A highly selective fluorescent chemosensor for Fe3+ based on a new diarylethene with a rhodamine 6G unit

Article abstract of DOI:10.1039/c7ra04728b

Herein, a new diarylethene derivative bearing rhodamine 6G (1O) was synthesized via Schiff base condensation. It exhibited a sensitive response to Fe³⁺ with the solution changing from colorless (no fluorescence) to distinct pink (strong fluores

Full text of DOI:10.1039/c7ra04728b

RSC Advances
View Article Online
View Journal | View Issue
PAPER
A highly selective fluorescent chemosensor for Fe3+
based on a new diarylethene with a rhodamine 6G
unit†
Cite this: RSC Adv., 2017, 7, 29827
* *
and Shouzhi Pu
Huitao Xu, Haichang Ding, Gang Li, Congbin Fan,
Gang Liu
Herein, a new diarylethene derivative bearing rhodamine 6G (1O) was synthesized via Schiff base
condensation. It exhibited a sensitive response to Fe3+ with the solution changing from colorless (no
fluorescence) to distinct pink (strong fluorescence) due to the transformation of the spirolactam ring to
the open ring of rhodamine 6G. The diarylethene derivative bound to Fe3+ in the binding stoichiometry
of 1 : 1, and the limit of detection (LOD) of the 1O chemosensor for Fe3+ detection was found to be
65 nM. In addition, 1O exhibited an obvious acidichromism to TFA and could function as a reversible
fluorescence photoswitch in response to UV/vis light irradiation. Based on these observations, a logic
circuit was constructed with the combinational stimuli of UV/vis light and Fe3+/EDTA as inputs and the
fluorescent emission intensity at 585 nm as the output.
Received 27th April 2017
Accepted 16th May 2017
DOI: 10.1039/c7ra04728b
rsc.li/rsc-advances
diacridylnaphthalene-derived uorosensor based on uores-
cence quenching. Therefore, the development of highly selective
Introduction
turn-on response chemosensors for Fe3+ is of signicance and
challenging.14 Photochromic materials can be potentially
applied to optical memories, photoswitches, logic circuits, and
chemosensors.15,16 Diarylethenes, one of the most promising
photoresponsive compounds, have attracted signicant research
interests due to their excellent thermal stability, notable fatigue
resistance, high sensitivity, and rapid response.17,18
Heavy metal cations, such as Hg2+, Cu2+, and Fe3+, naturally
exist and have been widely used in many industrial elds. They
are toxic at high concentrations and are responsible for many
incidents of industrial and agricultural pollution.1–3 Compared
to the time-consuming and expensive instrumental techniques
reported for heavy metal-ion detection, a chemosensor is
a faster, cheaper, more powerful, and highly sensitive molecular
tool for the detection of many biological and environmental
heavy metal pollutants.4–6 Among all chemosensors, uorescent
chemosensors have attracted signicant attention due to their
simple operation, high sensitivity, and real-time detection. Fe3+
plays a key role in many biochemical processes at the cellular
level and is indispensable for most of the organisms.7 It
provides oxygen-carrying capacity to heme and acts as a cofactor
in many enzymatic reactions involved in the mitochondrial
respiratory chain. However, high levels of Fe3+ within the body
can be associated with increased incidence of certain cancers
and dysfunction of organs such as heart, pancreas, and liver.8–11
Therefore, new simple and efficient chemosensors for Fe3+
detection are highly desired.12 Several uorescent sensors have
been developed for Fe3+ detection. However, most of them
detect Fe3+ based on uorescence quenching by the para-
In particular, they can function as a uorescence sensor
based on their reversible uorescence response to UV/vis lights
irradiation. Recently, many diarylethene-based sensors have
been reported. Zheng et al. prepared a dual-control molecular
switch based on photochromic hexahydrogen cyclopentene
bearing two rhodamine units and demonstrated it as an inte-
grated logic circuit at the molecular level. Pu et al. exploited
diarylethene-based uorescence sensors to detect Fe3+, Hg2+,
and Cu2+
.
Their study has contributed towards the compre-
19,20
hensive understanding of the sensors based on diarylethene-
bearing functional groups.
The rhodamine 6G-based uorescent chemosensor is an
excellent uorophore for metal ion detection and has attracted
extensive interest in recent years by virtue of its excellent pho-
tophysical properties such as long excitation and emission
wavelength, high uorescence quantum efficiency, and excel-
lent detection sensitivity.21,22 The off–on uorescence switching
of the chemosensor is based on the transformation between the
spirocyclic and open ring forms of rhodamine 6G. The chemo-
sensor is in the spirocyclic form in the absence of metal ions
and exhibits no color or uorescent emission. The addition of
suitable metal ions can open the spirocycle via coordination,
leading to chromogenic and uorogenic responses.
magnetic property of Fe3+ 13 For example, in an early study, Wolf
.
et al. selectively detected Fe3+ in aqueous solutions with a 1,8-
Jiangxi Key Laboratory of Organic Chemistry, Jiangxi Science and Technology Normal
University, Nanchang, Jiangxi 330013, PR China. E-mail: liugang0926@163.com;
pushouzhi@tsinghua.org.cn; Fax: +86-791-83831996; Tel: +86-791-83831996
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c7ra04728b
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 29827–29834 | 29827

View Article Online
RSC Advances
Paper
synthesized as described in the literature.23–27 Compound 3 was
coupled with 4 to afford compound 5, which was hydrolyzed to
produce compound 6. Compound 8 reacted with 6 in anhydrous
ethanol via Schiff base condensation to afford the target
compound 1O. The detailed procedure is described as follows.
A solution of n-BuLi/hexane (2.5 mol Lꢀ1, 4.90 mL) was added
dropwise to 60 mL of compound 3 (3.24 g, 10.00 mmol) solution
in anhydrous THF at 195 K under stirring and an argon atmo-
sphere and stirred for 30 min. Compound 4 (3.67 g, 10.00 mmol)
was slowly added to the reaction mixture at 195 K, further stirred
for 3 h at the same temperature, and quenched with water. The
product was extracted with dichloromethane, dried over Na2SO4,
ltered, and evaporated. The crude product was puried by
column chromatography using the petroleum ether–ethyl
acetate (v/v ¼ 10 : 1) as the eluent to afford the compound 5
(2.60 g, 4.40 mmol), which was reuxed in acetone–water (v/v ¼
4 : 1) for 2 h, extracted with dichloromethane, dried over
Na2SO4, ltered, evaporated, and puried by column chroma-
tography to afford compound 6 as a blue solid with a yield of
84%. Mp: 363–365 K. 1H NMR (CDCl3, 400 MHz), d (ppm): 1.90 (t,
3H, J ¼ 8.0 Hz), 1.93 (s, 3H), 7.21 (s, 1H), 7.25 (d, 1H, J ¼ 8.0 Hz),
7.32 (t, 2H, J ¼ 8.0 Hz), 7.37 (s, 1H), 7.47 (d, 2H, J ¼ 8.0 Hz), 7.63
(d, 2H, J ¼ 8.0 Hz), 7.83 (d, 2H, J ¼ 8.0 Hz), 9.94 (s, 1H).
Scheme 1 Photochromism of diarylethene 1O.
In the present study, a diarylethene derivative bearing
a rhodamine 6G moiety was synthesized to construct a uores-
cent chemosensor for Fe3+ detection. The chemosensor
exhibited excellent selectivity and sensitivity for Fe3+ detection
via the turn on uorescence signal in an aqueous acetonitrile
solution (v/v ¼ 1 : 1). Scheme 1 is the schematic of the photo-
chromism of the diarylethene derivative.
Experimental
General methods
Chemical reagents were obtained from J & K Scientic Ltd and
were used as received. All the reagents and solvents were of
analytical grade and diluted as required. All cations were added
in the form of metal nitrates except for K+, Ba2+, Mn2+, and Hg2+
that were added as metal chlorides. The stock solutions of the
metal ions were prepared in distilled water at the concentration
A solution of compound 8 (0.98 g, 0.20 mmol) in 15 mL
anhydrous ethanol was added to a solution of compound 6
(0.11 g, 0.20 mmol) under constant stirring, reuxed for 48 h,
cooled down to room temperature, and quenched with water.
The solvent was removed under reduced pressure. The residue
was extracted with dichloromethane, and the organic phase was
dried over Na2SO4, ltered, and evaporated. The crude product
was puried by column chromatography on a silica gel column
using petroleum ether–ethyl acetate (v/v ¼ 4 : 1) as the eluent to
afford 1O (0.10 g, 0.10 mmol) as a light purple solid in 51% yield.
of 0.1 mol Lꢀ1
.
NMR spectra were obtained using a Bruker AV400 (400 MHz)
spectrometer with CDCl3 and DMSO-d6 as the solvents and
tetramethylsilane (TMS) as the internal standard. Fluorescence
quantum yield was measured using an Absolute PL Quantum
Yield Spectrometer QY C11347-11. UV/vis spectra were obtained
using an Agilent 8453 UV/vis spectrophotometer. The uores-
cence spectra were obtained via a Hitachi F-4600 uorescence
spectrophotometer. Infrared spectra (IR) were obtained using
a Bruker Vertex-70 FT-IR spectrometer.
1
Mp: 430–432 K. H NMR (DMSO-d6, 400 MHz), d (ppm) 1.19 (t,
6H, J ¼ 8.0 Hz), 1.82 (s, 6H), 1.96 (s, 6H), 3.10–3.13 (m, 4H), 5.05
(s, 2H), 6.16 (s, 2H), 6.32 (s, 2H), 7.03 (d, 1H, J ¼ 8.0 Hz), 7.33 (d,
1H, J ¼ 8.0 Hz), 7.41 (d, 3H, J ¼ 4.0 Hz), 7.47 (s, 1H), 7.51 (s, 1H),
7.55–7.60 (m, 6H), 7.73 (s, 1H) 7.90 (d, 1H, J ¼ 8.0 Hz), 8.64 (s,
1H) (Fig. S1†). 13C NMR (DMSO-d6, 100 MHz), d (ppm): 13.97,
14.08, 16.86, 37.40, 62.73, 65.56, 95.67, 104.95, 118.15, 122.48,
122.92, 123.19, 123.72, 125.21, 125.48, 126.78, 127.37, 128.05,
128.10, 128.63, 128.80, 129.13, 132.42, 133.78, 134.08, 140.85,
141.13, 141.65, 141.83, 145.75, 147.74, 150.94, 151.29, 163.69
Synthesis of 1O
Scheme 2 shows the synthesis route of the target compound, [1-
(2-methyl-5-phenyl-3-thienyl)-2-{2-methyl-5-[4-N(rhodamine-
6G)-hydrazide]phenyl-3-thienyl}peruorocyclopentene] (1O). 3-
Bromo-2-methyl-5-(1,3-dioxolane)thiophene (3), (2-methyl-5-
phenyl-3-thieryl)peruorocyclopentene (4), and
8
were
Scheme 2 Synthesis route for diarylethene 1O.
29828 | RSC Adv., 2017, 7, 29827–29834
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
(Fig. S2†). MS (m/z): 959.28 [M + H]+ (Fig. S3†); IR (KBr, n, cmꢀ1):
1199, 1216, 1267, 1315, 1515, 1608, 1620, 1636, 1684, 1713.
Results and discussion
Photochromism of 1O
The photochromic properties of 1O were determined in aceto-
nitrile (C ¼ 2 ꢁ 10ꢀ5 mol Lꢀ1) at room temperature. The open
ring isomer 1O exhibited an absorption peak at 353 nm (Fig. 1A)
due to the p*–p transition.28 A new absorption band centered at
602 nm appeared, and the solution of 1O turned from colorless to
blue under the irradiation at 297 nm, indicating that the closed-
ring form 1C was formed. The blue solution of 1C could be
bleached to colorless under the visible light irradiation at l >
500 nm, and its absorption peak shied back to 353 nm. An
isosbestic point appeared at 370 nm, indicating that a two-
component photochromic reaction occured.29–31 The cyclization
and cycloreversion quantum yields of 1O were determined to be
0.232 and 0.003, respectively, with 1,2-bis(2-methyl-5-phenyl-3-
thienyl)peruorocyclopentene as a ref. 32 The fatigue resistance
of 1O revealed that 1O degraded only 8.3% aer 10 coloration–
discoloration cycles in response to the alternate irradiations of
UV/vis lights at room temperature (Fig. 1B).
Fig. 2 Changes in fluorescence of 1O in response to various metal
ions (10.0 equiv.) in aqueous acetonitrile solution (C ¼ 2.0 ꢁ 10ꢀ5 mol
L
ꢀ1, v/v ¼ 1 : 1). (A) Absorption spectral changes. (B) Changes in fluo-
rescence. (C) Color and fluorescence changes of 1O after the addition
of 10.0 equiv. of different metal ions.
showed weaker responses to Cr3+ and Al3+ with 45-fold and 28-
fold increases in uorescent emission peaks at 578 nm and
585 nm, respectively (Fig. S4†). These observations indicate that
1O can be potentially used as a selective uorescence sensor for
Fe3+ in an acetonitrile/water binary solvent system (v/v ¼ 1 : 1).
In addition, Fe3+ turned the 1O solution from colorless to pink
and from dark to a bright green yellow color under excitation at
515 nm due to the formation of the open ring amide form of
rhodamine 6G (1O0) (Fig. 2C). Other metal ions caused no
detectable increase in the emission intensity or solution color of
1O in the aqueous acetonitrile solution except for Cr3+, Al3+, and
Cu2+ that turned the 1O solution to pale pink and caused a weak
uorescent emission (Fig. 2C).
Spectral response of 1O to Fe3+
It has been reported that rhodamine 6G derivatives are subject
to signicant changes in absorption or uorescence spectra
upon coordination with metal ions and thus can be used as
a sensitive probe for metal ion detection.33 In the present study,
the uorescence of 1O (C ¼ 2.0 ꢁ 10ꢀ5 mol Lꢀ1) induced by
metal ions including Fe3+, Cr3+, Al3+, Hg2+, Cu2+, Mg2+, Ba2+,
Zn2+, Mn2+, Co2+, Ni2+, Ca2+, Cd2+, Pb2+, Sr2+, and K+ was
determined in an aqueous acetonitrile solution (v/v ¼ 1 : 1) at
room temperature. As shown in Fig. 2A, for the absorption
spectra of 1O in the presence of 10.0 equiv. of metal ions, only
Fe3+, Cr3+, and Al3+ were able to induce strong absorptions at
531 nm, and Fe3+ caused a much stronger absorption peak than
The chemosensing properties of 1O towards Fe3+ were
further investigated via absorption and uorescence titration.
As shown in Fig. 3, the solution of 1O changed from colorless to
pink (Fig. 3A), and a new absorption band centered at 530 nm
appeared with the increase of Fe3+ equiv. from 0 to 10.0 due to
the formation of 1O0 (Fig. 3B). Further increase in the Fe3+
amount caused no signicant change in the absorption of 1O.
Moreover, the uorescent emission of 1O at 585 under excita-
tion at 515 nm increased with the increase of Fe3+ equiv and
peaked at 10.0 equiv. (Fig. 3C). The absolute uorescence
quantum yield was determined to be 0.43. The uorescence
intensity changes with the addition of Fe3+ were also visibly
observed with the naked eye, with the solution turning from
dark to a bright green-yellow under excitation at 515 nm
(Fig. 3D).
Cr3+ and Al3+
.
Compound 1O in acetonitrile exhibited no obvious emission
signal under excitation at 515 nm. The addition of 10.0 equiv. of
Fe3+ to the 1O solution led to ca. 168-fold increase in the uo-
rescent emission intensity at 585 nm (Fig. 2B). The 1O solution
The uorescence was reverted by addition of an excess of
EDTA (10.0 equiv.), indicating that the coordination of 1O with
Fe3+ could be restored. Note that 1O0 also exhibited excellent
uorescent switching properties under alternate irradiations
with UV/vis lights in aqueous acetonitrile (v/v ¼ 1 : 1) (Fig. 3E).
In the photostationary state, the uorescence emission inten-
sity was quenched 82% due to the formation of 1C0 with the
Fig. 1 (A) Changes in the absorption spectra of diarylethene 1O in
acetonitrile (C ¼ 2.0 ꢁ 10ꢀ5 mol Lꢀ1) at room temperature. (B) Fatigue
resistance of 1O in acetonitrile (C ¼ 2.0 ꢁ 10ꢀ5 mol Lꢀ1) at room
temperature.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 29827–29834 | 29829

View Article Online
RSC Advances
Paper
Fig. 3 (A) Fluorescence properties of 1O in aqueous acetonitrile (C ¼ 2.0 ꢁ 10ꢀ5 mol Lꢀ1, v/v ¼ 1 : 1, lex ¼ 515 nm) induced by Fe3+/EDTA. (B)
Upon addition of different equivalents of Fe3+ and the emission intensity curve at 585 nm. (C) The absorption spectra of 1O0 in aqueous
acetonitrile (C ¼ 2.0 ꢁ 10ꢀ5 mol Lꢀ1, v/v ¼ 1 : 1) induced by Fe3+/EDTA. (D) The absorption intensity changes of 1O at 531 nm with different
equivalents of Fe3+. (E) Changes in the fluorescence of 1O0 in aqueous acetonitrile (C ¼ 2.0 ꢁ 10ꢀ5 mol Lꢀ1, v/v ¼ 1 : 1, lex ¼ 515 nm) upon
alternating irradiation with UV/vis light.
uorescence changing from bright green-yellow to dark yellow. be 5.9793 ꢁ 104 mol Lꢀ1 by the Benesi–Hildebrand equation
These results indicate that the diarylethene derivative 1O is (Fig. 4B),36 and the limit of detection of Fe3+ by 1O was found to
a promising candidate for uorescence-switching devices due to be 65 nM (3d per slope) (Fig. 4C). These results indicate that 1O
uorescence switching behavior induced by both Fe3+/EDTA is highly selective towards Fe3+ and can be used as a uores-
and UV/vis light.
cence sensor of Fe3+
The selectivity of a chemosensor towards the analyte over the
.
Job's plot analysis was conducted on the uorescence titra-
tion data, as previously reported, to calculate the binding ratio other competitive species is a very important parameter to
between 1O and Fe3+ 34,35 As shown in Fig. 4A, the concentration evaluate its sensing performance.37 To further conrm the high
.
of 1O0 reached a maximum as the molar fraction of [Fe3+]/([Fe3+] selectivity of the 1O sensor towards Fe3+, competitive tests were
+ [1O]) ¼ 0.5, indicating that the complex ratio between Fe3+ and conducted in the presence of metal ions with similar properties:
1O was 1 : 1 in the aqueous acetonitrile solution (v/v ¼ 1 : 1). Cd2+, Ba2+, Mg2+, Ca2+, Pb2+, K+, Co2+, Zn2+, Sr2+, Mn2+, Ni2+,
The association constant (Ka) of 1O with Fe3+ was determined to Al3+, Cr3+, Cu2+, and Hg2+. Fig. 5 shows the uorescence
response of 1O to Fe3+ in the aqueous acetonitrile solution as
different ions (20.0 equiv.) were added. No obvious interference
was observed from other competitive metal ions in aqueous
acetonitrile, indicating that 1O was highly selective towards
Fe3+. The present sensor was compared with other sensors
Fig. 4 (A) The Job's plot showing the 1 : 1 complex of 1O and Fe3+. (B) Fig. 5 Emission changes at 585 nm of 1O in the presence of different
Hildebrand–Benesi plot based on the 1 : 1 ratio between 1O and Fe3+
,
metal ions added in the amount of 20.0 equiv. (lex ¼ 515 nm) in
the binding constant of 1O with Fe3+ was calculated to be 5.9793 ꢁ acetonitrile/water binary solvent (C ¼ 2.0 ꢁ 10ꢀ5 mol Lꢀ1, v/v ¼ 1 : 1),
104 mol Lꢀ1. (C) The limit of detection (LOD) is 65 nM.
after the initial addition of Fe3+ (10.0 equiv.) to the above solution.
29830 | RSC Adv., 2017, 7, 29827–29834
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
reported for Fe3+ detection in recent years,38–44 as listed in TFA and the absolute uorescent quantum yield of the
Table 1. These sensors showed some good physical properties protonated 1O (1O00) was determined to be 0.55. The addition of
such as lower LOD, association constant, high sensitivity and so TEA to the 1O00 solution re-generated the spirolactam form of
on. For the 1O–Fe3+ complex, a moderate performance in all rhodamine. The uorescent emission at 583 nm disappeared,
aspects was observed, suggesting that diarylethene 1O could and the bright green-yellow uorescence of the solution
serve as a uorescence sensor for Fe3+
.
diminished (Fig. 6A). Further addition of TFA produced the
protonated 1O00. As shown in Fig. 6B, the spirolactam form of 1O
was non-absorbing, whereas the open ring form exhibited
a visible absorption band centered at 529 nm and the solution
changed from colorless to pink, which could be easily observed
with the naked eye. The absorption reached a maximum with
30.0 equiv. TFA and further increasing TFA equiv. caused no
signicant change in the absorption (Fig. S6†). The reversible
modulation of uorescent emission via alternating additions of
TFA and TEA for 10 cycles resulted in no signicant decrease in
the emission intensity of 1O (Fig. 6D).
Acidichromism
It is particularly well-known that the open ring form of the
rhodamine moiety in the presence of a proton emits strong
uorescence in the range of 540–700 nm.45,46 As shown in Fig. 6A
and Fig. S5,† the uorescence intensity of 1O (C ¼ 2.0 ꢁ
10ꢀ5 mol Lꢀ1) in acetonitrile at 595 nm under excitation at
515 nm was signicantly enhanced by TFA due to the formation
of an open ring uorescent rhodamine moiety. The uores-
cence intensity reached a maximum in the presence of 30 equiv.
Table 1 Comparative study of the analytical performance of 1O–Fe3+ with other recently reported sensors
Sensor
Approaches
LOD
Ka
Ref.
Fluorescence increase
737 nM
—
Sens. Actuators B, 2016, 224, 661–667
Fluorescence increase
Fluorescence increase
418 nM
31 nM
1.88 ꢁ 104
2.19 ꢁ 104
J. Lumin., 2015, 157, 143–148
Bioorg. Med. Chem., 2014, 22, 4826–4835
Fluorescence increase
105 nM
1.24 ꢁ 105
Talanta, 2014, 128, 69–74
Fluorescence increase
Fluorescence quenching
Fluorescence increase
2 ꢁ 104 nM
300 nM
—
Sens. Actuators B, 2012, 174, 231–236
Talanta, 2013, 106, 261–265
—
1.1 nM
log() ¼ 4.72 ꢂ 0.27
Sens. Actuators B, 2013, 178, 228–232
Fluorescence increase
65 nM
5.9793 ꢁ 104
This work
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 29827–29834 | 29831

View Article Online
RSC Advances
Paper
Fig.
7
(A) Dual-controlled fluorescent-switching behavior of 1O
induced by Fe3+/EDTA and UV/vis light stimuli. (B) The combinational
logic circuits equivalent to the truth table given in Table 1: In 1 (297 nm
light), In 2 (l > 500 nm light), In 3 (Fe3+), In 4 (EDTA) and output
(fluorescence at 585 nm).
Fig. 6 (A) Fluorescence (lex ¼ 515 nm) change of 1O in acetonitrile (C
¼ 2.0 ꢁ 10ꢀ5 mol Lꢀ1) induced by TFA/TEA. (B) Changes in absorption
spectra of 1O00 in acetonitrile (C ¼ 2.0 ꢁ 10ꢀ5 mol Lꢀ1) induced by TFA/
TEA. (C) Fluorescence (lex ¼ 515 nm) change of 1O00 upon alternating
irradiation with UV/vis light. (D) Acid–base cycle of 1O in acetonitrile (C
¼ 2.0 ꢁ 10ꢀ5 mol Lꢀ1) at room temperature. (E) Principle of reversible
molecular switching and the color changes of 1O.
including 297 nm UV light, visible light (l > 500 nm), Fe3+, and
EDTA. The uorescent emission intensity at 585 nm was set as
the output. The output with the emission intensity at 585 nm
higher than ca. 2500 was considered as the on state with
a Boolean value of 1 and the emission intensity lower than ca.
2500 was regarded as the off state with a Boolean value of 0. As
shown in Fig. 7B, the state can be either on (on ¼ 1) or off (off ¼
0) with different Boolean values. For example, In 1 can be
switched to the ‘on’ state with the Boolean value of 1 in response
As discussed above, the color of 1O00 solution could be
changed via alternating irradiating with UV/vis lights. Based on
this feature, it can be anticipated that the diarylethene deriva-
tives bearing chemo-responsive function groups offer a prom-
ising approach to the design of optical molecular switches.47,48
1O00 in acetonitrile underwent a photocyclization reaction under
irradiation at 297 nm, exhibiting a strong emission peak at
582 nm that signicantly decreased with the isomerization from
1O00 to 1C00 under visible light irradiation (Fig. 6C). The uo-
rescence intensity of 1O00 decreased 85%, accompanied by the
Table 2 Truth table for all possible strings of four binary-input data
and the corresponding output digit
uorescence change from bright green-yellow to dark at the Input
photostationary state, which was a typical behaviour of the
FRET mechanism. FRET usually occurs between the open ring
In 1
(UV light)
In 2
(vis light)
In 3
In 4
(EDTA)
Output lem
¼ 585 nm
(Fe3+
)
rhodamine acylhydrazine (the donor) and the closed-ring dia-
rylethene (the acceptor), resulting in intrinsic photo-
luminescence properties. The uorescence color and emission
spectrum of 1O00 can be restored via irradiation with visible light
of l > 500 nm. Fig. 6E shows the switching behavior of 1O
induced by the stimulations of proton and UV/vis lights. These
results indicate that 1O can be potentially used as a dual-control
molecular switch by TFA/TEA and UV/vis light.
0
1
0
0
0
1
1
1
0
0
0
1
1
1
0
1
0
0
1
0
0
1
0
0
1
1
0
1
1
0
1
1
0
0
0
1
0
0
1
0
1
0
1
1
0
1
1
1
0
0
0
0
1
0
0
1
0
1
1
0
1
1
1
1
0
0
0
1
0
0
0
0
1
0
0
1
0
0
0
0
Application in a logic circuit
As discussed above, the emission intensity of diarylethene 1O
was successfully modulated by either UV/vis light or Fe3+/EDTA
stimuli in an aqueous acetonitrile solution (Fig. 7A). Based on
this observation, a logic circuit was constructed by four inputs
29832 | RSC Adv., 2017, 7, 29827–29834
This journal is © The Royal Society of Chemistry 2017

View Article Online
Paper
RSC Advances
to irradiation at 297 nm and In 2 can be switched on by the 10 A. Malek, T. Thomas and E. Prasad, ACS Sustainable Chem.
irradiation of appropriate visible light (l > 500 nm). In 3 was 1
Eng., 2016, 4, 3497–3503.
with the addition of Fe3+ and In 4 was 1 with the addition of 11 T. Ganz, Blood, 2003, 102, 783–788.
EDTA. The output was on with the Boolean value of 1 under the 12 A. P. De Silva, H. Q. N. Gunaratne, T. Gunnlaugsson,
stimuli of all four inputs. The uorescent emission intensity at
585 nm below ca. 2500 was set as the initial state where the logic
A. J. Huxley, C. P. McCoy, J. T. Rademacher and T. E. Rice,
Chem. Rev., 1997, 97, 1515–1566.
circuit was off. The input strings In 3 ¼ 1, In1 ¼ 0, In 2 ¼ 0, and 13 X. Y. Qu, Q. Liu, X. N. Ji, H. C. Chen, Z. K. Zhou and Z. Shen,
In 4 ¼ 0 gave an output signal of 1 (on). Table 2 shows all
Chem. Commun., 2012, 48, 4600–4602.
14 C. Wolf, X. Mei and H. K. Rokadia, Tetrahedron Lett., 2004,
45, 7867–7871.
possibilities of the logic strings of the four inputs.
15 J. Zhang, Q. Zou and H. Tian, Adv. Mater., 2013, 25, 378–399.
16 A. Toriumi, S. Kawata and M. Gu, Opt. Lett., 1998, 23, 1924–
1926.
Conclusions
In summary, a new diarylethene derivative bearing a rhodamine
6G unit was designed and synthesized. It exhibited highly 17 M. Irie, Chem. Rev., 2000, 100, 1685–1716.
selective and sensitive turn-on uorescence and a color change 18 K. Y. Liu, Y. Wen, T. Shi, Y. Li, F. Y. Li, Y. L. Zhao,
response visible with the naked eye towards Fe3+ in aqueous
C. H. Huang and T. Yi, Chem. Commun., 2014, 50, 9141–9144.
acetonitrile. The Job's plot of experimental data reveals that 19 G. M. Liao, C. H. Zheng, D. D. Xue, C. B. Fan, G. Liu and
a 1 : 1 stoichiometry is the most favorable binding mode
S. Z. Pu, RSC Adv., 2016, 6, 34748–34753.
between 1O and Fe3+. In addition, the uorescent emission of 20 S. H. Jing, C. H. Zheng, S. Z. Pu, C. B. Fan and G. Liu, Dyes
the complex can be turned on/off by UV/vis lights irradiation. Pigm., 2014, 107, 38–44.
Based on these results, an integrated digital circuit was con- 21 S. Pal, N. Chatterjee and P. K. Bharadwaj, RSC Adv., 2014, 4,
structed with the uorescent emission intensity at 585 nm as
26585–26620.
the output.
22 X. Zeng, L. Dong, C. Wu, L. Mu, S. F. Xue and Z. Tao, Sens.
Actuators, B, 2009, 141, 506–510.
23 M. Morimoto and M. Irie, Chem. Commun., 2005, 31, 3895–
3905.
Acknowledgements
The authors are grateful for the nancial support received from 24 S. Yamamoto, K. Matsuda and M. Irie, Org. Lett., 2003, 5,
the National Natural Science Foundation of China (21662015, 1769–1772.
21363009, 221362013, 51373072), the Project of Jiangxi 25 R. J. Wang, S. Z. Pu, G. Liu and S. Q. Cui, Beilstein J. Org.
Academic and Technological leaders (20142BCB22010), the Chem., 2012, 8, 1018–1026.
Project of the Science Funds of the Jiangxi Education Office 26 Z. Wang, D. Wu, G. Wu, N. Yang and A. Wu, J. Hazard. Mater.,
(KJLD13069), and the innovation fund of graduate students
(YC2016-X02).
2013, 244, 621–627.
27 D. Wu, W. Huang, C. Duan, Z. Lin and Q. Meng, Inorg.
Chem., 2007, 46, 1538–1540.
28 Z. X. Li, L. Y. Liao, W. Sun, C. H. Xu, C. Zhang, C. J. Fang and
C. H. Yan, J. Phys. Chem. C, 2008, 112, 5190–5196.
Notes and references
1 E. Erdema, N. Karapinarb and R. Donata, J. Colloid Interface 29 S. Kawai, T. Nakashima, K. Atsumi, T. Sakai, M. Harigai,
Sci., 2004, 280, 309–314.
Y. Imamoto and T. Kawai, Chem. Mater., 2007, 19, 3479–
2 D. Wang, X. Y. Xiang, X. L. Yang, X. D. Wang, Y. L. Guo,
3483.
W. S. Liu and W. W. Qin, Sens. Actuators, B, 2014, 201, 30 M. Morimoto and M. Irie, Chem.–Eur. J., 2006, 12, 4275–
246–254. 4282.
3 W. Sun, D. Y. Hu, Z. B. Wu, B. A. Song and S. Yang, Chin. J. 31 T. Nakashima, K. Miyamura, T. Sakai and T. Kawai, Chem.–
Org. Chem., 2011, 31, 997–1010.
Eur. J., 2009, 15, 1977–1984.
4 G. J. Park, I. H. Hwang, E. J. Song, H. Kim and C. Kim, 32 M. Irie, T. Lia, S. Kobatake and N. Kato, J. Am. Chem. Soc.,
Tetrahedron, 2014, 70, 2822–2828.
2000, 122, 4871–4876.
5 K. Rurack, Spectrochim. Acta, Part A, 2001, 57, 2161–2195.
6 J. F. Zhang, Y. Zhou, J. Yoon and J. S. Kim, Chem. Soc. Rev.,
2011, 40, 3416–3429.
33 M. J. Yuan, Y. L. Li, J. B. Li, C. H. Li, X. F. Liu, J. Lv, J. L. Xu,
H. B. Liu, S. Wang and D. B. Zhu, Org. Lett., 2007, 9, 2313–
2316.
7 K. P. Carter, A. M. Young and A. E. Palmer, Chem. Rev., 2014, 34 X. B. Yang, B. X. Yang, J. F. Ge, Y. J. Xu, Q. F. Xu, J. Liang and
114, 4564–4601.
J. M. Lu, Org. Lett., 2011, 13, 2710–2713.
8 P. S. Hardikar, S. M. Joshi, D. S. Bhat, D. A. Raut, P. A. Katre, 35 R. Kato, S. Nishizawa, T. Hayashita and N. Teramae,
H. G. Lubree and C. S. Yajnik, Diabetes Care, 2012, 35, 797–
802.
9 J. Comin-Colet, M. Lainscak, K. Dickstein, G. S. Filippatos,
Tetrahedron Lett., 2001, 42, 5053–5056.
36 H. A. Benesi and J. H. Hildebrand, J. Am. Chem. Soc., 1949,
71, 2703–2707.
¨
P. Johnson, T. F. Luscher, C. Mori, R. Willenheimenr, 37 M. Saleem and K. H. Lee, RSC Adv., 2015, 5, 72150–72287.
P. Poniknowski and S. D. Anker, Eur. Heart J., 2013, 34, 30– 38 S. Li, D. Zhang, X. Y. Xie, S. G. Ma, Y. Liu, Z. H. Xu, Y. F. Gao
38.
and Y. Ye, Sens. Actuators, B, 2016, 224, 661–667.
This journal is © The Royal Society of Chemistry 2017
RSC Adv., 2017, 7, 29827–29834 | 29833

View Article Online
RSC Advances
Paper
39 C. C. Wang, Y. Q. Liu, J. Y. Cheng, J. H. Song, Y. F. Zhao and 44 V. Bhalla, N. Sharma, N. Kumar and M. Kumar, Sens.
Y. Ye, J. Lumin., 2015, 157, 143–148. Actuators, B, 2013, 178, 228–232.
40 X. F. Bao, J. X. Shi, X. M. Nie, B. J. Zhou, X. L. Wang, 45 K. Ghosh, T. Sarkar, A. Majumdar, S. K. Mandal and
L. Y. Zhang, H. Liao and T. Pang, Bioorg. Med. Chem., 2014,
22, 4826–4835.
A. R. Khuda-Bukhsh, Anal. Methods, 2014, 6, 2648–2654.
46 S. J. Lim, J. Seo and S. Y. Park, J. Am. Chem. Soc., 2006, 128,
14542–14547.
47 L. N. Lucas, J. J. D. de Jong, J. H. Van Esch, R. M. Kellogg and
B. L. Feringa, Eur. J. Org. Chem., 2003, 2003, 155–166.
48 W. R. Algar, M. Massey and U. J. Krull, TrAC, Trends Anal.
Chem., 2009, 28, 292–306.
41 C. C. Wang, D. Zhang, X. Y. Huang, P. G. Ding, Z. J. Wang,
Y. F. Zhao and Y. Ye, Talanta, 2014, 128, 69–74.
42 M. M. Chai, D. Zhang, M. Wang, H. J. Hong, Y. Ye and
Y. F. Zhao, Sens. Actuators, B, 2012, 174, 231–236.
43 Y. Y. Du, M. Chen, Y. X. Zhang, F. Luo, C. Y. He, M. J. Li and
X. Chen, Talanta, 2013, 106, 261–265.
29834 | RSC Adv., 2017, 7, 29827–29834
This journal is © The Royal Society of Chemistry 2017