An ensemble of Zn2+ with a rhodamine B-3-allylsalicylaldehyde hydrazone as novel photosensitive material: Photochromism, photopatterning, photoprinting and molecular logic gates

Article abstract of DOI:10.1016/j.saa.2019.03.003

An ensemble of Zn²⁺ with Rhodamine B-3-allylsalicylaldehyde hydrazone (1-Zn²⁺), has been synthesized and fully characterized using spectroscopic techniques. A solution of 1-Zn²⁺ in THF, displays color changes from light yellow to pink color in the presence UV light (λ, 405 nm). The process is reversible and owes to keto-enol tautomerism which allows the opening of spirolactam ring of rhodamine in the presence of UV light. It is corroborated by the appearance of a new peak at λ_max = 554 nm. The ensemble, 1-Zn²⁺ embedded in the matrix of silica gel, displays photo patterning phenomena initiated by the conventional light sources including sunlight. It also displays photoprinting property with a laser pen (λ 405 nm) and has been displayed by a videography. The module 1-Zn²⁺ meets real challenges through a simple synthetic route, fast response, and as a binary data storage system with non-destructive optical identity.

Full text of DOI:10.1016/j.saa.2019.03.003

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 216 (2019) 1–6
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular
Spectroscopy
journal homepage: www.elsevier.com/locate/saa
An ensemble of Zn2+ with a rhodamine B-3-allylsalicylaldehyde
hydrazone as novel photosensitive material: Photochromism,
photopatterning, photoprinting and molecular logic gates
Abhishek Rai a,2, Alok Kumar Singh b,1,2, Avinash Kumar Sonkar a, Kamini Tripathi a, Lallan Mishra a,
⁎
a
Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi, India
b
Department of Chemistry, Babasaheb Bhimrao Ambedkar University, Lucknow, India
a r t i c l e i n f o
a b s t r a c t
An ensemble of Zn2+ with Rhodamine B-3-allylsalicylaldehyde hydrazone (1-Zn2+), has been synthesized and
fully characterized using spectroscopic techniques. A solution of 1-Zn2+ in THF, displays color changes from
light yellow to pink color in the presence UV light (λ, 405 nm). The process is reversible and owes to keto-enol
tautomerism which allows the opening of spirolactam ring of rhodamine in the presence of UV light. It is corrob-
orated by the appearance of a new peak at λmax = 554 nm. The ensemble, 1-Zn2+ embedded in the matrix of sil-
ica gel, displays photo patterning phenomena initiated by the conventional light sources including sunlight. It
also displays photoprinting property with a laser pen (λ 405 nm) and has been displayed by a videography.
The module 1-Zn2+ meets real challenges through a simple synthetic route, fast response, and as a binary data
storage system with non-destructive optical identity.
Article history:
Received 18 December 2018
Received in revised form 20 February 2019
Accepted 3 March 2019
Available online 04 March 2019
Keywords:
Rhodamine B
Hydrazone
Photochromism
Photopatterning and logic gate
© 2019 Elsevier B.V. All rights reserved.
1. Introduction
et al. reported a phenanthrene-bridged photochromic diarylethene
recognizing Cu2+ and Hg2+ ions [12]. It had been reported earlier
Photochromism can be defined as a reversible transformation be-
tween two isomers with different characteristics induced by alter-
nating illumination with UV or visible light. Photochromic
materials are of immense interest owing to their potential applica-
tions in photonic devices and optical memory media [1], switches
[2], logic gates [3], optical data storage [4], photoresponsive, supra-
molecular self-assembly [5] and sensors [6].In this context, Fulgide,
spiropyran, spirooxazine, dithienylethene and diarylethene deriva-
tives were reported as photochromic materials based on photo-
induced isomerization involving ring-opening/closing reactions [7].
In some cases, it resulted out of enol–keto tautomerism [8]. Their ap-
plications as drug carrier and in molecular imaging processes are
quite significant [9]. There are several classes of organic or inorganic
materials which exhibited photochromic properties [10]. Tong et al
reported Crystal violet lactone, a classic halochromic dye whose
zinc complex acted as reversible photochromic material [11]. Zeng
[13] that diarylethene could be utilized as a multi-addressable fluo-
rescence switch in the presence of light, acids and bases. In this con-
text, diarylethene derivatives had also been reported as colorimetric
sensor for CN− ions and fluorescent relay-sensor for Al3+/Cr3+ ions
[14]. The MOF constructed on azobenzene and diarylethene ligands
displayed light modulating absorption behavior of guests (CO2,
C2H2, C2H4) [15]. The temperature and light dependent separation
of C2H2/C2H4 mixture had also been accomplished by diarylethene
based MOF [16]. Shouzhi Pu et al. reported a diarylethene derivative
as a turn-on fluorescence sensor for the detection of Zn2+ ions at
nano molar level [17]. Qianfu Luo et al. reported porous polymers
based on diarylethenes modified triptycene as reversible photochro-
mic material in solid and solution in THF. It also demonstrated char-
acteristic solvent-dependent photochromism [18].
Rhodamine B and its several derivatives are considered most
promising candidates for the construction of fluorescent switches
and design of photochromic materials [19]. They reside in the
home of dyes with long-wavelength absorption and emission, high
absorption coefficient and excellent photostability [20]. Thus, their
optical properties can be exploited for the development of novel
photochromic materials. Unlike dithienylethene, rhodamine deriva-
tives are less expensive and do not involve multi step synthesis [21].
The presence of phenolic group is imperative for enol-to-keto
⁎
Corresponding author.
E-mail address: lmishrabhu@yahoo.co.in (L. Mishra).
Current Address: Department of Chemistry, Deen Dayal Upadhyaya Gorakhpur
1
University, Gorakhpur, India.
2
These authors contributed equally to this work.
https://doi.org/10.1016/j.saa.2019.03.003
1386-1425/© 2019 Elsevier B.V. All rights reserved.

2
A. Rai et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 216 (2019) 1–6
Scheme 1. Synthesis of 1-Zn2+
.
conversion on exposure to UV radiation resulting into visual eye
color changes. Thus, modification on the skeleton of the reactants
by tuning of substituents may be considered an easy approach of
preparation of a novel synthetic material. Rhodamine derivatives
dispersed in a matrix, incorporated into the main chain of silica gel,
or connected to the polymer chain, are useful in the display devices
as they can be directly coated on a paper or any other solid surface
[22].
2. Experimental
2.1. Materials and methods
The reagents and solvents were obtained from commercial sources.
Solvents were dried and distilled prior to their use. Infrared and absorp-
tion spectra were recorded using Varian 3300 FT-IR and Shimadzu UV-
1601 spectrophotometers, respectively. 1H and 13C NMR spectra were
Thus, in view of excellent precedence of rhodamine B,
salicylaldehyde and allyl groups, judicious design and synthesis of rho-
damine B allyl salicylaldehyde hydrazone 1 has been carried out in view
of earlier report [23]. The incorporation of allyl group to 1 enhance over-
all optical properties of the system. Its ensemble with Zn2+ ions
(Scheme 1) exhibited photochromic properties in THF solution. It ex-
hibited good fatigue resistance, thermal bleaching rate, tunable detec-
tion of metal ions and photo printing.
recorded on
a
JEOL AL500 FT-NMR spectrometer using
tetramethylsilane (TMS) as an internal reference. Fluorescence was
measured on a Perkin Elmer fluorescence spectrophotometer in THF
at room temperature. Electrospray ionization mass spectrometry (ESI-
MS) was carried out in THF using an AMAZONSL Max ion trap mass
spectrometer. The photochromic experiment was carried out using dif-
ferent light sources, including sunlight, UV lamp (λ = 365 nm, VL-6.LC)
and UV torch (λ = 405 nm).
Fig. 1. (a) Images of 1-Zn2+ in THF upon irradiation (λ = 365 nm), and the recovery in dark at 25 °C. (b) Absorption and (c) fluorescence spectra of 1-Zn2+ in THF before and after UV
irradiation. [1] = 10 μmol/L, [Zn(II)] = 1000 μmol/L.

A. Rai et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 216 (2019) 1–6
3
Fig. 2. (a) Color changes of 1-Zn2+ at different volume % of THF in DCM at 25 °C. [1] = 10 μmol/L, [Zn(II)] = 1000 μmol/L, 1 = 100, 2 = 80, 3 = 60, 4 = 40, 5 = 20, 6 = 0. corresponding
absorbance changes at different time interval (b).
2.2. Synthesis of 1
ensemble with Zn2+ was obtained by the reaction of 1.0 eq of aqueous
Zn2+ ions solution to 1 in THF (Scheme 1). It was well characterized
by IR, NMR (1H, 13C) and ESI-MS spectra (Figs. S1–S4†, ESI). The FTIR
spectrum of 1 displayed peaks at 1647 and 1763 cm−1 assigned to ν
(NC_N) and ν (NC_O) vibrations respectively. These peaks shifted to
1612 and 1713 cm−1 respectively in the spectrum of 1-Zn2+. It sup-
ported the coordination of Zn2+ ion with 1. A peak observed at
3436 cm−1 supported the presence of the coordinated water molecule
in 1-Zn2+. The presence of counter anions (nitrate) was supported by
a peak observed at 1384 cm−1. Further, 1H NMR spectrum of 1-Zn2+
showed peak at δ 10.899 and 9.014 assigned to \\OH and \\CH_N
groups, respectively. They were shifted as compared to the peaks ob-
Rhodamine hydrazone 1 was prepared by one-step condensation of
rhodamine B hydrazide with 3-allyl salicylaldehyde in absolute ethanol
at room temperature as reported earlier by us [23].
2.3. Synthesis of 1-Zn2+ ensemble
1-Zn2+ ensemble was prepared by the addition of Zn(NO3)2 (1.1 eq.,
H2O) to the solutions of 1 (1.0 eq, THF). The reaction mixture was stirred
for 2 h at room temperature; a dark yellow colored solution was allowed
for its slow evaporation for getting its single crystals. But it turned out to
be a light yellow powder. The solid was obtained in 40%, Yield and it was
analyzed as: FT-IR (KBr, cm−1): 3436, 2967–2869, 1713, 1612, 1545,
1515, 1449, 1384, 1356, 1307, 1270, 1233, 1180, 1153, 1117, 1076,
998, 975, 915, 869, 823, 787, 753, 710, 684, 620, 577, 528, 450; 1H
NMR (500 MHz, CDCl3): δ 10.899 (s, 1H,\\OH), 9.014 (s, 1H,\\CH_N),
7.994 (d, J = 7.0 Hz, 1H, Ph\\Ph), 7.529 (t, J = 6.75 Hz, 2H,\\Ph), 7.157
(d, J = 7.5 Hz, 1H,\\Ph), 7.062 (d, J = 7.0 Hz, 1H,\\Ph), 6.959 (d, J =
7.5Hz, 1H,\\Ph), 6.733 (t, J = 7.5 Hz, 1H,\\Ph), 6.569 (d, J = 7.0 Hz,
4H,\\Ph), 6.384 (s, 2H,\\Ph), 5.950–5.936 (m, 1H), 5.056–4.981 (m,
1H), 3.359 (d, J = 8.0Hz, 10H, \\CH2), 1.164 (t, J = 6.75 Hz, 12H,
CH3); 13CNMR (125 MHz, CDCl3): δ164.195, 156.343, 153.137,
136.627, 133.594, 131.636, 129.716, 129.457, 128.718, 128.334,
127.959, 123.976, 123.486, 118.582, 117.862, 115.462, 67.948, 65.942,
33.547, 25.580, 12.228; ESI-MS calcd for [1-Zn2+·H2O]+ (m/z):
683.1465; found: 683.1910.
served in the spectrum of free 1 at δ 11.132 and 8.851 respectively. 13
C
NMR spectrum of 1-Zn2+, displayed a peak at δ 65.942 ppm, assigned
to tertiary carbon (sp3 hybridized) of closed spirolactam ring in consis-
tence with the earlier report [24]. ESI-mass data of the ensemble
displayed a peak at m/z 683.1910 and corroborates to [1-Zn2+·H2O]+
found very close to calcd., m/z: 683.1465. To investigate the stoichiometry
of ensemble, a solution of 1 (10 μM, THF) was titrated with the incremen-
tal addition of an aqueous solution of Zn2+ ions. The absorption bands of
1 were observed at λmax 276, 308, 346 nm. Its latter band was red-shifted
by ~72 nm on the addition of Zn2+ ions (1.1 eq) and was observed at λmax
418 nm with an isosbestic points at 330 and 372 nm (Fig. S5†, ESI). The
maximum absorbance was observed at 0.5 mol fractions, indicating a 1:
1 stoichiometry between 1 and Zn2+ ions (Fig. S6†, ESI). The binding con-
stant was calculated (Fig. S7†, ESI) using Benesi–Hildebrand method [25]
and was found to be 1.8 × 104 M−1
.
3. Results and discussion
3.1. Photochromism of 1-Zn2+ in solution
The compound 1 was prepared in good yield (75%) by a simple reac-
tion between rhodamine B hydrazide and 3-allylsalicylaldehyde. Its
As depicted in Fig. 1a, on the exposure of UV light to ensemble 1-Zn2
+ in THF solution, its color changed from light yellow to pink. Its original
Fig. 3. Colors of (a) silica gel + 1-Zn2+ (b) silica gel + 1-Zn2+ (daylight) (c) silica gel + 1-Zn2+ (UV light).

4
A. Rai et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 216 (2019) 1–6
Fig. 4. (a) Pattern of a flower created on a powder sample prepared by mixing the solid 1-Zn2+ with- silica gel and supported on a plate and (b) colored pattern of the flower after exposure
to sunlight/day light for 5.0 min.
light yellow color was again obtained in 10 min after the removal of UV
light source (ESI, Video 1). The photochromic behavior of 1-Zn2+ was
also monitored by UV–visible titrations as depicted in Fig. 1b. Upon ex-
posure to light, closed-ring (enolic form) of 1-Zn2+ progressively
photoisomerized to open keto form of 1-Zn2+ with concomitant ap-
pearance of a new band at λmax = 554 nm. This band had been reported
as a characteristic band of open ring formation. The pink colored solu-
tion appeared in the presence of light was bleached completely in the
dark and the changes were found reversible as shown in Fig. 1a. The
changes have also been demonstrated by their emission spectra as
shown in Fig. 1(c). The keto-form was found as a typical fluorescence
quencher owing to its strong electron-withdrawing nature. Therefore
upon exposure of UV light, emission intensity gradually decreases
with the appearance of two weaker peaks at λemission 516 and 580 nm
as shown in Fig. 1(c). However, in dark fluorescence emission from 1-
Zn2+ observed at λemission = 527 nm was found intense.
3.2. Photochromism of 1-Zn2+ in the matrix of silica gel
The photochromic property of 1-Zn2+ was also studied in a solid
matrix of silica gel. The photochromic system on silica gel was pre-
pared by mixing silica gel (10 g, 200–300 mesh), 0.5 g Zn(NO3)2
and 1 (0.2g) together with few drops of THF. After complete
mixing, THF was evaporated at room temperature which provided
a light yellow powder (Fig. 3(a)). After exposure to normal light
for few minutes, the color changes to pink color as shown in Fig. 3
(b). However, color deepens on the exposure to UV light (Fig. 3
(c)). The color changes were not reversible as it was observed in
the solution phase. It could be probably attributed to the acidic na-
ture of silica gel which may bring out some side reactions. Further-
more, all the conformist light sources even sunlight could induce
photochromism and prove the worth of the material as an added
advantage.
Among other tested metal ions, Cu2+ and Ni2+ ions were also able to
induce a keto-enol tautomerism. But their rates of conversion were ei-
ther too fast or too slow and they lack the essential property of revers-
ibility as observed in 1-Zn2+ ensemble (Fig. S8†, ESI).
It was further interesting to observe that a template of flower cre-
ated on the surface of this material (Fig. 4a), turned to colored template
of the flower on exposure of UV light as depicted in Fig. 4b. The novelty
of this material in photo printing has also been displayed in Video 2 at-
tached in the supplementary informations.
The polarity of the solvents significantly affects the dynamics of pho-
tochromism. In our present system, photochromic recovery was found
moderate in THF: DCM mixture (60:40, v/v) with respect to time as
depicted in Fig. 2(a). It was found fast in THF alone and slow in DCM.
This was further corroborated by corresponding changes in their absor-
bance as shown in Fig. 2(b). In contrast to metal ions under consider-
ation, anions such as F−, Cl−, Br−, I−, CN−, PO43−, were not able to
perturb the photochromic property of 1-Zn2+ system, (Fig. S9†, ESI) ex-
cept EDTA2−owing to its strong chelating ability with Zn2+ ions.
Evaluation of the fatigue resistance of 1-Zn2+ is an essential criterion
to be investigated to evaluate its performance as a reversible photochro-
mic material. As shown in Fig. 5, reversible transformation between two
states of Keto (open) and Enol (close) for 5 times, and the absorbance at
λmax = 554 nm stayed almost constant without any apparent
degradation.
Fig 5. Fatigue resistance of 1-Zn2+ upon irradiation with a light source of λ = 365 nm as
well as keeping in dark alternatively in THF, [1] = 10 μmol/L, [Zn(II)] = 1000 μmol/L, and
corresponding absorbance are recorded at λ max = 554 nm.
Scheme 2. Proposed mechanism for color change of 1-Zn2+ upon UV irradiation.

A. Rai et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 216 (2019) 1–6
5
Fig. 6. Truth table and sequential logic circuits displaying memory units with two inputs and two outputs in the presence of chemical inputs viz. I1 (UV light) and I2 (Dark).
3.3. Plausible mechanism
in a feedback loop exhibit the memory feature through OUT1 and OUT2
(Fig. 6).
The variation in the input sequences to generate varied outputs
Because of the presence of both rhodamine B and salicylaldehyde
moieties in 1-Zn2+ and the mandatory role of Zn(II) chelation in the
photochromism, a tentative mechanism of the color changes of ensem-
ble 1-Zn2+ upon exposure of UV light is shown in Scheme 2. The mech-
anism is based on the phenomenon of keto-enol tautomerization. The
photo conversion from the closed-ring isomer to the open-ring isomer
of 1 was also supported by the IR, 1H and 13C NMR spectral analysis
(Figs. S10–S12†, ESI) The IR spectrum showed shift in the carbonyl
peak from 1713 to 1716 cm−1 due to formation of keto form. The ab-
sence of\\OH peak and significant changes in the peak of phenyl pro-
tons indicated the formation of keto-form. Furthermore, the absence
of spiro carbon in 13C NMR supported the formation of open ring keto
form.
could also be realized to devise miniaturized information lock for
locking information at molecular level (Fig. 7). The UV light and dark
is coded as “B” and “H”, respectively. The first addition sequence of “B”
followed by “H” assumed as “ON” state. On the contrary, the inverted se-
quence order of “H” followed by “B” led to “OFF” state. Hence only the
correct password “BH” could unlock the absorbance keypad at λmax
= 556 nm whereas the incorrect entry “HB” fails to do so. Thus, the
cracking of the keypad lock becomes more difficult, thereby improving
the security of the molecular devices remarkably.
4. Conclusions
In conclusion, an ensemble of Zn2+ with a rhodamineB 3-allyl
salicylaldehyde hydrazone (1-Zn2+) displays photochromic property
in THF solution upon light irradiation. The light irradiation promotes
enol-keto tautomerism of the phenolic hydroxyl group present in the
skeleton of in salicylaldehyde moiety. Ensemble 1-Zn2+ turned from
light yellow to pink color on the exposure of UV light (λ = 365 nm).
The photochromic reaction is reversible with good fatigue resistance.
Remarkably, the system exhibits photochromic property in solution as
well as in a solid matrix of silica gel which enable it promising for
photo-patterning and photo printing and binary data storage
applications.
3.4. Gated photochromism
Stimulated by the excellent selectivity, sensitivity, switchability,
“turn-on” dual-optical signature, naked-eye readout, and rapid re-
sponse of 1-Zn2+ towards multi-stimuli in a large optical window (λ
= 450–700 nm) (vide supra), two-input and two-output sequential
logic circuits have been constructed [26]. Notably, the “turn-on” readout
allows measurement of low-concentration of the analyte and decreases
the probability of a false positive signal. In the set–reset of 1-Zn2+ by in-
puts UV light and dark, the logic circuit is planned in such a way that UV
light works as I1 whereas dark works as I2 (sequence 1). The deviations
in the absorbance at λmax = 556 nm (OUT1) and the color change by the
naked eye (OUT2) have been captured as the outputs. The threshold
values have been fixed at 0.025 for OUT1 (Fig. S13†, ESI). The color
changes from light yellow to pink are allocated as “0” and “1” respec-
tively. When I1 is high (considered as input signal “1–0”) the absorbance
arises at OUT1 and the color changes to pink at OUT2 (output signal
“1–1”). Conversely, successive addition of I2 (input signal “1–1”) regains
its initial absorbance and color with a signal pattern of “0–0” (Fig. 6).
The reversible and reconfigurable sequences of set–reset logic functions
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.saa.2019.03.003.
Acknowledgements
The financial assistance from UGC-BSR (LM), CSIR (AR) for senior re-
search fellowship, UGC (AKS) for SRF, UGC (KT) for non-NET fellowship
and Banaras Hindu University is gratefully acknowledged. AKS grate-
fully acknowledge the support of DST, India INSPIRE grant (DST/IN-
SPIRE/04/2015/002555).
References
[1] (a) M. Irie, T. Fukaminato, K. Matsuda, S. Kobatake, Photochromism of diarylethene
molecules and crystals: memories, switches, and actuators, Chem. Rev. 114 (24)
(2014) 12174–12277;
(b) H. Tian, S. Yang, Recent progresses on diarylethene based photochromic
switches, Chem. Soc. Rev. 33 (2004) 85–97;
(c) M. Irie, Diarylethenes for memories and switches, Chem. Rev. 100 (2000)
1685–1716.
[2] (a) I. Yildiz, E. Deniz, F.M. Raymo, Fluorescence modulation with photochromic
switches in nano structured constructs, Chem. Soc. Rev. 38 (2009) 1859–1867.
(b) van Dijken D J, Kovaříček P, Ihrig S P, and Hecht S, Acylhydrazones as widely tun-
able photoswitches, 14982–14991.
[3] (a) D. Liu, W. Chen, K. Sun, K. Deng, W. Zhang, Z. Wang, X. Jiang, Resettable multi-
readout logic gates based on controllably reversible aggregation of gold nano-
particles, Angew. Chem. Int. Ed. 50 (2010) 4103–4107;
Fig. 7. Schematic representation of molecular keypad locks to access a secret code by
monitoring the absorbance at 556 nm with different input sequences.

6
A. Rai et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 216 (2019) 1–6
(b) C. Liu, D. Yang, Q. Jin, L. Zhang, M. Liu, A. Chiroptical Logic, Circuit based on self-
[12] (a) N.S. Bell, M. Piech, Photophysical effects between spirobenzopyran-methyl
methacrylate-functionalized colloidal particles, Langmuir 22 (2006)
1420–1427;
assembled soft materials containing amphiphilic spiropyran, Adv. Mater. 28
(2016) 1644–1649.
[4] Y. Wu, Y. Xie, Q. Zhang, H. Tian, W. Zhu, A.D.Q. Li, Quantitative photoswitching in bis
(dithiazole)ethene enables modulation of light for encoding optical signals, Angew.
Chem. Int. Ed. 53 (2014) 2090–2094.
[5] J. Park, L.B. Sun, Y.P. Chen, Z. Perry, H.C. Zhou, Azobenzene-functionalized metal-
organic polyhedra for the optically responsive capture and release of guest mole-
cules, Angew. Chem. Int. Ed. 53 (2014) 5842–5846.
[6] V. Lemieux, N.R. Branda, Reactivity-gated photochromism of 1,2-dithienylethenes
for potential use in dosimetry applications, Org. Lett. (14) (2005) 2969–2972.
[7] (a) R. Pardo, M. Zayat, D. Levy, Photochromic organic–inorganic hybrid materials,
Chem. Soc. Rev. 40 (2011) 672-68;
(b) T. He, J.N. Yao, Photochromism in transition-metal oxides, Res. Chem. Intermed.
30 (2004) 459–488.
[13] C.B. Fan, S. Pu, G. Liu, Effects of solvents on the growth of an asymmetrical photo-
chromic diarylethene crystal, Dyes Pigments 113 (2015) 61–69.
[14] E. Feng, C. Fan, N. Wang, G. Liu, S. Pu, A highly selective diarylethene chemosensor
for colorimetric detection of CN− and fluorescent relay-detection of Al3+/Cr3+
Dyes Pigments 151 (2018) 22–27.
,
[15] C.B. Fan, Z.Q. Liu, L.L. Gong, A.M. Zheng, L. Zhang, C.S. Yan, H.Q. Wu, X.F. Feng, F. Luo,
Photoswitching adsorption selectivity in a diaryletheneazobenzene MOF, Chem
comm. 53 (2017) 763–766.
(b) J. Zhang, Q. Zou, H. Tian, Photochromic materials: more than meets the eye, Adv.
Mater. 25 (2013) 378–399;
(c) M.Q. Zhu, L. Zhu, J.J. Han, W. Wu, J.K. Hurst, A.D.Q. Li, Spiropyran-based photo-
chromic polymer nanoparticles with optically switchable luminescence, J. Am.
Chem. Soc. 128 (2006) 4303–4309;
(d) F.Y. Liu, K. Morokuma, Multiple pathways for the primary step of the spiropyran
photochromic reaction: a CASPT2//CASSCF study, J. Am. Chem. Soc. 135 (2013)
10693–10702;
[16] C.B. Fan, L.L. Gong, L. Huang, F. Luo, R. Krishna, X.F. Yi, A.M. Zheng, L. Zhang, S.Z. Pu,
X.F. Feng, Luo M. Biao, G.C. Guo, Significant enhancement of C2H2/C2H4 separation
by a photochromic diarylethene unit: a temperature- and light-responsive separa-
tion switch, Angew. Chem. Int. Ed. 56 (2017) 1–8.
[17] F. Liu, C.B. Fan, S. Pu, A new “turn-on” fluorescent chemosensor for Zn2+ based on a
diarylethene derivative and its practical applications, Journal of Photochemistry &
Photobiology A: Chemistry 371 (2019) 248–254.
[18] W. Li, C. Xiong, L. Wang, Q. Luo, Triptycene-based porous polymers regulated by
(e) F. Krohm, J. Kind, R. Savka, Ben M.A. Jan, D. Herald, H. Plenio, C.M. Thiele, A.A.
Brunsen, Photochromic spiropyran- and spirooxazine-homopolymers in meso-
porous thin films by surface initiated ROMP, J. Mater. Chem. C 4 (2016)
4067–4076;
diarylethenes, Dyes Pigments 159 (2018) 72–76.
[19] K. Li, Y. Xiang, X. Wang, J. Li, R. Hu, A. Tong, B.Z. Tang, Reversible photochromic sys-
tem based on rhodamine B salicylaldehyde hydrazone metal complex, J. Am. Chem.
Soc. 136 (2014) 1643–1649.
(f) S.Z. Pu, Q. Sun, C.B. Fan, R.J. Wang, G. Liu, J. Mater. Chem. C 4 (2016) 3075–3093;
(g) S. Kobatake, Y. Terakawa, Acid-induced photochromic system switching of
diarylethene derivatives between P- and T-types, Chem. Commun. (2007)
1698–1700;
(h) S.D. Straight, P.A. Liddell, Y. Terazono, T.A. Moore, A.L. Moore, D. Gust, All-
photonic molecular XOR and NOR logic gates based on photochemical control
of fluorescence in a fulgimide–porphyrin–dithienylethene triad, Adv. Funct.
Mater. 17 (2007) 777–785;
(i) A.S.C. Wei, M. Pan, K. Li, S.J. Wang, J.Y. Zhang, C.Y. Su, Multistimuli-responsive
photochromic metal-organic gel, Adv. Mater. 26 (2014) 2072–2077;
(j) A. Fihey, A. Perrier, W.R. Browne, D. Jacquemin, Multiphotochromic molecular
systems, Chem. Soc. Rev. 44 (2015) 3719–3759;
(k) W. Liu, F. Hu, Z. Chen, Z. Li, J. Yin, G.A. Yu, S.H. Liu, Dithienylethenes containing
aromatic carbons: synthesis, photochromism and anion recognition, Dyes Pig-
ments 115 (2015) 190–196.
[20] (a) Y. Xiang, A. Tong, P. Jin, Y. Ju, New fluorescent rhodamine hydrazone
chemosensor for Cu(II) with high selectivity and sensitivity, Org. Lett. 8
(2006) 2863–2866;
(b) A. Rai, A.K. Singh, A.K. Sonkar, A. Prakash, J.K. Roy, R. Nagarajan, L. Mishra, A
smart switchable module for the detection of multiple ions via turn-on dual-
optical readout and their cell imaging studies, Dalton Trans. 45 (2016)
8272–8277 (ref.therein.);
(c) Y. Yang, S.K. Seidlits, M.M. Adams, V.M. Lynch, C.E. Schmidt, E.V. Anslyn, J.B.
Shear, A highly selective low-background fluorescent imaging agent for nitric
oxide, J. Am. Chem. Soc. 132 (2010) 13114–13116.
[21] H.B. Cheng, H.Y. Zhang, Y. Liu, Dual-stimulus luminescent lanthanide molecular
switch based on an unsymmetrical diarylperfluorocyclopentene, J. Am. Chem. Soc.
135 (2013) 10190–10193.
[22] Q. Best, A. Xu, R. Mccarroll, E.M., L. Wang, D.J. Dyer, Design and investigation of a se-
ries of rhodamine-based fluorescent probes for optical measurements of pH, Org.
Lett. 12 (2010) 3219–3221.
[23] A. Rai, A.K. Singh, K. Tripathi, A.K. Sonkar, B.S. Chauhanm, S. Srikrishna, T.D. James, L.
Mishra, A quick and selective rhodamine based “smart probe” for “signal-on” optical
detection of Cu2+ and Al3+ in water, cell imaging, computational studies and solid
state analysis, Sensors and Actuators B:Chemical 266 (2018) 95–105.
[24] V. Dujols, F. Ford, A.W. Czarnik, A long-wavelength fluorescent chemodosimeter se-
lective for Cu(II) ion in water, J. Am. Chem. Soc. 119 (1997) 7386–7387.
[25] H.A. Benesi, J.H. Hildebrand, A spectrophotometric investigation of the interaction of
iodine with aromatic hydrocarbons, J. Am. Chem. Soc. (8) (1949) 2703–2707.
[26] A. Kumar, M. Chhatwal, P.C. Mondal, V. Singh, A.K. Singh, D.A. Cristaldi, R.D. Gupta, A.
Gulino, A ternary memory module using low-voltage control over optical properties
of metal-polypyridyl monolayers, Chem. Commun. 50 (2014) 3783–3785.
[8] E. Hadjoudis, I.M. Mavridis, Photochromism and thermochromism of Schiff bases in
the solid state: structural aspects, Chem. Soc. Rev. 33 (2004) 579–588.
[9] (a) A.A. Beharry, G.A. Woolley, Azobenzene photoswitches for biomolecules, Chem.
Soc. Rev. 40 (2011) 4422–4437;
(b) W. Szymański, J. Beierle, M. Kistemaker, W.A. Velema, B.L. Feringa, Reversible
photocontrol of biological systems by the incorporation of molecular
photoswitches, Chem. Rev. 113 (2013) 6114–6178;
(c) J. Broichhagen, D. Trauner, The in vivo chemistry of photoswitched tethered li-
gands, Curr. Opin. Chem. Biol. 21 (2014) 121–127.
[10] K. Li, Y. Li, J. Tao, L. Liu, L. Wang, H. Hou, A. Tong, Crystal violet lactone
salicylaldehyde hydrazone Zn(II) complex: a reversible photochromic material
both in solution and in solid matrix, Sci. Rep. 5 (2015), 14467.
[11] J.J. He, J.X. He, T.T. Wang, H.P. Zeng, Ion-induced cycle opening of a diarylethene and
its application on visual detection of Cu2+ and Hg2+ and keypad lock, J. Mater.
Chem. 2 (2014) 7531–7540.