Facile and green preparation of colorimetric and fluorescent sensors for mercury, silver, and carbonate ions visual detecting: Spectroscopy and theoretical studies

Article abstract of DOI:10.1016/j.molstruc.2021.130626

Two new fluorescent and colorimetric chemosensors based on benzimidazole derivatives (A, B) have been successfully synthesized through a facile and green catalytic reaction of ortho-phenylenediamine (O-PDA) and two different aldehydes in the presence of S

Full text of DOI:10.1016/j.molstruc.2021.130626

Journal of Molecular Structure 1241 (2021) 130626
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstr
Facile and green preparation of colorimetric and fluorescent sensors
for mercury, silver, and carbonate ions visual detecting: Spectroscopy
and theoretical studies
Mahdieh Darroudia,∗, Ghodsi Mohammadi Ziarania,∗, Jahan B. Ghasemib, Alireza Badieib
a Department of Chemistry, Faculty of Physic and Chemistry, Alzahra University, P.O. Box 1993893973, Tehran, Iran
b School of Chemistry, College of Science, University of Tehran, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Two new fluorescent and colorimetric chemosensors based on benzimidazole derivatives (A, B) have been
successfully synthesized through a facile and green catalytic reaction of ortho-phenylenediamine (O-PDA)
and two different aldehydes in the presence of SBA-Pr-SO3H. These chemosensors used to the successive
Received 29 September 2020
Revised 25 April 2021
Accepted 3 May 2021
Available online 9 May 2021
2−
2−
detection of Hg2+, Ag+, and CO3 ions. The stoichiometric ratio of sensors toward Ag+/CO3 ions for in
the case of A was 2:1 and of Hg2+ B was 1:1. Both A and B probes have shown rapid and short response
times (1 min). Furthermore, the optimized structures, binding mechanisms, and electronic transitions
were supported with a high correlation and agreement by spectroscopy, DFT and NCI calculations
Keywords:
Benzimidazole
UV-Vis
© 2021 Elsevier B.V. All rights reserved.
Fluorescence
Chemosensor
Mercury, silver, and carbonate ion
Density functional theory
1. Introduction
ably broad stokes shift with a good spectral response. Recently,
with the development of fluorescent and UV–Vis probes, benzimi-
The design and synthesis of selective fluorescent and UV–
Vis chemosensors have been an important field in chemistry and
coordination chemistry during the last two decades [1,2]. Recently,
Imidazole scaffolds have provoked significant interests, which have
been not only broadly investigated for biological applications but
also implemented as a vital unit for numerous synthetic hetero-
cycles and novel chemosensors [3–5]. For instance, the benzimi-
dazole derivatives are found to be bioactive and have been used
as anthelmintic and antifungal drugs [6,7]. Benzimidazole scaf-
fold is an outstanding building block often used in the molecular
system for optical sensing applications. The development and de-
sign of these scaffold sensing systems rely on the structure, which
is responsible for desirable photophysical properties [8–11]. They
also serve as potentially selective binding sites for several analytes
enabling applications in solvatochromic probes, photosensitizers,
tracing of water in solvents, photocatalysts, and sensors for ions.
Most of these chromophores displayed excited-state intramolec-
ular proton and charge transfer aided by the lone pair electron
of the N atom in the molecular moiety and exhibited remark-
dazole derivatives have also significantly been focused on the de-
sign of fluorescent and UV–Vis probes for anions, metal cations,
and biomolecules [12–14].
Many transition metal ions are included in diverse essential bi-
ological processes and vital elements in human health [15]. Among
the metal ions, silver is one of the precious metal elements and
plays a pivotal role as an antimicrobial agent against a large num-
ber of bacteria and anti-infective [16,17]. However, during such ac-
tivities, a large amount of silver is released into an environment
that is harmful to aquatic organisms and the human body, cause
some disease and also lead to pollution of water [15,18]. The ex-
cessive intake of silver in the human body causes long term in-
soluble precipitates accumulation in the skin and eyes [19]. Sil-
ver ion binds with an amine, imidazole, carboxyl groups present
in various metabolites and inactive the sulfhydryl enzyme, lead to
harmful effects on human health [20]. According to the US envi-
ronmental protection agency, the acceptable amount of silver ion
as a secondary maximum contaminant level in drinking water is
0.93 μmol/L [21,22]. Hence, the convenient and efficient method
for silver detection is exceedingly necessary for the protection of
both the environment and human health.
∗
Moreover, mercury ion is a biological toxicity chemical. The
detrimental effects of mercury ion on humans are principally con-
Corresponding authors.
E-mail
addresses:
M.darroudi@alzahra.ac.ir
(M.
Darroudi),
gmohammadi@alzahra.ac.ir (G. Mohammadi Ziarani).
https://doi.org/10.1016/j.molstruc.2021.130626
0022-2860/© 2021 Elsevier B.V. All rights reserved.

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
centrated in the central nervous system, digestive system, and in-
ternal organs due to its high affinity to proteins [23,24], and also
it has some influence on the blood, skin, eyes, and respiratory sys-
tem. It has turn out to be one of the most notable environmental
pollutants in the world due to its easy mobility, persistence, and
high bioaccumulation [25]. So, accurate detection of trace level of
mercury ion is crucial.
of the reaction, which was monitored by TLC, the reaction mix-
ture was cooled to room temperature, and then dissolved in hot
ethanol (10 mL). The heterogeneous solid catalyst was removed by
filtration, and then, the reaction solution was filtered off, and the
filtrate was cooled to give the pure crystals of A and B (Scheme 1).
2.3. UV–Vis studies
On the other hand, carbonate has been extensively used in dif-
ferent industries, agricultural planning, biological processes, and
geology sciences [26–28]. Additionally, prolonged exposure to car-
bonate ion as a toxic chemical in high dosage can result in ab-
dominal pain, vomiting, diarrhea, collapse, and even death [29,30].
Thus, the rapid detection of carbonate ion at low concentration is
also vital.
The study of ion recognition was performed at 25
1 ̊C, and
before recording any spectrum, sufficient time was given to en-
sure the uniformity of the solution. UV–Vis spectral studies of sen-
sor A toward Ag+ in the presence of other metal ions and to-
2−
ward CO3
in the presence of other anions were investigated,
and the results were exhibited in Figs. 1a and 1b. The solution
of chemosensor A (5 × 10−5 mol L−1, EtOH) displayed an absorp-
tion band at wavelength 265 nm. After Ag+ ion addition, an ab-
sorption peak appeared at 470 nm, which possibly is due to the
intramolecular charge transfer (ICT). While the addition of com-
petitive ions showed no substantial spectral changes, representing
that chemosensor A had a higher binding affinity toward Ag+ ion
2−
In the past decades, for Ag+, Hg2+, and CO3 ion detection, nu-
merous analytical tools were employed as atomic absorption spec-
troscopy and inductively coupled plasma atomic emission spec-
trometry, which has some restrictions as moderately high cost,
time-consuming analysis, and complicated operation. As an alter-
native to these traditional procedures, a colorimetric method has
been explored. It has attracted much attention owing to merits like
simplicity, quick response to the analyte, inexpensive devices, and
high selectivity. The emission or absorption properties of the sig-
naling unit – either quenching the fluorescence [31], or UV–Vis by
a defined mechanism (electron or energy transfer) or increasing
it through repressing a pre-existing quenching process [32–34].
The optical sensor systems are based on the usage of light as a
most valuable and versatile output signal, and several chromato-
graphic and fluorogenic sensors have been recently established.
However, despite that much of work, particular problems that de-
serve upcoming investigations are mostly related to the design of
chemosensors for target ions and the development of sensitive and
selective probes for poorly coordination metal ions and anions [35–
38].
in comparison with other cations. Also, the spectral properties of
2−
probe A to CO3
in the presence of different anions were also
2−
investigated. Upon addition of CO3 concentration, a similar spec-
tral variation to a robust absorption band at 410 nm was exhibited,
as can be seen in Fig. 1b. The addition of competitive anions to
the chemosensor A displayed no significant changes, demonstrated
2−
that the UV–Vis response was highly specific for CO3
ion.
Moreover, the UV–Vis spectral behavior of chemosensor
B
(1 × 10−4 mol L−1, in ethanol) were evaluated with the addition of
different ions. Among all studied anions, only Hg2+ ion has drasti-
cally changed the UV–Vis absorption spectrum of chemosensor B,
whereas other metal ions exhibited no significant influence on the
UV-Visible spectrum of the chemosensor B (Fig. 1c) (Fig S10-S11,
S13).
To date, several fluorescents and UV–Vis chemosensors
have been designed and reported, which some of them are
benzimidazole-based, for various cations [33,39] and anions
2.4. Fluorescence studies
[32,40]. As
a part of our ongoing research on the design of
For the investigation of the binding properties of chemosen-
sor A and B with anions and metal ions, the fluorescent spectra
of chemosensor A and chemosensor B by the addition of different
anions and different metal ions were determined, respectively, and
the results are shown in Fig. 2. The fluorescence measurements
were carried out at 365 nm ass excitation wavelength for probe A
at room temperature. The fluorescence intensity of the chemosen-
chemosensors for cations, anions, and neutral molecules [41–44],
we report the study on synthesized of some benzimidazole based
compounds through acidic mesoporous catalyst SBA-Pr-SO3H in
a solvent-free situation. In this way, the benzimidazole A and
B are synthesized and used for considering the fluorescent and
UV–Vis spectra for efficient sensing of copper, mercury, and car-
bonate ions over other ions and remarkable colorimetric responses
in the solution. Furthermore, the experimental observations for
probable binding modes were justified by computational studies
implementing DFT and NCI-Plot analysis.
2−
sor A decreased gradually by the incremental addition of CO3
ions in 5 × 10−5 mol L−1 chemosensor A (ethanol). Upon addition
2−
of CO3
ion, a fluorescence quenching (30%) was observed, de-
tected by the naked eye, which can be attributed to the electron
transfer process (PET). However, the addition of individual cations
promoted no significant fluorescence changes. The result indicates
2. Experimental
2−
that chemosensor A demonstrates a high selectivity to CO3
ion,
and this is depicted in Fig. 2a. The same results were also ob-
served in the fluorescent spectra of chemosensor B by the addition
of Hg2+ (Fig. 2b). Addition of Hg2+ ion to probe B (5 × 10−5 mol
2.1. Synthesis of SBA-Pr-SO3H
The SBA Pr-SO3H was synthesized as reported articles [45–47].
The experimental method was demonstrated in the Supporting in-
formation file (Fig S1-S3).
L
−1, in ethanol) induced a prominent fluorescence decreased with
the emission maximum at 425 nm. Also, the addition of differ-
ent metal ions exhibited no substantial variations. Therefore, the
chemosensor B could be employed as a high specific sensor for the
detection of Hg2+ ion (Fig S12-S14).
2.2. Synthesis of benzimidazole
The mesoporous catalyst SBA-Pr- SO3H (0.02 g) was placed in
a round bottom flask, and activated under vacuum condition at
100 °C for 1 hour. O-phenylenediamine (108.1 mg, 1 mmol) and
aldehydes (2 mmol) were added to the flask. The mixture of the re-
action was stirred for 20 min for compound B and 50 min for com-
pound A at 100 °C under solvent-free condition. After completion
2.5. Computational studies
The Gaussian-09 program package was implemented for all cal-
culations [48–51]. The geometries of all structures were optimized
utilizing DFT with WB97XD [52] functionals using the Lanl2dz ba-
sis set, which were found to be suitable for the whole molecules
2

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
Fig. 1. Absorption spectra changes (a) response of chemosensor
A
(5
×
10−5 mol L−1
,
in ethanol,) toward Ag+ in ethanol solution (b) response of chemosensor
A
(5 × 10−5 mol L−1, in ethanol) toward CO3
in the ethanol solution, and (c) response of chemosensor B toward Hg2+ (1 × 10−4 mol L−1, in ethanol) upon addition of
2−
different metal ion.
Fig. 2. Fluorescence spectra response of (a) chemosensor A (5 × 10−5 mol L−1, in ethanol) upon addition of different anions (100 μL, 0.01 mol L−1) with λex at 365 nm and
(b) chemosensor B (1 × 10−4 mol L−1, in ethanol) upon addition of different metal ion (100 μL, 0.01 mol L−1) with λex at 425 nm.
[53–56]. Solvent effects were considered using CPCM calculations
[57]. The reported energies are based on Gibbs free energies (G).
Moreover, zero-point vibrational corrections (E), entropy (S), and
thermal (H) corrections and solvation energies at 298 K are con-
sidered in ꢀG. Also, the noncovalent interaction (NCI) topological
analysis was performed on the prepared complex with the Multi-
Wfn program.
3. Results and discussion
3.1. Synthesis of benzimidazole
The classical method for synthesis of benzimidazole scaffolds
A and B involves the reaction of O-PDA with 3-formyl indole
and para-nitrobenzaldehyde using SBA-Pr-SO3H as nanocatalyst in
the solvent-free condition in good yield and short reaction time
(Scheme 1) (Fig S4-S9).
3

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
3.2. UV–Vis absorption studies
the absorption profile, the colorimetric DL of receptor A for Ag+
ion was found to be 1.82 μM (Fig. 4b). This result showed that
chemosensor A is potentially useful for Ag+ detection. The sto-
ichiometry during the binding of Ag+ with sensor A was found
1:2. Potential interferences by other cations were assessed through
competition experiments, which were done by taking the absorp-
tion spectra of A in the presence of Ag+ ion mixed with the
analogous equivalent of other interfering cations to estimate the
chemosensor specificity. The results demonstrated that the inten-
sity peak around 480 nm because of A-Ag+ complexation was not
influenced by the other metal ions addition.
The selective colorimetric sensing capabilities of fabricated
chemosensor A and B were examined by UV–Vis absorption spec-
trometry in ethanol solution with various anions (Br−, CH3COO−−,
Cl−, CN−, CO32−, Cr2O72−, F−, HPO42−, HSO3−, I−, NO2−, NO3
SCN−, and SO42−) and cations (Ba2+, Ca2+, Cd2+, Cs+, Co2+Cr3+
,
,
Fe3+, Fe2+, Hg2+, K+, Li+, Mg2+, Mn2+, Na+, Ni2+, Sr2+, and Zn2+
)
as shown in Fig. 4. Spectral studies of chemosensor A toward
Ag+ in the presence of other cations were investigated by means
of UV–Vis spectroscopy (Fig. 3). The solution of free sensor A
(1 × 10−4 mol L−1, in ethanol) exhibited a strong absorption band
at 275 nm. After the addition of Ag+, a new weak peak was ex-
hibited at 475 nm, which may be owing to ICT and the coor-
dination of Ag+with probe A. While, the addition of competitive
cations showed no tangible spectral changes, indicating high bind-
ing affinity of chemosensor A toward Ag+ in comparison with
The absorption spectra of probe A and B presented a distinct
band at 260 nm corresponds to π-π∗ transition absorbance re-
lated to the C=N bond, in which the maximum emission intensity
centered at 445 nm (Fig. 1). On the other hand, the 490 nm band
corresponds to the n-π∗ transition and also intermolecular charge
transfer (ICT) of the whole conjugated molecule [65–66].
2−
other cations. Also, the spectral properties of this probe to CO3
Also, the naked-eye sensing properties of the probe B toward
various metal ions were investigated by monitoring the color in
ethanol at ambient temperature. The UV–Vis absorption spectrum
of free probe B exhibited maximum absorbances at 270 nm and
480 nm (Fig. 3c). Upon the addition of Hg2+ ion, the solution
of chemosensor B exhibited a color change from deep yellow to
light yellow and the changes from a narrow weak absorption
band at 480 nm to a broad peak centered at 610 nm. Among all
tested cations, only the addition of Hg2+ induced distinct spectral
changes. This alteration could be ascribed in terms of the coordi-
nation of B with Hg2+ and the ICT effect.
in the presence of various anions were investigated, and the re-
sults are demonstrated in Fig. 4a. A new weak peak was observed
2−
at 410 nm after the addition of CO3
and its coordination.
ion, which results from ICT
The anion binding ability of chemosensor A was studied by UV–
Vis spectroscopy in ethanol with a wide range of anions. The addi-
2−
tion of CO3
to the solution of A caused no interference, which
displays no tangible change in the visible spectra, as shown in
Fig. 3a. The plot inset in Fig. 3a indicates that under motioning
conditions, the possible interference by other anions is not a prac-
tical problem in carbonate sensing by chemosensor A. The recog-
Moreover, the addition of other competitive metal ions dis-
played no significant changes, which demonstrated that the UV–
Vis response of chemosensor B was extremely specific for Hg2+ ion
and can be attended as a naked-eye Hg2+ indicator (Fig. 3c). The
DL obtained from the titration curves was found to be 9.73 μM
for Hg2+ ion, which is decidedly smaller than the WHO guideline
for drinking water. This chemosensor B can be applied as a visual
colorimetric probe towards Hg2+ ion (Fig. 4c).
2−
nition ability of this chemosensor toward CO3
was carried out
2−
upon titration of the probe solution with the addition of CO3
and subsequent measurement of absorption spectra (Fig. 4a). The
UV–Vis absorption spectra of chemosensor A dominated by an ab-
sorption band at 270 nm before the addition of any ions. Upon
2−
the addition of the CO3
to chemosensor A, a new absorption
band emerged at 410 nm with progressively increasing due to
the complexation between guest-host specious. During the titra-
2−
tion study, after the addition of 2.0 equivalent CO3
to a solu-
3.3. Fluorescence study
tion of chemosensor A, an equilibrium between A and its deproto-
nated form was established. After the addition of CO32−, the color
changed from colorless to yellow, which correlated to the deproto-
nation of compound A in the presence of CO32−. The deprotonation
phenomena affected the electronic properties of the chromophore,
concluding a color change with a subsequent new ICT between ac-
ceptor and donor. This state showed that the chemosensor A could
be considered as a “naked-eye” sensor. Also, the ratiometric re-
sponse of probe A on carbonate addition indicated a 1:2 stoichio-
metric adduct. The detection limit (DL) calculated from the titra-
tion profile was found to be 2.13 μM, which is one of the lowest
amounts reported before.
To investigate the binding properties of chemosensor A to an-
ions, the fluorescence emission behavior of probe A in the pres-
ence of different anions was determined, as demonstrated in Fig. 2.
The emission behavior of A was evaluated by fluorescence mea-
surements in ethanol at 365 nm as the excitation wavelength. In
the fluorescence spectra, the free receptor A displayed an emis-
sion of about 445 nm. The fluorescence variations upon a wide
2−
range of anions addition including Br−, CH3COO−, Cl−, CN−, CO3
,
Cr2O72−, F−, HPO42−, HSO3−, I−, NO2−, NO3−, SCN−, and SO42−, in
2−
EtOH (Fig. 2). As is seen, only CO3
has diminished the emission
intensity under identical conditions, which may be attributed to
To determine the sensitivity of chemosensor A toward Ag+
ion, the UV/-Vis absorption titrations were individualistically im-
plemented by the successive addition of Ag+ to the receptor A
solution. The solution of chemosensor A showed a new peak at
480 nm, accompanied by the continuous redshift by the gradual
addition of Ag+ to the solution (Fig. 3b). The A-Ag+ absorption
spectra can be devoted to complex formation, metal-probe charge
transfer, and lessening of the energy gap [58]. On the other hand,
the consecutive addition of Ag+ to the sensor led to a new absorp-
tion band that emerged in the visible region around 480 nm, and
its intensity progressively enhanced with the sequential addition of
Ag+ (Fig. 4b).
higher ICT and intrinsic quenching nature [59]. Upon addition of
2−
CO3
concentration to the solution of A, the emission peak de-
creased gradually.
In order to have a better understanding of the mechanism, flu-
orescence titration experiments were implemented in ethanol. The
weak emission at 442 nm of sensor A is due to the photoinduced
electron transfer process from the C=N to the photoexcited imida-
zole units, which leads to reduced emission.
2−
Interestingly, the addition of CO3 to the chemosensor solution
led to a decrease and slightly change in emission intensity because
of electron transfer from carbonate to chemosensor A. In contrast,
the addition of other anions displayed no significant fluorescence
For Hg2+ ion, in comparison to Ag+, pointed out the formation
of diverse, complex species from the B-Hg2+ with different elec-
tronic properties (Fig. 3a). The DL of chemosensor A for Ag+ is
also a pivotal parameter for applied purposes. Therefore, based on
intensity. These results demonstrated a high selectivity of probe A
2−
to CO3
ion.
2−
To further explore the sensitivity of chemosensor A to CO3
,
the fluorescence titration experiment was performed (Fig. 5a). The
4

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
2−
Fig. 3. The effect of interfering ion on the of chemosensor (a) A (2.5 mL, 5 × 10−5 mol L−1, in ethanol), CO3 ion (100 μL, 0.01 M) at 480 nm addition of different anions,
and inset: Absorbance spectra of chemosensor A (5 × 10−5 mol L−1, in ethanol) after addition of various anions (100 μL, 0.01 mol L−1).,(b) A (2.5 mL, 5 × 10−5 mol L−1, in
ethanol), Ag+ ion (100 μL, 0.01 mol L−1) at 410 nm upon other metal ions, and inset: Absorbance spectra of chemosensor A (5 × 10−5 mol L−1, in ethanol) after addition of
various cations (100 μL, 0.01 mol L−1), (c)B (2.5 m L, 1 × 10−4 mol L−1, in ethanol), Hg2+ ion (100 μL, 0.01 mol L−1) at 620 nm upon other metal ions, and inset: Absorbance
spectra of chemosensor B (1 × 10−4 mol L−1, in ethanol) after addition of various metal ions (100 μL, 0.01 mol L−1).
5

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
2−
Fig. 4. UV–Vis changes of Chemosensor (a) A (5 × 10−5 mol L−1, in ethanol) upon addition of the different amount of CO3
ion (0–1 equiv.) in ethanol solution, (b) A
(5 × 10−5 mol L−1, in ethanol) upon addition of the different amounts of Ag+ ion (0–1 equiv.) in ethanol solution, (c) B (1 × 10−4 mol L−1, in ethanol) upon addition of
different amount of Hg2+ ion (0–1 equiv.) in ethanol solution.
6

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
2−
Fig. 5. Fluorescence spectra response of (a) chemosensor A (5 × 10−5 mol L−1, in ethanol), CO3
ion (100 μL, 0.01 M) upon addition of different anions in EtOH λ at
442 nm, and inset: Fluorescence spectra of chemosensor A after addition of various anions and (c) chemosensor B (1 × 10−4 mol L−1, in EtOH), Hg2+ ion (100 μL, 0.01 M)
upon addition of different ions in EtOH with λ at 545 nm addition of different cations, and inset: Fluorescence spectra of chemosensor B after addition of various cations.
fluorescence intensity of probe A was gradually decreased with
nate with B and caused strong fluorescence quenching, which re-
vealed that chemosensor B recognizes Hg2+ without interference
from other cations. To check the sensitivity of probe B toward Hg2+
ion, titration experiments were performed. The variations in flu-
orescence spectra of probe B upon the addition of the different
amounts of Hg2+ are shown in Fig. 6b. The fluorescence inten-
sity of probe B gradually decreased by the stepwise addition of
Hg2+ concentration from 0 to 40 equivalent and leveled off beyond
this limit of concentration. An excellent linear relationship was ob-
served between fluorescence intensity and concentration of Hg2+
2−
the increase of CO3
ion concentration. This fluorescent behav-
ior could be ascribed to the interaction of chemosensor A with
2−
CO3
and deprotonation of chemosensor A, and consequently in-
creased the PET process. Additionally, there was a linear relation-
2−
ship between fluorescence intensity and concentration of CO3
(R2=0.9953), which can propose the 1:1 binding stoichiometry of
2−
chemosensor A with CO32−. Furthermore, the DL of CO3
ion by
chemosensor A was calculated to be as low as 22 μM. All these
results indicated that sensor A has a high sensitivity (Fig. 6a).
Moreover, to obtain a clear insight into the fluorescent spec-
tra of probe B, qualitative experiments were performed by mixing
chemosensor B and various metal ions (Fig. 2b). To consider the
interaction mechanism, the fluorescence titration experiment was
carried out in ethanol, showing a fluorescence emission at 545 nm,
which is due to the photoinduced electron transfer process from
the C=N, and the nitro group with poor emission, when it was
excited at 425 nm. Upon addition of 10.0 equivalent Hg2+ ion, a
remarkable naked eye fluorescence quenching was observed (80%)
(Fig. 5b).
(R2= 0.9993), indicating a 1:1 complexation of probe B and Hg2+
.
The DL for Hg2+ was determined as 1.83 μM. The results proved
that both chemosensors A and B exhibited excellent specificity to-
ward Ag+ and Hg2+ ions.
3.4. Computational study
The molecular orbital (MO) level of energy and distribution of
the chemosensor A and B was carried out by DFT calculation at the
WB97XD/ Lanl2dz level of theory. The electron clouds of HOMO-
2, HOMO-1, HOMO, and LUMO+2 level of energy for chemosensor
A, mainly distributed on both benzimidazole and imidazole scaf-
folds (Fig. 7a-i). While the electron density of HOMO was delocal-
The chemosensor B behavior in the presence of potentially
competitive ions was investigated by UV–Vis spectroscopy, too.
Even in the presence of various cations, Hg2+ could still coordi-
7

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
2−
Fig. 6. The fluorescence spectra of (a) chemosensor A (5 × 10−5 mol L−1, in ethanol) with increasing concentration of CO3 ion (0- 32 equiv.) at 442 nm, and inset: plot of
2−
fluorescence spectra of chemosensor A at 485 nm vs. the CO3 ion addition, and (b) chemosensor B (1 × 10−4 mol L−1, in ethanol), with increasing concentration of Hg2+
ion (0- 40 equiv.) at 545 nm, and inset: plot of fluorescence spectra of chemosensor B at 545 nm vs. the Hg2+ ion addition.
and Hg2+ ions have been shown in Figs. 78b, 7c, and 7g. No-
ized over the C=N bond (Fig. 8a), the electron density of HOMO-
1 was almost concentrated on the whole molecule, and also the
electron density of HOMO-2 was populated on the five-membered
rings. Therefore, chemosensor A had transitions between all MO
levels, and these levels are much accessible for electron transfer,
which is disposed to have a robust fluorescence. Furthermore, for
chemosensor A, the electron distribution and the orbital energies
of HOMO-2, to LUMO+2 levels (−4.60, −4.71, −4.86, −8.16, −8.42,
and −8.76 eV, respectively) were sequentially increased, which in-
dicates that chemosensor A could be coordinated with ion eas-
ily (Fig. S17). Compared with chemosensor A, the density of elec-
trons of LUMO+2, LUMO+1, HOMO-2 for chemosensor B were
mainly populated on the nitro group. While the electron density
of LUMO+1 was collectively gathered on a five-membered ring
and the benzene ring, the electron densities of HOMO, HOMO-1
were mainly concentrated on C=N structure (Fig. 7f). The elec-
tron density distribution of chemosensor B and the orbital dis-
tribution based on orbital energies raised sequentially, as −4.61,
−5.05, −5.33, −8.69, −8.77, and – 9.08, respectively, indicating that
chemosensor B could be easily coordinated to a cation (Fig. S15-
S17).
tably, the calculated energy gaps between LUMO and HOMO vary
2.42 < 3.31 eV for A, A-Ag+ complex. Also, the estimated HOMO-
LUMO gap for probe B and B-Hg2+ complex decreased from 3.36 to
2.71 eV. Such lowering HOMO-LUMO gaps of probe A and B upon
Ag+ and Hg2+ complexation ascribed to the electron’s distribution
after bindings and electron’s redistributions led to the alteration
in fluorescence and absorbance spectra with subsequent shifts. In
the case of the B-Hg2+ complex, the LUMO electron density was
2+
–
populated on the locality of N Hg
complex while the HOMO
was distributed on imidazole moiety. For the A-Ag+ complex, its
electron density of HOMO is more strongly concentrated on the
whole complex, and the LUMO of the complex was mainly popu-
lated on the N-Ag+ region. On the other hand, upon the addition
of carbonate ion to probe A, deprotonation occurred. Also, it was
revealed that both HOMO and LUMO energy levels increased, sug-
gesting lower stability of complex A-CO32−. Also, the HOMO-LUMO
energy gap was enhanced in the presence of the carbonate ion.
2−
The LUMO electron density population of A-CO3
was localized
over the whole of the chemosensor structure (A), but HOMO was
centered at one benzimidazole an imidazole moiety. Moreover, the
2−
Computational investigations of the chemosensor A in the ab-
calculated MO energy gaps for A and A-CO3 complex was consid-
2−
sence and presence of Ag+ and CO3
and chemosensor B in the
erably increased upon coordination (3.31, and 7.0 eV, respectively).
It was calculated that A-Ag+ and B-Hg2+ ion bindings could be
lowered HOMO orbitals level of energies, which led to the turn-on
sensing mechanism by the electron charge transfer process. More-
absence and presence of Hg2+ were performed to understand and
unscramble the possible binding mechanism. The selected LUMO
2−
and HOMO orbitals of probe A and B complexes with Ag+, CO3
,
8

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
2−
Fig. 7. FMO and HOMO-LUMO energy gap of (a)chemosensor A; (b) Complex A-CO3
(c) Complex A-Ag+ (d) Optimized geometry chemosensor A (e) ESP contour of
chemosensor A (f) FMO and HOMO-LUMO energy gap chemosensor B and (g) Complex B-Hg2+(h) Optimized geometry chemosensor B, and (i) ESP contour of chemosensor
B.
over, the NCI gradient isosurface of chemosensors A and B toward
anion and cations are presented in Fig. 8a-e. Here, the blue surface
zole scaffold. The NCI gradient of chemosensor A exhibited a den-
sity electron on the whole of the molecule. Also, the NCI gradient
isosurface of chemosensors B to Hg2+ and fluorophore B demon-
strated that it is extended, especially between the nitrogen atom
of the benzimidazole ring to Hg2+ion. The blue color is associated
2−
also appears between CO3
of A, which the surface extended im-
idazole ring and one benzimidazole scaffold, while for Ag+ exhib-
ited strong interaction between benzimidazole groups and imida-
9

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
2−
Fig. 8. NCI gradient isosurface (isovalue= 0.5 a.u.) of (a)chemosensor A; (b) Complex A-CO3 (c) Complex A-Ag+ (d) chemosensor B, and (e) Complex B-Hg2.
Also, the optimized structure and contours of spin density are
shown in Fig. 7d, e, h, and i. The structure configuration of bis
benzimidazole substituted was overall different due to their intrin-
sic feature of nitro electron-withdrawing substituent and indole as
an electron releasing substituent. As shown in Fig. 7e and i, the
binding site for two structures were completely distinguished. The
structure A can bind the ions between two indole moieties; oth-
erwise, chemosensor B can make complex toward ion in the re-
gion between one benzimidazole moiety and a phenyl group. Also,
chemosensor B has more possibility for accepting electron due to
the much lower energy of FMOs in comparison with chemosensor
A, which has much more affinity to accept an electron. The calcu-
lated emission and absorption peaks of the chemosensor A and B
were investigated, which are in good agreement with experimental
Scheme 1. Synthesis of chemosensor A and B in the presence of SBA-Pr-SO3H.
results.
In order to demonstrate a comparison between the stability of
A-Ag+, and B-Hg2+ complexes, the corresponding binding energies
with strong interactions, and the weak favorable or non-favorable
are described in Table 1. It was exhibited that a stronger interac-
van der Waals interactions could be recognized by NCI green color.
10

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
Table 1
Alireza Badiei: Validation, Writing-review and editing.
ORCID:0000-0002-6985-7497
The changes in binding energy ꢀE, enthalpy
and Gibbs free energy in kcal/mol.
Entry
ꢀE
ꢀH
ꢀG
Declaration of Competing Interest
The authors declare no conflict of interest.
Funding
A-Ag+
B-Hg2+
−75.99
−76.58
−78.23
−79.36
−76.97
−75.60
tion between the chemosensors A and B toward metal ions Ag+
and Hg2+ were calculated, and also binding energy slightly de-
creased for the A-Ag+ complex. So, it could be inferred that com-
plexation of probes A and B should be classified as the most favor-
able interaction in 2:1 for A and 1:1 for B stoichiometry.
The authors declare no funding from government agency.
Acknowledgement
We gratefully acknowledge the financial support from the Re-
search Council of Alzahra University and the University of Tehran.
The numerical calculations reported in this paper were fully per-
formed at SANCAR, Turkish-German University System and Nodes
of Computational Applications and Research.
3.5. Mulliken charge analysis
Mulliken charge analysis was done through the calculation of
the electron population for an individual atom. For chemosensor
A, the negative charge strongly found at N7, N9, N14, and N22,
and moderately on C17, C18, C26, and C27, and also the positive
charge strongly found at C4 and C8. These results exhibited that
the nitrogen atoms have the best position for coordinating metal
ions. Furthermore, the H35 and H42 are much more positive be-
cause of the presence of electronegative atom N, which is reason-
able for the deprotonation in the presence of carbonate ion. Also,
for chemosensor B, the negative charge strongly found at N7, N9,
O26, and O27. Thus, the best position for coordination between the
metal ion and probe B are nitrogen atoms. MEP is allied to electron
density and is a very suitable descriptor in acceptor sites for the
nucleophilic and electrophilic attack as hydrogen bonding interac-
tions. It is obvious that the negative electron density localized on
the nitrogen atom of benzimidazole structures resulted in coordi-
nation with metal ions.
Supplementary materials
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.molstruc.2021.130626.
Reference
[1] A. Mobed, B. Baradaran, M. de la Guardia, M. Agazadeh, M. Hasanzadeh,
M.A. Rezaee, J. Mosafer, A. Mokhtarzadeh, M.R. Hamblin, Advances in detection
of fastidious bacteria: from microscopic observation to molecular biosensors,
TrAC - Trends Anal. Chem. 113 (2019) 157–171, doi:10.1016/j.trac.2019.02.012.
[2] M. Mahmudi, N. Shadjou, M. Hasanzadeh, Synthesis and adsorption behav-
ior of dendritic Fibrous Nano-silica (DFNS) grafted by d-penicillamine as an
advanced nanomaterial for the removal of some metal ions from contami-
nated water, J. Electroanal. Chem. 848 (2019) 113272, doi:10.1016/j.jelechem.
2019.113272.
[3] Y. Qiu, Q. Zhang, B. Gao, M. Li, Z. Fan, W. Sang, H. Hao, X. Wei, Removal mech-
anisms of Cr(VI) and Cr(III) by biochar supported nanosized zero-valent iron:
synergy of adsorption, reduction and transformation, Environ. Pollut. (2020)
115018, doi:10.1016/j.envpol.2020.115018.
4. Conclusion
In summary, two benzimidazole-based turn-offs, fluorescent
and colorimetric chemosensors A and B, were successfully synthe-
sized through a facile and green solvent-free reaction between o-
PDA and benzaldehyde substituted in a good yield for the visual
detection of metal ions and anions. The dual-mode chemosensor
[4] K. Krishnaveni, M. Iniya, A. Siva, N. Vidhyalakshmi, S. Sasikumar, U.K. Pandian
Ramesh, S. Murugesan, Naphthyl hydrazone anchored with nitrosalicyl moiety
as fluorogenic and chromogenic receptor for heavy metals (Ag+, Hg2+) and
biologically important F− ion and its live cell imaging applications in HeLa
cells and Zebrafish embryos, J. Mol. Struct. 1217 (2020) 128446, doi:10.1016/j.
molstruc.2020.128446.
[5] A.A. Bhatti, M. Oguz, M. Yilmaz, New water soluble p-sulphonatocalix[4]arene
chemosensor appended with rhodamine for selective detection of Hg2+ ion, J.
Mol. Struct. 1203 (2020) 127436, doi:10.1016/j.molstruc.2019.127436.
[6] N.A. Zhukova, V.A. Mamedov, Advances in the synthesis of benzimidazol-2-
ones, Russ. Chem. Rev. 86 (2017) 968–997, doi:10.1070/rcr4749.
2−
A and B exhibited an outstanding sensing ability towards CO3
and Hg2+ ions besides fluorescence decrease, attributing to the ICT
process. Moreover, the chemosensor A and B could act as a col-
2−
orimetric sensor able to naked-eye detection of Ag+, CO3
and
[7] S. Mostarda, T.G. Maz, A. Piccinno, B. Cerra, E. Banoglu, Optimisation by de-
sign of experiment of benzimidazol-2-one synthesis under flow conditions,
Molecules 24 (2019) 2447, doi:10.3390/molecules24132447.
Hg2+ ions, respectively. The colorimetric DLs were calculated for
chemosensor A to be as low as 1.82 for Ag+, 2.13 for CO32−, and
9.73 for Hg2+ ion toward chemosensor B., the fluorometric DLs for
[8] A. Mobed, P. Mehri, M. Hasanzadeh, A. Mokhtarzadeh, Binding of Leishmania
spp with gold nanoparticles supported polyethylene glycol and its application
for the sensitive detection of infectious photogenes in human plasma samples:
a novel biosensor, J. Mol. Recognit. (2020) 33, doi:10.1002/jmr.2839.
[9] A. Mobed, M. Hasanzadeh, S. Hassanpour, A. Saadati, M. Agazadeh,
A. Mokhtarzadeh, An innovative nucleic acid based biosensor toward detec-
tion of Legionella pneumophila using DNA immobilization and hybridization:
a novel genosensor, Microchem. J. 148 (2019) 708–716, doi:10.1016/j.microc.
2019.05.027.
2−
chemosensor A and B, were calculated to be 22 μM for CO3
and
1.65 μM for Hg2+, respectively. These chemosensors have excellent
selectivity and sensitivity to sense by changes in Fluorescence and
UV–Vis spectra over a variety of ions. Moreover, DFT and NCI gradi-
ent studies were implemented for the binding mechanism, the as-
sessment of stoichiometry, and spectral transition behavior of the
chemosensor A and B toward different ions. The calculations were
in good agreement with the experimental results.
[10] S. Hassanpour, A. Saadati, M. Hasanzadeh, pDNA conjugated with citrate
capped silver nanoparticles towards ultrasensitive bio-assay of haemophilus
influenza in human biofluids: a novel optical biosensor, J. Pharm. Biomed. Anal.
180 (2020) 113050, doi:10.1016/j.jpba.2019.113050.
[11] J. Soleymani, M. Hasanzadeh, N. shadjou, M.H. Somi, A. Jouyban, The role of
nanomaterials on the cancer cells sensing based on folate receptor: analyti-
cal approach, TrAC - Trends Anal. Chem. 125 (2020) 115834, doi:10.1016/j.trac.
2020.115834.
[12] S. Shahab, H.A.H.A. Almodarresiyeh, L. Filippovich, F.H.F.H. Hajikolaee, R. Ku-
mar, M. Darroudi, M. Mashayekhi, Geometry optimization and excited state
properties of the new symmetric (E)-Stilbene derivative for application in ther-
mostable polarizing PVA-films: a combined experimental and DFT approach, J.
Mol. Struct. 1119 (2016) 423–430, doi:10.1016/j.molstruc.2016.04.092.
[13] S. Shahab, F.H.F.H. Hajikolaee, L. Filippovich, M. Darroudi, V.A.V.A. Loiko, R. Ku-
mar, M.Y.M.Y. Borzehandani, Molecular structure and UV–Vis spectral analysis
of new synthesized azo dyes for application in polarizing films, Dye. Pigment.
129 (2016) 9–17, doi:10.1016/j.dyepig.2016.02.003.
Authors’. contribution
Mahdieh Darroudi: Conceptualization, Software, Visualization,
Formal analysis, Data curation, Analysis data, Writing Original
draft. ORCID:0000-0002-9152-2642
Ghodsi Mohammadi Ziarani:, Methodology, Supervision,
Writing-review and editing, Validation. ORCID:0000-0001-5177-
7889
Jahan B. Ghasemi: Methodology, Validation, Writing-review and
editing. ORCID:0000-0002-0380-8000
11

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
[14] S. Shahab, R. Kumar, M. Darroudi, M.Yousefzadeh Borzehandani, Molecu-
lar structure and spectroscopic investigation of sodium(E)-2-hydroxy-5-((4-
rescence switch for Hg 2+ and UV/vis lights based on diarylethene-rhodamine
derivative, Tetrahedron 75 (2019) 1517–1524, doi:10.1016/j.tet.2019.01.071.
[37] Z. Guo, Q. Niu, T. Li, E. Wang, Highly chemoselective colorimetric/fluorometric
dual-channel sensor with fast response and good reversibility for the se-
lective and sensitive detection of Cu2+, Tetrahedron 75 (2019) 3982–3992,
doi:10.1016/j.tet.2019.06.019.
sulfonatophenyl)diazenyl)benzoate:
a DFT study, J. Mol. Struct. 1083 (2015)
198–203, doi:10.1016/j.molstruc.2014.11.064.
[15] H.E. Okda, S. El Sayed, I. Otri, R.C.M. Ferreira, S.P.G. Costa, M.M.M. Raposo,
R. Martínez-Máñez, F. Sancenón,
A simple and easy-to-prepare imidazole-
based probe for the selective chromo-fluorogenic recognition of biothiols and
Cu(II) in aqueous environments, Dye. Pigment. 162 (2019) 303–308, doi:10.
1016/j.dyepig.2018.10.017.
[38] P. Smyth, T.J. Gibson, G. Irvine, G. Black, D. Lavery, M. Semsarilar, C.J. Scott,
E. Themistou, pH-Responsive benzaldehyde-functionalized PEG-based poly-
meric nanoparticles for drug delivery: effect of preparation method on mor-
phology, dye encapsulation and attachment, Eur. Polym. J. (2020) 124, doi:10.
1016/j.eurpolymj.2019.109471.
[16] A.P. Richter, J.S. Brown, B. Bharti, A. Wang, S. Gangwal, K. Houck, E.A. Cohen
Hubal, V.N. Paunov, S.D. Stoyanov, O.D. Velev, An environmentally benign an-
timicrobial nanoparticle based on a silver-infused lignin core, Nat. Nanotech-
nol. 10 (2015) 817–823, doi:10.1038/nnano.2015.141.
[39] C. Cao, J. Huang, Y. Guo, C.N. Yan, J. Xiao, Y.X. Ma, J.L. Liu, W.Z. Guan, Long-
term effects of environmentally relevant concentration of Ag nanoparticles on
the pollutant removal and spatial distribution of silver in constructed wetlands
with Cyperus alternifolius and Arundo donax, Environ. Pollut. 252 (2019) 931–
940, doi:10.1016/j.envpol.2019.05.144.
[17] N.M. Hahn, T.J. Bivalacqua, A.E. Ross, G.J. Netto, A. Baras, J.C. Park, C. Chap-
man, T.A. Masterson, M.O. Koch, R. Bihrle, R.E. Greenberg, D.M. Geynisman,
A phase II trial of dovitinib in BCG-unresponsive urothelial carcinoma with
FGFR3 mutations or overexpression: Hoosier Cancer Research Network trial
HCRN 12-157, Clin. Cancer Res. 23 (2017) 3003–3011, doi:10.1158/1078-0432.
CCR-16- 2267.
[18] Y.F. Xie, Y.Y. Cheng, M.L. Liu, H.Y. Zou, C.Z. Huang, A single gold nanoprobe for
colorimetric detection of silver(i) ions with dark-field microscopy, Analyst 144
(2019) 2011–2016, doi:10.1039/c8an02397b.
[40] Y.G. Ko, W.S. Na, N.Singh Mayank, D.O. Jang, Triazole-coupled benzimidazole-
based fluorescent sensor for silver, bromide, and chloride ions in aqueous me-
dia, J. Fluoresc. 29 (2019) 945–952, doi:10.1007/s10895-019-02407-y.
[41] S¸ .N. Karuk Elmas, F. Ozen, K. Koran, A.O. Gorgulu, G. Sadi, I. Yilmaz, S. Erdemir,
Selective and sensitive fluorescent and colorimetric chemosensor for detection
of CO32- anions in aqueous solution and living cells, Talanta 188 (2018) 614–
622, doi:10.1016/j.talanta.2018.06.036.
[19] A. Townshend, Metals and their compounds in the environment. Occurrence,
analysis and biological relevance, Anal. Chim. Acta 271 (1993) 331–332, doi:10.
1016/0003-2670(93)80064-r.
[42] G. Shiravand, A. Badiei, H. Goldooz, M. Karimi, G.M. Ziarani, F. Faridbod,
M.R. Ganjali,
A fluorescent g-C3N4 nanosensor for detection of dichromate
[20] H. Peng, B.W. Brooks, R. Chan, O. Chyan, T.W. La Point, Response of Ceriodaph-
nia dubia to ionic silver: discrepancies among model predictions, measured
concentrations and mortality, Chemosphere 46 (2002) 1141–1146, doi:10.1016/
S0045-6535(01)00137-0.
ions, Curr. Anal. Chem. (2018) 14, doi:10.2174/1573411014666180627150248.
[43] R. Arab, L. Hajiaghababaei, A. Badiei, M. Karimi, M.R. Ganjali,
G.Mohammadi Ziarani, 8-Hydroxyquinoline grafted nanoporous SBA-15 as a
novel solid phase extractor for preconcentration of trace amount of copper, Int.
J. Nano Dimens. 10 (2019) 340–349 http://www.ijnd.ir/article_664536.html.
accessed February 10, 2020.
[44] T. Ahmadi, S. Bahar, G. Mohammadi Ziarani, A. Badiei, Formation of function-
alized silica-based nanoparticles and their application for extraction and de-
termination of Hg (II) ion in fish samples, Food Chem. 300 (2019) 125180,
doi:10.1016/j.foodchem.2019.125180.
[45] G. Mohammadi Ziarani, N. Lashgari, A. Badiei, Sulfonic acid-functionalized
mesoporous silica (SBA-Pr-SO3H) as solid acid catalyst in organic reactions, J.
Mol. Catal. A Chem. 397 (2015) 166–191, doi:10.1016/j.molcata.2014.10.009.
[46] D. Zhao, Q. Huo, J. Feng, B.F. Chmelka, G.D. Stucky, Nonionic triblock and star
diblock copolymer and oligomeric sufactant syntheses of highly ordered, hy-
drothermally stable, mesoporous silica structures, J. Am. Chem. Soc. 120 (1998)
6024–6036, doi:10.1021/ja974025i.
[47] G. Mohammadi Ziarani, A.R. Badiei, Y. Khaniania, M. Haddadpour, One pot syn-
thesis of polyhydroquinolines catalyzed by sulfonic acid functionalized SBA-15
as a new nanoporous acid catalyst under solvent free conditions, Iran. J. Chem.
Chem. Eng. 29 (2010) 1–10 https://www.sid.ir/en/Journal/ViewPaper.aspx?ID=
180572. accessed June 24, 2020.
[21] EPA,
National
primary
drinking
water
regulations;
radionu-
clides; final rule, Fed. Regist. 65 (2000) 76708–76753 https:
//www.federalregister.gov/documents/2000/12/07/00-30421/
national-primary-drinking-water-regulations-radionuclides-final-rule.
cessed April 8, 2020.
ac-
[22] R.A. Howd, J.P. Brown, D.W. Morry, Y.Y. Wang, J. Bankowska, J.D. Budroe,
M. Campbell, M.J. Dibartolomeis, J. Faust, L. Jowa, D. Lewis, T. Parker, J. Po-
lakoff, D.W. Rice, A.G. Salmon, R.S. Tomar, A.M. Fan, Development of California
Public Health Goals (PHGs) for chemicals in drinking water, J. Appl. Toxicol.
20 (2000) 365–380, doi:10.1002/1099-1263(200009/10)20:5ꢀ365::AID-JAT700ꢁ
3.0.CO;2-7.
[23] E.K. Silbergeld, I.A. Silva, J.F. Nyland, Mercury and autoimmunity: implications
for occupational and environmental health, in: Toxicol. Appl. Pharmacol., Aca-
demic Press Inc., 2005, pp. 282–292, doi:10.1016/j.taap.2004.11.035.
[24] R.K. Zalups, S. Ahmad, Homocysteine and the renal epithelial transport and
toxicity of inorganic mercury: role of basolateral transporter organic anion
transporter 1, J. Am. Soc. Nephrol. 15 (2004) 2023–2031, doi:10.1097/01.ASN.
0000135115.63412.A9.
[25] I. Onyido, A.R. Norris, E. Buncel, Biomolecule - Mercury interactions: modal-
[48] M. Robert, 40 Sleep hacks, Fhjgfd 11 (1990) 79–170 https://doi.org/222.
[49] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A... Robb, J.R. Cheese-
man, G... Scalmani, V. Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji, M.
Caricato, X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnen-
berg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Naka-
jima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. Montgomery, J. A., J.E... Peralta,
F. Ogliaro, M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R.
Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J.
Tomasi, M. Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken,
C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R.
Cammi, C. Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski,
G.A. Voth, P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, Ö. Farkas, J.B.
Foresman, J.V. Ortiz, J. Cioslowski, D.J. Fox, Gaussian 09, Revision A., (2009).
http://www.gaussian.com/g_tech/g_ur/m_citation.htm (accessed December 21,
2016).
ities of DNA base
Chem. Rev. 104 (2004) 5911–5929, doi:10.1021/cr030443w.
[26] A. Ghorai, J. Mondal, R. Chandra, G.K. Patra, reversible fluorescent-
- mercury binding mechanisms. Remediation strategies,
A
colorimetric chemosensor based on a novel Schiff base for visual detection
of CO32- in aqueous solution, RSC Adv. 6 (2016) 72185–72192, doi:10.1039/
c5ra24549d.
[27] H. Zhao, S.J. Park, F. Shi, Y. Fu, V. Battaglia, P.N. Ross, G. Liu, Propylene car-
bonate (PC)-based electrolytes with high coulombic efficiency for lithium-ion
batteries, J. Electrochem. Soc. 161 (2014) A194–A200, doi:10.1149/2.095401jes.
[28] Z.K. Kordi, G.M. Ziarani, A. Badiei, N. Lashgari, Synthesis of 1,4-dihydropyridine
as a fluorescent and colorimetric chemosensor for detection of Fe 3+ ion, Sens.
Lett. 17 (2019) 747–754, doi:10.1166/sl.2019.4137.
[29] A.K. Jain, V.K. Gupta, J.R. Raisoni, Anion recognition using newly synthesized
hydrogen bonding diamide receptors: PVC based sensors for carbonate, Elec-
trochim. Acta 52 (2006) 951–957, doi:10.1016/j.electacta.2006.06.037.
[30] N. Abramova, S. Levichev, A. Bratov, The influence of CO2 on ISFETs with poly-
mer membranes and characterization of a carbonate ion sensor, Talanta 81
(2010) 1750–1754, doi:10.1016/j.talanta.2010.03.034.
[50] C. Gonzalez, H.B. Schlegel, An improved algorithm for reaction path following,
J. Chem. Phys. 90 (1989) 2154, doi:10.1063/1.456010.
[51] C. Gonzalez, H.B. Schlegel, Reaction path following in mass-weighted internal
coordinates, J. Phys. Chem. 94 (1990) 5523–5527, doi:10.1021/j100377a021.
[52] Y. Zhao, D.G. Truhlar, The M06 suite of density functionals for main group
thermochemistry, thermochemical kinetics, noncovalent interactions, excited
states, and transition elements: two new functionals and systematic testing
of four M06-class functionals and 12 other function, Theor. Chem. Acc. 120
(2008) 215–241, doi:10.1007/s00214-007-0310-x.
[31] L. Fabbrizzi, M. Licchelli, A. Taglietti, The design of fluorescent sensors for an-
ions: taking profit from the metal–ligand interaction and exploiting two dis-
tinct paradigms, J. Chem. Soc. Dalt. Trans. 3 (2003) 3471–3479, doi:10.1039/
b304172g.
[32] M. Darroudi, G. Mohammadi Ziarani, S. Bahar, J.B. Ghasemi, A. Badiei,
Lansoprazole-based colorimetric chemosensor for efficient binding and sensing
of carbonate ion: spectroscopy and DFT studies, Front. Chem. 8 (2021) 626472,
doi:10.3389/fchem.2020.626472.
[53] M. Darroudi, Y. Sarrafi, M. Hamzehloueian, An efficient synthesis of novel tri-
azoles incorporating barbituric motifs via [3+2] cycloaddition reaction: ex-
perimental and theoretical study, J. Serbian Chem. Soc. 83 (2018) 821–835,
doi:10.2298/JSC170618038D.
[33] M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi, A. Badiei, Acenaphtoquinox-
aline as
a
Selective Fluorescent Sensor for Hg (II) Detection: Experimental
[54] M. Darroudi, M. Hamzehloueian, Y. Sarrafi, An experimental and mecha-
nism study on the regioselective click reaction toward the synthesis of
and Theoretical Studies, 6, Heliyon, 2020 e04986, doi:10.1016/j.heliyon.2020.
e04986.
thiazolidinone-triazole, Heliyon
e06113.
7 (2021) e06113, doi:10.1016/j.heliyon.2021.
[34] H. Rouh, Y. Liu, N. Katakam, L. Pham, Y.L. Zhu, G. Li, Synthesis of functional-
ized chromene and chroman derivatives via cesium carbonate promoted for-
[55] M. Darroudi, Y. Sarrafi, M. Hamzehloueian, Theoretical exploration of mecha-
nism of carbapenam formation in catalytic Kinugasa reaction, Tetrahedron 73
(2017) 1673–1681, doi:10.1016/j.tet.2017.01.071.
ꢂ
mal [4 + 2] annulation of 2 -hydroxychalcones with allenoates, J. Org. Chem.
83 (2018) 15372–15379, doi:10.1021/acs.joc.8b02627.
[35] L. Ling, J. Hu, H. Zhang, Ferrocene containing N-tosyl hydrazones as optical and
electrochemical sensors for Hg 2+, Cu 2+ and F − ions, Tetrahedron 75 (2019)
2472–2481, doi:10.1016/j.tet.2019.03.023.
[56] V. Barone, M. Cossi, V.B. and, M. Cossi∗, V. Barone, M. Cossi, Quantum calcu-
lation of molecular energies and energy gradients in solution by a conductor
solvent model, J. Phys. Chem. A 102 (1998) 1995–2001, doi:10.1021/jp9716997.
[36] S. Wang, H. Ding, Y. Wang, C. Fan, G. Liu, S. Pu, Novel multi-responsive fluo-
12

M. Darroudi, G. Mohammadi Ziarani, J.B. Ghasemi et al.
Journal of Molecular Structure 1241 (2021) 130626
[57] M.D. Liptak, G.C. Shields, Accurate pKa calculations for carboxylic acids us-
ing Complete Basis Set and Gaussian-n models combined with CPCM contin-
uum solvation methods, J. Am. Chem. Soc. 123 (2001) 7314–7319, doi:10.1021/
ja010534f.
[59] N. Roy, H.A.R. Pramanik, P.C. Paul, S.T. Singh, A sensitive schiff-base fluorescent
chemosensor for the selective detection of Zn2+, J. Fluoresc. 24 (2014) 1099–
1106, doi:10.1007/s10895-014-1390-3.
[58] Y. Dong, R. Fan, W. Chen, P. Wang, Y. Yang, A simple quinolone Schiff-base
containing CHEF based fluorescence “turn-on” chemosensor for distinguishing
Zn2+ and Hg2+ with high sensitivity, selectivity and reversibility, Dalt. Trans.
46 (2017) 6769–6775, doi:10.1039/c7dt00956a.
13