Aminostyrylquinoxalines derived organic materials with remarkable solvatochromic and mechanofluorochromic properties

Article abstract of DOI:10.1016/j.dyepig.2019.107578

Four multi-responsive fluorophores (DMQA₁, DMQA₂, DMQB₁, DMQB₂) based on 2,3-dimethylquinoxaline were successfully designed and synthesized. It was found that all these fluorophores presented remarkable red-shifted solvatochromic behavior with increasing solvent polarity, in which, DMQA₂ displayed 117 nm red-shift from cyclohexane to DCM. Interestingly, these four compounds all exhibited high contrast mechanofluorochromism and DMQA₂ received the largest MFC spectral shift (Δλ_MFC = 84 nm). Moreover, Power wide-angle X-ray diffraction (PXRD) and Differential scanning calorimetry (DSC) were carried out to clarify the crystalline-amorphous transformation upon grinding. In this work, the quinoxaline template was introduced to develop high-performance MFC materials.

Full text of DOI:10.1016/j.dyepig.2019.107578

DyesandPigments170(2019)107578
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Aminostyrylquinoxalines derived organic materials with remarkable
solvatochromic and mechanofluorochromic properties
Jia Yua,1, Zhifang Liua,1, Bowei Wanga,b,c,∗∗, Yuqi Caoa, Dongqi Liua, Fuchao Lia, Xilong Yana,b,c,∗
a School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300350, PR China
b Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin, 300072, PR China
c Tianjin Engineering Research Center of Functional Fine Chemicals, Tianjin, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
2,3-Dimethylquinoxaline
Solvatochromism
Intramolecular charge transfer
Aggregation-induced emission
High contrast mechanofluorochromism
Four multi-responsive fluorophores (DMQA1, DMQA2, DMQB1, DMQB2) based on 2,3-dimethylquinoxaline
were successfully designed and synthesized. It was found that all these fluorophores presented remarkable red-
shifted solvatochromic behavior with increasing solvent polarity, in which, DMQA2 displayed 117 nm red-shift
from cyclohexane to DCM. Interestingly, these four compounds all exhibited high contrast mechano-
fluorochromism and DMQA2 received the largest MFC spectral shift (ΔλMFC = 84 nm). Moreover, Power wide-
angle X-ray diffraction (PXRD) and Differential scanning calorimetry (DSC) were carried out to clarify the
crystalline-amorphous transformation upon grinding. In this work, the quinoxaline template was introduced to
develop high-performance MFC materials.
1. Introduction
reported MFC materials experienced a tedious and complex synthesis
routine, which takes up too much time of researchers [17]. Therefore,
Multi-responsive organic fluorescent materials have received tre-
mendous attention for their potential applications as pressure sensors
[1], security ink [2], and water detectors in organic solvents [3,4].
However, most conventional luminogens suffer from the infamous ag-
gregation-caused quenching (ACQ) effect [5], which hinders their fur-
ther applications to a great extent.
exploring simple and short synthesis routines for developing high
contrast MFC materials is still of great challenge.
In this work, we introduced four luminophores (DMQs) based on
2,3-dimethylquinoxaline with phenothiazine or carbazole as electron
donor in only three steps, respectively (Scheme 1). These targeted
compounds exhibited significant mechanofluorochromic and solvato-
chromic properties. For instance, the maximum emission peaks of
DMQA1, DMQA2, DMQB1, and DMQB2 experienced 42 nm, 84 nm,
30 nm, and 37 nm red-shift, respectively, upon grinding. It should be
noted that our work has enriched AIE-active MFC templates and pro-
vided new members to high- performance MFC materials.
Luckily, Tang et al. reported the aggregation-induced emission (AIE)
phenomenon of 1-methyl-1,2,3,4,5-pentaphenylsilole, which emits ex-
tremely weak fluorescence in pure solutions but several times enhanced
emission in solid state [6]. Luminescent materials with AIE properties
have fundamentally overcome the limitation of ACQ effect and arise
extensive research interest [7–10]. In 2010, Park firstly designed the
mechanofluorochromic (MFC) materials based on AIE property [11].
Combining the advantage of both AIE and MFC materials, series AIE-
active MFC templates such as distyrylanthrancene derivatives [12],
triphenylamine derivatives [13], silole derivatives [14], tetra-
phenylethene (TPE) derivatives [15], cyano-substituted diarylethene
derivatives [11] and pyrone derivatives [16] have been explored.
Nevertheless, few AIE-active MFC materials have been designed based
on flattened quinoxaline derived templates and only a tiny part of them
displayed high contrast MFC behavior. Moreover, the majority of these
2. Experimental
2.1. Materials and characterizations
All these raw materials and reagents were purchased from com-
mercial sources. 1H NMR (400 MHz) and 13C NMR (100 MHz) spectra
were measured on a Bruker Avance (III) spectrometer with CDCl3 as the
solvent. High resolution mass spectrum was acquired on Bruker
Daltonics micrOTOF-Q II instrument. UV–vis spectra were recorded by
∗ Corresponding author. School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300350, PR China.
∗∗ Corresponding author. School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300350, PR China.
E-mail addresses: bwwang@tju.edu.cn (B. Wang), yan@tju.edu.cn (X. Yan).
1 These authors contributed equally to this work.
https://doi.org/10.1016/j.dyepig.2019.107578
Received 18 March 2019; Received in revised form 21 May 2019; Accepted 21 May 2019
Availableonline13June2019
0143-7208/©2019ElsevierLtd.Allrightsreserved.

J. Yu, et al.
DyesandPigments170(2019)107578
Scheme 1. Synthesis routes of DMQA1, DMQA2, DMQB1 and DMQB2.
using Evolution 300 spectrophotometer. Photoluminescence spectra of
liquid and Photoluminescence spectra of solid-state were performed on
Hitachi F-2500 spectrophotometer and Horiba Jobin Yvon Fluorolog-3
spectrophotometer, respectively. Thermal gravimetric analysis (TGA)
was measured on an STA 409 PC with a heating rate of 10 °C/min from
room temperature to 800 °C in a stream of nitrogen (40 mL/min).
Differential scanning calorimetry (DSC) was carried out on a Perkin-
Elmerat and the heating rate is 10 °C/min under N2 atmosphere. The
XRD measurements were measured on a Bruker D8 Focus Powder X-ray
diffraction instrument with the Cu Kα source radiation at room tem-
perature. Data points were obtained at a scanning rate of 5°/min from
2θ = 5°–60°. Single crystal X-ray diffraction (SXRD) data were
characterized on a Bruker AXS Smart APEX II diffractometer. The
structure was solved with direct methods by the SHELXL-97 programs.
Element analysis was carried on VarioEL cube and the IR spectra of
these compounds were characterized on a Nicolet 380 FT-IR spectro-
meter.
2.2. Synthesis
10-methyl-10H-phenothiazine [18] and 9-ethyl-9H-carbazole [19]
were synthesized as the literature reported.
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J. Yu, et al.
DyesandPigments170(2019)107578
found 633.2135. Elemental analysis calcd (%) for
2.2.1. Synthesis of 2,3-dimethylquinoxaline (DMQ)
(M
+
H)+
,
2,4-Pentanedione (0.50 mmol) and 1, 2-phenylendiamine
(0.55 mmol) were added into glacial CH3COOH (4.0 mL). The solution
was stirred at 60 °C for 2 h. Then, the mixture was poured into ice and
extracted with 1,2-dichloromethane. The organic layer was dried with
Na2SO4 and purified with silica-gel column chromatography using
petroleum ether/ethyl acetate (v:v = 5:1) as eluent [20].
C40H32N4S2: C, 75.92; H, 5.10; N, 8.85; S, 10.13. Found: C, 75.60; H,
4.941; N, 8.82; S, 10.451.
2.2.6. Synthesis of 9-ethyl-3-(2-(3-methylquinoxaline-2-yl) vinyl-9H-
carbazole (DMQB1)
By following the synthesis procedure of DMQA1, DMQB1 was ob-
tained. The crude product was purified with petroleum ether/1,2-di-
chloromethane (v:v = 1:3) as eluent. Yellow-green product was ob-
tained. Yield: 68%; m.p. 122–125 °C; 1H NMR (400 MHz, CDCl3) δ 8.04
(dd, J = 16.2, 7.5 Hz, 3H), 7.84 (d, J = 7.8 Hz, 1H), 7.78–7.64 (m, 2H),
7.43 (t, J = 7.6 Hz, 1H), 7.36 (d, J = 8.1 Hz, 1H), 7.23–7.09 (m, 4H),
6.80 (d, J = 12.4 Hz, 1H), 4.28 (q, J = 7.1 Hz, 2H), 2.56 (s, 3H), 1.37
(t, J = 7.1 Hz, 3H). 13C NMR (100 MHz, CDCl3) δ 152.60, 150.40,
141.65, 141.04, 140.66, 140.46, 138.81, 129.04, 128.82, 128.69,
128.28, 127.68, 126.12, 125.53, 123.44, 122.98, 120.62, 120.38,
119.60, 119.41, 108.80, 37.76, 23.28, 13.90. HRMS (ESI): calcd. for
2.2.2. Synthesis of 10-ethyl-10H-phenothiazine-3-carbaldehyede (PAD)
As reported in the literature [21], 1.6 mL Phosphorus oxychloride
was added into 5.0 mL N,N-Dimethylformamide dropwise at 0 °C under
continuous stirring for 40 min. After the brown-red mixture was
formed, 10-methyl-10H-phenothiazine (3.40 g, 16.00 mmol) in 20 mL
DMF was added dropwise in ice-bath under vigorous stirring, and then
the reaction mixture was heated at 60 °C for 14 h. After that, the red
reaction-mixture was poured into ice slowly and the pH of the solution
was adjusted to 7.0 using sodium hydroxide. The organic layer was
extracted with dichloromethane and dried over anhydrous magnesium
sulfate. Then, the solution was removed by vacuum evaporation and the
residue was purified with silica-gel column chromatography using
petroleum ether/ethyl acetate (v:v = 6:1) as eluent. Yellow powder was
obtained. Yield: 85%.
C
25H21N3: 364.1803 (M + H)+, found 364.1806. Elemental analysis
calcd (%) for C25H21N3: C, 82.61; H, 5.82; N, 11.56. Found: C, 80.34; H,
6.03; N, 11.44.
2.2.7. Synthesis
of
2,3-bis-2-(9H-ethyl-9H-carbazol-3-yl)
vinyl)
quinoxaline (DMQB2)
2.2.3. Synthesis of 10-ethyl-10H-carbazole-3-carbaldehyede (CBD)
The synthesis process of 10-ethyl-10H-carbazole-3-carbaldehyede is
similar to that of 10-ethyl-10H-phenothiazine-3-carbaldehyede. White
powder was obtained. Yield: 83% [22].
Similar to the synthesis procedure of DMQA2, DMQB2 was syn-
thesized. The crude product was purified with petroleum ether/1,2-
dichloromethane (v:v = 1:2) as eluent. Green product was obtained.
Yield: 35%; m.p. 300–301 °C; 1H NMR (400 MHz, CDCl3) δ 8.45 (s, 2H),
8.26 (d, J = 15.5 Hz,2H), 8.18 (d, J = 7.7 Hz, 2H), 8.13–8.04 (m, 2H),
7.89 (dd, J = 8.5, 1.4 Hz, 2H), 7.77 (d, J = 15.5 Hz, 2H), 7.72–7.63 (m,
2H), 7.55–7.40 (m, 6H), 7.33–7.20 (m, 2H), 4.41 (q, J = 7.2 Hz, 4H),
1.48 (t, J = 7.2 Hz, 6H). 13C NMR (100 MHz, CDCl3) δ 149.79, 141.58,
140.57, 140.46, 138.99, 129.01, 128.77, 127.93, 126.08, 125.53,
123.43, 123.02, 120.69, 120.43, 120.09, 119.37, 108.82, 108.78,
2.2.4. Synthesis
of
10-ethyl-3-(2-(3-methylquinoxaline-2-yl)-10H-
pehnothiazine (DMQA1)
THF (5 mL) was slowly added into the mixture of NaH (70%, 0.15 g,
4.50 mmol) and 2,3-dimethylquinoxaline (0.63 g, 4.00 mmol) at 0 °C
under vigorous stirring for 45 min. After that, the 10-ethyl-10H-phe-
nothiazine-3-carbaldehyede (1.00 g, 4.00 mmol) in THF solution was
added dropwise. The mixture was stirred at room temperature under
nitrogen atmosphere for 16 h and poured into ice, then neutralized with
5% HCl solution. After extracted with 1,2-dichloromethane and washed
with water, the organic layer was separated with silica-gel column
37.79, 13.84. HRMS (ESI): calcd. for C40H32N4: 569.2694 (M + H)+
,
found 569.2699. Elemental analysis calcd (%) for C40H32N4: C, 84.48;
H, 5.67; N, 9.85. Found: C, 80.92; H, 5.886; N, 9.46.
3. Results and discussion
chromatography
using
petroleum
ether/1,2-dichloromethane
(v:v = 1:2) as eluent. Yellow product was obtained after recrystalliza-
tion. Yield: 62%; m.p. 171–174 °C; 1H NMR (400 MHz, CDCl3) δ
8.09–8.00 (m, 1H), 7.99–7.87 (m, 2H), 7.75–7.58 (m, 2H), 7.43 (d,
J = 16.5 Hz, 2H), 7.33 (s, 1H), 7.21–7.09 (m, 2H), 6.99–6.82 (m, 3H),
3.96 (d, J = 6.1 Hz, 2H), 2.87 (s, 3H), 1.45 (t, J = 7.0 Hz, 3H). 13C NMR
(100 MHz, CDCl3) δ 152.55, 149.91, 145.64, 144.15, 141.53, 141.12,
136.29, 130.86, 129.10, 128.92, 128.81, 128.28, 127.67, 127.42,
125.63, 124.53, 123.54, 122.71, 120.55, 115.16, 114.92, 42.05, 23.16,
12.96. HRMS (ESI): calcd. for C25H21N3S: 396.1529 (M + H)+, found
396.1535. Elemental analysis calcd (%) for C25H21N3S: C, 75.92; H,
5.35; N, 10.62; S, 8.11. Found: C, 75.33; H, 5.35; N, 10.36; S, 8.02.
3.1. Synthesis
DMQs were synthesized from the condensation between DMQ,
phenothiazine and carbazole derivatives. NMR spectroscopy and high-
resolution mass spectrometry were employed to confirm the structures
of the four compounds (Figs. S1, S2, S3 and S4 ESI).
3.2. Photophysical property
As shown in Fig. S5, UV–vis absorption spectra of these four DMQs
in DCM were quite similar. They all displayed two absorption peaks.
The maximum absorption peak was attributed to the intramolecular
charge transfer (ICT) transition and the other one was referred to the π-
π∗ transition [23].
2.2.5. Synthesis of 2,3-bis-2-(10H-ethyl-10H-phenothiazin-3-yl-vinyl)
quinoxaline (DMQA2)
The synthesis of DMQA2 is similar to that of DMQA1, DMQA2 was
obtained from 2,3-dimethylquinoxaline (0.63 g, 4.00 mmol) and 10-
ethyl-10H-phenothiazine-3-carbaldehyede (2.00 g, 8.00 mmol) with
NaH (70%, 0.31 g, 9.00 mmol) as the base. The crude product was
purified with petroleum ether/1,2-dichloromethane (v:v = 1:2) as
eluent. Light orange product was obtained. Yield: 43%; m.p.
216–218 °C; 1H NMR (400 MHz, CDCl3): δ 8.00 (dt, J = 16.5, 3.2 Hz,
2H), 7.88 (d, J = 15.5 Hz, 2H), 7.69–7.61 (m, 2H), 7.47 (dd, J = 11.6,
9.9 Hz, 6H), 7.20–7.12 (m, 4H), 6.94–6.87 (m, 6H), 3.97 (q, J = 7.0 Hz,
4H), 1.46 (t, J = 7.0 Hz, 6H); 13C NMR (100 MHz, CDCl3) δ 149.17,
145.55, 144.21, 141.56, 136.65, 130.99, 129.23, 128.78, 127.46,
127.44, 127.39, 125.91, 124.45, 123.61, 122.67, 120.58, 115.14,
114.96, 42.06, 12.99. HRMS (ESI): calcd. for C40H32N4S2: 633.2136
Considering their D-π-A structures and explicit ICT effect, solvato-
chromism performance was examined. As described in Fig. 1, these four
fluorophores all exhibited fantastic solvatochromism. The emission of
DMQA1, DMQA2, DMQB1, and DMQB2 was located at 510 nm, 520 nm,
437 nm, 449 nm in cyclohexane and red-shifted to 599 nm, 637 nm,
522 nm, and 538 nm in DMF, respectively, accompanied with a quickly
decreased emission intensity. Generally, this significant red-shift ten-
dency can be explained by the larger polarity of the excited state than
the ground state during π-π∗ transition process, which contributes to a
greater solvent stabilization effect on the excited state [24].
As to gain further insight into the solvochromic properties of these
compounds, their frontier orbital distributions were calculated with
Gaussian 09. Depicted in Fig. 2, the highest occupied molecular orbitals
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DyesandPigments170(2019)107578
Fig. 1. The PL spectra in solvents with different polarity of (a) DMQA1 (b) DMQA2 (c) DMQB1 (d) DMQB2. The concentration of the solutions is 1.0 × 10−4 mol L−1
.
(HOMOs) of DMQA1 and DMQA2 were mainly concentrated on phe-
nothiazine unit while their lowest unoccupied molecular orbitals
(LUMOs) were basically distributed on the 2,3-dimethylquinoxaline
part. Such a distribution difference of HOMOs and LUMOs of DMQA1
and DMQA2 leads to a strong charge transfer and a narrow energy gap
of 2.96 and 2.87 eV, respectively. However, the electron donor ability
of carbazole is better than phenothiazine, which results in a different
electrons distribution. The HOMOs of DMQB1 and DMQB2 were spread
over the whole molecule while the LUMOs were mainly distributed on
the 2,3-dimethyquinoxaline, leading to an energy gap of 3.38 and
3.17 eV, respectively. Such a large charge separation between D (donor)
and A (acceptor) in these four molecules strongly sustained their
Fig. 2. B3LYP/6-31G(d) calculated molecular orbital amplitude plots and their calculated HOMO-LUMO energy gap (eV) of the four molecules.
4

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DyesandPigments170(2019)107578
Fig. 3. Fluorescence spectra of the four compounds in DCM solution (a) DMQA1; (b) DMQA2; (c) DMQB1 and (d) DMQB2. Insert pictures are photos of the solution
with different n-hexane fraction under 365 nm UV lamp. (e) Fluorescence spectra of the DMQB1 in THF solution; (f) Plots of I/I0 of the DMQB1, I0 refers to the PL
intensity of 0% water fraction.
distinct ICT effect and narrower energy gap of DMQA1 and DMQA2
guaranteed their better solvochromism [25].
characterized in THF-water mixture to get a further understand. As il-
lustrated, the emission intensity firstly increased with the addition of
water and reached the maximum value at 40% fn and then decreased,
corresponding to the phenomenon observed in DCM-n-hexane mixture.
As for DMQB2, the emission intensity declined when fn was below 10%
for the ICT effect and experienced an increase when fn is between 10%
and 60% for the RIR mechanism [23]. Along with the further addition
of n-hexane, amorphous aggregation formed and the PL intensity de-
clined again.
Fluorescence properties of these four compounds were character-
ized in DCM-n-hexane mixtures. As depicted in Fig. 3 and Fig. S7, the
emission intensity of DMQA1, DMQA2, and DMQB1 increased upon
addition of n-hexane, which can be ascribed to the restriction of in-
tramolecular rotation (RIR) [26]. Different from DMQA1 and DMQA2,
the PL intensity of DMQB1 decreased when n-hexane fraction (fn) ex-
ceeded 20%, which is probably attributed to the formation of amor-
phous particles [27]. The PL spectrum of DMQB1 was also
5

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DyesandPigments170(2019)107578
Fig. 4. PL spectra in solid states of the original and grounded samples. (a) DMQA1; (b) DMQA2; (c) DMQB1 and (d) DMQB2.
3.3. Mechanofluorochromic properties
crystalline states. However, the intensity of the ground samples was
weaker than the pristine, accompanied by several small peaks missing.
This phenomenon can be explained by partial destruction of the crys-
talline state. As for DMQA2, the curves of the original sample were
sharp and strong while the peaks of the ground sample were almost flat,
which was corresponded with the crystalline-amorphous transforma-
tion [12,17]. These results indicated that these compounds adopted two
different packing mode before and after ground [29]. As has been re-
ported [30], MFC properties were corresponded with the crystalline
destruction and the transformation of molecule configuration. When
external force was applied to the original sample, the crystal collapsed
and transformed into a disordered amorphous state, which was further
proved by the flattening and disappeared peaks in the XRD spectra
[31].
Then, the mechanofluorochromic properties of these DMQs were
characterized. As described in Fig. 4 and Fig. 5, these four compounds
all displayed distinct MFC properties. DMQA1, DMQA2, DMQB1 and
DMQB2 emitted greenlish-yellow, yellow, blue-green, and green fluor-
escence in original state and changed to orange, red, dark green, light-
yellow light upon grinding, accompanied with 42 nm, 84 nm, 30 nm,
and 37 nm red-shift, respectively(Table S1, ESI). Generally, the red-shift
of these four molecules can be attributed to the planarization induced
by external force. These AIE molecules tend to adopt twisted config-
urations and loose packing modes in solid state and grinding will push
the configuration planarization, thus leads to a bathochromic-shift in
spectra. As for the better MFC properties of DMQA1 and DMQA2, it can
be explained by the more twisted bowl-shaped molecule configuration
of phenothiazine [16,28].
According to Li et al. [10], the packing modes of these compounds
have an inherent correlation with their MFC properties. However, it is
hard to infer the packing mode in solid-state for the complicated af-
fecting factors such as molecular configurations, special groups, elec-
tronic interactions [32]. Thus, single crystal is the most efficient and
To reveal the MFC mechanism, PXRD of these DMQs were char-
acterized. As demonstrated in Fig. 6, both of original and ground
samples presented sharp curves, except DMQA2, implying their
Fig. 5. Colors of the original and ground sample of (a) DMQA1 and (b) DMQA2 observed without the UV-lamp. (For interpretation of the references to colour in this
figure legend, the reader is referred to the Web version of this article.)
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DyesandPigments170(2019)107578
Fig. 6. XRD patterns of the original and grounded samples. (a) DMQA1; (b) DMQA2; (c) DMQB1 and (d) DMQB2.
Interestingly, the original sample of DMQB2 presented an extra exo-
thermic peak at around 160 °C, which was referred to as the exothermic
crystallization peak. As for DMQB1, the original sample only exhibited
a Tm peak while the ground sample presented an extra TL before the Tm
[12]. These results proved that the ground samples were in a more
stable state and the pressing or grinding process brought morphology
transformation, which was corresponded with the red-shifted MFC
properties [31,35].
Based on the above discussion, we inferred that the better MFC
properties of these phenothiazine substituted DMQs were attributed to
their larger dihedral angle and the bowl shape configuration. As for the
largest red-shift MFC property of DMQA2 was also partly due to the
completed packing mode transformation.
Fig. 7. (a) Single crystal and (b) basic unit of DMQB1.
intensified way to clarify the packing mode and their MFC properties.
We tried our best but only single crystal of DMQB1 was obtained in
DCM/CH3CN system and characterized. As shown in Fig. 7. and Table
S2, the DMQB1 adopted a twisted conformation in crystal with torsion
angles between the 2,3-dimethylquinoxaline template and the carba-
zole unit of 79.8°. The packing mode was very loose and it is hard to
find face-to-face π-π staking between two molecules. Upon grinding,
the dihedral angle decreased and molecular layers slipped, leading to
planarization of the twisted configuration and increased π-π interac-
tion. Thus, the discussed comprehensive factors contributed to the red-
shifted MFC properties [33,34].
Furthermore, thermal properties of these DMQs were studied by
DSC and TGA. Moreover, the DSC spectra of these four compounds were
quite different. As illustrated in Fig. 8, both pristine and ground samples
of DMQA1, DMQA2, and DMQB2 displayed two endothermic peaks in
the spectra. The peak in the low-temperature zone referred to the
crystalline to liquid crystal transition (TL) and the peak in high-tem-
perature zone was ascribed to the isotropic melt transition (Tm). In
addition, the TL of these samples was broader after grinding.
4. Conclusion
Four 2,3-dimethylquinoxaline derivatives, DMQA1, DMQA2,
DMQB1 and DMQB2 were designed and synthesized. All these targeted
DMQs displayed outstanding MFC properties, in which the phenothia-
zine substituted DMQs presented better MFC performance. This phe-
nomenon is attributed to the more twisted bowl-shape configuration of
phenothiazine unit. Moreover, these D-π-A type molecules also pre-
sented outstanding bathochromic solvatochromism for ICT effect and
confirmed by DFT calculation. PXRD and DSC were carried out and
indicated the intrinsic relationship between MFC properties and
stacking patterns transformation upon grinding. Conclusively, our work
enriched AIE-active MFC templates and introduced new members to
high contrast MFC materials.
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J. Yu, et al.
DyesandPigments170(2019)107578
Fig. 8. TGA curves of (a) DMQA1 and (b) DMQA2; DSC curves of (C) DMQA1 and (D) DMQA2.
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