Solvatochromic behavior of a pyrene-pyrimidine-based Schiff base and detection of heavy metal ions in aqueous media

Article abstract of DOI:10.1080/00958972.2021.1897980

The synthesis and solvatochromic behavior of pyrimidine based Schiff-base (PYPH) were studied to develop a fluorescent chemo sensor for the detection of Hg²⁺ in aqueous solution. The characterization of PYPH was investigated on the basis of UV–vis, FTIR, ¹H-NMR and mass spectral data. PYPH displays selective fluorescent turn-off response to Hg²⁺ in aqueous solution. The sensitivity and selectivity of PYPH toward Hg²⁺ among different metal ions was examined by absorption, fluorescence, ¹H-NMR and mass spectral studies. Binding stoichiometry (2:1) has been confirmed by a Job’s plot, HRMS spectral studies and ¹H-NMR analysis. A low detection limit was 4.2 × 10^?6 M for Hg²⁺. Ground state geometry of PYPH has been optimized using density functional theory (DFT). These results demonstrate that PYPH has promise to detect Hg²⁺ ion in environmental analysis systems.

Full text of DOI:10.1080/00958972.2021.1897980

Journal of Coordination Chemistry
ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/gcoo20
Solvatochromic behavior of a pyrene-pyrimidine-
based Schiff base and detection of heavy metal
ions in aqueous media
Swadesh Ghosh, Dipti Singharoy, Saugata Konar, Jnan Prakash Naskar &
Subhash Chandra Bhattacharya
To cite this article: Swadesh Ghosh, Dipti Singharoy, Saugata Konar, Jnan Prakash Naskar
& Subhash Chandra Bhattacharya (2021) Solvatochromic behavior of a pyrene-pyrimidine-
based Schiff base and detection of heavy metal ions in aqueous media, Journal of Coordination
Chemistry, 74:8, 1272-1283, DOI: 10.1080/00958972.2021.1897980
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JOURNAL OF COORDINATION CHEMISTRY
2021, VOL. 74, NO. 8, 1272–1283
https://doi.org/10.1080/00958972.2021.1897980
Solvatochromic behavior of a pyrene-pyrimidine-based
Schiff base and detection of heavy metal ions in
aqueous media
Swadesh Ghosha, Dipti Singharoya, Saugata Konarb, Jnan Prakash Naskara and
Subhash Chandra Bhattacharyaa
b
aDepartment of Chemistry, Jadavpur University, Kolkata, India; Department of Chemistry, The
Bhawanipur Education Society College, Kolkata, India
ABSTRACT
ARTICLE HISTORY
Received 13 July 2020
Accepted 26 January 2021
The synthesis and solvatochromic behavior of pyrimidine based
Schiff-base (PYPH) were studied to develop a fluorescent chemo sen-
sor for the detection of Hg2þ in aqueous solution. The characteriza-
1
KEYWORDS
tion of PYPH was investigated on the basis of UV–vis, FTIR, H-NMR
Synthesis; solvent study;
mercury detection;
selectivity
and mass spectral data. PYPH displays selective fluorescent turn-off
response to Hg2þ in aqueous solution. The sensitivity and selectivity
of PYPH toward Hg2þ among different metal ions was examined by
absorption, fluorescence, 1H-NMR and mass spectral studies. Binding
stoichiometry (2:1) has been confirmed by a Job’s plot, HRMS spectral
studies and 1H-NMR analysis. A low detection limit was 4.2ꢀ 10ꢁ6 M
for Hg2þ. Ground state geometry of PYPH has been optimized using
density functional theory (DFT). These results demonstrate that PYPH
has promise to detect Hg2þ ion in environmental analysis systems.
CONTACT Subhash Chandra Bhattacharya
Prakash Naskar jpnaskar@rediffmail.com
sbjuchem@yahoo.com, scbhattacharyya@chemistry.jdvu.ac.in; Jnan
Department of Chemistry, Jadavpur University, Kolkata, 700032 India
Supplemental data for this article is available online at https://doi.org/10.1080/00958972.2021.1897980.
ß 2021 Informa UK Limited, trading as Taylor & Francis Group

JOURNAL OF COORDINATION CHEMISTRY
1273
1. Introduction
Sensing and reporting of chemical species is of major importance [1]. Metals are pre-
sent in living or non-living species. Some metals, e.g., iron, copper, zinc are essential
for biological processes and enzymatic reactions that occur in the human body; con-
versely some metals are unsafe for living organisms. Among them mercury is a heavy
metal occurring in different forms, all of which can produce deadly toxic effects in the
human body. Zero oxidation state of Hg exists as vapor or as liquid metal, þ1 oxida-
tion state of Hg exists as inorganic salts and þ2 oxidation state of Hg may form either
inorganic salts or organomercury compounds; the three oxidation states differ in toxic
effects [2]. Even at a low concentration, mercury is one of the most dangerous metal
ions for the ecosystem [3]. It can accumulate in a human body through the food chain
leading to many diseases, nervous system defects, erythrism, arrhythmia, cardiomyop-
athy, and kidney damage [4–8]. Mercury shows high permeability to skin and seriously
damages respiratory, gastrointestinal and excretory systems, prenatal brain damage,
serious cognitive, motion disorders, deafness, minamata and alzheimer [9, 10].
Additionally, it shows a high affinity for thiol groups in proteins and leads to the mal-
function of cells and consequently leads to many diseases [11]. Due to its affinity for
sulfhydryl and thiol groups, it can change the macromolecular structure and also dam-
age DNA [12]. Mercury has been shown to induce oxidative stress and mitochondrial
dysfunction [13] resulting in alterations in calcium homeostasis and increased lipid
peroxidation [14]. Mercury may also increase radical oxygen species levels because of
its ability to act as a catalyst. Therefore, the need for highly sensitive and selective
determination of mercury ions is of importance.
Pyrimidine containing Schiff bases are promising with broad spectrum of biological
activity and for the detection of toxic heavy metal ions [15]. To develop the Schiff
base as a sensor, pyrene derivatives are widely used due to their excellent photolumi-
nescence and chemical stabilities. Among heterocycles, pyrimidines represent a par-
ticularly important class of compounds due to their diverse applications for
pharmaceutical properties. Schiff bases have biological activity, such as antitumor [16,
17], anticancer [18], antifungal, and antimicrobial activities [19–21]. Biological activity is
related to hydrogen bonding through the imino group of Schiff bases with the active
centers of the cell constituents [22]. Based on these factors we focus on Schiff bases,
which are prepared using simple steps and can be applied to many cation and anion
sensors. Pyrimidine is the structural unit of DNA and RNA playing a vital role with the
most abundant pyrimidines uracil, cytosine and thymine. Pyrene has also a remarkable
range of biological activity as anti-bacterial agents, [23] anti-tumor [24] and anti-fungal
[25] compounds.
In this study, due to biological significance of pyrimidines we have synthesized a
pyrimidine based Schiff base ligand 2-(4,6-dimethylpyrimidin-2-yl)-1-((pyren-8-yl)methy-
lene)hydrazine (PYPH) as a new chemosensor for detection of Hg2þ. There are many
mercury ion sensor Schiff bases but the biologically active pyrimidine moiety in the
Schiff base was absent. The influences of solvent on absorbance and fluorescence
spectra of PYPH are reported and it shows high selectivity and sensitivity to Hg2þ over
other metal ions. Selective and sensitive detection of PYPH towards Hg2þ has been
confirmed by absorbance, fluorescence, 1H-NMR titration and HRMS spectroscopic

1274
S. GHOSH ET AL.
studies. The present system is simple, cost effective and sensitive towards Hg2þ ion
which may be employed in eco-friendly aqueous medium.
2. Experimental
2.1. Materials
The spectral grade solvents ethanol (EtOH), methanol (MeOH), conc. HCl, 1-pyrene car-
boxaldehyde, phosphorous oxy chloride (POCl3), acetyl acetone, hydrazine hydrate,
potassium bromide (KBr) and urea were purchased from E. Merck, India. Solvents were
purified and dried according to standard methods [26] and used only after checking
their purity fluorimetrically in the wavelength range of interest. DMSO-d6 as received
1
from Sigma-Aldrich, USA was used for H-NMR experiments. Perchlorate salts of Fe3þ
,
Co2þ, Cd2þ, Hg2þ, Ni2þ and Zn2þ were purchased from Sigma-Aldrich and other metal
salts like Al(NO3)3, CrCl3, MnCl2 and Cu(ClO4)2 were procured from commercial sources
(SRL); all were used as received. Millipore water was used throughout the experiments.
2.2. Synthesis
2.2.1. Synthesis of 2-(4,6-dimethylpyrimidin-2-yl)-1-((pyren-8-yl)methylene)hydra-
zine (PYPH)
PYPH was synthesized by refluxing an ethanolic solution (20 ml) of 4,6-dimethyl
2-hydrazino pyrimidine (10 mmol, 1.39 g) [27–29] with 1-pyrenecarboxaldehyde
(10 mmol, 2.30 g) also in ethanol (20 ml). Reflux was continued for 2 h at water bath
temperature during which a solid compound separated. It was filtered, washed with
ethanol and dried over fused CaCl2. The crude product was recrystallized from etha-
nol–water mixture. It is soluble in DMSO, DMF, THF and MeCN but insoluble in MeOH,
DCM, CHCl3, n-hexane and n-pentane. (Yield: 79.30%); Anal. Calc. for C23H18N4:
1
C, 78.86; H, 5.14; N, 16.00. Found: C, 78.79; H, 5.10; N, 16.05%. H-NMR (in d6-DMSO,
300 MHz) d 11.33 (1H, s), 9.17 (1H, s), 8.73 (1H, J ¼ 9 Hz, 1H), 8.55 (1H, J ¼ 8 Hz, 1H),
8.33-8.06 (m, 7H), 6.66 (1H, S), 2.354 (s, 6H) (Figure S1, supplementary material).
ESI-MS: m/z calculated for C23H18N4 [PYPH þ H]þ 351.15, found 351.26 (Figure S2, sup-
plementary material); IR (KBr, cm-1) t: 3417 (N-H), 1667 (C ¼ N) (Figure S3, supplemen-
tary material).
2.2.2. Synthesis and formulation
PYPH is a 1:1 molar Schiff base condensate of 4,6-dimethyl 2-hydrazino pyrimidine
and 1-pyrenecarboxaldehyde in EtOH. PYPH was spectroscopically characterized by
1
FT-IR, ESI-MS and H-NMR. In Scheme 1, the synthetic scheme of PYPH is outlined.
2.3. Methods
1H-NMR spectra were obtained with a Bruker Avance DPX 300 spectrometer using
DMSO-d6 solution. Infrared spectra (4000 ꢁ 400 cmꢁ1) were taken as KBr pellets using
a Perkin Elmer Spectrum BX-II IR spectrometer. Mass spectroscopic analysis of PYPH
was obtained from a QTOF Micro YA263 ESI-TOF mass spectrometer using methanol

JOURNAL OF COORDINATION CHEMISTRY
1275
Scheme 1. Synthesis outline of PYPH.
as solvent. Elemental analyses (carbon, hydrogen and nitrogen) were obtained from a
Perkin Elmer CHN analyzer 2400. Absorption and fluorescence spectra were recorded
using a Shimadzu (model UV1700) UV–vis spectrophotometer and Shimadzu spectro-
fluroimeter (model RF 5301), respectively. Fluorescence decay curves were obtained
from time resolved intensity decay by time-correlated single photon counting (TCSPC)
using a nanosecond diode LED at 370 nm (IBH, nano LED) as a light source. The data
stored in a multichannel analyzer were routinely transferred to IBH DAS-6 decay ana-
lysis software. For lifetime measurements, the fluorescence decay curves were ana-
lyzed by an exponential iterative fitting program provided by IBH using Eq. (1),
X
ai exp ðꢁ
(1)
t
Þ
=
s
i
FðtÞ ¼
i
where ai is the pre exponential factor representing the fractional contribution to the
time resolved decay of the component with lifetime. Ground state geometries of PYPH
were optimized employing density functional theory [30, 31] using the B3LYP [32, 33]
functional with the standard basis set, 6-311 G (d, p), for all atoms in the Gaussian 09
program [34].
3. Results and discussion
3.1. Solvent modulated properties of PYPH
Absorption and emission spectra of PYPH has been studied in solvents of different
polarity. Absorption spectra of PYPH (Figure 1(a)) have a broad band with a maximum
between 384 and 405 nm (Table 1) in the solvents of different polarity (H2O to CyHex,
ꢂ
respectively). This band can be ascribed to p-p transition to singly excited state (S1)
of molecule. The absorption is intense and peak position is sensitive to the polarity of
the medium. The typical solvent shift on changing the polarity of solvents suggests
that the ground state of the molecule is polar.
Emission spectra of PYPH, recorded in solvents of different polarity, are represented
in Figure 1b. On excitation of PYPH at the absorption maxima in the corresponding
solvents, an emission band appears at 470-441 nm. The intensity of the band is low in

1276
S. GHOSH ET AL.
Figure 1. (a) Absorption and (b) emission spectra of PYPH in different homogeneous solvents.
Table 1. Absorbance maximum (kabs), fluorescence maximum (kfl), stokes shift (Dm) and ET (30)
values in different homogeneous solvents.a
Solvents
kabs /nm
kfl /nm
D m (cmꢁ1
)
ET(30) (kcal/mol)
H2O
EG
398
385
384
384
380
384
385
393
393
470
454
458
456
453
443
436
442
441
3849
3947
4207
4111
4240
3468
3038
2820
2769
63.1
56.3
55.4
51.9
46.0
43.8
36.0
31.1
30.9
MeOH
EtOH
ACN
DMF
DiOX
n-hept
Cyhex
aACN ¼ acetonitrile, DiOX ¼ dioxane, n-hept ¼ n-heptane.
nonpolar solvents (Figure 1(b)) but with increase of polarity fluorescence intensity is
increased. A red shifted fluorescence is observed on increasing solvent polarity. The
effect of the polarity of the medium on the fluorescence maximum is greater than
that on the absorption maximum. This observation suggested that the emitting state
of PYPH is more polar than the ground state.
A plot of Stokes shift (Dm ¼ difference between transition energy of absorption
maxima E(A) and fluorescence maxima E(F)) versus the microscopic solvent polarity
parameter, ET(30) [35], is presented in Figure S4 (supplementary material) where
Stokes shift increases sharply from cyclohexane (CyHex) to MeOH and then decreases
steeply on changing from ethylene glycol (EG) to water. PYPH exhibits an overall
increase in Stokes shift from nonpolar to polar solvents (except water and EG) due to
increasing polarity of the medium. Changing the medium from nonpolar to polar sta-
bilizes the excited state of PYPH, which causes a red shift and consequently, Stokes
shift increases. But in water and EG, the Stokes shift is decreased due to strong inter-
molecular hydrogen bonding interactions.
In addition steady state anisotropy of PYPH has been investigated in fully saturated
condition of different types of solvent (polar protic, H2O; polar aprotic, ACN and non-
polar, n-hexane (n-hex)). Steady state fluorescence anisotropy helps to understand the

JOURNAL OF COORDINATION CHEMISTRY
1277
Figure 2. (a) Absorption spectra of PYPH upon addition of Hg2þ ions up to 64.1 lM; (b) emission
spectra of PYPH upon addition of Hg2þ ions up to 21.6 lM.
motional restriction of the molecule due to interaction with different solvents. The
anisotropy of PYPH is 0.12 in aqueous media whereas the anisotropy of PYPH is 0.02
and 0.05, respectively, in acetonitrile and n-hex (Figure S5, supplementary material).
Hence, anisotropy of PYPH in water is greater than that of polar aprotic ACN and non-
polar n-hex solvents, supporting that strong intermolecular hydrogen bonding inter-
action takes place. Hydrophobic interaction of PYPH in non-polar solvent indicates
higher anisotropy of PYPH than polar aprotic solvents. Time-resolved fluorescence
measurements were performed for PYPH in three different solvents to characterize the
spectral properties and dynamics, considering the polarity in the excited state (Table
S1, supplementary material). The excited state decay profiles in different homoge-
neous environments are shown in Figure S6 (supplementary material) which has been
fitted with a single exponential decay with v2 value near one (Table S1, supplementary
material). Fluorescence lifetime values of PYPH increases with polarity of solvents and
lies between 3.8 and 4.7 ns. Lifetime value of PYPH in water is higher than that in
other solvents, which supports the higher fluorescence intensity of PYPH in water.
3.2. Absorbance and emission studies
The absorption spectra of PYPH (9.1 mM) were recorded with kabs at 398 nm in H2O
due to a p-p transition. Upon stepwise addition of Hg2þ (up to 64.1 mM) to solution
ꢂ
of PYPH, absorbance of PYPH decreased (Figure 2(a)). No significant spectral change of
PYPH was observed due to addition of other metal cations Naþ, Kþ, Ca2þ, Co2þ, Ni2þ
,
Cu2þ, Zn2þ, Fe3þ, Pb2þ, Agþ, Cd2þ, Al3þ, Zn2þ, Cr3þ and Fe2þ. The absorbance
decrease indicates that ground state interaction takes place between PYPH and Hg2þ
.
To understand selectivity of PYPH towards Hg2þ, under similar circumstances in the
presence of other metal cations, the fluorescence intensity changes were systematic-
ally studied in aqueous medium. On excitation at 398 nm, PYPH showed a strong
emission band at 470 nm (kem). Upon addition of Hg2þ (up to 21.6 mM) to solution of
PYPH (9.1 mM), the fluorescence of PYPH was quenched at 470 nm with a red shift of
10 nm (Figure 2(b)), indicating formation of complex between PYPH and Hg2þ. With
the presence of other metal ions, such as Co2þ, Ni2þ, Hg2þ, Fe3þ, Cu2þ, Zn2þ, Cd2þ
,

1278
S. GHOSH ET AL.
Figure 3. (a) Bar diagram indicates the emission intensity of PYPH (4.97 mM) and concentration of
all metal ions (M2þ and M3þ) are 9.92 mM. (b) Plot of fluorescence intensity of PYPH (9.9 mM) vs.
concentration of Hg2þ with an error bar (4.6%).
Al3þ, Zn2þ, Cr3þ and Fe2þ, no change in fluorescence intensity (shown in bar diagram
of Figure 3(a)) has been observed.
The quenching of fluorescence of PYPH with the addition of Hg2þ occurs due to non-
fluorescent complex formation with metal ions [36–40]. The limit of detection (LOD) of
Hg2þ by PYPH has been calculated by the 3r method [41] (LOD ¼ 3r/m where ‘r’ and ‘m’
are the standard deviation of blank and the slope of the fluorescence intensity vs. concen-
tration of Hg2þ plot, respectively, Figure 3(b)) and the value is 4.2 ꢀ 10ꢁ6 M.
3.3. Binding studies
In order to determine the binding stoichiometry between PYPH and Hg2þ, a Job’s plot
was performed with fluorescence intensity data. From the Job’s plot (Figure 4(a)),
intensity minima were observed at 0.61 mole fraction, indicating 2:1 stoichiometry
complex was formed. This was further confirmed by ESI mass spectra of the complex
in methanol. ESI mass spectral peak at m/z ¼ 937.87 for [C46H34HgN4þK]þ supported
the 2:1 stoichiometry of the complex (Figure S7, supplementary material).
Fluorescence spectra were also used for determination of binding constant values
between PYPH and Hg2þ using the Benesi–Hildebrand (B–H) equation [42] (eq. 2),
1
1
1
¼
þ
(2)
If ꢁ If0 If= ꢁ If0 KðIf= ꢁ If0 Þ½Hg2þ
ꢃ
where K is binding constant, If0 is initial fluorescence intensity of free host, If is the
intermediate fluorescence intensity of PYPH:Hg2þ and If’ is the maximum fluorescence
/
intensity of the PYPH:Hg2þ adduct formed. A plot of 1/(If-If0) vs. 1/[Hg2þ] provides a
straight line through the entire range of Hg2þ concentration (Figure 4(b)), indicating a
2:1 adduct. From the slope of B-H plot calculated binding constant values for complex
formation is 4.1 ꢀ 104 Mꢁ1. Both results suggested that the receptor PYPH was sensi-
tive towards mercuric ion.

JOURNAL OF COORDINATION CHEMISTRY
1279
Figure 4. (a) Jobs’ plot of PYPH:Hg2þ system from fluorescence spectra. (b) B–H plot from the
emission spectra of PYPH:Hg2þ
.
Figure 5. (a) Time resolved fluorescence decay of PYPH upon addition of Hg2þ up to 119.2 mM;
(b) plot of F0/F vs. [Hg2þ] with an error bar (6.25%).
3.4. Quenching mechanism
We studied the time resolved fluorescence measurement to understand fluorescence
quenching process of PYPH. Fluorescence lifetime serves as a sensitive parameter to
investigate the environment around a fluorophore, and it is sensitive to excited state
interactions. There was no change of fluorescence lifetime of PYPH upon addition of
Hg2þ ions (Figure 5(a)). Quenching of fluorescence intensity of PYPH with the addition
of Hg2þ may be due to static quenching. The quenching of fluorescence of PYPH with
addition of Hg2þ was analyzed by the Stern–Volmer equation (eq. 3) [43],
F0
F
¼ 1 þ KSV½Qꢃ
(3)
where F0 and F are fluorescence intensities of PYPH in the absence and presence of
Hg2þ ions, respectively, KSV is the Stern-Volmer constant and [Q] is the Hg2þ concen-
tration. A linear curve in the Stern–Volmer plot (Figure 5(b)) was obtained. The KSV
value for PYPH is 4.0 ꢀ 104 mol dmꢁ3, which also agrees with binding constant value.

1280
S. GHOSH ET AL.
Figure 6. 1H-NMR spectra of PYPH and PYPH with Hg2þ ions in DMSO-d6.
1
3.5. H-NMR titration of complex
To establish possible binding mode of PYPH, 1H-NMR titration experiment was car-
ried out. Proton NMR spectra of PYPH were recorded in the absence and presence
of Hg2þ in DMSO-d6 (Figure 6). The -NH proton of PYPH appeared at 11.0 ppm
(Figure 6) but with addition of Hg2þ to PYPH solution, it disappeared (Figure 6); all
the protons of PYPH displayed a slightly upfield shift except the -NH proton. These
observations clearly indicate that Hg2þ coordinated to the N of –NH group after
deprotonation to satisfy the primary and secondary valency. This has been further
supported by mass spectrometry. ESI mass spectral peak of PYPH, [PYPH þ Hþ] and
PYPH:Hg2þ were at m/z ¼ 350.15 [C23H18N4], 351.26 [C23H18N4þH]þ (Figure S2, sup-
plementary material) and 937.87 [C46H34HgN4þK]þ, respectively (Figure S7, supple-
mentary material).

JOURNAL OF COORDINATION CHEMISTRY
1281
Figure 7. Ground state optimized structure of PYPH.
Table 2. Theoretical spectral data with the corresponding experimental absorption, dipole
moment, energy of HOMO and LUMO of PYPH.
theo
Theoretical kabs
(nm)
411.98
0.7110
398
Oscillator strength (f)
exp
Experimental kabs (nm)
Dipole Moment( m) debye
Energy of HOMO (eV)
Energy of LUMO (eV)
Energy gap (eV)
1.5721
ꢁ5.25
ꢁ2.24
3.01
3.6. Theoretical calculations
Calculations of PYPH have been completed to understand the above experimental
spectral properties. In the first step, ground state geometry of PYPH was optimized.
Next, TD-DFT method has been applied to determine the transition energy and oscilla-
tor strength (f). The optimized geometrical structures with the Mulliken charge distri-
bution (-0.481 to þ0.481) and the HOMO-LUMO energy gap of 3.01 eV of PYPH is
shown in Figure 7. The theoretical absorbance maximum of PYPH is 411.98 nm with
oscillator strength (f) 0.7110 (Figure S8, supplementary material), which is close to the
experimental findings (398 nm). Due to having different electronegative elements of
PYPH molecule, a dipole moment (m) of 1.5721 D is present (Table 2). The bond
lengths of (26 C-28N), (28 N-29N), (29 N-31C), (32 N-31C), (31 C-35N), (32 N-34C) and
(35 N-33C) of PYPH are 1.284 Å, 1.343 Å, 1.397 Å, 1.333 Å, 1.342 Å, 1.337 Å and 1.334 Å,
respectively (Table 3). The bond angles of (<16 C-25C-28N), (<28 N-29N-31C) and the
(<26 C-28N-29N) of PYPH are 125.7ꢄ, 123.2ꢄ, 117.5ꢄ, respectively (Table 3).
4. Conclusion
A Schiff base fluorescent chemosensor, PYPH, containing biologically active pyrimidine
was synthesized and its sensing properties were investigated in aqueous solutions.

1282
S. GHOSH ET AL.
Table 3. Bond lengths and angles of PYPH.
Bond lengths (Å)
(26C-28N)
(28N-29N)
(29N-31C)
(32N-31C)
1.284
1.343
1.397
1.333
1.342
1.337
1.334
(31C-35N)
(32N-34C)
(35N-33C)
Bond angles (ꢄ)
(<16C-25C-28N)
(<28N-29N-31C)
(<26C-28N-29N)
125.7
123.2
117.5
The solvatochromic behavior of PYPH depends not only on polarity of the medium
but also hydrogen bonding properties of the solvent. PYPH can be used as a fluores-
cent chemosensor for Hg2þ detection. The sensing mechanism based on nonfluores-
cent complexation between sensor PYPH and Hg2þ was confirmed by Job’s plots and
ESI mass spectra. Therefore, PYPH can serve as a potential sensor for quantitative
detection of Hg2þ in different samples.
Acknowledgements
All the authors are thankful to Jadavpur University, Kolkata, India for the research facilities.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Funding
S.C.B. acknowledges financial assistance from DST-SERB (grant no. EMR/2015/000678).
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