Effects of metal-ligand coordination on the self-assembly behaviour of a crown ether functionalised perylenetetracarboxylic diimide

Article abstract of DOI:10.1080/10610278.2012.731063

A novel perylenetetracarboxylic diimide (PDI) derivative, N,N-di(4-benzo-15-crown-5-ether)-1,7-di(4-tert-butyl-phenoxy)perylene-3,4;9, 10-tetracarboxylic diimide (CRPDI), has been synthesised and characterised. Dimerisation of CRPDI is induced by the presence of K⁺ in CHCl ₃ or spontaneously occurs in methanol, as revealed by absorption and emission spectroscopy. In particular, the formation of co-facial dimer in the presence of K⁺ proceeds in a three-stage process, as indicated by absorption spectroscopy. The belt- and rope-like nanostructures of CRPDI fabricated from methanol and CHCl₃ solution in the presence of K ⁺ are obtained by scanning electron microscopy. Furthermore, the conductivity of the rope-like nanostructures from the cation-induced dimeric species is more than ca. 1 order of magnitude higher than the belt-like nanostructures from the solvent-induced dimeric species. The present result represents the further effort towards realisation of controlling and tuning the morphology of self-assembled nanostructures of PDI derivatives through molecular design and synthesis. It will be valuable for the design and preparation of PDI-based nano-(opto)electronic devices with good performance due to the close relationship between the molecular ordering and dimensions of nanostructures and the performance of nanodevices.

Full text of DOI:10.1080/10610278.2012.731063

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Effects of metal–ligand coordination on the self-
assembly behaviour of a crown ether functionalised
perylenetetracarboxylic diimide
Ao You a , Jian Gao a , Dapan Li a , Marcel Bouvet b & Yanli Chen a
a Shandong Provincial Key Laboratory of Fluorine Chemistry and Chemical Materials, School
of Chemistry and Chemical Engineering, University of Jinan, Jinan, 250022, P.R. China
b Institut de Chimie Moléculaire de l'Université de Bourgogne, CNRS UMR 5260, Université de
Bourgogne, 21078, Dijon, France
Published online: 18 Oct 2012.
To cite this article: Ao You , Jian Gao , Dapan Li , Marcel Bouvet & Yanli Chen (2012) Effects of metal–ligand coordination
on the self-assembly behaviour of a crown ether functionalised perylenetetracarboxylic diimide, Supramolecular Chemistry,
24:12, 851-858, DOI: 10.1080/10610278.2012.731063
To link to this article: http://dx.doi.org/10.1080/10610278.2012.731063
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Supramolecular Chemistry
Vol. 24, No. 12, December 2012, 851–858
Effects of metal–ligand coordination on the self-assembly behaviour of a crown ether
functionalised perylenetetracarboxylic diimide
Ao Youa, Jian Gaoa, Dapan Lia, Marcel Bouvetb and Yanli Chena*
aShandong Provincial Key Laboratory of Fluorine Chemistry and Chemical Materials, School of Chemistry and Chemical Engineering,
b
University of Jinan, Jinan 250022, P.R. China; Institut de Chimie Moleculaire de l’Universite de Bourgogne, CNRS UMR 5260,
´
Universite de Bourgogne, 21078 Dijon, France
´
´
(Received 21 August 2012; final version received 13 September 2012)
A novel perylenetetracarboxylic diimide (PDI) derivative, N,N0-di(40-benzo-15-crown-5-ether)-1,7-di(4-tert-butyl-phenoxy)
perylene-3,4;9,10-tetracarboxylic diimide (CRPDI), has been synthesised and characterised. Dimerisation of CRPDI is induced
by the presence of Kþ in CHCl3 or spontaneously occurs in methanol, as revealed by absorption and emission spectroscopy.
In particular, the formation of co-facial dimer in the presence of Kþ proceeds in a three-stage process, as indicated by absorption
spectroscopy. The belt- and rope-like nanostructures of CRPDI fabricated from methanol and CHCl3 solution in the presence of
Kþ are obtained by scanning electron microscopy. Furthermore, the conductivity of the rope-like nanostructures from the cation-
induced dimeric species is more than ca. 1 order of magnitude higher than the belt-like nanostructures from the solvent-induced
dimeric species. The present result represents the further effort towards realisation of controlling and tuning the morphology of
self-assembled nanostructures of PDI derivatives through molecular design and synthesis. It will be valuable for the design and
preparation of PDI-based nano-(opto)electronic devices with good performance due to the close relationship between the
molecular ordering and dimensions of nanostructures and the performance of nanodevices.
Keywords: perylenetetracarboxylic diimide; crown ether; self-assembly; nanostructure; semiconductor
1. Introduction
in the past decade (10–16). However, crown ethers that
have both remarkable recognition and metal-binding
properties have wide applications also in molecular
electronic devices (17). The combination of these two
functional subunits for the purpose of constructing novel
supramolecular structures would be helpful for improving
the semi-conducting properties of some disk-shaped
molecules, apparently owing to the increased interaction
between adjacent disk-shaped molecules by metal–crown
ethers interaction (18–20). However, no system that
directly exploits intermolecular interactions and corre-
sponding nanostructures based on PDI derivatives contain-
ing crown ethers has been reported thus far.
The construction of organic nano-assembly into a
prerequisite structure with controlled morphology by
modifying the molecular structure and programming the
supramolecular interaction is a great challenge in the field
of molecular self-assembly (1). The major driving force
operating in these precisely controlled nanoscopic
architectures arises from various non-covalent interactions
including p–p interaction, van der Waals forces, hydrogen
bonding, hydrophilic/hydrophobic interactions, electro-
static and metal–ligand coordination (2–4). As a result,
comprehensive understanding of the interplay between
these factors to create different morphologies has formed
the focus of current research interests in this field.
With these ideas in mind, in this paper, we
endeavoured to design and synthesise a new PDI
compound containing two 4-benzo-15-crown-5-ether
units at two imide nitrogen positions of a PDI core,
named as N,N0-di(40-benzo-15-crown-5-ether)-1,7-di
(4-tert-butyl-phenoxy)perylene-3,4;9,10-tetracarboxylic
diimide (CRPDI; Scheme 1). The self-assembling proper-
ties of CRPDI in the absence and presence of potassium
ions were comparatively investigated by electronic
absorption, fluorescence and scanning electronic
microscopy (SEM), revealing the effect of the interaction
between potassium ions and crown ether groups on the
As an important functional dye with outstanding photo
and chemical stability, as well as interesting photophysical
and photochemical properties, perylenetetracarboxylic
diimide (PDI) derivatives have been intensively studied
as advanced molecular materials for sensors (5, 6), organic
solar cell and thin-film transistor applications (7–9). For
most of the applications, the properties of the molecular
materials are closely related to the structure of nano-
assembly. Therefore, the fabrication of ordered nano-
structures with different morphology of this functional
molecular material has become an attracting research area
*Corresponding author. Email: chm_chenyl@ujn.edu.cn
ISSN 1061-0278 print/ISSN 1029-0478 online
q 2012 Taylor & Francis
http://dx.doi.org/10.1080/10610278.2012.731063
http://www.tandfonline.com

852
A. You et al.
Scheme 1. Synthesis of CRPDI.
morphology and dimension of self-assembled nano-
structures. In addition, better semi-conducting properties
of the nanostructures fabricated from CRPDI in the
presence of potassium ions than those in the absence of
potassium ions were also revealed by current–voltage (I–
V) measurements.
Kþ were obtained with a Keithley 4200 semiconductor
characterisation system at room temperature in air. I–V
curves were registered in the 2100 to 100 V voltage range
with 1 V increments. All experiments have been repeated
for at least twice to ensure reproducibility. The
interdigitated electrode array is composed of 10 pairs of
indium tin oxide (ITO) electrode digits deposited onto a
glass substrate with the following dimensions: 125 mm
electrode width, 75 mm spacing, 5850 mm overlapping
length and 20 nm electrode thickness. Conductivity, s, can
be calculated by Equation (1) (21, 22):
2. Experimental section
2.1. Materials
4-Aminobenzo-15-crown- 5-ether was purchased from
Tokyo Chemical Industry Co., Ltd, Tokyo, Japan. All other
reagents and solvents were used as received. Column
chromatography was carried out on silica gel. 1,7-Di(4-tert-
butyl-phenoxy)perylene-3,4;9,10-tetracarboxylic dianhy-
dride was prepared following the literature method (8, 21).
dI
s ¼
;
ð1Þ
ð2n 2 1Þ £ L £ h £ V
where d is the interelectrode spacing, I is the current, n is
the number of electrode digits, L is the overlapping length
of the electrodes and h is the film thickness if it is less than
that of the electrodes or the electrode thickness when the
film thickness exceeds that of the ITO electrodes.
2.2. General remarks
1H NMR spectra were recorded on a Bruker DPX 400
spectrometer in CDCl3. Spectra were referenced internally
1
using the residual solvent resonance (d ¼ 7.26 ppm for H
NMR) relative to SiMe4. MALDI–TOF mass spectra were
taken on a Bruker BIFLEX III ultra-high-resolution mass
spectrometer with alpha-cyano-4-hydroxycinnamic acid as
matrix. Electronic absorption spectra were recorded on a
Hitachi U-4100 spectrophotometer. Fluorescence spectra
were measured on a K2 system (ISIS product) at room
temperature. The fluorescence quantum yields were calcu-
lated using N,N0-di(cyclohexyl)-1,7-di(4-tert-butyl-phenox-
y)perylene-3,4;9,10-tetracarboxylic diimide as standard.
SEM images were obtained using a JEOL JSM-6700F
field-emission SEM. For SEM imaging, Au (1–2 nm) was
sputtered onto the substrate to prevent the charging effects
and to improve the image clarity. Chemical compositions of
the nanostructure were studied by energy-dispersive spec-
trometry (EDS) with an Oxford INCA X-sight instrument.
2.4. Synthesis and characterisation of CRPDI
A mixture of 1,7-di(4-tert-butyl-phenoxy)perylene-
3,4;9,10-tetracarboxylic dianhydride (58 mg, 0.08 mmol),
40-aminobenzo-15-crown-5-ether (90 mg, 0.33 mmol),
imidazole 2 g and toluene (10 ml) was heated to 1168C
under N2 atmosphere and continuously stirred for 5 h at this
temperature. Then the reaction mixture was cooled to room
temperature. After the solvent was evaporated under
reduced pressure and the residue was purified by column
chromatography on silica gel with 3% MeOH in CHCl3 as
eluent, CRPDI (10 mg, yield 10.3%) was collected as
bright red solid. MS (m/z): 1221.3 found, 1243.2 (Mþ
þ Naþ), 1259.2(Mþ þ Kþ). 1H NMR (CDCl3, 400 MHz):
d 9.62–9.60 (d, 2H), 8.60–8.58 (d, 2H), 8.33 (s, 2H),
7.52–7.45 (m, 4H), 7.12–7.10 (m, 4H), 7.01 (d, 2H), 6.97
(d, 2H), 6.85–6.83 (d, 2H), 4.20 (m, 4H), 4.06 (m, 4H),
3.95 (m, 4H), 3.85 (m, 4H), 3.79–3.77 (m, 16H), 1.37
(s, 18H).
2.3. Device fabrication and measurement
The I–V characteristics of CRPDI nanostructures fabri-
cated from methanol and CHCl3 solution in the presence of

Supramolecular Chemistry
853
3. Results and discussion
structureless emission band with bathochromic shift of
about 70 nm (Figure 1(B), dotted line). Such spectral
feature are similar to those observed previously for
aggregates of core-twisted perylene bisimide dyes (34) and
can be related to a pronounced structural and energetical
relaxation process of the excited dimer aggregate (35).
Furthermore, the fluorescence quantum yield of CRPDI is
reduced from 70.7% for the isolated CRPDI to about
3.54% upon aggregation by using N,N0-di(cyclohexyl)-
1,7-di(4-tert-butyl-phenoxy)perylene-3,4;9,10-tetracar-
boxylic diimide in CHCl3 as a reference (25, 36), which is
consistent with electronic coupling between a pair (or
more) of PDI units formed by the interaction between
adjacent CRPDI molecules in the co-facial arrangement
(34, 37).
3.1. UV–vis absorption and fluorescence spectra in
solution
The electronic absorption and emission spectra of CRPDI
in CHCl3 and in the presence of Kþ ions with the
concentration ratio of [Kþ]/[CRPDI] ¼ 1 in this solution
are shown in Figure 1, while the corresponding
experimental data compiled in Table A1 (Appendix). As
expected, CRPDI in chloroform showed typical feature of
the diphenoxy-substituted PDI chromophores in the
electronic absorption spectra (8, 23), revealing the non-
aggregated (monomeric) molecular spectroscopic nature
of the compound in CHCl3 (Figure 1(A), solid line). In
light of the previous observations as reported in the
literature with regard to absorption characteristics of
similar PDI derivatives (24–26), the absorptions at about
551 and 515 nm can be attributed to the 0–0 and 0–1
vibronic band of the S0–S1 transition, respectively, while
the observed absorption band around 407 nm is attributed
to the electronic S0–S2 transition. The fluorescence
spectrum of CRPDI in CHCl3 presented as a mirror
image of the absorption, which gives no indication of
aggregation (Figure 1(B), solid line) (27). After potassium
ions are added into CHCl3 solution of CRPDI with the
concentration ratio of [Kþ]/[CRPDI] ¼ 1 in this solution,
the absorption of CRPDI changed significantly in the ratio
of the intensities of the 0–0/0–1 peaks, while peak
positions of absorption maxima of CRPDI remained
almost unaltered (Figure 1(A), dotted line). With reference
to previous spectroscopic work on crown ether appended
porphyrin/phthalocyanine analogues (16, 18, 28–31),
those kinds of changes on the absorption spectra are
attributed to the formation of a co-facial and eclipsed
configurated species by complexation of the two crown
ether units of CRPDI with potassium ions (16, 32, 33). In
comparison with the fluorescence spectrum of CRPDI in
CHCl3, addition of Kþ ions affected CRPDI fluorescence
emission by a loss of the fine structures and a broad and
3.2. Cation complexation leading to stepwise formation
of a co-facial dimeric CRPDI supramolecular structure
The process of Kþ-induced co-facial dimer formation
from monomeric CRPDI is studied by Kþ-triggered
spectroscopic evolution of CRPDI in the region of 300–
800 nm recorded in CHCl3, as shown in Figure 2. It can be
seen that the low-energy 0–0 vibronic band at 551 nm
decreases significantly, whereas the high-energy 0–1 band
at 515 nm decreases slightly with gradual addition of Kþ
ions into solution of CRPDI ([Kþ]/[CRPDI] ¼ 0 to 2 with
a step of 0.2). However, there was a markedly decrease in
the ratio of the intensities of the 0–0/0–1 peaks along with
an increase of [Kþ]/[CRPDI] in solution, indicating that
the addition of Kþ is giving rise to co-facial dimer
formation (16, 37). As seen from the inset of Figure 2,
from about [Kþ]/[CRPDI] ¼ 1 onward, the ratio of the
intensities of the 0–0/0–1 peaks remains unchanged,
indicating that the aggregation process reaches a steady
state.
The co-facial dimer formation was monitored by
variation of the absorbance at 515 nm (the so-called dimer
band) and 551 nm (monomer band) of CRPDI during the
Figuþre 1. UV–vis absorption (A) and fluorescence (þB) spectra of CRPDI in 0.01 mM chloroform solution (solid line) and after addition
of K ions (KOAc) with the concentration ratio of [K ]/[CRPDI] ¼ 1 in this solution (dotted line). The excited wavelength was 515 nm.

854
A. You et al.
Figure 4. Plot of log [monomer] vs. log [dimer·Kþn ] in
CHCl3/CH3OH. The inset shows the dependence of monomer
and dimer concentrations on [Kþ]/[CRPDI].
Figure 2. þAbsorption spectra of CRPDI with various mole
ratios of K ions. A solution of KOAc (1 mM) in CHCl3/CH3OH
(95:5 v/v) was added gradually to a solution of CRPDI (0.01 mM,
3 ml) in CHCl3. The arrows indicate the direction of the
spectroscopic change from progressivelyþ increasing the
concentration ratio of Kþ ions to CRPDI: [K ]/[CRPDI] from
0 to 2 with a step of 0.2. Inset shows the changes in the ratio of
vibronic bands A 0–0/A 0–1 of CRPDI with various mole rations
of Kþ ions.
0.5 , [Kþ]/[CRPDI] # 1 the transition from a non-co-
facial dimer to a co-facial dimer conducts by binding the
second Kþ ion; finally, the change reached saturation at
[Kþ]/[CRPDI] $ 1, the complete formation of a co-facial
dimer is achieved. In other words, the first stage dimer is
non-co-facial while the final dimer is a co-facial species.
addition of KOAc in CHCl3/CH3OH (95:5 v/v). As can be
seen from Figure 3, the reversed change of the relative
intensity of two characteristic bands indicates that upon
addition of Kþ ions, monomer (CRPDI) is converted into
the dimeric supermolecular structure (CRPDI–Kþn –
CRPDI), in which Kþ ions are sandwiched between two
crown ether units belonging to two different CRPDIs. In
this case, the process of Kþ-induced dimerisation of
CRPDI is proposed in the following three stages (18, 38):
firstly, two monomeric 15-crown-5-substituted PDI
molecules combine with the first Kþ ion to form a
eclipsed and/or linear (non-co-facial) dimer in the region
of 0 , [Kþ]/[CRPDI] # 0.5; secondly, in the region of
K
nKþ þ 2 monomer ðCRPDIÞ !dimerꢀKþn ðCRPDI
ð2Þ
2 Kþn 2 CRPDIÞ:
Equation (2) is proposed with the speculation that the
equilibrium between monomer CRPDI (upon addition of
Kþ ions) and the corresponding dimer (CRPDI–
Kþn 2 CRPDI) should exist in the present system. The
monomer and dimer concentrations could be calculated
from the spectral changes during titration using the method
described by West and Pearce (39). If Equation (2) was
available, the slope of 2 from a plot of log [monomer]
versus log [dimer·Kþn ] would be obtained. As expected, the
region with a slope of ca. 2.0 is revealed in Figure 4. When
Kþ ions are added to the CRPDI solution, the monomer
concentration decreases sharply, and a region with
slope < 2.0 continues until [Kþ]/[CRPDI] ¼ 0.5. After
this point, the slope of the plot approaches 0, especially
beyond the region [Kþ]/[CRPDI] . 1 (18). Furthermore, a
very high binding constant, K ¼ (1.76 ^ 0.02) £
1011 l2 mol22, for Equation (2) with n ¼ 1 is obtained
when two CRPDI units bind one Kþ cation and start to
form the dimer in the first stage (18, 19).
3.3. Optical properties in the solid state
The aggregation behaviour of CRPDI in solid state
was studied by UV–vis and fluorescence spectroscopy.
Figure 3. Variation of the absorbance at 515 and 551 nm of
CRPDI during addition of KOAc in CHCl3/CH3OH (95:5 v/v).

Supramolecular Chemistry
855
Two kinds of solid films were prepared from the
evaporation of a drop of CRPDI solution in CHCl3 with
or without Kþ([Kþ]/[CRPDI] ¼ 1) on the quartz sub-
strates for analysis, named film 1 and 2, respectively. For
comparison, the solids that precipitated by injecting a
small volume of solution of CRPDI in CHCl3 solution
(1 mM) into a large volume of methanol were transferred
to a quartz substrate (film 3). In comparison with the
absorption spectrum of CRPDI in CHCl3, obvious band
broadening was observed in films 1–3 (Figure 5(A)) due to
the effect of the closely compacted molecular assembly.
Furthermore, the relative enhancement of the 0–1
transition in the order of film 2 . film 3 . film 1 was
revealed by the normalised absorption spectra, which
implied the formation of H-type aggregation in films 1–3,
and in particular the increasing excitonic interactions
between the stacked CRPDI chromophores in the same
order (37, 40, 41). Consistent with the absorption
measurement, all the fluorescence spectra in the films 1–
3 showed a new emission at about 694 nm for film 1 and
698 nm for films 2–3, respectively (Figure 5(B),
Appendix, Table A1), which is a typical emission of PDI
excimer-like state, suggesting strong p–p stacking and a
typical H-type aggregation configuration (32, 42, 43).
with long 1D rope-like bundles. As shown in Figure 6(B),
long 1D nanoropes display uniform orientation and size
with an average width of ca. 75 nm and a length of over
2 mm. The success in preparing ordered 1D nanoropes
from CRPDI by introducing potassium ions (KOAc) was
confirmed by the elemental signatures of C, O, N and K in
EDS as shown in the inset of Figure 6(B). CRPDI
molecules precipitated from methanol result in belt-like
nanostructures with an average width of 200 nm and length
of ca. 5 mm. The obvious difference on the morphology of
films 1–3 of CRPDI indicates the effect of a synergistic
interplay among non-covalent interactions, including p–p
interaction, metal–ligand coordination and the inter-
actions between CRPDI molecules and solvent on fine
controlling and tuning the molecular packing confor-
mation of the corresponding self-assembled aggregates. It
is worth note that the size- and morphology-adjustable
nanostructures are highly desired for fabricating nano-
scale molecular (opto)-electronic devices which often
require a wide variety of channel lengths to achieve the
optimum gate or optical modulation (3, 44).
3.5. I–V properties
The uniform aggregates of CRPDI with well-defined
nanostructures would be promising candidates for appli-
cations in electronic devices. To demonstrate the potentials
of these nanostructures, thin films of 1–3 of CRPDI were
carefully prepared onto glass substrates with ITO
interdigitated electrode structures, respectively. After
complete evaporation of the solvents, the densely packed
nanostructures (films) remained and adhere to ITO
interdigitated electrodes (IDEs)/glass substrate tightly,
and the electron conductivitywas measured. Figure 7shows
the I–V characteristics of nanoropes and nanobelts from
CRPDI. According to the equation reported in the
literatures (21, 22), the electronic conductivity is calculated
to be around 2.6 £ 1025 and 3.5 £ 1026 S cm21 for the
3.4. Morphology of the aggregates
The morphology of the films 1–3 formed from CRPDI was
examined by SEM. As seen from Figure 6, the CRPDI
aggregate morphology shows either cation- or solvent-
dependent variation. Film 1 prepared from evaporation of
a drop of CRPDI solution in CHCl3 results in disordered
flake aggregates on the surface of this film (Figure 6(A)).
After the addition of Kþ ions in CRPDI solution with
[Kþ]/[CRPDI] ¼ 1, due to metal–ligand (15C5–Kþ–
15C5) coordination between neighbouring CRPDI
molecules in cooperation with intermolecular p–p inter-
action, CRPDI molecules assembled into nanostructures
Figure 5. UV–vis absorption (A) and fluorescence (B) spectra of CRPDI films prepared from evaporation of a drop of CRPDI solution
in CHCl3 on a quartz substrate (solid line), and in the presence of Kþ ions in this solution with [Kþ]/[CRPDI] ¼ 1 on a quartz substrate
(dashed line), CRPDI solids precipitated from methanol (dotted line). The excited wavelength was 515 nm. The absorption spectra are
normalised at 515 nm.

856
A. You et al.
Figure 7. I–V curves measured on nanoropes (solid line) and
nanobelts (dashed line) from CRPDI.
structure. Comparing with nanobelts for CRPDI, the
improved conductivity of nanoropes for CRPDI might be
attributed to both readily p-stacks with adjacent planar
molecules and higher ordered molecular arrangement (24,
45). The fewer traps and/or defects in these 1D aggregates
with more efficient p–p stacks and metal–ligand
coordination interactions should favour charge transport.
These aggregates with high current modulation could be
useful for a wide range of electronic and sensor devices. In
order to evaluate the effect of adding one molar equivalent
of KOAc itself and the effect of using different casting
solvents (CHCl3 vs. methanol), the I–V characteristics of
two kinds of thin films (films 4 and 5) of a non-crown ether-
functionalised PDI derivative [N,N0-di(cyclohexyl)-1,7-
di(4-tert-butyl-phenoxy)perylene-3,4;9,10-tetracarboxylic
diimide (CHPDI, Appendix, Scheme A1)] were investi-
gated comparatively. Film 4 was prepared by drop-casting
from CHPDI solution in CHCl3 with KOAc ([Kþ]/
[CHPDI] ¼ 1), whereas film 5 by transferring the solids
that precipitated from methanol. Only valuable I–V curve
was obtained from film 5 (Appendix, Figure A1). This
result further proved that the addition of the Kþ improved
the aggregates of CRPDI due to efficient metal–ligand
coordination interactions between CRPDI molecules.
Figure 6. SEM images of CRPDI solids prepared from
evaporation of a drop of CRPDI solution in CHCl3 on a quartz
substrate (A), and after addition of Kþ ions in this solution with
[Kþ]/[CRPDI] ¼ 1 on a quartz substrate (B), CRPDI solids
precipitated from methanol (C). The inset of Figure 6(B) shows
the energy-dispersive analysis of a single nanorope of CRPDI.
4. Conclusions
We have synthesised a novel PDI with two benzo-15-
crown-5 substituents at the two imide nitrogen positions,
CRPDI. The aggregation properties were investigated. The
co-facial dimeric supramolecular structures of this
molecule in the presence of Kþ is formed through a two-
step three-stage process in CHCl3. Aggregates with
distinct morphologies and nanostructures for CRPDI
were controllably prepared by the addition of Kþ or
changing the solvent. The I–V measurements on these
nanoropes (film 2) and nanobelts (film 3) of CRPDI,
respectively (the experiments were repeated for more than
two times on different pieces of films). However, no
valuable I–V curve from film 1 (CRPDI aggregates formed
in chloroform solution) was obtained due to its disordered

Supramolecular Chemistry
857
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Acknowledgements
Financial support from the Natural Science Foundation of China
(20871055), Natural Science Foundation of Shandong Province
(ZR2011BZ005) and University of Jinan in China is gratefully
acknowledged.
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Appendix A
Table A1. Peak positions of absorption (la) and emission (le) maxima for CRPDI in chloroform and in the presence of Kþ ions with the
concentration ratio of [Kþ]/[CRPDI] ¼ 1 in this solution together with CRPþDI films prepared from evaporþation of a drop of CRPDI
solution in CHCl3 on a quartz substrate (film 1), and after the addition of K ions in this solution with [K ]/[CRPDI] ¼ 1 on a quartz
substrate (film 2), CRPDI films precipitated from methanol (film 3).
CRPDI
la (nm)
le (nm)
Solution in CHCl3
407, 515, 551
411, 517, 557
408, 504, 552
408, 508, 553
409, 508, 554
584
668
694
698
698
Solution with [Kþ]/[CRPDI] ¼ 1
Film 1
Film 2
Film 3
Note: The excited wavelength was 515 nm.
Scheme A1. Schematic structures of CHPDI.
Figure A1. I–V curve measured on film 5 of CHPDI from
methanol.