Novel fluorescent perylene liquid crystal with diphenylacrylonitrile groups: Observation of a large pseudo stokes shift based on AIE and FRET effects

Article abstract of DOI:10.1016/j.dyepig.2017.08.027

A novel perylene liquid crystal with diphenylacrylonitrile groups on 1,7-bay positions was synthesized in high yield. This highly decorated perylene bisimide showed the ordered hexagonal columnar liquid crystalline behaviour between 124.9 and 189.5 °C. Up

Full text of DOI:10.1016/j.dyepig.2017.08.027

Accepted Manuscript
Novel fluorescent perylene liquid crystal with diphenylacrylonitrile groups: Observation
of a large pseudo stokes shift based on AIE and FRET effects
Mingguang Zhu, Youzhen Zhuo, Kaicong Cai, Hongyu Guo, Fafu Yang
PII:
S0143-7208(17)31402-X
10.1016/j.dyepig.2017.08.027
DYPI 6189
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 22 June 2017
Revised Date: 15 August 2017
Accepted Date: 15 August 2017
Please cite this article as: Zhu M, Zhuo Y, Cai K, Guo H, Yang F, Novel fluorescent perylene liquid
crystal with diphenylacrylonitrile groups: Observation of a large pseudo stokes shift based on AIE and
FRET effects, Dyes and Pigments (2017), doi: 10.1016/j.dyepig.2017.08.027.
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ACCEPTED MANUSCRIPT
The novel perylene liquid crystal bearing diphenylacrylonitrile groups exhibited the
hexagonal columnar mesophase and good fluorescence in THF/H2O mixtures based
on AIE and FRET effect.

ACCEPTED MANUSCRIPT
Novel fluorescent perylene liquid crystal with diphenylacrylonitrile
groups: Observation of a large pseudo Stokes shift based on AIE and
FRET effects
5
Mingguang Zhu,a Youzhen Zhuo,a Kaicong Cai,a Hongyu Guo,*a,b and Fafu Yang,*a,c
aCollege of Chemistry and Chemical Engineering, Fujian Normal University, Fuzhou 350007, P. R.
China ;Tel: +0086-591-83465225; E-mail: yangfafu@fjnu.edu.cn
bFujian Key Laboratory of Polymer Materials, Fuzhou 350007, P. R. China
10 cFujian provincial Key Laboratory of Advanced Materials Oriented Chemical Engineering, Fuzhou
350007, P. R. China
A novel perylene liquid crystal with diphenylacrylonitrile
Keywords: Perylene; Diphenylacrylonitrile; Fluorescence
groups on 1,7-bay positions was synthesized in high yield. 30 resonance energy transfer; Aggregation-induced emission;
15 This highly decorated perylene bisimide showed the
ordered hexagonal columnar liquid crystalline behaviour
between 124.9 and 189.5 oC. Upon excitation of 480 nm, an
attenuation of fluorescent intensity was observed with the
increase of water fraction in THF/H2O mixtures. However,
20 the fluorescence intensity enhanced dramatically and
attained a maximum value at water fraction of 40% in
THF/H2O systems when excited at 330 nm. The
fluorescence intensity increased by 10 times and the
pseudo Stokes shift achieved 251 nm. These phenomena
25 were well elucidated by the AIE and FRET effect, which
were supported by the investigation of fluorescence
quantum yield and fluorescence lifetime.
Mesophase
1. Introduction
Perylene bisimides (PBIs) are important organic dyes
with excellent photoluminescence, which exhibit promising
35 applications in fluorescent emitters and biosensors, organic
light harvesting systems, organic electronic devices and self-
assembling nanostructures [1-5]. In order to prepare the high
ordered PBI materials [6, 7], the thermotropic PBI liquid
crystals (LC) were paid much attention due to their excellent
40 supramolecular self-assembling abilities [8, 9]. Up to now,
various PBI liquid crystals, of which the imide groups were
modified by siloxane [10, 11], organosilica [12, 13], dendritic
peptides [14], alkoxyl or alkyl groups [15, 16, 17, 18, 19, 20],
ester-bridging chains [21], cholesterol groups [22, 23], and

triphenylene groups [24-28], were synthesized and exhibited
Therefore, the design and synthesis of perylene liquid crystal
with large Stokes shift based on AIE and FRET effect remains
unknown. In this paper, by introducing two AIE-active
ACCEPTED MANUSCRIPT
interesting mesomorphic properties. However, these studies
implied that, although the mesomorphic properties were tuned
effectively by the structures of the substituents on imide 35 diphenylacrylonitrile groups onto the 1,7-bay positions of
5
positions, the fluorescent properties were difficult to be
improved due to their same perylene skeleton. Moreover, their
small Stokes shifts (20-30nm) and the strong π-π interaction
in the polar solvents usually resulted in re-absorption, self-
perylene bisimides, the first AIE-active diphenylacrylonitrile-
modified perylene liquid crystal was conveniently obtained.
This perylene derivative not only exhibited stable columnar
liquid crystalline behavior but also showed strong
quenching or aggregation-caused quenching (ACQ) effect [29, 40 fluorescence with large pseudo Stokes shift in polar solution.
10 30]. Thus, the study on perylene liquid crystal with both good
liquid crystalline property and unique photophysical property
is still challenging task.
The FRET phenomenon and AIE effect were observed for
perylene liquid crystal for the first time, indicating that AIE
and the FRET effect are good strategy for design and
synthesis of novel perylene liquid crystal with unique
In order to avoid the re-absorption of small Stokes shift,
some perylene derivatives with large Stokes shifts were 45 photophysical property.
15 prepared by enlarging the perylene conjugated system. But the
2. Experimental
syntheses were complicated in most cases [31-33]. Recently,
2.1 General
the technique of fluorescence resonance energy transfer
All chemical reagents were purchased from Aladdin Co.
(FRET) provided an effective solution by the formation of a
large Stokes shift based on the substantial overlap between
20 emission of donor and absorption of acceptor [34-37]. But this
strategy has not been applied for preparing perylene liquid
crystal with large Stokes shifts. On the other hand, Tang’s
group reported the aggregation-induced emission (AIE) effect
recently [30, 38, 39]. Based on this strategy, the ACQ effect
25 of perylene bisimides was avoided successfully by
introducing tetraphenylethene onto bay positions of perylene
[41, 42]. This strategy had been also applied in preparing the
liquid crystalline molecules by using AIE-active units such as
tetraphenylethene and diphenylacrylonitrile as rigid cores [43-
30 50]. However, as to perylene liquid crystal, no AIE-active
perylene liquid crystal with good fluorescence was reported.
50 Ltd and used directly. The other organic solvents were treated
with purification according to standard process before use.
Column chromatography was done by using silica gel (200-
300 mesh) as adsorbent. NMR spectra were obtained in
CDCl3 on a Bruker-ARX 400 instrument at 26oC. Chemical
55 shifts were recorded in ppm with tetramethylsilane (TMS) as
internal standard. MS spectra were carried out on Bruker mass
spectrometer. UV-Vis spectra were performed on Varian
spectrometer. Fluorescence spectra were obtained in
a
conventional quartz cell (10×10×45 mm) at 25oC on a Hitachi
60 F-4500 spectrophotometer. The excitation and emission slits
were 10 nm wide. The fluorescence absolute ΦF values and
fluorescence lifetime were investigated on FLS920
Fluorescence Spectrometer with a 6-inch integrating sphere.

POM (Leica DMRX) was done on a hot stage (Linkam 25 column chromatography (DCM/ethyl acetate (6/1, v/v) as
ACCEPTED MANUSCRIPT
THMSE 600) to confirm phase transitions. Thermal analysis
of the materials was performed by DSC (Thermal Analysis
Q100) with the scanning rate of 10oC/min under N2
atmosphere. XRD experiments were done on SEIFERT-FPM
eluent). The compound 6 was then collected as red purple
solid in the yield of 70%. Compound 6: FT-IR(KBr), v/cm-1:
2923. 2852, 1697, 1660, 1594, 1500, 1340, 1262, 1227, 1116;
1H NMR (400 MHz, CDCl3) δ (ppm): 9.50 (d, J = 8.0 Hz, 2H,
5
(XRD7). Compounds 2 and 3 were prepared according to the 30 ArH), 8.61(d, J = 8.0 Hz, 2H, ArH), 8.34(s, 2H, ArH), 8.03
literature method [20]. Compound 4 was synthesized by the
reported procedure [49]. Compound 5 was obtained according
to the published method [17].
(bs, 2H, NH), 7.93(d, J = 8.0 Hz, 4H, ArH), 7.78(d, J = 8.0 Hz,
4H, ArH), 7.59(s, 2H, C=CH), 7.45-7.52 (m, 6H, ArH),
7.21(d, J = 8.0 Hz, 4H, ArH), 6.93(s, 4H, ArH), 4.50 (bs, 4H,
NCH2), 3.80-3.99(m, 16H, OCH2 and NCH2), 1.18-1.85(m,
35 120H, CH2), 0.87(t, J = 8.0Hz, 18H, CH3); 13C NMR (100
MHz, CDCl3) δppm: 167.55, 164.02, 163.10, 155.66, 154.30,
152.81, 142.46, 140.62, 133.55, 133.33, 131.63, 130.78,
129.90, 129.20, 129.02, 128.94, 125.38, 124.73, 124.36,
123.76, 122.00, 119.45, 117.62, 116.81, 110.27, 105.27, 73.42,
40 69.05, 39.43, 35.43, 30.32, 29.74, 29.69, 29.45, 29.39, 29.34,
26.08, 22.71, 14.14; MALDI-TOF-MS Calcd.for m/z = 2268.4,
found: m/z = 2269.9 (MK+). HR-MS (ESI) (C144H190N6O14)
[M]+: Calcd.: 2228.4368. found: 2228.4368.
C12H25
O
C12H25
O
HO
HO
HO
NH2
O
C12H25Br
O
H2N
O
C12H25O
C12H25
O
NH2
K2CO3, MeCN
MeOH
N
H
OMe
OMe
C12H25O
C12H25
O
3
2
1
CN
NaOH
EtOH
CHO
+
OH
HO
O
NC
4
O
O
O
Br
C12H25
O
O
O
N
O
O
OC12H25
OC12H25
OC12H25
O
H
N
3
Br
C12H25
O
N
O
Br
DMF
N
H
O
C12H25
5
Br
O
O
4
K2CO3, DMF
CN
O
C12H25
O
O
N
O
O
N
O
OC12H25
O
H
N
C12H25O
OC12H25
OC12H25
N
H
O
C12H25O
O
NC
6
10
Scheme 1 The synthetic route of perylene liquid crystal 6 with
diphenylacrylonitrile group on bay-positions
45 3. Results and discussion
2.2. Synthesis of target compound 6
3.1. Synthesis and characterization
15
Under N2 atmosphere, the mixture of compound 5
(0.195g, 0.1 mmol), compound 4 (0.066g, 0.3 mmol) and
anhydrous K2CO3 (0.050g, 0.036mmol) were stirred in DMF
solution (30 mL) at 100oC for 24 h. This reaction was
monitored by TLC, indicating the disappearance of compound
The previous literatures has shown that the multiple alkyl
chains (6 chains usually) on imides positions of perylene were
favourable for columnar perylene liqud crystals [17-20]. And
50 the introduction of functional groups on bay-positions
improved the photophysical properties based on the
conjugated and sterically hindered effect for perylene skeleton
[47-49]. On the other hand, the diphenylacrylonitrile moiety
had shown a strong AIE effect [30, 38, 39], and its emission
55 band is overlapped with the absorption band of perylene,
20 5 in 24 h. After reaction completion, HCl solution (1M, 60
mL) was poured in reaction system, and the solution was
extracted of CHCl3 (50 mL). The organic layer was separated,
washed by brine solution and dried over anhydrous MgSO4,
and filtrated and concentrated. The residue was purified by

which is favourable for FRET effect. Thus, the target
THF, DMF).
ACCEPTED MANUSCRIPT
molecule was designed as compound 6, in which the six
3.2. Mesomorphic properties
chains located at the amide positions ensured the columnar
mesophase and the two diphenylacrylonitrile units on bay
positions would produce novel photophysical properties based
on AIE and FRET effect. The synthetic route to the new
molecules 6 is depicted in Scheme 1. According to the
published procedure [20], gallic ether derivative 2 with three
alkyl chains was synthesized by treating methyl gallate 1 with
35
As target compound 6 was prepared, its mesomorphic
property was studied by DSC, polarising optical microscopy
(POM) and XRD. The DSC curve was illustrated in Figure 1
and the phase transition temperatures and enthalpy changes
were summarized in Table 1. The corresponding DSC data of
5
40 its precursor 5 were quoted for the purpose of comparison,
showing the influence of two diphenylacrylonitrile groups on
liquid crystalline behaviour. It can be seen that compound 6
exhibited good reversible phase transition behaviours with
two obvious phase transition temperatures on cooling and
45 second heating. The two endothermic peaks at 124.9 and
10 bromodecane in yield of 80%. Subsequently, compound 2 was
converted to compound 3 by reacting compound 2 with excess
ethylenediamine in yield of 86%. By refluxing compound 3
with
1,7-dibrominated
perylene
bisanhydride
in
formdimethylamide (DMF) at 1100C for 12 h, the perylene
15 bisimides 5 was collected after column chromatography in
50% yield [17]. On the other hand, the diphenylacrylonitrile
o
189.5 C on heating, and two exothermic peaks at 120.1 and
o
180.2 C on cooling were observed. These results certainly
supported the phase transition process of the crystal phase-
mesophase-isotropic phase for compound 6. The slight
50 hysteresis phenomenon for phase transition temperatures on
cooling was observed, which was normal for this kind of
viscous material with a large molecular weight. Comparing
with its precursor 5, the crystal phase-mesophase transition
derivative
4
was prepared by condensating 4-
hydroxyphenylacetonitrile with benzaldehyde. As reactants 4
and 5 were prepared, compound 6 was prepared by further
20 treating 4 and 5 in K2CO3/DMF system at 100oC for 24 h. The
yield was 70% after column chromatography. The structure of
new perylene derivative 6 was confirmed by IR spectrum,
NMR spectrum, and high-resolution mass spectral analysis.
The molecular ion peak appeared at 2228.4368 in HR-MS
25 spectrum, which was exactly in accordance with the
molecular weight of compound 6. In the 1H NMR spectrum of
compound 6, the proton NMR signals agreed well with the
proposed structure (see SI). The signals in 13C NMR spectrum
also supported the structure of compound 6. This novel
30 perylene derivative possesses good solubility in a wide range
of organic solvents (such as CHCl3, toluene, CH2Cl2, DMSO,
o
temperature of compound 6 increased from 41.3 C to 124.9
55 oC but their mesophase-isotropic phase transition temperature
were almost same. Correspondingly, the scope of phase
o
transition temperature narrowed from 160 C of compound 5
o
to 65 C of compound 6 after calculation. These phenomena
were in accordance with the structure of compound 6, in
60 which the bulky diphenylacrylonitrile units on the bay-
positions enlarged the area of rigid perylene core, enhanced
the π-π action and resulted in the higher crystal phase-

mesophase transition temperature. On the other hand, the 25 Table 1 Transition temperatures (oC) and enthalpy changes
ACCEPTED MANUSCRIPT
bulky diphenylacrylonitrile units on bay-positions were
probably oriented near perpendicular to the perylene core and
thus the whole unit was no longer planar, which might
counteract the enhanced π-π action at mesophase, and leaded
to the similar mesophase-isotropic phase transition
temperatures finally. These analyses also agreed with the
previous reports that the bulky substituents on bay positions
increased the phase transition temperatures and destroyed π-π
(kJ/mol) of compound 6 and its precursor 5
compound Phase
Heating scan
Cooling scan
T(ꢀH)
transition[a] T(ꢀH)
5
6
Cr-Col
124.9(18.36)
189.5(4.34)
41.3(16.86)
190.1(1.44)
202.8(18.75)
120.1(19.98)
180.2(5.79)
35.6(12.74)
171.9(0.24)
188.8(14.08)
Col-Iso
Cr-Colh
Colh-Cold
Cold-Iso
5[b]
[a] Cr=crystalline, Col=columnar mesophase, Colh=hexagonal
columnar mesophase, Cold=disordered columnar mesophase,
Iso=isotropic; [b] These data were quoted from reference [17].
10 action to a certain degree [17, 51]. Based on these DSC data,
it could be concluded that, although the bulky
diphenylacrylonitrile units were introduced onto bay positions,
compound 6 still possessed stable and reversible mesophase
from 124.9 to 189.5 oC.
15
The mesomorphic property of compound 6 was further
investigated by POM. The phase transitions of Cr-Col and
Col-Iso phase were clearly observed. Their phase transition
temperatures were consistent with the DSC data
approximately. Figure 2 exhibited the mesomorphic texture at
30
Figure 2 The texture of compound 6 obtained with POM on
cooling at 150oC (Zooming in 200 times for big picture and
500 times for small picture)
20 1500C. This type of pseudo-confocal conic texture was typical
columnar mesophase, which was also confirmed by XRD.
The XRD analysis of mesophase of compound 6 was
1.2
1.0
0.8
35 investigated at 150oC as shown in Figure 3. In the small-angle
region, one strong reflection and two weak reflections were
observed at 1.98o, 3.43o and 3.97o, respectively. After
calculation according to the Bragg equation, the
corresponding distances for these reflections were 44.58 Å,
40 25.73 Å, and 22.24 Å, which agreed with the ratio of
1:1/√3:1/√4, indicating the [d100], [d110] and [d200] reflections
of hexagonal columnar liquid crystal for compound 6. In the
wide-region, the broad halo at 2θ = 15~30o implied the mean
cooling
0.6
0.4
0.2
0.0
second heating
-0.2
100
150
200
250
Temperature (oC)
Figure 1 The DSC trace of compound 6 on second heating
and cooling (scan rate 10oC min-1)

distance of 4.4Å and the short correlation length for the
precursor 5 in THF solution were presented in Figure 4. It can
be seen that, compound 5 exhibited strong peak at λ = 450-
550 nm for perylene skeleton only, but sample 6 showed the
strong absorption at λ = 300-350 nm and 450-600 nm for
ACCEPTED MANUSCRIPT
molten alkyl chains. A small reflection at 22.51o suggested the
distance of 3.95 Å, which was in accordance with the typical
values of intracolumnar distance of π-π interaction of the
5
ordered hexagonal columnar liquid crystal. On the other hand, 30 diphenylacrylonitrile moiety and perylene skeleton,
the lattice parameter ɑ for compound 6 could be calculated as
51.48 Å, which was smaller than the diameter of compound 6
(~64 Å) obtained by CPK molecular model. This result might
suggest that the soft alkyl chains in compound 6 were folding
respectively. The results suggested little interaction between
the two moieties of perylene and diphenylacrylonitrile. In
Figure 5, their fluorescence spectra of 6 presented a strong
emission at λ = 525-650 nm. In comparison with compound 5,
10 conformation or the possible interdigitation in the 35 the small bathochromic shift in both absorption and emission
neighbouring columns. Thus, the possible molecular stacking
for hexagonal columns of compound 6 was proposed in
Figure 3 (as shown in inserted box). Combining all the results
of DSC, POM and XRD experiments, it could be deduced that,
15 despite of the bulky diphenylacrylonitrile units onto perylene
skeleton, compound 6 maintained the ordered hexagonal
columnar mesophase between 124.9 and 189.5 oC.
spectra for sample 6 could be attributed to the introduction of
substituents on bay-posiutions leading in the twisting of
perylene skeleton and the loss of rigidity and planarity of
perylene bisimide chromophore [51-53].
The Abs of perylene moiety
The Abs of diphenylacrylonitrile moiety
1.0
compound 5
compound 6
0.5
600
500
400
300
200
100
0
d100
1.98(d100
)
ɑ
d110
0.0
CN
O
N
O
O
O
O
O
H
N
O
O
N
O
NC
O
O
O
O
N
H
300
400
Wavelength (nm)
500
600
d001
O
40
columnar stacking model
Figure 4 The absorption spectra of compounds 5 and 6 in
THF solution (2×10-6 M)
3.43
(
d110
)
3.97
(
d200
)
22.51(d001
)
400
20
40
compound 5
degree (2θ)
300
compound 6
0
Figure 3 XRD trace of compound 6 measured at 150 C and
200
100
0
20 the proposed molecular stacking model for hexagonal column
3.3. photophysical properties
500
550
600
650
700
Wavelength (nm)
The photophysical property of compound 6 was investigated
to study the influence of diphenylacrylonitrile units on
25 luminescence. The UV/Vis spectra of compound 6 and its
Figure 5 The emission spectra of compounds 5 and 6 in
THF solution (2×10-6 M) excited at λ= 480 nm for
compound 5 and 500 nm for compound 6.
45

25 the structure of compound 5 without AIE-active group. With
ACCEPTED MANUSCRIPT
the increase of water fraction, the solubility of compound 5
decreased slowly, resulting in the aggregation of compound 5
gradually and ACQ effect finally.
350
300
250
200
150
100
50
H2O fraction (%)
350
300
250
200
150
100
50
0
10
20
30
40
50
60
70
80
90
95
However, by comparison with precursor 5, compound 6
30 with AIE-active diphenylacrylonitrile unit exhibited markedly
different changes when excited at 330 nm or 480 nm. As
shown in Figure 9 excited at 330nm, the fluorescence
intensitybetween 550-650 nm for perylene skeleton of
compound 6 was weak (30 a.u.) in pure THF solution, which
0
0
20
40
60
80
100
H2O fraction(%)
0
350
400
450
500
550
600
Wavelength (nm)
Figure 6 The emission spectra of compound 4 with different
fractions of H2O in THF/H2O mixtures (4×10-6 M) excited at λ 35 was similar with that of compound 5 under same condition.
5
= 330 nm. (The square inserted: Variation in intensity with
fractions of H2O in THF/H2O mixtures)
With the increase of water fraction, the fluorescence intensity
enhanced rapidly and attained a maximum value at a water
fraction 40%. The highest intensity at water fraction of 40%
was 300 a.u., which was ten times than that in pure THF
Furthermore, the AIE and FRET effect of compound 6
were studied in THF/H2O mixtures. Firstly, the AIE activity 40 solution. With the water fraction increased further (> 40%),
10 of diphenylacrylonitrile 4 was explored at λex = 330 nm as
shown in Figure 6. With the increase of water fraction, the
fluorescence of compound 4 increased gradually and attained
a maximum at the water fraction of 80%. This result
the fluorescence intensity decreased quickly to 20 a.u. at
water fraction of 90%. In addition, although the strong
fluorescence intensity appeared at 400-500 nm for
diphenylacrylonitrile 4 with the increase of water fraction
suggested compound 4 possessed good AIE effect. Secondly, 45 (Figure 6), no obvious fluorescence emission for sample 6
15 the AIE activity of precursor 5 was also investigated at either
330 nm or 480 nm, respectively, for the purpose of comparing
with the data of compound 6 bearing diphenylacrylonitrile
units. The results were illustrated in Figure 7 and Figure 8.
with diphenylacrylonitrile units was observed at 400-500 nm
with the increase of water fraction. On the other hand, when
excited at 480 nm, the fluorescence intensity of compound 6
decreased with the increase of water fraction, which was
One can see that the fluorescence intensity decreased 50 similar to the changes of precursor 5 (Figure 10). Obviously,
20 gradually with the increase of water fraction THF/H2O
mixtures when excited at both 330 nm and 480 nm for
precursor 5. Moreover, the strongest fluorescence intensity
excited at 330 nm (33 a.u.) was far smaller than that excited at
480 nm (398 a.u.). These phenomena were in accordance with
the different change for compound 6 excited at 330 nm and
480 nm suggested the different fluorescence emission
mechanism, which could be explained smoothly by the AIE
and FRET effect as following analysis.

increased from 0% to 40%, the enhanced AIE effect produced
ACCEPTED MANUSCRIPT
40
20
0
H2O fraction (%)
20 stronger FRET effect, leading to the increase of fluorescence
intensity for perylene unit finally. On the other hand, with the
increase of the water fraction, the solubility of compound 6
decreased rapidly and the strong aggregation for perylene
skeleton appeared, leading to the ACQ effect. When the water
25 fraction was smaller than 40%, the AIE and FRET effect of
diphenylacrylonitrile unit were stronger than the ACQ effect,
resulting in the enhancement of fluorescence intensity with
the increase of water fraction. As the water fraction exceeded
40%, the ACQ effect of perylene skeleton was stronger than
30 the AIE and FRET effect of diphenylacrylonitrile unit, leading
to the decrease of fluorescence intensity for perylene skeleton.
These results suggested the existence of delicate balance
between AIE-FRET effect and ACQ effect. The water fraction
of 40% was the balance point with the strongest emission for
35 compound 6. However, when excited at 480 nm, the perylene
skeleton of compound 6 could emitted as compound 5, but the
diphenylacrylonitrile moiety of sample 6 showed little
emission at this excited wavelength and produced little AIE
effect. Thus, compound 6 when excited at λ = 480 nm showed
40 similar fluorescence change as compound 5.
0
40
20
0
10
20
30
40
50
60
70
80
90
0
20
H
40
60
80 100
Ofraction (%)
2
400
450
500
550
600
650
Wavelength (nm)
Figure 7 The emission spectra of compound 5 with different
fractions of H2O in THF/H2O mixtures (2×10-6 M) excited at λ
= 330 nm. (The square inserted: Variation in intensity with
fractions of H2O in THF/H2O mixtures)
5
400
400
300
200
100
0
350
300
250
200
150
100
50
H
O fraction (%)
2
0
10
20
30
40
50
60
70
80
90
0
20
40
60
80 100
H2Ofraction (%)
0
400
450
500
550
Wavelength (nm)
600
650
700
Figure 8 The emission spectra of compound 5 with different
fractions of H2O in THF/H2O mixtures (2×10-6 M) excited at λ
= 480 nm. (The square inserted: Variation in intensity with
10 fractions of H2O in THF/H2O mixtures)
As compound 6 possessed two absorption peaks for perylene
unit and diphenylacrylonitrile unit independently, the strong
fluorescence for diphenylacrylonitrile unit should appear
based on the AIE effect with the increase of water fraction
15 when excited at 330 nm. Therefore, no fluorescence emission
observed at 400-500 nm for sample 6 in THF/H2O mixture
might indicate the FRET effect between diphenylacrylonitrile
and perylene moiety. As a result, when the water fraction
300
300
H2O fraction (%)
200
0
10
200
20
30
40
50
60
70
80
90
100
0
0
20
40
60
80 100
H2Ofraction (%)
100
No emission for
diphenylacrylonitrile units
0
400
450
500
550
600
650
Wavelength (nm)
Figure 9 The emission spectra of compound 6 with different

fractions of H O in THF/H O mixtures (2×10-6 M) excited at λ
Furthermore, this deduction for mechanism was confirmed
ACCEPTED MANUSCRIPT
2
2
= 330 nm. (The square inserted: Variation in intensity with 20 by the fluorescence quantum yield and fluorescence lifetime
fractions of H2O in THF/H2O mixtures)
of compound 6 excited at 330nm and 480 nm in pure THF and
THF/H2O with water fraction of 40%, respectively. Table 2
exhibited all these data of photophysical properties of
compounds 5 and 6. The values (τ) of fluorescence lifetime of
25 compound 6 excited at 330 nm and 480 nm was 4.86 ns and
4.63 ns, respectively. The obvious difference for these
fluorescence lifetimes indicated the different emission
mechanism at 330 nm and 480 nm. The value (ФF) of
fluorescence quantum yield of compound 6 in THF/H2O with
30 water fraction of 40% was as high as 0.36, which was far
higher than that in pure THF solution. This result was also in
accordance with the AIE and FRET effect of compound 6 in
THF/H2O mixture. Combining all these above analysis, it
could be concluded that the effective AIE and FRET process
35 existed for compound 6 with diphenylacrylonitrile units when
excited at 330 nm in THF/H2O mixture. The fluorescence
intensity at THF/H2O with water fraction of 40% was 10
times higher than that in pure THF solution. The pseudo
Stokes shift was as large as 251 nm for this fluorescence
40 emission. After calculated with the density functional theory
(DFT) method at the B3LYP/6-31G(d) level by Gaussian 09
program, the optimized structure of compound 6 with lowest
energy was obtained as shown in Figure 11. Based on this
optimized structure, the proposed AIE effect and energy-
45 transfer process was exhibited in Figure 11. In a word,
perylene derivative 6 bearing diphenylacrylonitrile groups not
only was the novel hexagonal columnar perylene liquid
crystal, but also exhibited good fluorescence with large
pseudo Stokes shift based on AIE and FRET effects.
H2O fraction (%)
250
0
10
20
30
40
50
60
70
80
90
200
250
200
150
150
100
50
100
50
0
0
0
20
40
60
80 100
H2Ofraction(%)
400
450
500
550
600
650
700
Wavelength (nm)
5
Figure 10 The emission spectra of compound 6 with different
fractions of H2O in THF/H2O mixtures (2×10-6 M) excited at λ
= 480 nm. (The square inserted: Variation in intensity with
fractions of H2O in THF/H2O mixtures)
10 Table 2 Absorption and fluorescent data of compounds 6 and
5 (2×10-6 M).
Stokes shift
(nm)
λabs
λem
τ
[e]
[f]
Comp.
(nm) (nm)
(ns)
ФF
ФF
6
6
5
5
324[a]
541[b]
/
575
575
556
556
4.86[c]
4.63[d]
3.94[c]
3.93[d]
251
34
/
0.04[c] 0.36
0.30[d] 0.07
0.03[c] 0.02
0.34[d] 0.06
528[b]
28
[a] The absorption maximum of diphenylacrylonitrile unit.
[b] The absorption maximum of perylene unit.
[c] The λex = 330 nm.
15 [d] The λex = 480 nm.
[e] The ΦF values in THF solution.
[f] The ΦF values in THF/H2O mixture with water fraction of
40%.

mechanism was also confirmed by the investigation of
ACCEPTED MANUSCRIPT
fluorescence quantum yield and fluorescence lifetime of
compound 6. This type of AIE and FRET effect was observed
for the first time for a perylene liquid crystal, which opens
30 new strategy to design and synthesis of novel perylene liquid
crystal possessing unique fluorescence with large Stokes shift.
Figure 11 The proposed AIE and FERT mechanism for
compound 6
Acknowledgment. Financial support from the National
Natural Science Foundation of China (No: 21406036), Fujian
35 Natural Science Foundation of China (No. 2017J01571) and
the National Undergraduate Innovation Program in Fujian
Normal University were greatly acknowledged.
5
4. Conclusion
In summary,
a novel perylene liquid crystal with
diphenylacrylonitrile groups on the 1,7-bay positions was
designed and synthesized in 70% yield. Its structure was
confirmed by FT-IR, NMR and HR-MS. Its mesomorphic
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ACCEPTED MANUSCRIPT
Novel perylene liquid crystal with diphenylacrylonitrile groups was synthesized.
It showed the ordered hexagonal columnar mesophase.
Its fluorescence increased in THF/H2O mixtures when excited at 330 nm.
The pseudo Stokes shift was as large as 251 nm.
The AIE and FRET effect was firstly observed for perylene liquid crystal.