Sandanayaka, Y. Araki, O. Ito, G.R. Deviprasad, P.M. Smith, L.M. Rogers,
M.E. Zandler, F. D’Souza, Chem. Phys. 325 (2006) 452.
[48] F. Würthner, Chem. Commun. 14 (2004) 1564.
[49] M.J. Ahrens, M.J. Tauber, M.R. Wasielewski, J. Org. Chem. 71 (2006) 2107.
[50] T. Förster, Ann. Phys. 2 (1948) 55.