Novel liquid crystals with high fluorescence: Synthesis, mesomorphic and photophysical properties of cholesterol-triazine-BODIPY trimers

Article abstract of DOI:10.1016/j.molstruc.2018.03.093

By step-by-step etherification on cyanuric chloride with BODIPY unit and cholesterol units, two novel cholesterol-triazine-BODIPY trimers (compounds 6 and 7 with one and two cholesterol unit, respectively) were designed and synthesized in high yields. The investigation on mesomorphic properties suggested that compound 6 with one cholesterol unit was a nematic liquid crystal but compound 7 with two cholesterol units was a hexagonal columnar liquid crystal. Both compounds 6 and 7 exhibited the strong fluorescence with high quantum yields and larger Stokes shifts than their precursors. The cholesterol-triazine moiety played crucial role for producing liquid crystalline property and enhancing fluorescence.

Full text of DOI:10.1016/j.molstruc.2018.03.093

Accepted Manuscript
Novel liquid crystals with high fluorescence: Synthesis, mesomorphic and
photophysical properties of cholesterol-triazine-BODIPY trimers
Yuzhi Xiong, Sining Zheng, Ling Zhu, Hongyu Guo, Fafu Yang
PII:
S0022-2860(18)30388-0
10.1016/j.molstruc.2018.03.093
MOLSTR 25032
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 6 February 2018
Revised Date: 14 March 2018
Accepted Date: 22 March 2018
Please cite this article as: Y. Xiong, S. Zheng, L. Zhu, H. Guo, F. Yang, Novel liquid crystals with high
fluorescence: Synthesis, mesomorphic and photophysical properties of cholesterol-triazine-BODIPY
trimers, Journal of Molecular Structure (2018), doi: 10.1016/j.molstruc.2018.03.093.
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ACCEPTED MANUSCRIPT
Novel liquid crystals with high fluorescence:
Synthesis, mesomorphic and photophysical
properties of cholesterol-triazine-BODIPY trimers
YUZHI XIONGa, SINING ZHENGa, LING ZHUa, HONGYU GUOa*, AND FAFU
YANGa,b*
a College of Chemistry and Chemical Engineering, Fujian Normal University, Fuzhou 350007, P.
R. China
E-mail: yangfafu@fjnu.edu.cn
Tel.: 0086-591-83465225
b Fujian Key Laboratory of Polymer Materials, Fuzhou 350007, P. R. China
Running Title: cholesterol-triazine-BODIPY trimers
Keywords: Cholesterol; Bodipy; triazine; mesophase ; fluorescence.
1

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GRAPHICAL ABSTRACT
H
H
H
H
O
H
H
F
B
O
O
O
N
O
O
O
O
F
F
F
N
N
N
N
N
N
B
O
N
N
O
O
O
N
O
H
H
O
O
O
λem = 522 nm
H
H
H
O
H
O
Novel cholesterol-triazine-BODIPY trimers 7 bearing two cholesterol units was a hexagonal
columnar liquid crystal with strong fluorescence, and the cholesterol-triazine moiety played
crucial role for producing liquid crystalline property and enhancing fluorescence.
2

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Abstract By step-by-step etherification on cyanuric chloride with BODIPY unit and cholesterol
units, two novel cholesterol-triazine-BODIPY trimers (compounds 6 and 7 with one and two
cholesterol unit, respectively) were designed and synthesized in high yields. The investigation on
mesomorphic properties suggested that compound 6 with one cholesterol unit was a nematic
liquid crystal but compound 7 with two cholesterol units was a hexagonal columnar liquid
crystal. Both compounds 6 and 7 exhibited the strong fluorescence with high quantum yields and
larger Stokes shifts than their precursors. The cholesterol-triazine moiety played crucial role for
producing liquid crystalline property and enhancing fluorescence.
3

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Introduction
In the past decades, liquid crystalline materials have been paid much attention due to their unique
and excellent optical application [1-4]. Columnar discotic liquid crystals, as an important
subclass of liquid crystals, presented the π-π stacking arrangement in one direction, leading to
high 1D charge and/or energy transport with potential application in the fields of organic light-
emitting diodes, gas sensors, organic photovoltaic cells, organic field-effect transistors, etc [5-9].
Especially, the columnar luminescent liquid crystals attracted much research interests due to the
effective combination of intrinsic luminescent capability and the supramolecular self-assembly
within a mesophase [10, 11], such as perylene liquid crystals with high fluorescence [12-18].
BODIPY (4,4-Difluoro-4-borata-3a,4a-diaza-s-indacene) is a kind of dye with high
fluorescence, good photochemical stability and energy- and electron-transfer abilities [19-22].
Some BODIPY liquid crystals were also investigated by introducing soft alkyl chains to
BODIPY skeleton [23-32]. However, due to the irregular and asymmetric structures of BODIPY
unit, it was difficult to obtain the columnar BODIPY liquid crystal. On the other hand, it was
well known that cholesterol moiety was a good alkyl unit to construct all kinds of liquid crystal
materials [33-38]. Some examples of cholesterol-BODIPY derivatives were also synthesized, but
no liquid crystalline property was reported due to the defect of BODIPY unit as rigid moiety for
mesophase [39-42]. Recently, cyanuric chloride, possessing three Cl groups with stepwise
reaction activity [43, 44], was used as a good platform to construct liquid crystals by bridging
multiple mesogens onto rigid triazine core. Inspiring by this synthetic strategy, in this paper, the
novel cholesterol-triazine-BODIPY trimers were prepared conveniently by grafting sequentially
the BODIPY unit and cholesterol units onto cyanuric chloride. Moreover, the studies on
4

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mesomorphic properties revealed that the cholesterol-triazine-BODIPY trimer with one
cholesterol unit was a nematic liquid crystal and the one with two cholesterol units was a
columnar liquid crystal. These results not only showed the first examples of cholesterol-
BODIPY liquid crystals, but also suggested the molecular stacking behaviors in mesophase
could be tuned by the number of cholesterol units.
Experimental
Materials and Methods
The chemical reagents were purchased from Aladdin L.L.C. and used directly. TLC analysis was
carried on pre-coated glass plates. Column chromatography was purformed on silica gel (200-
300 mesh). NMR spectra were measured on a Bruker-ARX 600 instrument at 25oC. MS spectra
were done on Bruker mass spectrometer. Compound 1 was synthesized by the literature method
[45]. Compounds 4 and 5 were prepared by the reported procedures.14 UV-Vis spectra were
measured on Varian UV-Vis spectrometer. Fluorescence spectra were obtained in a conventional
o
quartz cell (10×10×45 nm) at 25 C on a Hitachi F-4500 spectrometer, with excitation and
emission slits 5 nm wide. The fluorescence quantum yields (ΦF) were measured on Edinburgh
Instruments FLS920 Fluorescence Spectrometer with a 6-inch integrating sphere. Leica DMRX
POM with a hot stage (Linkam THMSE 600) was used to examine phase transitions. Thermal
analysis of the materials was performed on DSC (Thermal Analysis Q100) at a scanning rate of
10oC/min under N2 atmosphere. XRD data were obtained on SEIFERT-FPM (XRD7), using Cu
Kα 1.5406Å as the radiation source with 40 kV, 30 mA power.
Synthesis of compound 2
Under N2 atmosphere, a mixture of cyanuric chloride (0.12 g, 0.65 mmol), compound 1
(0.18 g, 0.53 mmol) and NaHCO3 (0.065 g, 0.77 mmol) was stirred in 20 mL of dry acetone at 0-
5

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5 oC for 1.5 h. The TLC detection indicated the disappearance of compound 1. Then the reaction
mixture was poured into 100 mL of ice water. The obtained mixture was stirred and the red
precipitate emerged gradually. The red precipitate was filtered, washed by ice water and dried
under vacuum. Compound 2 was obtained as the red solid in yield of 88%. 1H NMR (400 MHz,
CDCl3) δ (ppm): 1.46 (s, 6H, CH3), 2.56 (s, 6H, CH3), 6.01 (s, 2H, ArH), 7.31 (d, J = 8.0 Hz, 2H,
ArH), 7.40 (d, J = 8.0 Hz, 2H, ArH). 13C NMR (100 MHz, CDCl3) δppm: 14.53, 29.72, 121.55,
122.28, 129.90, 131.33, 133.95, 139.90, 143.03, 151.61, 155.98, 171.25, 173.17; MS(MALDI-
TOF)(m/z) : 489.338 (M+H)+. MS(ESI) (m/z): calcd for C22H18BCl2F2N5O 488.1026 (M+H)+,
found 488.1028.
Synthesis of compound 6
Under nitrogen protection, the mixture of compound 2 (0.26 g, 0.53 mmol), compound 5
(0.29g, 0.53 mmol) and Na2CO3 (0.074 g, 0.7 mmol) was stirred in 30 mL of dry acetone at 25oC
for 6 h. The reaction mixture was monitored by TLC technique, suggesting the disappearance of
strarting materials. Then 80 mL of ice water was added in the reaction mixture. The obtained
mixture was continually stirred and the red precipitate appeared. The red precipitate was
collected and purified by column chromatography (eluent: petroleum ether : CH2Cl2=2:1).
1
Compound 6 was obtained as the red solid in yield of 83%. Compound 6: H NMR (400 MHz,
CDCl3) δ (ppm): 0.68~2.36 (m, 49H, CH3 and H of cholesterol), 2.58 (s, 6H, CH3), 4.59 (s, 2H,
OCH2CO), 4.76 (bs, 1H, OCH), 5.43 (s, 1H, CH=C on cholesterol), 6.02 (s, 2H, ArH), 6.94 (d, J
= 8.0 Hz, 2H, ArH), 7.11 (d, J = 8.0 Hz, 2H, ArH), 7.33 (d, J = 8.0 Hz, 2H, ArH), 7.38 (d, J =
13
8.0 Hz, 2H, ArH). C NMR (100 MHz, CDCl3) δppm:173.32, 168.62, 168.05, 155.67, 152.85,
152.05, 145.81, 142.90, 140.65, 139.24, 131.41, 129.26, 129.17, 123.02, 122.27, 121.69, 121.43,
115.88, 115.47, 75.39, 71.79, 56.79, 56.04, 50.03, 42.33, 39.74, 39.53, 37.99, 37.29, 36.92, 36.57,
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36.21, 35.80, 31.93, 31.44, 29.70, 28.23, 27.88, 24.30, 23.85, 22.81, 21.10, 19.40, 18.60, 14.33,
11.87; HR-ESI-MS (m/z): calcd for C57H69BClF2N5O5: 987.5052(M+), found 987.5013.
Synthesis of compound 7
Under the protection of N2 atmosphere, the mixture of compound 5 (0.11 g, 0.2 mmol),
compound 6 (0.20 g, 0.2 mmol), and Na2CO3 (0.1 g, 0.9 mmol) was refluxed in 30 mL of dry
THF for 10 h. The reaction system was monitored by TLC analysis, indicating the strarting
materials were used out. Then the reaction mixture was poured into 60 mL of ice water. After
stirring for another 20 min, the obtained mixture was extracted by 40 mL of CH2Cl2. The organic
layer was partitioned and concentrated. The residue was further purified by chromatographic
column (eluent: petroleum ether : CH2Cl2 =2:1). Compound 7 was collected as red solid in 75%
yield. 1H NMR (400 MHz, CDCl3) δ (ppm): 0.68~2.36 (m, 92H, CH3 and H of cholesterol), 2.57
(s, 6H, CH3), 4.56 (s, 4H, OCH2CO), 4.76 (bs, 2H, OCH), 5.36 (s, 2H, CH=C on cholesterol),
6.01 (s, 2H, ArH), 6.90 (d, J = 8.0 Hz, 4H, ArH), 7.08 (d, J = 8.0 Hz, 4H, ArH), 7.35 (d, J = 7.2
Hz, 2H, ArH), 7.38 (d, J = 8.0 Hz, 2H, ArH). 13C NMR (100 MHz, CDCl3) δppm: 173.90,
173.12, 172.40, 156.41, 155.42, 152.03, 144.78, 143.05, 140.64, 139.69, 132.45, 131.37, 128.80,
122.68, 122.18, 121.26, 114.72, 74.08, 67.13, 56.51, 55.81, 49.73, 42.00, 39.31, 37.81, 37.10,
36.58, 35.82, 35.69, 31.96, 28.74, 28.26, 28.02, 27.82, 24.53, 24.30, 23.87, 22.86, 22.61, 21.05,
19.33, 18.75, 14.17, 11.71. HR-ESI-MS (m/z): calcd for C92H120BF2N5O9: 1487.9155(M+), found
1487.9155.
Results and Discussion
Synthesis and characterization
7

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Scheme 1 exhibited the synthetic routes for cholesterol-triazine-BODIPY trimers 6 and 7. Due to
the different reaction activity of the three Cl groups [43, 44], the BODIPY unit and cholesterol
units were introduced sequentially by adjusting the reaction condition. According to the reported
procedure, the hydroxyl BODIPY 1 and cholesterol derivative 5 with phenolic hydroxyl group
were prepared beforehand in moderate yields [14, 45]. Then, by the nucleophilic substitution in
o
NaHCO3 / acetone system at 0-5 C, the triazine derivative with one BODIPY unit 2 was
synthesized in yield of 88% after precipitation. Subsequently, reacting compound 2 with
compound 5 under the condition of Na2CO3 / acetone at room temperature, triazine derivative 6
with both BODIPY unit and a cholesterol unit was smoothly obtained in yield of 83% after
column chromatography. Furthermore, the triazine derivative 7 with one BODIPY unit and two
cholesterol units was prepared by refluxing compound 6 with compound 5 in Na2CO3 / THF
system. The yield was as high as 75% after column chromatography.
The structures of novel cholesterol-triazine-BODIPY trimers 6 and 7 were confirmed by HR-
MS and NMR spectra. In their HR-MS spectra, the corresponding molecular ion peaks at
987.5013 and 1487.9155 (the deviations < 5 ppm) certainly supported that the one cholesterol
unit and two cholesterol units were introduced onto compounds 6 and 7, respectively. Moreover,
1
the proton signals in their H NMR spectra were well in accordance with the structures. For
example, the clear doublets were observed for the protons on aromatic groups (see supported
13
information). The C NMR spectra were also in agreement with the structures of compounds 6
13
and 7. Although the C signals for cholesterol unit were complicated to be distinguished, two
singlets for OCH and OCH2 at 60-75 ppm and the signals for carbon atoms on aromatic groups
were in consistent with their structures.
8

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OH
OH
TFA
DDQ
Et3N
+
BF3-OEt2
THF, rt
N
H
CHO
N
N
B
F
F
Cl
1
Cl
N
N
N
NaHCO3
acetone, 0-5oC
N
N
F
F
N
N
+
1
Cl
N
O
B
Cl
Cl
2
O
Cl
H
HO
OH
H
H
Cl
H
H
H
H
DCM
Cl
K2CO3, MeCN
H
H
O
O
O
3
O
HO
4
5
O
HO
H
H
Cl
H
O
N
N
F
F
N
Na2CO3
acetone, rt
2 + 5
O
O
N
B
O
O
N
6
5, Na2CO3
H
H
THF, refluxing
H
O
O
F
N
O
B
O
N
F
N
N
O
N
O
H
H
O
O
H
O
7
Scheme 1. The synthetic routes of compounds 6 and 7
Mesomorphic properties
The mesomorphic properties of samples 6 and 7 were studied by differential scanning
calorimetry (DSC) firstly. The results were exhibited in Figure 1 and the corresponding
thermodynamic parameters were summarized in Table 1. One can see that both samples 6 and 7
showed two thermic peaks upon cooling and second heating, suggesting that they might possess
mesophase during these thermic processes. Compound 6 presented two broad endothermic peaks
9

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o
o
o
at 76.5 oC and 136.8 C on heating and two exothermic peaks at 72.0 C and 128.6 C upon
cooling. As to compound 7, two broad endothermic peaks at 71.5 oC and 124.7 oC on heating and
o
o
two broad exothermic peaks at 60.3 C and 118.2 C for cooling were observed. Based on the
changes of DSC traces, it could be deduced that novel cholesterol-triazine-BODIPY trimers 6
and 7 displayed the phase transitions of solid state-mesophase-isotropic phase upon cooling and
second heating, which were further supported by the studies of polarizing optical microscopy
(POM) and X-ray diffraction (XRD) analysis. On the other hand, the phase transition
temperatures of sample 6 with one cholesterol unit were higher than that of sample 7 with two
cholesterol units, indicating the more cholesterol units were favorable for decreasing the
mesophase temperature. Moreover, after calculation, the scopes of mesophase temperature for
compounds 6 and 7 were 60.3 oC and 53.2 oC, respectively, implying that both of them possessed
liquid crystalline behaviors at broad temperature scopes.
Cr
LC
Iso
Iso
7
cooling
heating
Cr
LC
6
Cr
Cr
LC
Iso
LC
cooling
heating
Iso
0
50
100
150
200
250
Temperature (oC)
Figure 1. The DSC traces of compounds 6 and 7 on second heating and cooling (scan rate 10oC
min-1). Cr = crystalline, LC = liquid crystal, Iso = isotropic
10

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Table 1. Transition temperatures (oC) and enthalpies (kJ·mol-1) of samples 6 and 7
Comp.
T(ꢀH)
T(ꢀH)
Phase transition[a]
Cr-LC(LC -Cr)
LC-Iso(Iso-LC)
Cr-LC (LC-Cr)
LC-Iso(Iso-LC)
Heating scan
76.5(15.8)
136.8(8.2)
71.5(16.8)
124.7(15.9)
Cooling scan
72.0(11.9)
128.6(7.6)
60.3(7.1)
118.2(8.8)
6
7
[a] Cr=crystalline, LC=liquid crystal, Iso=isotropic
Figure 2. Mesomorphic textures of compounds 6 and 7 at 100 oC (×400) under POM on cooling.
Furthermore, the mesomorphic textures of compounds 6 and 7 were investigated under POM
observation. The phase transitions of solid state-mesophase-isotropic phase were observed for
compounds 6 and 7 on both heating and cooling. The phase transition temperatures also agreed
with the thermic peaks of DSC traces approximately. As cooling slowly from the isotropic phase,
the orderly mesomorphic textures could be distinguished gradually. One can see that sample 6
showed the schlieren texture (Figure 2), indicating the nematic mesophase for sample 6.
11

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However, sample 7 exhibited the focal-conic and band texture, suggesting the columnar
mesophase for sample 7. These textures were further confirmed by XRD analysis.
4.54o
6
7.87o
9.08o
20.16o
7
10
20
30
40
50
60
Scattering angle 2
θ
(degree)
Figure 3. XRD traces of samples 6 and 7 at 100 oC.
o
The XRD traces of samples 6 and 7 at 100 C for their mesophases were displayed in
Figure 3. It can be seen that only the broad halo at 2θ = 13~25o for the molten cholesterol and
alkyl chains of sample 6 was observed, and no other obvious peak appeared, indicating the
nematic mesophase for sample 6, which was in accordance with the previous texture analysis.
However, sample 7 presented completely different XRD trace from that of sample 6. At the
small-angle region, three reflections at 4.54o, 7.87o and 9.08o were observed for sample 7
obviously. Based on Bragg’s formula d = λ/(2Sinθ), the corresponding d-spacings were 19.45,
11.22 and 9.73 Å after calculation. The ratios of these d-spacings were consistent with 1:1/√3:1/2
for the [100], [110] and [200] planes of hexagonal columnar mesophase. Furthermore, the broad
halo at 2θ = 13~25o for sample 7 indicated the very short correlation length of the molten
cholesterol and alkyl chains. The small reflection at 20.16o (d-spacing of 4.4 Å) could be
identified as the typical intracolumnar distance of π-π interactions of ordered hexagonal
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columnar mesophase. The above XRD analysis suggested that sample 6 with one cholesterol unit
had the nematic mesophase but sample 7 with two cholesterol units possessed the hexagonal
columnar mesophase. The difference of mesophase for samples 6 and 7 could be explained by
their structures. Sample 6 with one cholesterol unit was a rodlike structure, preferring to the
nematic mesophase. But sample 7 with two cholesterol units showed higher molecular symmetry
than sample 6, which might be favorable for columnar molecular stacking. The possible
schematic representation of sample 7 in hexagonal columnar mesophase was proposed in Figure
4. Based on all the analysis of DSC, POM and XRD data, it could be concluded that novel
cholesterol-triazine-BODIPY trimers 6 and 7 exhibited good liquid crystalline behaviors and two
cholesterol units on triazine skeleton were favorable for not only decreasing the mesophase
temperature, but also producing hexagonal columnar mesophase.
H
d
100
H
H
O
d
110
O
O
O
F
F
N
N
N
N
d
001
B
O
N
O
O
O
O
H
H
H
Figure 4. The proposed schematic representation of sample 7 in hexagonal mesophase
Photophysical properties
The photophysical properties of novel cholesterol-triazine-BODIPY trimers 6 and 7 were
investigated and their precursors 1 and 2 were used for data comparison. Their absorption spectra
and fluorescence spectra in toluene with concentrations of 1.0×10-6 M were exhibited in Figure 5
and 6. The photophysical data for samples 6, 7 and their precursors 1 and 2 were summarized in
13

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Table 2. One can see that samples 6 and 7 showed similar absorption spectra, but the absorbance
of sample 6 was larger than that of sample 7. Their maximum absorption wavelengths were at
about 505 nm, which were in accordance with the precursors 1 and 2. These results might
suggest the non coplanar structure of BODIPY unit and triazine group, leading to little influence
on the absorption spectra of BODIPY skeleton. However, the fluorescence spectra of samples 6
and 7 exhibited different changes as compared with their precursors 1 and 2. It can be seen that
the maximum emission wavelength exhibited the order of 1 (511 nm) < 2 (516 nm) < 6 (521 nm)
< 7 (522 nm). These phenomena could be explained by the intramolular charge transfer (ICT)
effect. Due to alkoxy, phenoxy and triazine group were introduced onto BODIPY unit, their
electron donating capabilities enhanced the ICT effect, and the more cholesterol units resulting in
stronger ICT effect. Thus, the stoke shifts of samples 6 and 7 were obvious larger than precursors
1 and 2, which were favorable for reducing the self-absorption in fluorescent emission. On the
other hand, both the fluorescence intensities and fluorescence quantum yields of compounds 2, 6
and 7 were higher than that of precursor 1. Moreover, by adding 0.5 mL of corresponding
solutions of toluene (1.0×10-3 M with compounds 1, 2, 6, and 7, respectively) on quartz glass, the
corresponding solid films of compounds 1, 2, 6, and 7 were prepared after natural vaporization of
solvents. As shown in Table 2, samples 6 and 7 displayed the solid fluorescence, while their
precursors 1 and 2 showed no fluorescence in solid films. These results could be explained by
that the introduction of triazine group and cholesterol units on BODIPY unit produced large
steric effect and then reduced the aggregation fluorescence quenching. The fluorescence in liquid
crystalline phase by heating the solid films was also investigated, but little emission was
observed due to the strong aggregation fluorescence quenching of the ordered π-π stacking in
mesophase. It was interesting that sample 6 with one cholesterol unit exhibited the little stronger
14

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fluorescence intensity and higher fluorescence quantum yield than sample 7 with two cholesterol
units. This fact might be ascribed to that, by comparing with sample 6, sample 7 possessed
higher molecular symmetry and stronger self-assembly aggregation ability (as analyzed in liquid
crystalline section). Combing the above photophysical analysis, it could be summarized that
novel cholesterol-triazine-BODIPY trimers 6 and 7 had high fluorescence with large Stokes
shifts. The triazine group and cholesterol units were favorable for good fluorescent performance.
0.08
1
0.06
6
0.04
7
2
0.02
0.00
350
400
450
500
550
600
650
700
Wavelength (nm)
Figure 5. Adsorption spectra of samples 6, 7 and precursors 1 and 2 in toluene (10-6 M)
5500
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
6
7
2
1
0
-500
480
500
520
540
560
580
600
Wavelength (nm)
Figure 6. Fluorescence spectra of samples 6, 7 and precursors 1 and 2 in toluene (10-6 M). All of
compounds were excited at 470 nm.
15

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Table 2. Absorption and fluorescence data for samples 6 and 7 in toluene at 298K
Samples
λabs
(nm)
504
505
503
505
λem
(nm)
521
522
511
516
Stokes shift
ФF
(toluene)
0.98
ФF
(films)
0.08
(nm)
17
17
8
6
7
1
2
0.95
0.06
0.94
none
none
11
0.96
Conclusions
In conclusion, the novel cholesterol-triazine-BODIPY trimers 6 and 7 were designed and
synthesized in good yields by orderly introducing BODIPY unit and cholesterol units onto
cyanuric chloride. The cholesterol-triazine-BODIPY trimer with one cholesterol unit was a
nematic liquid crystal but the one with two cholesterol units was a hexagonal columnar liquid
crystal. The studies on photophysical properties indicated that compounds 6 and 7 possessed the
strong fluorescence intensity with higher quantum yields and larger Stokes shifts than their
precursors. This research not only showed the first examples of cholesterol-BODIPY liquid
crystals, but also implied that the introduction of cholesterol unit was favorable for both liquid
crystalline behavior and excellent fluorescence, which provides a good strategy on design and
synthesis of novel Bodipy liquid crystal with high fluorescence.
Supplementary information (SI)
All additional information pertaining to characterization of the new compounds using NMR
spectra and MS technique are given in the supporting information.
16

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Acknowledgments
Financial support from the National Natural Science Foundation of China (No:
21406036), Fujian Natural Science Foundation of China (No. 2017J01571) and Undergraduate
innovation program of FJNU (2018) were greatly acknowledged.
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The first examples of cholesterol-BODIPY liquid crystals 6 and 7 were prepared.
The mesophase and fluorescence were tuned by cholesterol-triazine moiety.
Both compounds 6 and 7 exhibited strong fluorescence with high quantum yields.
Compound 6 with one cholesterol unit was a nematic liquid crystal.
Compound 7 with two cholesterol units was a hexagonal columnar liquid crystal.