Synthesis, electrochemical, and spectroscopic properties of soluble perylene monoimide diesters

Article abstract of DOI:10.1016/j.tet.2008.02.104

Perylene derivatives are an important class of n-type semiconductors. With the exceptions of bay-substituted and N-swallow-tail alkyl/tert-butyl substituted derivatives, most perylene diimides are insoluble. The recently reported perylene tetraesters are highly soluble, but are less electron-deficient. In this paper, a series of perylene monoimide diesters have been synthesized, which have good solubility and acceptable electron-accepting property due to the introducing of imide and ester groups in one perylene molecule. Their electrochemical properties and structural ordering were examined by cyclovoltammetry and X-ray diffraction technique, respectively. Their absorption and emission spectra are reported and discussed.

Full text of DOI:10.1016/j.tet.2008.02.104

Tetrahedron 64 (2008) 5404–5409
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis, electrochemical, and spectroscopic properties of soluble perylene
monoimide diesters
,
,
b
,
a
,
,b,
Lanying Yang a b, Minmin Shi a , Mang Wang b, Hongzheng Chen a
*
*
a Department of Polymer Science and Engineering, State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, PR China
b Key Laboratory of Macromolecule Synthesis and Functionalization, Zhejiang University, Ministry of Education, Hangzhou 310027, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Perylene derivatives are an important class of n-type semiconductors. With the exceptions of bay-
substituted and N-swallow-tail alkyl/tert-butyl substituted derivatives, most perylene diimides are insol-
uble. The recently reported perylene tetraesters are highly soluble, but are less electron-deficient. In this
paper, a series of perylene monoimide diesters have been synthesized, which have good solubility and
acceptable electron-accepting property due to the introducing of imide and ester groups in one perylene
molecule. Their electrochemical properties and structural ordering were examined by cyclovoltammetry
and X-ray diffraction technique, respectively. Their absorption and emission spectra are reported and
discussed.
Received 17 September 2007
Received in revised form 26 February 2008
Accepted 29 February 2008
Available online 18 March 2008
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
preferred, which needs soluble perylene derivatives to be devel-
oped. In fact, soluble perylene diimides have been developed
Optoelectronic devices based on organic semiconductors, such
as organic field-effect transistors (OFETs),1 light-emitting diodes
(OLED),2 solar cells,3 sensors,4 and organic memory devices,5
have recently gained great attention due to their advantages over
conventional inorganic devices, including low cost of fabrication,
simple package, compatibility with flexible substrate, and immense
variety of molecular semiconductors. In addition, the promise of
eventually being able to synthetically optimize molecular materials
for desired properties also motivates this work. n-Type organic
semiconductors are key components of organic p–n junctions, bi-
polar transistors, and complementary integrated circuits, leading
to flexible, large-area, and low cost electronic applications.6 But
compared with p-type organic semiconductors, such as penta-
cene,7 oligothiophenes,8 and phthalocyanines,9 n-type semicon-
ductors are not fully developed. To obtain high electron mobility,
n-type organic semiconductors should be highly ordered with
strong intermolecular interactions and should also have a proper
LUMO energy level. In addition, soluble materials are more
designed due to the superiority of solution-processing.
successfully either by introducing solubilizing N-substituents, e.g.,
long-chain secondary (swallow-tail) alkyl groups and tert-butyl
groups,11 or by introducing substituents at the carbocyclic scaffold
(the so-called bay-area).12 For example, Mu¨llen designed inge-
niously a series of perylene diimide-based dendrimers, making it
possible to investigate thoroughly energy and electron transfer at
single-molecule level;13 Wu¨rthner built many functional supramo-
lecular architectures through hydrogen bonding, metal ion coordi-
nation, and p–p stacking interactions with soluble perylene
dimides as building blocks;14 Tian also synthesized some new
soluble perylene dyes, and explored their potential applications
in solar cells, electron acceptors, luminescent materials, and light
switches.15 Unfortunately, the solubility of perylene diimide is
gained at the expense of the coupling offset between adjacent per-
ylene molecules as a result of the steric effect or the twisting of the
perylene core.11,16 It is believed that the coupling between chromo-
phores is an important factor in realization of high-performance
photoconductive devices.17
Recently, the tetraalkyl esters of perylene-3,4,9,10-tetracarboxy-
lic acid (perylene tetraesters) were reported to be a potentially
large new class of self-organizing electron transport materials.18
They are highly soluble in common organic solvents resulted
from the introduction of four flexible alkyl chains, and thus are
solution-processible. Due to the weak intermolecular coupling as
deduced from the similar absorption spectra in solid and solution,18
films of perylene tetraesters exhibited weak emission quenching
and thus have been successfully used as light-emitting layer in
red OLEDs.19 However, the device performance was poor when
Perylene diimides are a particularly promising class of dyes for
n-type semiconductors available to date.10 However, they are gen-
erally insoluble and therefore have to be deposited by sublimation.
To fully exploit the cost advantage associated with organic semi-
conductors, solution-processing such as spin- or dip-coating is
* Corresponding authors. Tel.: þ86 571 8795 2557; fax: þ86 571 8795 3733.
E-mail addresses: minminshi@zju.edu.cn (M. Shi), hzchen@zju.edu.cn (H. Chen).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.02.104

L. Yang et al. / Tetrahedron 64 (2008) 5404–5409
5405
perylene tetraesters were used in solar cells due to the limit of dis-
3
sociation of excitons,20 which was the result of their less electron-
deficient property compared with perylene diimides owing to the
much less coplanarity with perylene core of the ester groups than
imide groups.21
-1.02
-0.77
2
Considering the above demonstrations, we think that the com-
bination of imide and ester groups in one molecule should result in
good solubility and acceptable electron-accepting property simul-
taneously. In this paper, such a type of perylene derivatives, namely
perylene monoimide diesters, were designed and synthesized for
the first time through a simple phase-transfer catalysis reaction.
The molecular structure, electrochemical properties, and the struc-
tural ordering were fully characterized. The absorption and emis-
sion spectra were recorded and were explained in detail by the
exciton theory and film ordering, respectively.
1
0
-0.95
-1
-0.70
-1.6
-1.2
-0.8
Potential (vs SCE, V)
-0.4
0.0
2. Results and discussion
2.1. Synthesis
Figure 1. Cyclovoltammogram of 3c tested in 0.1 M solution of Bu4NClO4 in dichloro-
methane with a scan rate of 50 mV/s.
The target compounds studied in this paper were prepared via
a two-step procedure outlined in Scheme 1. First, the monoimide
2 was synthesized by treating dianhydride 1 with ammonia in
water and was separated from the diimide byproduct and the
unreacted dianhydride 1 based on their different solubility in alka-
line aqueous solution.22 The further purified 2 via vacuum sublima-
tion was then subjected to a phase-transfer catalysis reaction to
produce the final product 3.23 By changing the length of the alkyl
substituents from 4, 8 to 12 carbon atoms, 3 compounds abbrevi-
ated as 3a–c were obtained. The target compounds were character-
ized with FTIR spectroscopy and 1H NMR. The purity of the
compounds was determined by elemental analysis, which was in
good agreement with the calculated values, indicating that these
perylene derivatives were obtained in high purity.
dichloromethane with a saturated calomel electrode (SCE) as the
reference and Pt as the counter electrode. All compounds 3a–c ex-
hibit two reversible reduction waves, and Figure 1 shows the typi-
cal cyclovoltammogram of 3c. The reduction potentials of 3a–c
are given in Table 1. Taking the first reduction potential and
the potential of SCE versus the vacuum level (ꢀ4.74 eV) into
account, the LUMO energy levels of 3a–c can be calculated as
24
ELUMO¼ꢀEA¼ꢀ4.74ꢀEred
,
and the results are listed in Table 1.
The reduction potentials and ELUMO of exemplified perylene diimide
(DPP) and perylene tetraester (PTE8) are also listed in Table 1 for
a clear comparison.25,26 It is obvious that both the reduction poten-
tials and ELUMO of compounds 3a–c show no obvious difference due
to the energy node at the imide nitrogen and the ether oxygen.14e
As expected, the ELUMO of compounds 3a–c is located between
that of perylene diimide and that of perylene tetraester, which is
the result of the different electron-withdrawing effects of the car-
bonyl in ester groups and imide groups due to their different copla-
narity with perylene core. Compared with perylene tetraester, the
lower ELUMO of compounds 3a–c would improve the electron-
accepting property and thus favor the exciton dissociation at the
donor/acceptor interface,20 making 3a–c potential n-type organic
semiconductors for optoelectronic application.
R
N
H
N
O
O
O
O
O
O
O
R=
3a
:
C4H9
a
b, c
3b
:
:
C8H17
3c
C12H25
COORCOOR
O
O
1
O
O
O
2
O
3
2.3. X-ray diffraction
Scheme 1. Synthesis of the perylene monoimide diesters 3a–c; (a) NH3, H2O, 90 ꢁC,
2 h, 21%; (b) KOH, H2O, 90 ꢁC, 2 h; (c) TOAB, RBr, reflux, 1.5 h, 42% (3a), 58% (3b),
84% (3c).
To investigate the influence of alkyl chain length on the struc-
tural ordering, X-ray diffraction (XRD) patterns of the sublimed
3a–c thin films were recorded. As shown in Figure 2, all the XRD
patterns of 3a–c thin films show a peak at a small angle corre-
sponding to a d spacing of 24.1, 27.6, and 22.6 Å, respectively, which
is considered to be the distance between the adjacent p–p stacked
Compounds 3a–c are highly soluble in many common organic
solvents, such as chloroform, dichloromethane, tetrahydrofuran,
toluene, xylene, hexane, etc. The solubility of 3a–c is several thou-
sand times higher than that of the corresponding perylene diimides
due to the attachment of the two flexible ester groups instead of
one imide group onto one end of perylene core. The good solubility
of 3a–c will facilitate the fabrication of optoelectronic devices by
solution-processing, such as spin-coating and cast-coating, which
are extremely attractive for commercial applications in optoelec-
tronic technologies due to the adaptability, simplicity, and low
cost of manufacture.
Table 1
Half-wave reduction potentials (in V vs SCE) and LUMO energy levels of compounds
3a–ca
DPPb
3a
3b
3c
PTE8c
E (3/3ꢀ)
ꢀ0.51b
ꢀ0.72b
ꢀ4.23b
ꢀ0.77
ꢀ1.04
ꢀ3.97
ꢀ0.74
ꢀ1.00
ꢀ4.00
ꢀ0.74
ꢀ0.99
ꢀ4.00
ꢀ1.09c
ꢀ1.39c
ꢀ3.65c
E (3ꢀ/32ꢀ
)
ELUMO (eV)
2.2. Electrochemical properties
a
Measured in 0.1 M solution of Bu4NClO4 in dichloromethane with a scan rate of
50 mV/s.
b
DPP: N,N0-diphenyl perylene diimide. Cited from Ref. 25.
PTE8: perylene tetraoctyl ester. Cited from Ref. 26.
The electrochemical properties of compounds 3a–c were inves-
tigated by cyclic voltammetry in a 0.1 M solution of Bu4NClO4 in
c

5406
L. Yang et al. / Tetrahedron 64 (2008) 5404–5409
3a
3b
3c
A
505
1.0
475
0.8
0.6
0.4
0.2
446
0.0
350
400
450
Wavelength (nm)
500
550
600
Figure 2. X-ray diffraction patterns of sublimed 3a–c thin films on glass substrates.
B
1.0
0.8
0.6
0.4
0.2
0.0
perylene columns separated from each other by the alkyl chains.27
Contrary to the expectation, 3c has the shortest d spacing, indicat-
ing a significantly increased interdigitation of the long alkyl chains
in 3c and/or a large tilt angle of 3c to the substrate. In addition,
compound 3a shows another peak at 10.46ꢁ with a d spacing of
8.45 Å, relating to the space of edge-to-edge arranged perylene
cores,27 which implies the formation of a more ordered film. How-
ever, the intensity of the diffraction peak of 3c film is very weak,
implying lower order as compared with 3a and 3b films. Therefore,
it can be concluded that shortening of the alkyl chains results in
an increase in film order. This effect was also found in perylene
tetraester series.28
3a
3c
3b
2.4. UV–vis spectroscopy
400
450
500
550
Wavelength (nm)
600
650
700
As shown in Figure 3A, the absorption spectra of compounds
3a–c in chloroform are identical, which exhibit a fine structure
with two peaks and one shoulder at 505, 475, and 446 nm, respec-
tively. It is obvious that the alkyl chain length has no influence on
the absorption spectra in solution, which is in agreement with ear-
lier observations on perylene-based materials including perylene
diimides and perylene tetraesters,18,22 and is due to the nodes of
the HOMO and LUMO orbitals at the imide nitrogen and the ether
oxygen.14e In addition, the absorption peaks of compounds 3a–c
are located between those of perylene diimides (at 523, 487, and
454 nm) and those of perylene tetraesters (at 472, 444, and
417 nm),22,28 which could be explained by their different p-elec-
tron delocalization owing to the different coplanarity with perylene
core of the ester groups and imide groups.
Subsequently, the absorption spectra of compounds 3a–c in
evaporated films were recorded and were shown in Figure 3B. Un-
like to the solution spectra, the absorption spectra of the evapo-
rated 3a–c films are obviously different. In the spectrum of 3a
film, four bands can be distinguished centered at about 549, 505,
481, and 458 nm. Compared with the solution spectrum, the spec-
trum of 3a film shows an additional red-shifted absorption band at
549 nm. The absorption bands observed between 400 and 530 nm
approximately coincide with those observed in the solution spec-
trum, but with vast differences in intensity compared with those
in solution and strongly overlapping. It is considered that in this
region the film shows at least one additional absorption band at
around 480 nm as compared with the absorption maximum in so-
lution.27 Therefore, the film spectrum of 3a shows two additional
absorption bands, i.e., a blue-shifted band and a red-shifted band,
upon going from (dilute) solution to film. On the contrary, the
Figure 3. Normalized UV–vis absorption spectra of 3a–c in chloroform (A) and in films
vacuum-deposited on glass substrates at room temperature (B).
absorption spectra of 3b and 3c in evaporated films are similar,
where the order of intensity for 0/0 (446 nm) and 0/2
(505 nm) vibronic transitions is thoroughly reversed compared
with that in solution. In other words, the absorption maxima of
3b and 3c are blue-shifted, upon going from dilute solution to film.
Spectral shifts observed upon aggregation of molecules are re-
lated to interchromophore distance and orientation and are often
explained using the exciton coupling theory.27,29 If the transition di-
poles involved are oriented in a parallel fashion, a spectral shift to
red or blue is expected depending on the angle between the cen-
ter-to-center vector and the transition dipole moments of the adja-
cent chromophores. The critical angle is 54.7ꢁ. Above this critical
value, a blue-shifted band is often observed and contrary is a red-
shifted band appeared. If the transition dipoles involved are not
parallel, a blue- and a red-shifted absorption bands are expected
simultaneously, which may be the case with transition dipoles
rotated with respect to each other while keeping the adjacent
molecules parallel or the case with adjacent molecules oblique.
So, the spectral shift of 3a upon going from dilute solution to film
can be explained in two ways: (i) more than one type of aggregates
is present, and/or (ii) the transition dipole moments of adjacent
molecules were not parallel. The above-mentioned XRD results of
3a film have indicated that both head-to-tail and edge-to-edge con-
figurations are present in 3a aggregate, which will result in the

L. Yang et al. / Tetrahedron 64 (2008) 5404–5409
5407
appearance of red-shifted and blue-shifted bands, respectively.
A
3a
3b
3c
525
However, considering the inverse cube dependence of the exciton
splitting on the intermolecular distance30 and the large intermole-
cular distance in the two dimensions (2.41 and 0.845 nm, respec-
tively), the spectral shift originated from the intermolecular
interaction in the two directions might be ignored. Therefore, the
spectral shift mostly originated from the p–p stacking of neighbor-
ing perylene cores in columnar stacks. Taking the parallel orienta-
tion of perylene skeletons in stacks of bay-unsubstituted perylene
derivatives into account,14e,31 we consider that the origin of the
spectral shift of 3a film should be the existence of a significant ro-
tation between the transition dipole moments of adjacent 3a mol-
ecules within one stack. This result is in agreement with earlier
observations of a liquid crystalline perylene diimide.27 On the con-
trary, aggregates as 3b and 3c films, which exhibit blue-shifted
bands relative to the monomer absorption maxima, are conven-
tionally referred to as H-aggregates and are thought of as untilted
or slightly tilted ladder-like stacks.32 It is noteworthy that there is
a weak but detectable shoulder at about 535 nm in the spectra of
3b and 3c, which results from a nonvanishing transition probability
between the ground and the lowest exciton state. This weak band
may originate from vibronic coupling or a small rotational twist be-
tween adjacent chromophores.32c,33 In addition, the spectrum of 3b
film is more blue-shifted compared with that of 3c film, which may
be due to a smaller difference of the van der Waals intermolecular
energies in the ground and excited state (DD) resulting from the
weak interdigitation of the alkyl chains.29c,30,34
It is well known that all highly photoactive materials show a sub-
stantial red-shifted absorption band coupled with substantial band
broadening on aggregation.32c It is the stabilization of excitons in
materials with substantial absorption broadening manifested as
red shifts on aggregation that leads to an increase in exciton life-
time and thus allows more diffusion to the donor/acceptor interface
in order to form separated holes and electrons. Therefore, 3a with
substantial band broadening is believed to be the most potential
optoelectronic material in compounds 3a–c. However, 3b and 3c
might be potential electron transport materials due to the large
overlap of p orbitals resulted from the slightly tilted ladder-like
stacking configuration.
1.0
0.8
0.6
0.4
0.2
0.0
561
613
500
550
600
Wavelength (nm)
650
700
B
3a 3b 3c
1.0
0.8
0.6
0.4
0.2
0.0
500
600
700
Wavelength (nm)
800
900
Figure 4. Normalized fluorescence spectra of compounds 3a–c in chloroform (A) and
in films vacuum-deposited on glass substrates at room temperature (B). The excited
wavelength is 470 nm.
2.5. Fluorescence spectroscopy
The solutions of compounds 3a–c in chloroform show a bright
yellow fluorescence even under daylight, which is scarcely ob-
served for the perylene-based fluorophores with the exception of
the recently reported core-fluorinated perylene bisimides.35
Figure 4A shows the fluorescence spectra of compounds 3a–c in di-
luted chloroform solution, which exhibit a fine structure with two
peaks and one shoulder at 525, 561, and 613 nm. The alkyl chain
length has almost no influence on the fluorescence spectra in solu-
tions. In addition, the fluorescence spectra of compounds 3a–c ful-
fill the mirror image conditions to the absorption spectra (Fig. 3A)
with Stokes shift of about 20 nm, which is larger than that of the
corresponding perylene diimide (w14 nm)22 due to the introduc-
tion of the flexible ester chains. Similar result was also observed
for the corresponding perylene tetraesters.28 Similarly, the fluores-
cence peaks of compounds 3a–c are located between those of per-
ylene tetraesters (at 493, 522, and 569 nm) and those of perylene
diimides (at 536, 574, and 628 nm).22,28 The emissive colors of
perylene tetraesters, compounds 3a–c, and perylene diimides in
solution are bright green-yellow, bright yellow, and orange,
respectively. Therefore, it is feasible to tune the emissive color of
perylene-based fluorophores by attaching different kinds of substi-
tutions on perylene core.
instead of the well-defined vibronic fine structure presented in
the solution fluorescence spectra (Fig. 4A). The fluorescence max-
ima of films show remarkable red-shift (>100 nm) compared
with those in solutions. Both the loss of fine structure and the large
color shift are typical for fluorescence resulting from excimers
(equal to excited dimers).18 According to the above discussions on
absorption spectra in films, 3a–c films formed ground-state stable
aggregates, so the excimers were formed when one monomer
molecule in the stable aggregates was electronically excited due to
absorption of a photon. Obviously, the emission maxima for 3a–c
films are greatly influenced by the length of the attached alkyl
chains on perylene chromophores, and are 647, 670, and 682 nm
for 3a, 3b and 3c, respectively. It is noteworthy that a very weak
shoulder appears at about 568 nm in addition to the band emission
at 647 nm for 3a; the shorter and longer wavelength emissions can
be assigned to radiation from free and self-trapped excitons, re-
spectively.36 We consider that the main emission band for com-
pounds 3a–c results from the self-trapped excitons. Therefore, we
conclude that the high different emission maxima of 3a–c films
originate from the different energy of emissive exciton traps, which
is the result of their different order. With increasing the length
of the alkyl chains, the film order decreases as verified by the
above-mentioned XRD results, which means the existence of
Figure 4B shows the fluorescence spectra of the evaporated 3a–c
films. It is found that one broad and featureless peak appears

5408
L. Yang et al. / Tetrahedron 64 (2008) 5404–5409
increased amount of grain boundaries and lower energy of emissive
exciton traps, and thus the fluorescence maximum is red-shifted.
Similar relationship between film order and fluorescence maxima
was also observed in perylene films upon solvent vapor
annealing.32a
several times. All the collected filter cakes, i.e., the potassium salt of
2, were washed with 10% aqueous solution of potassium chloride
until the filtrate was colorless in order to remove the more soluble
salt of 1 completely (note: water should not be used). The filter cake
was then dissolved in water at 90 ꢁC and filtered using a frittered-
glass funnel under vacuum to remove the insoluble byproduct thor-
oughly. After acidifying the filtrate with a minimum amount of 10%
hydrochloric solution, the precipitate was collected, and washed
with distilled water until the washings were neutral. The solid
was then dried under vacuum, giving compound 2 with the yield
of 21% (0.82 g). Compound 2 was further purified by train sublima-
tion and used for characterization. IR (KBr): n 1780, 1732 cmꢀ1
(C]O in anhydride), 1695 cmꢀ1 (C]O in imide). Elemental analysis
(%) calcd for 2 (C24H9NO5): C, 73.66; H, 2.32; N, 3.58. Found: C,
73.97; H, 2.23; N, 3.72.
3. Conclusions
Soluble perylene monoimide diesters were designed and syn-
thesized for the first time, which exhibited essentially identical op-
tical and electrochemical properties in solution located between
those of perylene diimides and those of perylene tetraesters. While
combining the absorption spectra of films with exciton coupling
theory, it was deduced that the perylene moieties within a column
were rotated in going from one layer to the other, and the rotation
angle might dramatically decrease with increasing the alkyl chain
length from 4 to 12 carbon atoms due to strong interdigitation be-
tween long alkyl chains. In addition, the emission maxima of films
were red-shifted with the lengthening of alkyl chains, mainly due
to the decreased order of films as proved by XRD measurements.
In summary, by introducing imide and ester groups in one mole-
cule, the resulting perylene monoimide diesters possess good solu-
bility, acceptable electron-accepting ability, potential high charge
carrier mobility and/or good photovoltaic property, which make
these materials to be promising candidates in organic electronics
applications. Our future interests are detailed characterization of
their n-type semiconducting properties in application to organic
field-effect transistors and solar cells.
4.3.2. N-(n-Alkyl)-perylene-3,4-dicarboximide-9,10-di-(n-alkoxy-
carbonyl) (3)
A typical synthesis procedure for N-(n-alkyl)-perylene-3,4-
dicarboximide-9,10-di-(n-alkoxy-carbonyl) (3a) was as follows: 2
(117 mg, 0.3 mmol) was converted to the dipotassium salt via stir-
ring in aqueous potassium hydroxide solution (0.15 g in 150 mL
water) at 90 ꢁC. After filtration, the violet filtrate was acidified
with 1 M hydrochloric solution until the pH value was 8–9. Then
tetraoctylammonium bromide (TOAB) (60 mg) and 1-bromobutane
(0.2 ml, w1.8 mmol) was introduced, and the mixture was refluxed
under vigorous stirring. After 1.5 h, the reactant solution became
colorless and the reaction was ended. The product was collected
by filtration and then was dissolved in chloroform. After filtration,
the filtrate was collected and washed with 15% sodium chloride
aqueous solution. The resulting chloroform solution was concen-
trated and precipitated by ethanol. After being washed with etha-
nol and deionized water, the product was dried under vacuum at
110 ꢁC to give 72 mg (42% yield) 3a as a red solid. FTIR (KBr): n
2960, 2933, 2872, 1720, 1699, 1651, 1593, 1261, 1174, 746 cmꢀ1. 1H
NMR (300 MHz, CDCl3), d (ppm vs TMS)¼1.00 (t, 9H, J 7.5), 1.43–
1.51 (m, 6H), 1.75–1.80 (m, 6H), 4.21 (t, 2H, J 6.5), 4.35 (t, 4H, J
6.9), 8.08 (d, 2H, J 8.0), 8.42 (dd, 4H, J 8.0 and J 8.2), 8.58 (d, 2H, J
8.2). Elemental analysis (%) calcd for 3a (C36H35NO6): C, 74.85; H,
6.11; N, 2.42. Found: C, 74.79; H, 6.08; N, 2.49.
4. Experimental
4.1. Materials
All solvents and reagents were obtained from commercial sour-
ces and used as received.
4.2. Equipments
FTIR spectra were measured on a Bruker Vector 22 FT-IR spec-
trometer. 1H NMR spectra were obtained on a Bruker Avance
DRX-300 NMR spectrometer. Elemental analyses data were deter-
mined on a Thermo Electron Flash EA-1112 element analysis appa-
ratus. Cyclic voltammetry (CV) measurements were carried out on
a CHI660A electrochemical workstation, tested in dichloromethane
solutions containing 0.1 M supporting electrolyte of tetrabutylam-
monium perchlorate (Bu4NClO4) in a three electrode cell, where
Pt disk, Pt wire, and saturated calomel electrode (SCE) were used
as working electrode, counter electrode, and reference electrode,
respectively. X-ray diffraction (XRD) measurements were per-
formed on a Rigaku D/max diffractometer with Cu Ka radiation.
The UV–vis absorption spectra and emission spectra were recorded
on a Varian Cary 100 Bio spectrophotometer and on a Perkin Elmer
LS55 fluorescence spectrophotometer, respectively.
Compounds 3b and 3c were prepared in a similar way and their
characterizations were shown below.
4.3.2.1. Compound 3b. Yield 58%. FTIR (KBr): n 2956, 2922, 2854,
1714, 1693, 1649, 1597, 1267, 1170, 748 cmꢀ1 1H NMR (300 MHz,
.
CDCl3), d (ppm vs TMS)¼0.85–0.90 (m, 9H), 1.20–1.54 (m, 30H),
1.76–1.84 (m, 6H), 4.19 (t, 2H, J 6.3), 4.33 (t, 4H, J 7.2), 8.10 (d, 2H,
J 8.0), 8.42 (dd, 4H, J 8.0 and 8.0), 8.58 (d, 2H, J 8.0). Elemental anal-
ysis (%) calcd for 3b (C48H59NO6): C, 77.28; H, 7.97; N,1.88. Found: C,
77.55; H, 8.04; N, 2.00.
4.3.2.2. Compound 3c. Yield 84%. FTIR (KBr): n 2956, 2918, 2849,
1725, 1698, 1654, 1598, 1257, 1163, 750 cmꢀ1 1H NMR (300 MHz,
.
CDCl3), d (ppm vs TMS)¼0.84–0.89 (m, 9H), 1.14–1.52 (m, 54H),
1.76–1.84 (m, 6H), 4.20 (t, 2H, J 6.6), 4.36 (t, 4H, J 7.2), 8.11 (d, 2H,
J 8.0), 8.42 (dd, 4H, J 8.0 and 8.0), 8.59 (d, 2H, J 8.0). Elemental anal-
ysis (%) calcd for 3c (C60H83NO6): C, 78.82; H, 9.15; N, 1.53. Found: C,
78.96; H, 9.19; N 1.74.
4.3. Synthesis
4.3.1. 3,4,9,10-Perylenetetracarboxylic-3,4-anhydride-9,10-imide (2)
A mixture of 3,4,9,10-perylenetetracarboxylic dianhydride (1)
(3.92 g, 10 mmol), water (100 ml), and aqueous ammonia solution
(25%, 7.75 ml) was stirred at room temperature for 4 h. The mixture
was then warmed to 90 ꢁC and stirred at this temperature for 2 h.
After the addition of a solution of 8 g potassium hydroxide in
200 mL water, the mixture was stirred for a further hour at 90 ꢁC
and the suspension was filtered to separate the insoluble diimide.
Potassium chloride (30 g) was then added to the filtrate in order
to precipitate out the potassium salt of 2. The process was repeated
Acknowledgements
This work was supported by National Natural Science Founda-
tion of China (Grant No. 50433020, 50403022, 50520150165,
20774083) and by the Major State Basic Research Development
Program (2007CB613402).

L. Yang et al. / Tetrahedron 64 (2008) 5404–5409
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