The role of distance between donor and acceptor in configuration stability of Z/E isomers based on cyanostilbene

Article abstract of DOI:10.1016/j.jphotochem.2019.03.035

Cyanostilbene has been widely used in the design of photoelectrical materials, and our previous work has confirmed its Z/E isomerization reaction under photoirradiation can be suppressed by forming a suitable donor-acceptor (D-A) structure. In this work, we report two D-A cyanostilbene derivatives with AIE activity, abbreviated as PZPNC and PZNC, whose chemical structures only differ by one more phenyl between donor and acceptor. Their Z/E isomers were characterized with single crystal structures and the impact of D-A distance on their stability of Z/E configuration was studied. The in-situ UV–vis spectra and HPLC results of Z/E-PZPNC and Z/E-PZNC under photoirradiation demonstrated that the Z/E isomerization reaction of PZNC was slower than PZPNC, indicating that the shorter D-A distance is conductive to the stability of cyanostilbene due to the relatively stronger charge transfer state with lower energy.

Full text of DOI:10.1016/j.jphotochem.2019.03.035

JournalofPhotochemistry&PhotobiologyA:Chemistry377(2019)67–74
Contents lists available at ScienceDirect
Journal of Photochemistry & Photobiology A: Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
The role of distance between donor and acceptor in configuration stability of
Z/E isomers based on cyanostilbene
Chendong Xua, Yujie Donga,⁎, Weijun Lia, Ruiyang Zhaob, Yuyu Daia, Cheng Zhanga,⁎,1
,
Qingbao Songa,⁎
a State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014, PR
China
b College of Chemical Engineering, Qingdao University of Science and Technology, Qingdao, 266042, PR China
A R T I C L E I N F O
A B S T R A C T
Keywords:
Cyanostilbene has been widely used in the design of photoelectrical materials, and our previous work has
confirmed its Z/E isomerization reaction under photoirradiation can be suppressed by forming a suitable donor-
acceptor (D-A) structure. In this work, we report two D-A cyanostilbene derivatives with AIE activity, abbre-
viated as PZPNC and PZNC, whose chemical structures only differ by one more phenyl between donor and
acceptor. Their Z/E isomers were characterized with single crystal structures and the impact of D-A distance on
their stability of Z/E configuration was studied. The in-situ UV–vis spectra and HPLC results of Z/E-PZPNC and
Z/E-PZNC under photoirradiation demonstrated that the Z/E isomerization reaction of PZNC was slower than
PZPNC, indicating that the shorter D-A distance is conductive to the stability of cyanostilbene due to the rela-
tively stronger charge transfer state with lower energy.
Organic photo-electronic
D-A structure
Stable Z/E structure
Cyanostilbene
AIE
1. Introduction
constructing a reasonable D-A structure, in which the Z/E isomerization
reaction at the higher-energy located excited (LE) state is suppressed by
As a significant role in organic photoelectric functional materials,
cyanostilbene (CNS) has attracted more and more attention to construct
fluorescent molecules especially since that reported by Park etc. [1].
Various organic fluorescent molecules based on CNS have been re-
ported and extensively exploited in nanomaterials [2–4], organic lasers
[5,6], cell imaging [7–9], sensors [10–12], organic light-emitting
diodes (OLEDs) [13,14], security ink [15], optical switching [16], lu-
minous multifunctional materials [17,18] and so on. However, the
different impact on luminescenc;1;e from Z- and E- configuration was
scarcely reported, although the isomerization reaction under photo ir-
radiation is so common for the most of fluorescent materials based on
CNS. Definitely, to design and obtain this kind of molecules with stable
Z/E configuration is beneficial to their practical applications.
Recently, we reported the Z- and E- isomers of two pairs of donor-
acceptor (D-A) molecules (TPNCF and PZNCF) with CNS as acceptor,
and triphenylamine [19] and phenoxazine [20] as donor respectively.
The spectroscopy investigation indicated that both of TPNCF and
PZNCF could keep their stable Z/E configuration in high polar solvents
under photo irradiation. These work demonstrated that stable Z/E
configuration under photo irradiation can be obtained through
the rapid internal conversion process from LE to the lower-energy
charge transfer (CT) state [19–21].
In order to further investigate the relationship between molecular
structure and configuration stability, herein, we report two pairs of D-A
type Z/E isomers of PZPNC and PZNC based on phenoxazine and CNS,
whose chemical structures only differ by one more phenyl between
phenoxazine and CNS. The pure four compounds of Z-PZPNC, E-PZPNC,
Z-PZNC and E-PZNC as well as their crystal structures were obtained.
The photophysical properties and density functional theory (DFT) cal-
culation suggested the formation of CT state in their excited state. In-
situ UV–vis absorption spectra and high performance liquid chroma-
tography (HPLC) demonstrated that the Z/E isomerization reaction rate
in the case of Z-PZNC and E-PZNC became slower than that of Z-PZPNC
and E-PZPNC under photo irradiation, i.e., the shorter distance between
phenoxazine and CNS induced a more stable Z/E configuration in ex-
cited state. The results provide a strong evidence for the truth that Z/E
isomerization reaction of CNS can be effectively restrained at excited
state by modifying the D-A distance. It paves the way for further ra-
tional design of organic luminescent molecules containing double bond
units.
⁎ Corresponding authors.
E-mail addresses: dongyujie@zjut.edu.cn (Y. Dong), czhang@zjut.edu.cn (C. Zhang), qbsong@zjut.edu.cn (Q. Song).
1 Homepage: http://www.czhang.zjut.edu.cn/chinese/index.htm.
https://doi.org/10.1016/j.jphotochem.2019.03.035
Received 17 January 2019; Received in revised form 9 March 2019
Availableonline25March2019
1010-6030/©2019ElsevierB.V.Allrightsreserved.

C. Xu, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry377(2019)67–74
Scheme 1. The scheme of synthesis route and molecule structures of Z/E-PZPNC and Z/E-PZNC.
2. Results and discussion
configurations also impact the packing modes of the two pairs of iso-
mers in their crystals. For their Z-type crystals, the adjacent molecules
pack to form weak π–π interactions between the less overlapped phe-
noxazine units (Z-PZPNC) and stilbene part (Z-PZNC). It is obvious that
no coaxial π–π interactions in their E-type crystals due to the large
intermolecular distance. Generally, all these molecules in their crystals
display highly twisted configuration, which prevents the forming of
strong π–π interactions and ensures the higher-efficiency fluorescence
emission in crystal.
2.1. Design and synthesis
To add a phenyl between phenoxazine and CNS group, we synthe-
sized M3 by two-step Suzuki coupling reaction [22]. The Z/E-PZPNC
and Z/E-PZNC were prepared via the Knoevenagel reaction of phe-
noxazine-substituted benzyl cyanide (M3 and M4) and benzaldehyde, as
shown in Scheme. 1 [23,24]. The Z/E isomers can be obtained directly
by column chromatography. All compounds were fully characterized by
NMR spectral analysis, MS spectroscopy and X-ray crystallography.
2.3. Photophysical properties
2.2. Crystal structure
The UV–vis and PL spectra of Z/E-PZPNC and Z/E-PZNC were
measured in toluene. As shown in Fig. 2a, there are two obvious ab-
sorption bands with λmax around 318 nm and 309 nm at short wave-
length and 414 and 401 nm at long wavelength in Z-PZNC and E-PZNC.
Compared with PZNC, PZPNC molecules exhibit a continuous broad
absorption band, which is actually contributed by two main absorption
bands with λmax around 329 nm and 400 nm for Z-PZPNC and 314 nm
and 388 nm for E-PZPNC. Considering the nearly no conjugation be-
tween phenoxazine and cyanostilbene, the absorption at long wave-
length should be attributed to the generation of lower-energy charge
transfer transition. Thus, in comparison with PZPNC, the relatively red
shifted absorption bands at long wavelength in PZNC suggest there is a
stronger CT state in PZNC molecules. This also can be observed in the
normalized PL spectra (Fig. 2b) of these four molecules, in which Z-
PZNC (λmax = 571 nm) and E-PZNC (λmax = 587 nm) displayed
By slow diffusion of methanol vapour into chloroform solution, we
successfully obtained single crystal of Z/E-PZNC and Z/E-PZPNC suited
for X-ray structural analysis. All the crystals are of yellow emissions
under UV light. The single crystal structures clearly demonstrated the
corresponding Z and E configurations of the four molecules. As shown
in Fig. 1, Z-PZPNC and Z-PZNC show an almost planar stilbene structure
with phenyl groups at the double bond ends forming a conjugated
plane, while E-PZPNC and E-PZNC show a relatively twisted config-
uration at the stilbene part. All four molecules have a large twist angle
(67–86°) between the nearly planar phenoxazine and the adjacent
phenyl, which effectively break the conjugation between the donor of
phenoxazine and acceptor of cyanostilbene, and are beneficial to the
generation of charge transfer transition. On the other hand, the Z and E
68

C. Xu, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry377(2019)67–74
Fig. 1. the single crystal structures and packing diagrams of Z/E-PZPNC and Z/E-PZNC molecules.
obvious redshifts of ˜50 nm in comparison with Z-PZPNC
(λmax = 529 nm) and E-PZPNC (λmax = 535 nm) under the same con-
ditions.
2.4. DFT analysis
To confirm the charge transfer excited state properties of the four
compounds, theoretical calculation of electronic orbital distribution
and energy level were carried out by B3LYP method. As shown in Fig. 5,
DFT analysis demonstrated that the highest occupied molecular orbitals
(HOMO) of all the four compounds were mainly located at the phe-
noxazine part, while their lowest unoccupied molecular orbitals
(LUMO) were completely distributed at cyanostilbene group. The to-
tally separate HOMO and LUMO distribution indicated the charge
transfer character in the excited state for both Z/E-PZNC and Z/E-
PZPNC. There were no obvious differences in the electron cloud dis-
tributions and electron transition characters between Z/E-PZNC and Z/
E-PZPNC molecular cases. The calculated energy levels of HOMO are
−4.66 eV (Z-PZPNC), −4.68 eV (E-PZPNC), −4.70 eV (Z-PZNC), and
−4.74 eV (E-PZNC). Meanwhile, the LUMOs are calculated to be
−2.26 eV (Z-PZPNC), −2.16 eV (E-PZPNC), −2.30 eV (Z-PZNC) and
−2.19 eV (E-PZNC). These similar separated electron cloud distribution
and close energy level results of electronic orbitals demonstrate the
similar strong charge transfer transition character in the four molecules.
The solvent effect of the four compounds was also studied to further
investigate their excited state properties. As shown in Fig. 3, all the four
compounds displayed strong emission in non-polar solvent of hexane.
Upon increasing the solvent polarity, the emission decreased obviously
in intensity and even plummeted to nearly invisible in ethyl acetate.
Meanwhile, obvious red-shifts can be observed with increasing the
solvent polarity for all molecules, indicating again there is a CT state in
their excited state of the four compounds.
Due to the lower-energy CT state, all these compounds show weak
emission in dilute solutions. However, the stronger luminescence in
their film demonstrates that they are aggregation-induced emission
(AIE) active molecules, which are weak or non-luminescent in solution
but show stronger luminescence in aggregate state [25]. This can be
easily verified by testing the PL spectra in mixed solvent with the de-
creasing of solubility. As shown in Fig. 4, in an acetonitrile/water
(ACN/H2O) mixture system, all compounds are nonluminous in pure
acetonitrile solution and the PL spectra did not show any obvious
changes below 60% of water content. Upon further increasing the water
fraction, the PL intensity was gradually increased, indicating their ag-
gregates were formed in the solution mixtures with higher ratio of
water and the fluorescent emission was boosted at the same time.
2.5. Electrochemistry
The electrochemical properties of PZPNC and PZNC were in-
vestigated to evaluate their electronic energy levels [26–28]. As shown
Fig. 2. The UV–vis and PL spectra of Z/E-PZPNC and Z/E-PZNC in toluene at 10−5 M.
69

C. Xu, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry377(2019)67–74
Fig. 3. The PL spectra of Z/E-PZPNC and Z/E-PZNC molecules in different solvents.
in Table 1, Z-PZPNC and E-PZPNC exhibited similar onset oxidative
potential (0.70 V and 0.71 V) and the two isomers of PZNC also showed
similar onset oxidative potential (0.74 V and 0.75 V). The HOMOs were
calculated by the cyclic voltammetry method with Z-PZPNC and E-
PZPNC (−5.10 eV, −5.11 eV) a little higher than Z-PZNC and E- PZNC
(−5.14 and −5.15 eV), which is consistent with the results of theore-
tically calculation. The LUMOs of Z/E-PZPNC (−2.34/−2.29 eV) and
Z/E-PZNC (−2.59/−2.54 eV) were calculated from the energy gap
(Eg), which is estimated from the onset energy of the absorption curve
(see Fig. 2). Obviously, the LUMOs of PZNC is lower than those of
PZPNC, and charge transfer can easier happened in PZNC than PZPNC
[29].
in rate without reaching the equilibrium in 30 min. We also measured
their 1H NMR spectra in non-polar deuterated toluene (Toluene-D8)
and observed obvious chemical shift alteration between Z and E type for
both of PZPNC and PZNC after 20 min photo irradiation (Fig. S3). These
results are consistent with our previous conclusions, i.e., the stable Z/E
configuration under photo irradiation is achievable by stabilizing CT
state to be the lowest excited state.
In order to investigate the Z/E isomerization or configuration sta-
bility of PZPNC and PZNC, we further compared their in-situ UV–vis
spectra in toluene. As shown in Fig. 6, both of Z/E-PZPNC and PZNC
isomers started to move on the contrary under UV irradiation, in-
dicating the happen of isomerization reaction. It is noticeable that the
Z/E isomerization reaction of E-PZPNC happened quickly and reached
the equilibrium in 2 min, but Z-PZPNC needed above 5 min to reach the
equilibrium. However, for both of Z-PZNC and E-PZNC, their iso-
merisation process became obviously slower without reaching the
equilibrium in 10 min under photo irradiation. The results indicate
PZPNC molecules with a longer D-A distance are less stable than PZNC
molecules in Z/E configuration.
2.6. Z/E configuration stability
As a strong electron donating group, phenoxazine has exhibited the
ability to stabilize the Z/E configurations of cyanostilbene in our pre-
vious work [19–21]. A distinct characteristic of this kind of D-A type
molecules is that the isomerization reactions become slow as the in-
creasing of solvent polarity. This could be confirmed by the in-situ
UV–vis spectra and in-situ NMR spectra in solvents with different po-
larity. As shown in Figs. S1 and S2, under UV-irradiation, the Z and E
isomers display a fast isomerization process with their absorption
curves shift toward each other in the low-polar solvents (hexane, to-
luene and ether). However, when measured in the moderate-polar
solvent of ethyl acetate, their isomerization reaction became very slow
To further demonstrate the result, the HPLC of these molecules
pretreated with UV light (365 nm) in different irradiation time was
performed and analysed. As shown in Fig. 7, the ratio of Z-PZNC, E-
PZNC, Z-PZPNC and E-PZPNC decrease to 94%, 83%, 91% and 69%
after 10 min irradiation, and were further reduced to 93%, 75%, 87%
and 55% after 20 min irradiation. We could find that the Z/E iso-
merization reaction rate of E-type isomers was much faster than Z-type
70

C. Xu, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry377(2019)67–74
Fig. 4. PL spectra of PZPNC and PZNC in acetonitrile/water mixtures with different water fractions.
ones, and that of PZPNC was faster than PZNC. The analytical HPLC
results agree to in-situ UV–vis spectra, and again confirm that the
longer distance between donor and acceptor of CNS group is not con-
ductive to the configuration stability of Z/E isomers.
were recorded on Bruker AVANCE III instrument (Bruker, Switzerland).
Mass spectra (MALDI-TOF-MS) analysis was recorded using an AXIMA-
CFRTM plus instrument and Mass spectra (ESI-MS) analysis was re-
corded using the ThermoFisher LCQTM Deca XP plus and Agilent 1200-
6210 instrument. Photophysical properties were investigated by a
Shimadzu UV-1800 spectrophotometer (Shimadzu, Japan) and
a
3. Conclusions
Perkin-Elmer LS-55 luminescence spectrophotometer (the integration
time were set to be 0.01 s in order to shorten the measurement time to
be less than 20 s). The photo irradiation was carried in a ZF-20D ul-
traviolet analyzer (YUHUA, China) with a UV light (365 nm, 24 W).
High Performance Liquid Chromatography (HPLC) of the four isomers
were recorded by the Agilent Technologies 1260 Infinity (Agilent,
We synthesized two pairs of D-A type Z/E isomers (PZPNC and
PZNC) based on phenoxazine and cyanostilbene with different D-A
distance between donor and acceptor, and studied their Z/E config-
uration stability. The spectroscopy investigation demonstrated a longer
distance between donor and acceptor could not help to stabilize Z/E
configuration. These results further confirmed our previous mentioned
mechanism, that is the Z/E configuration, which is stable under photo
irradiation, could be obtained by constructing a reasonable D-A struc-
ture. We believed this guideline could be further developed in other
molecular structural design with double bond to achieve more config-
uration-stable molecules for organic photo-electronic applications.
America). Electrochemical measurements were conducted by
a
CHI660E electrochemical analyser (Chenhua, China), with glassy
carbon as the working electrode, platinum wire as the auxiliary elec-
trode and Ag/Ag+ as the reference electrode, 0.1 mol L−1 tetra-
butylammonium hexafluorophosphate (Bu4NPF6) dissolved in acetoni-
trile was employed as the supporting electrolyte.
4. Experimental section
4.2. Synthesis of 10-(4-bromophenyl)-10H-phenoxazine(M1)
4.1. General remarks
In a dry nitrogen atmosphere, a mixture of phenoxazine (0.92 g,
5 mmol), 1-bromo-4-iodobenzene (1.7 g, 6 mmol), sodium tert-butoxide
(1.06 g, 11 mmol), cuprous iodide (0.02 g, 0.11 mmol) and 1, 2-diami-
nocyclohexane (0.07 g, 0.6 mmol) in 20 ml dry 1, 4-dioxane was heated
All the reagents or chemicals were commercial products without
further purification. 1H NMR spectra of the synthesized compounds
71

C. Xu, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry377(2019)67–74
Fig. 5. The electron cloud distribution of electronic orbitals HOMO and LUMO for optimized Z/E-PZPNC and Z/E-PZNC molecules.
6.1 mmol) in 20 ml dry 1,4-dioxane was heated under 110 ℃ for 24 h.
After the reaction, the mixture was cooled to room temperature and
quenched with water and extracted with chloroform. The combined
organic layer was washed with distilled water three times and dried
over anhydrous magnesium sulfate. Then the solvent was evaporated in
a vacuum. The crude product was purified by column chromatography
on silica gel using petroleum ether/dichloromethane (2/1 v/v) as the
eluent to obtain the product as white solid (0.12 g, 53%). 1H NMR
(500 MHz, CDCl3) δ (TMS, ppm) 8.05 (d, J = 7.7 Hz, 2H), 7.37 (d,
J = 7.9 Hz, 2H), 6.47–6.80 (m, 6H), 5.92 (d, J = 5.2 Hz, 2H), 1.4 (s,
12H). MS (ESI) (mass m/z): 386.2 [M+H]+, C24H24BrNO3 calc. 385.2.
Table 1
Physical property of PZPNC and PZNC.
a
b
c
d
e
f
Compd.
Eox [V] λabs
EHOMO [eV] ELUMO [eV] Eg [eV] λmax
[nm]
[nm]
Z-PZPNC 0.70
E-PZPNC 0.71
Z-PZNC
E-PZNC
450
440
487
475
−5.10
−5.11
−5.14
−5.15
−2.34
−2.29
−2.59
−2.54
2.76
2.82
2.55
2.61
529
535
571
587
0.74
0.75
a
Eox = the onset oxidative potential.
b
c
λ
abs = the onset value of the absorption peak.
EHOMO = highest occupied molecular orbitals calculated from the onset
oxidative potential.
4.4. Synthesis of 2-(4′-(10H-phenoxazin-10-yl)-[1, 1′-biphenyl]-4-yl)
acetonitrile (M3)
d
ELUMO = lowest unoccupied molecular orbitals estimated using EHOMO and
Eg.
e
Eg = energy band gap calculated from the onset absorption spectrum.
f
In a dry nitrogen atmosphere, a mixture of M2 (0.51 g, 1.3 mmol), 4-
bromophenylacetonitrile (0.38 g, 1.95 mmol), tetrakis(triphenylpho-
sphine)palladium (0) (0.11 g, 0.10 mmol) and potassium carbonate
(1.8 g, 13 mmol) in 25 ml H2O/toluene (2/3 v/v) mixture solvent was
heated under 90 °C for 24 h. After the reaction, the mixture was cooled
to room temperature and quenched with water and extracted with
chloroform. The combined organic layer was washed with distilled
water three times and dried over anhydrous magnesium sulfate. Then
the solvent was evaporated in a vacuum. The crude product was pur-
ified by column chromatography on silica gel using petroleum ether/
dichloromethane (2/5 v/v) as the eluent to obtain the product as or-
ange solid (0.30 g, 62%). 1H NMR (500 MHz, CDCl3) δ (TMS, ppm) 7.81
(d, J = 8.4 Hz, 2H), 7.69 (d, J = 8.3 Hz, 2H), 7.47 (d, J = 8.4 Hz, 2H),
7.44 (d, J = 8.4 Hz, 2H), 6.58–6.75 (m, 6H), 6.01 (d, J = 7.9 Hz, 2H),
3.85 (s, 2H, vinyl-H). MS (ESI) (mass m/z): 375.2 [M+H]+ C26H18N2O
calc. 374.3.
λmax = the peak value of PL curve [23–25].
under 110 °C for 6 h. After the reaction, the mixture was cooled to room
temperature and quenched with water and extracted with chloroform.
The combined organic layer was washed with distilled water three
times and dried over anhydrous magnesium sulfate. Then the solvent
was evaporated in a vacuum. The crude product was purified by column
chromatography on silica gel using petroleum ether/dichloromethane
(9/1 v/v) as the eluent to obtain the product as white solid (1.13 g,
67%). 1H NMR (500 MHz, CDCl3) δ (TMS, ppm) 7.75 (d, J = 8.5 Hz,
2H), 7.26 (d, J = 8.5 Hz, 2H), 6.61–6.73 (m, 6H), 5.94 (d, J = 7.8 Hz,
2H). MS (ESI) (mass m/z): 338.3 [M+H]+, C18H12BrNO calc. 338.2.
4.3. Synthesis of 10-(4-(4, 4, 5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl)
phenyl)-10H-phenoxazine (M2)
In a dry nitrogen atmosphere, a mixture of M1 (0.2 g, 0.59 mmol),
bis(pinacolato) diboron (0.19 g, 0.74 mmol), 1,1′-Bis(diphenylpho-
4.5. Synthesis of Z-PZPNC and E-PZPNC
sphino)ferrocene-palladiumdichloride
dichloromethane
adduct
(PdCl2(dppf)·CH2Cl2) (0.1 g, 0.13 mmol) and potassium acetate (0.6 g,
To a mixture of M3 (0.37 g, 1 mmol) and benzaldehyde (0.11 g,
72

C. Xu, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry377(2019)67–74
Fig. 6. The in-situ UV spectra of a) PZPNC and b) PZNC under different photo irradiated time of UV light (365 nm) in toluene.
1 mmol) in 10 ml ethanol, sodium hydroxide (0.04 g, 1 mmol) was
added. The mixture was heated under 45 °C for 24 h, then cooled to
room temperature and filtered. The residue was washed with cold
ethanol by three times, and further purified by column chromatography
via eluent (CH2Cl2/petroleum ether = 2/1) to obtain the products.
(Z)-2-(4′-Phenoxazin-10-yl-biphenyl-4-yl)-3-phenyl-acrylonitrile (Z-
PZPNC). Yellow solid, 0.45 g, yield: 97%. 1H NMR (500 MHz, CDCl3) δ
(TMS, ppm) 7.95 (d, J = 7.1 Hz, 2H), 7.86 (d, J = 8.4 Hz, 2H), 7.83 (d,
J = 8.5 Hz, 2H), 7.76 (d, J = 8.6 Hz, 2H), 7.65 (s, 1H), 7.48–7.54 (m,
3H), 7.46 (d, J = 8.4 Hz, 2H), 6.72 (dd, J = 7.7 Hz, 1.7 Hz, 2H), 6.66
(dt, J = 15.2 Hz, 7.4 Hz, 4H), 6.03 (dd, J = 7.8 Hz, 1.6 Hz, 2H). MALDI-
TOF MS (mass m/z): 463.8 [M+H]+, C33H22N2O calc. 462.5.
(E)-2-(4′-Phenoxazin-10-yl-biphenyl-4-yl)-3-phenyl-acrylonitrile (E-
PZPNC). Yellow solid, 0.01 g, yield: 3%. 1H NMR (500 MHz, CDCl3) δ
Fig. 7. The relative content of isomers recorded by HPLC (Samples were pretreated with 365 nm UV-irradiation for different time).
73

C. Xu, et al.
JournalofPhotochemistry&PhotobiologyA:Chemistry377(2019)67–74
(TMS, ppm) 7.84 (d, J = 8.2 Hz, 2H), 7.67 (d, J = 8.3 Hz, 2H), 7.53 (d,
J = 8.3 Hz, 2H), 7.41–7.84 (m, 3H), 7.28–7.36 (m, 3H), 7.26 (dd,
J = 8.5 Hz, 1.5 Hz, 2H), 6.72 (d, J = 7.5 Hz, 2H), 6.61–6.66 (m, 4H),
Appendix A. Supplementary data
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.jphotochem.2019.03.
035.
6.00 (d, J = 7.0 Hz, 2H). MALDI-TOF MS (mass m/z): 463.8 [M+H]+
,
C
33H22N2O calc. 462.5.
4.6. Synthesis of 2-(4-(10H-phenoxazin-10-yl) phenyl) acetonitrile (M4)
References
In a dry nitrogen atmosphere, a mixture of phenoxazine (0.37 g,
2 mmol), 4-bromophenylacetonitrile (0.47 g, 2.4 mmol), tri-tert-butyl-
phosphine (0.11 g, 0.52 mmol), palladium acetate (0.03 g, 0.12 mmol)
and sodium tert-butoxide (0.50 g, 5.2 mmol) in 30 ml toluene was he-
ated under 115 °C for 24 h. After the reaction, the mixture was cooled to
room temperature and quenched with water and extracted with
chloroform. The combined organic layer was washed with distilled
water three times and dried over anhydrous magnesium sulfate. Then
the solvent was evaporated in a vacuum. The crude product was pur-
ified by column chromatography on silica gel using petroleum ether/
dichloromethane (1/3, v/v) as the eluent to obtain the product as white
solid (0.60 g, 50%). 1H NMR (500 MHz, CDCl3) δ (TMS, ppm) 7.59 (d,
J = 8.4 Hz, 2H), 7.40 (d, J = 8.3 Hz, 2H), 6.56–6.75 (m, 6H), 5.90 (dd,
J = 7.9 Hz, 1.4 Hz, 2H), 3.87 (s, 2H, alkyl-H). MS (ESI) (mass m/z):
297.1 [M+H]+, C28H17F3N2O calc. 298.3.
[1] Byeong Kwan An, Deug Sang Lee, Jong Soon Lee, Yil Sung Park, Hyung Su Song,
Soo Young Park, J. Am. Chem. Soc. 126 (2004) 10232–10233.
[2] Hyeong Ju Kim, Paramjyothi C. Nandajan, Johannes Gierschner, Soo Young Park,
Adv. Funct. Mater. 28 (2018) 1705141–1705151.
[3] Xue Jin, Dong Yang, Yuqian Jiang, Pengfei Duan, Minghua Liu, Chem. Commun. 54
(2018) 4513–4516.
[4] Yanming Ren, Ruilin Zhang, Chao Yan, Tingyan Wang, Huifang Cheng,
Xiaohong Cheng, Tetrahedron 73 (2017) 5253–5259.
[5] Byeong Kwan An, Johannes Gierschner, Soo Young Park, Acc. Chem. Res. 45 (4)
(2012) 544–554.
[6] Yujie Dong, Suqian Ma, Xiaoyu Zhang, Jingyu Qian, Nianyong Zhu, Bin Xu, Cheuk
Lam Ho, Wenjing Tian, Wai Yeung Wong, Sci. China Chem. 62 (2) (2019) 212–219.
[7] A. Gopinath, K. Ramamurthy, Mamangam Subaraja, Chellappan Selvaraju,
A. Sultan Nasar, New J. Chem. 42 (2018) 10243–10253.
[8] Weijie Zhang, Chris Y.Y. Yu, Ryan T.K. Kwok, Jacky W.Y. Lam, Ben Zhong Tang, J.
Mater. Chem. B 6 (2018) 1501–1507.
[9] Ka Young Kim, Hanyong Jin, Jaehyeon Park, Sung Ho Jung, Ji Ha Lee,
Hyesong Park, Sung Kuk Kim, Jeehyeon Bae, Jong Hwa Jung, Nano Res. 11 (2)
(2018) 1082–1098.
[10] Yao Ma, Massimo Cametti, Zoran Dzˇolic´, Shimei Jiang, J. Mater. Chem. C 6 (2018)
9232–9237.
4.7. Synthesis of Z-PZNC and E-PZNC
[11] Yuyang Zhang, Jianyan Huang, Lin Kong, Yupeng Tian, Jiaxiang Yang,
CrystEngComm 20 (2018) 1237–1244.
[12] Bin Wang, Chun Ying Wei, RSC Adv. 8 (2018) 22806–22812.
[13] Wenyan Fang, Wang Zhao, Pan Pei, Rui Liu, Yuyang Zhang, Lin Kong,
Jiaxiang Yang, J. Mater. Chem. C 6 (2018) 9269–9276.
[14] Yujie Dong, Jingyu Qian, Yang Liu, Nianyong Zhu, Bin Xu, Cheuk Lam Ho,
Wenjing Tian, Wai Yeung Wong, New J. Chem. 43 (2019) 1844–1850.
[15] Kenneth Yin Zhang, Xiaojiao Chen, Guanglan Sun, Taiwei Zhang, Shujuan Liu,
Qiang Zhao, Wei Huang, Adv. Mater. 28 (2016) 7137–7142.
[16] Dojin Kim, Eon Kwon Ji, Soo Young Park, Adv. Funct. Mater. 28 (2018)
1706213–1706219.
To a mixture of M4 (0.30 g, 1 mmol) and benzaldehyde (0.11 g,
1 mmol) in 10 ml ethanol, sodium hydroxide (0.04 g, 1 mmol) was
added. The mixture was heated under 45 °C for 24 h, then cooled to
room temperature and filtered. The residue was washed with cold
ethanol by three times, and further purified by column chromatography
via eluent (CH2Cl2/petroleum ether = 2/1) to obtain the products as
yellow solid.
[17] Marta Martínez-Abadía, Raquel Giménez, María Blanca Ros, Adv. Mater. 30 (2018)
(Z)-2-(4-(10H-phenoxazin-10-yl)phenyl)-3-phenyl-acrylonitrile (Z-
PZNC). Yellow solid, 0.33 g, yield: 87%. 1H NMR (500 MHz, CDCl3) δ
(TMS, ppm) 7.90–7.99 (m, 4H), 7.64 (s, 1H), 7.49–7.56 (m, 3H), 7.47
(d, J = 8.5 Hz, 2H), 6.73 (dd, J = 8.5 Hz, 1.7 Hz, 2H), 6.66 (dt,
J = 15.2 Hz, 7.3 Hz, 4H), 5.98 (dd, J = 7.9 Hz, 1.4 Hz, 2H). MALDI-TOF
MS (mass m/z): 387.4 [M+H]+, C27H18N2O calc. 386.4.
1704161–1704199.
[18] Yujian Zhang, Moge Qile, Jingwei Sun, Minhong Xu, Kai Wang, Feng Cao,
Weijun Li, Qingbao Song, Zou Bo, Cheng Zhang, J. Mater. Chem. C 4 (2016)
9954–9960.
[19] Weijun Li, Shizhao Wang, Yujian Zhang, Yujie Dong Yu Gao, Xiang Zhang,
Qingbao Song, Bing Yang, Yuguang Ma, Cheng Zhang, J. Mater. Chem. C 5 (2017)
8097–8104.
[20] Yujie Dong, Chendong Xu, Shizhao Wang, Weijun Li, Qingbao Song, Cheng Zhang,
Acta Phys. Chim. Sin. 35 (6) (2019) 637–643.
[21] Jin Liu, Weijun Li, Minjie Liu, Yujie Dong, Yuyu Dai, Qingbao Song, Jianli Wang,
Cheng Zhang, Phys. Chem. Chem. Phys. 20 (2018) 28279–28286.
[22] InSeob Park, Sae Youn Lee, Chihaya Adachi, Takuma Yasuda, Adv. Funct. Mater. 26
(2016) 1813–1821.
[23] Chunbo Duan, Jing Li, Chunmiao Han, Dongxue Ding, He Yang, Ying Wei, Hui Xu,
Chem. Mater. 28 (2016) 5667–5679.
[24] Regis Guillot, Andre Loupy, Abdelkrim Meddour, Michele Pelletd, Alain Petit,
Tetrahedron 61 (2005) 10129–10137.
[25] Yuanjing Cai, Lili Du, Kerim Samedov, Xinggui Gu, Fei Qi, Herman H.Y. Sung, Brian
O. Patrick, Zhiping Yan, Xiaofang Jiang, Haoke Zhang, Jacky W.Y. Lam, Ian
D. Williams, David Lee Phillips, Anjun Qin, Ben Zhong Tang, Chem. Sci. 9 (2018)
4662–4670.
(E)-2-(4-(10H-phenoxazin-10-yl)phenyl)-3-phenyl-acrylonitrile (E-
PZNC). Yellow solid, 0.02 g, yield: 5%. 1H NMR (500 MHz, CDCl3) δ
(TMS, ppm) 7.62 (d, J = 8.4 Hz, 2H), 7.48 (s, 1H), 7.33–7.40(m, 3H),
7.30(t, J = 7.4 Hz, 2H), 7.24 (d, J = 7.3 Hz, 2H), 6.59–6.77 (m, 6H),
5.97 (d, J = 7.8 Hz, 2H). MALDI-TOF MS (mass m/z): 387.4 [M+H]+
,
C
27H18N2O calc. 386.4.
Conflicts of interest
There are no conflicts to declare
Acknowledgements
[26] Yuyu Dai, Weijun Li, Xingxing Qu, Jin Liu, Shuanma Yan, Mi Ouyang, Xiaojing Lv,
Cheng Zhang, Electrochim. Acta 229 (2017) 271–280.
[27] Weijun Li, Lan Chen, Yuyu Pan, Shuanma Yan, Yuyu Dai, Jin Liu, Yue Yu,
Xingxing Qu, Qingbao Song, Mi Ouyang, Cheng Zhang, J. Electrochem. Soc. 164 (4)
(2017) E84–E89.
[28] Weijun Li, Yuyu Pan, Ran Xiao, Qiming Peng, Shitong Zhang, Dongge Ma, Feng Li,
Fangzhong Shen, Yinghui Wang, Bing Yang, Yuguang Ma, Adv. Funct. Mater. 24
(2014) 1609–1614.
[29] Weijun Li, Liang Yao, Haichao Liu, Zhiming Wang, Shitong Zhang, Ran Xiao,
Huanhuan Zhang, Ping Lu, Bing Yang, Yuguang Ma, J. Mater. Chem. C 2 (2014)
4733–4736.
This study was supported by the Zhejiang Provincial Natural Science
Foundation, China (LQ19E030016, LY19E030006, and LZ17E030001),
the China Postdoctoral Science Foundation (2018M632498), the
Zhejiang Provincial Postdoctoral Fellowship, China (Z71101009) and
the National Natural Science Foundation of China (51603185,
51673174, 51703112 and 21875219).
74