Highly sensitive and selective "naked eye" sensing of Cu(ii) by a novel amido-imine based receptor: A spectrophotometric and DFT study with practical application

Article abstract of DOI:10.1039/c6ra01269h

We report the synthesis of a novel compound (E)-bis-N′-((1H-pyrrol-2-yl)methylene)-pyridine-2,6-carbohydrazide and its sensing ability to detect copper(ii) ion in aqueous medium by a sharp color change from yellow to brown, the sensing limit being 4.0 × 10^-9 M. Theoretical modeling of the compound and its copper complex was performed. Practical utility was explored by successful paper strip response.

Full text of DOI:10.1039/c6ra01269h

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Highly sensitive and selective “naked eye” sensing of Cu (II) by a novel amido-imine based
receptor: a spectrophotometric and DFT study with practical application
Arghyadeep Bhattacharyya, Soumen Ghosh, Nikhil Guchhait*
Department of Chemistry, University of Calcutta, 92, A.P.C. Road, Kolkataꢀ700009, India
*Corresponding author. Tel.: +913323508386; fax: +913323519755.
Eꢀmail address: nguchhait@yahoo.com (N. Guchhait).
Abstract: We report the synthesis of a novel compound (E)ꢀBISꢀN'ꢀ((1Hꢀpyrrolꢀ2ꢀyl)
methylene)ꢀpyridineꢀ2, 6ꢀcarbohydrazide and its sensing ability to detect copper (II) ion in
ꢀ9
aqueous medium by a sharp color change from yellow to brown, the sensing limit being 4.0×10
M. Theoretical modeling of the compound and its copper complex was performed. Practical
utility was explored by successful paper strip response.
Keywords: copper (II) ion, naked eye, sensing limit, 1:2 binding, theoretical modeling, paper
strip.

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Introduction
Among the various transition metals important for sustaining life processes, copper holds
2
+
special importance, owing to a very interesting “twoꢀfaced” property. In one hand, Cu plays an
indispensable role in proper functioning of mammalian metabolism due to its presence in various
enzymes such as amine oxidases, ceruloplasmin, Hephaestin, Lysyl oxidase and Superoxide
dismutase (along with zinc)[1] along with its various industrial [2] and agricultural [3] uses. On
the other hand, excess copper intake opens up an array of physiological disorders as well as
causes diseases of serious concern. Whereas nausea, vomiting, tissue damage are some of the
minor effects, gastrointestinal catarrh, kidney damage, hypoglycemia and dyslexia are effects of
deep concern [4]. Neurodegenerative diseases which pose a serious threat such as Alzheimer’s
disease, Menkes disease and Wilson’s disease are supposed to be aggravated by excess copper
due to its participation in the formation of reactive oxygen species (ROS) [5]. As a major amount
of copper accumulates in the body through drinking water, detection of copper in water by
simple techniques poses an important and enticing challenge in research.
With the advent of sophisticated techniques, various sensors have been reported for
detection of copper such as fluorescence ‘turnꢀon/off’ sensors, quantum dotꢀbased assays and
electrochemical sensors [6]. But sensing by the above mentioned techniques requires use of
sophisticated instruments, hence is expensive and time consuming. Moreover, in most cases the
sensing experiments were carried out using metal solutions in water and organic solvent mixture
[
7] and hence are of greater academic than practical interest. Thus, there is still need for
selective, sensitive copper sensors in aqueous medium. In the present work, we report a simply
synthesized Schiff base receptor (E)ꢀbisꢀN'ꢀ((1Hꢀpyrrolꢀ2ꢀyl)methylene)ꢀpyridineꢀ2,6ꢀ
carbohydrazide by the condensation of pyridine 2, 6 dicarboxyhydrazide and pyrroleꢀ2ꢀaldehyde

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for visual sensing of copper in water/methanol mixed solvent accompanied by a sharp color
ꢀ9
change. The sensing limit of our reported sensor (~4.0×10 (M)) is much lower compared to
other reports utilizing ‘naked eye’ change/ change in emission as the tool for detection [8].
Furthermore, test strips coated with the receptor molecule showed a change in color when
aqueous copper solution was dropped onto them.
Experimental
Reagents and apparatus: Pyridine 2, 6 dicarboxylic acid, pyrroleꢀ2ꢀaldehyde, Hydrazine
hydrate and metal perchlorate salts were purchased from SigmaꢀAldrich and were used without
1
13
further purification. HꢀNMR and CꢀNMR were recorded on Bruker Advanced Supercon 300
MHz and chemical shifts are expressed in ppm using TMS as internal standard. IR spectrum was
recorded on Perkin Elmer spectrumꢀ100 and UVꢀVis titrations and related experiments were
conducted in Hitachi Uꢀ3501 Spectrophotometer. UVꢀVIS titration with copper was carried out
ꢀ4
with 1.0x10 (M) aqueous solution of copper. Mass spectra were recorded on Waters Xevo G2ꢀS
Q TOF mass spectrometer.
Synthesis of (E)-bis-N'-((1H-pyrrol-2-yl)methylene)-pyridine-2,6-carbohydrazide: The
synthesis of receptor (E)ꢀBISꢀN'ꢀ((1Hꢀpyrrolꢀ2ꢀyl)methylene)ꢀpyridineꢀ2,6ꢀcarbohydrazide(1)
was achieved in three steps (Scheme 1)
Synthesis of Ethyl Pyridine-2, 6-dicarboxylate: It was prepared according to reported
procedure and used without further characterization [9].
Synthesis of Pyridine-2, 6-dicarboxyhydrazide: It was prepared using procedure reported
elsewhere and used in the final step without further characterization [10].

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Synthesis of (E)-bis-N'-((1H-pyrrol-2-yl)methylene)-Pyridine-2,6-carbohydrazide (1): 0.1 g
of Pyridineꢀ2,6ꢀdicarboxyhydrazide (~0.5 millimoles) was taken in a 50 mL round bottomed
flask and dissolved in 20 mL dry methanol. 0.095 g of Pyroleꢀ2ꢀaldehyde (~1.0 millimole) was
added in portions to the aforesaid solution of Pyridineꢀ2, 6ꢀ dicarboxyhydrazide. The solution
was stirred under reflux for 4 hours on a water bath. The resulting solution was cooled and
allowed to stand for overnight when shining greenish yellow crystals of 1 separated out. The
product was filtered under suction, dried in vaccum under reduced pressure and was
1
13
characterized by HꢀNMR, CꢀNMR and IR spectroscopy. Yield: 0.139 g (79.65%); IR (KBr,
ꢀ1
cm ): 3358.80(pyrrole –NH), 3212.65(amide –NH), 2923.49, 2852.66, 1649.14 (imine),
1
1
615.47(amide –C=O), 1587.19,1531.57, 1117.66, 1032.48, 733.74, 680.18(ESI, Fig 1); H ꢀ
NMR (300 MHz, DMSOꢀd , 290 K, TMS): 12.029 (s, 2H, ꢀNH), 11.635(s, 2H, ꢀCONH), 8.515
6
(s, 2H, ꢀCH=N),8.293ꢀ8.315(m, 3H, ArꢀH), 6.996(s, 2H, ArꢀH), 6.589(s, 2H, ArꢀH), 6.180(s, 2H,
1
3
ArꢀH) (ESI, Fig 2); CꢀNMR(300 MHz, DMSOꢀd , 290 K, TMS): 159.45, 148.90, 143.28,
6
140.32, 127.53, 125.52, 123.55, 114.61, 110.00(ESI, Fig 3).

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2
EtOH, H SO4
O
Hydrazine Hydrate
O
O
O
O
O
N
N
N
EtOH, Reflux
Reflux
O
O
NH
HN
OH
OH
H N
NH2
2
O
O
N
N
H
OHC
N
MeOH,Reflux
NH
HN
O
O
+
N
N
2
H
H
N
NH
HN
N
H N
2
NH2
1
Scheme 1: Synthesis of compound 1
Results and discussions
Receptor 1 has been synthesized by a simple condensation reaction between Pyridineꢀ2, 6ꢀ
1
13
dicarboxyhydrazide and pyrroleꢀ2ꢀ aldehyde. It has been characterized by H NMR, C NMR
and IR spectroscopy. The presence of a singlet at 12.02 corresponds to the pyrrole –NH proton,
ꢀ1
the signal for the same is obtained at 3358.80 cm in IR spectrum [26]. The singlet at 11.635
ꢀ1
corresponded to 3212.65 cm in IR spectrum [26]. The singlet at 8.515 appeared for imine
ꢀ1
proton and the signal for the same functional group is obtained at 1649.14 cm in the IR
spectrum [26].
Visual sensing of Cu (II): For checking the optical response of receptor 1 towards metal ions,
the receptor was dissolved in aqueous methanol mixture (methanol: water 3:7) and perchlorate

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salts of transition metals dissolved in deionised water were added (2 equiv.) individually to it. To
our delight, the receptor instantaneously showed a sharp change from light yellow to brown by
addition of Cu (II) only (Fig 1), indicating a likely interaction between 1 and copper. The sharp
color change can be attributed to a possible intramolecular charge transfer due to complexation
with copper [11, 12]. Under similar conditions, no addition of other metals, including those
commonly available in water, showed any significant color change (ESI, Fig 4). The selective
2
+
color change for Cu is a probable outcome of judicious balance between N and O donor centre,
2
+
2+
for which Cu shows a particular affinity as well as the matching of ionic radius of Cu with
the cavity size of receptor 1.
ꢀ4
Fig 1: Color change of receptor 1 upon addition of 10 equivalents of metal solutions (~ 10
M))
(
UV-Vis Experiments:
To further check the selectivity of receptor 1 towards Cu (II) ion, 10 equivalent of 0.1
mM aqueous solution of transition metals in the form of perchlorate salts were added to 10 µM
solution of receptor 1 in aqueous methanol (methanol: water 3:7,v:v) and absorption spectra were
recorded using UVꢀVis spectrophotometer. The selectivity of sensor 1 towards Cu (II) was
satisfyingly ensured with the generation of a new red shifted peak at ~392 nm with two shoulders

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at ~375 and ~416 nm respectively, whereas receptor 1 furnished a strong peak at ~330 nm (π→
π* transition), followed by a weak shoulder at 260 nm respectively. However, addition of other
metals (10 equivalents, 0.1mM aqueous solution) produced too small a change in the absorbance
to take into account (ESI, Fig 5a) and thus the response for Cu(II) was much greater than any
other metal ions (Fig 2). The interaction of 1 with Cu(II), though already indicated from optical
color change, could now be rationalized to be the result of complexation between 1 and Cu(II)
due to the aforesaid spectral change and the selectivity of compound 1 towards copper can be
firmly concluded. In order to investigate the nature of complexation between 1 and Cu(II) a
titration experiment was performed using a stock aqueous solution of copper of concentration
ꢀ4
1
.0×10 (M). As already mentioned, the receptor 1 (dissolved in 30% aq. methanol) exhibited
two peaks at ~260 nm and ~330 nm. Upon addition of 1 equivalent of Cu(II) a broad peak was
generated at ~405 nm along with decrease in the intensity of the peak at ~330 nm. However,
further addition of Cu (II) up to 12 equivalents i.e., until saturation resulted in the resolution of
the aforesaid broad peak into one sharp peak at ~392 nm accompanied by two shoulders at ~375
nm and ~416 nm (Fig 3). Thus, the gradual increase in absorbance value of the newly generated
red shifted peak at the ~392 nm wavelength occurs at the expanse of decrease in absorbance of
the receptor’s own peak.

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2
+
Fig 2: UVꢀVis response upon addition of 10 equivalents of Cu , bar graph showing response of
2
+
Cu to receptor 1(10 equivalents of other metals also added).
2
+
Fig 3: UVꢀVisible titration of 10 µM solution of receptor 1 with Cu
Stoichiometry of complexation and formation constant: With the aim of finding out the
stoichiometry and binding constant of the generated complex, the Benesi−Hildebrand (BꢀH)
method was employed, the data sets of absorbance and concentration used in UVꢀVis titration
being reused. The BꢀH equation is: 1/(AꢀA )=1/(bꢀε[G] [H] K )+1/(bꢀε[H] ), where A and A
0
0
0
a
0
0
stand for the absorbance values of the hostꢀguest complex and the host (receptor 1 in this case),
ε represents the difference in molar extinction coefficients of the hostꢀguest complex and host
whereas b is a constant. The plot of 1/ (AꢀA ) vs. [G] (the guest concentration) shows a linearity
ꢀ
0
0
when the host guest interaction is 1:1 in nature. However, for nonꢀlinear interactions (say 1: n)
n
0
the physical quantity in the abscissa is to be raised to the appropriate order ([G] ) to obtain
linearity. The absorbance of the peak at ~392 nm was considered for construction of the BꢀH
plot. The plot of 1/ (AꢀA ) showed a linearity (with the fitting parameter being 0.99026) when
0

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2
+
2+
plotted against the reciprocal of the concentration of Cu squared (Cu being the ‘guest’ in this
2
+
case), hinting at a 1:2 binding between 1 and Cu . The value of binding constant (K ), which is
a
1
2
ꢀ2
the ratio of intercept to slope, turned out to be (6.25±1.35) ×10 M (Fig 4). So the binding of
this ligand with Cu(II) ion is really very strong.
2
+
ꢀ4
Fig 4: BꢀH plot for UVꢀVis titration of 1 with Cu (1.0×10 M)
Detection limit: The detection limit of receptor 1 for Cu (II) ion was calculated from the
calibration curve constructed from the UVꢀVis titration data set according to IUPAC definition
[
13] (ESI, Fig 7). A linear fit of absorbance at 395nm vs Cu(II) ion concentration plot obtained
from the UVꢀtitration curve is used for detection limit measurement. Receptor 1 showed an
ꢀ9
exceptional detection limit of 4.0×10 M for Cu (II). As the detection limit for Cu (II) is
comparable to that obtained by sensitive and costly measurement techniques such as
fluorescence spectroscopy as also by colorimetry [8], compound 1 stands out among other
available chemosensors owing to ‘naked eye’ color change, mild solvent system (methanol:

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water, 3:7), rapid response and use of cheap instrumental assistance in determining trace amount
of copper in water.
Mass spectral and IR analysis: As mentioned previously, BꢀH plot indicated 1:2 complex
between 1 and Cu(II). To unravel the complexation phenomenon, the complex of receptor 1 and
Cu(II) was prepared by refluxing stoichiometric amount of the two complexing partners in
methanol, followed by cooling, when a brown powdery mass was obtained. It was filtered under
suction, dried in vaccum overnight and then a very dilute solution of the formed complex in
methanol was subjected to ESIꢀMS spectroscopy. A signal at m/z 507.2655 (calculated 506.98)
was obtained (Fig 5). The observed value supports the formation of a 1:2 complex between 1 and
Cu(II). Next up, with the task of investigating the participation of the functional groups in 1
responsible for complexation, the IR spectrum of the prepared complex was recorded (ESI Fig
8). The shift in the position of imine moiety’s peak in the aforementioned spectrum(from a sharp
ꢀ1
ꢀ1
band at ~1649 cm to a mere hinge at ~1616 cm ) clearly proves its involvement in the
ꢀ1
complexation as also a broad band corresponding to water(~3434.97 cm ) was obtained, along
ꢀ1
with disappearance of the pyrrole –NH signal at ~3358 cm . Finally, to merge our findings from
IR and Mass spectrometry to visualize the complex, it can be concluded that the pyrrole moieties
lost one proton each and the imine moieties as also the tautomerised amide functionality in 1
were involved in the complexation, the coꢀordination number being satisfied by two water
molecules (Fig 5).

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2+
Fig. 5: Mass spectrum of complex of 1 with Cu along with the proposed structure
DFT calculations
The urge of delving into the electronic structure of receptor 1 and its copper complex
along with the purpose of supporting our experimental findings prompted us to carry on
theoretical modeling for receptor 1 (Fig. 6) as well as its complex (Fig.7) with copper (II) by the
aid of Gaussian 09W using B3LYP hybrid functional (6ꢀ311++g** basis set) [14]. The
optimized structure of complex explains its remarkable stability over receptor 1 as evident from
the lower HOMOꢀLUMO energy gap of the complex compared to receptor 1 (Fig.6 and 7). The
alteration in the bond distances of major functional groups responsible for complexation agrees
with our experimental findings (ESI, Tableꢀ2). A quick analysis of the data provided in table 1

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furnishes the following conclusions: I) the increment of C=O bond length indicates its
2
+
involvement in complexation with Cu . II) The tautomerism of the amidic proton which renders
a partial double bond character to the amidic CꢀN bond is evident from decrease in the bond
length value of CꢀN bond. III) The lengthening of the imine bond length establishes its donation
2
+
to the metal centre, Cu in the present case. Thus, the hypothetical structure of the complex can
be well justified from our theoretical findings.
Fig 6: DFT (B3LYP/6ꢀ311++g**) optimized structure of receptor 1 showing energy difference
between HOMO and LUMO.

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2+
Fig 7: B3LYP optimized structure of complex of 1 with Cu and difference in HOMOꢀLUMO
energy
Practical application
Encouraged by the high selectivity and sharp color change of receptor 1 toward Cu (II) in
aqueous medium, we attempted to explore its potential to detect copper in the solid state.
Keeping in mind that of late, several reported Schiff base receptors furnished satisfactory results
for paper strip test [15] we attempted to carry out paper strip test for copper with compound 1.
ꢀ4
Test paper coated with receptor 1 was treated with copper solution (perchlorate salt, ~10 M) and
much to our satisfaction, readily changed color from yellow to light brown( Fig.8), thereby
revealing the practical utility of compound 1.

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2
+
ꢀ4
Fig. 8: Change in color of paper strip coated with 1 upon addition of Cu (~10 M, 2 equiv.)
Conclusion
To conclude, we reported the synthesis of a copper selective amidoꢀimine based
chemosensor 1 and studied its interaction with copper by spectrophotometric methods and
employed mass spectrometry to explore the mode of complexation. Theoretical modeling was
ꢀ9
also conducted using G09W. The sensing limit of receptor 1 was found to be ~4.0×10 (M) for
copper in water, which is well lower than the WHO recommended amount of copper in water (30
2
+
µM). Furthermore, 1 responds to paper strip test for Cu by a color change from yellow to light
brown. Thus, our reported chemosensor is of significance due to easy synthetic outline, high
selectivity and sensitivity and extremely low limit of detection. The practical applicability of our
reported chemosensor 1 was demonstrated by successful test kit experiment.

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Acknowledgements
AB and SG would like to acknowledge CSIR and UGC for granting their respective
fellowships. NG would like to acknowledge UPE and CRNN, University of Calcutta for
financial support. The authors would like to give a heartfelt thanks to Prof Dilip K Maiti for his
invaluable suggestions.
References:
[
1] G.W. Gokel, W.M. Leevy, M.E. Weber, Crown ethers: Sensors for ions and molecular
scaffolds for materials and biological models, Chem. Rev , 2004, 104 2723–2750.
2]. G.W. Stratton, in: E. Hodgson (Ed.), Review in Environmental Toxicology, Elsevier,
Amsterdam, 1987, pp. 85–94.
[
[
3]. N.N. Greenwood, A. Earnshow, Chemistry of the Elements, Pergamon Press,
New York, 1984, p. 628
[
4] I.H. Scheinberg, A.G. Morell, in: G.L. Eichhorn (Ed.), Inorganic Biochemistry,
Elsevier, Amsterdam, 1973, pp. 306–343.
[
5] D. Strausak, J.F.B. Mercer, H.H. Dieter, W. Stremmel, G. Multhaup, Copper in disorders
with neurological symptoms: Alzheimer’s, Menkes, and Wilson diseases,
Brain Res. Bull., 2001, 55, 175–185.
[
6] (a) T. Kato, S. Nakamur, M. Mirita, Determination of nickel, copper, zinc, silver,
cadmium and lead in seawater by isotope dilution inductively coupled plasma
mass spectrometry, Anal. Sci., 1990, 6, 623–626;

RSC Advances
Page 16 of 21
View Article Online
DOI: 10.1039/C6RA01269H
(b) S. Hong, T. Kang, J. Moon, S. Oh, J. Yi, Surface plasmon resonance analysis
of aqueous copper ions with aminoꢀterminated selfꢀassembled monolayers,
Coll. Surf. A, 2007, 292, 264–270;
(c) B.ꢀC. Yin, P. Zuo, H. Huo, X.ꢀH. Zhong, B.ꢀC. Ye, DNAzyme selfꢀassembled gold
nanoparticles for determination of metal ions using fluorescence anisotropy
assay, Anal. Biochem. , 2010, 401, 47–52;
(
d) K.ꢀM. GattasꢀAsfura, R.M. Leblanc, Peptideꢀcoated CdS quantum dots for
the optical detection of copper(II) and silver(I), Chem. Comm., 2003, 21, 2684–2685;
e) M. Kupper, J.W. Schultze, A new copper ion selective microelectrode for
electrochemical applications, J. Electroanal. Chem., 1997, 427, 129–135;
f) W. Lin, L. Yuan, W. Tan, J. Feng, L. Long, Construction of fluorescent probes via
(
(
protection/deprotection of functional groups: a ratiometric fluorescent probe
for Cu2+, Chem. – A Eur. J., 2009, 15, 1030–1035.
[
7] (a) P. Kaur, S. Kaur, K. Singh, P.R. Sharma, T. Kaur, Indoleꢀbased chemosensor for
Hg2+ and Cu2+ ions: applications in molecular switches and live cell imaging,
Dalton Trans., 2011, 40, 10818–10821;
2
+
(
b) D. Maity, T. Govindaraju, Highly selective visible and nearꢀIR sensing of Cu
based on thiourea–salicylaldehyde coordination in aqueous media, Chem. – A Eur. J., 2011, 17,
410–1414;
c) P. Kaur, M. Kaur, K. Singh, Ferrocene based chemosensor for Cu – a dual
channel signaling system, Talanta, 2011, 85, 1050–1055;
d) S. Dalapati, S. Jana, Md. A. Alam, N. Guchhait, Multifunctional fluorescent
1
2
+
(
(

Page 17 of 21
RSC Advances
View Article Online
DOI: 10.1039/C6RA01269H
probe selective for Cu(II) and Fe(III) with dualꢀmode of binding approach, Sens. Actuat. B, 2011,
60, 1106–1111;
e) S.H. Mashraqui, T. Khan, S. Sundaram, S. Ghadigaonkar, Phenothiazinepyridyl
1
(
chalcone: an easily accessible colorimetric and fluorimetric ‘on–off’
dual sensing probe for Cu2+, Tet. Lett., 2008, 49, 3739–3743;
(f) D. Zhang, M. Wang, M. Chai, X. Chen, Y. Ye, Y. Zhao, Three highly sensitive and
2
+
selective colorimetric and off–on fluorescent chemosensors for Cu in aqueous
solution, Sens. Actuat. B, 2011, 168, 200–206;
(g) X. Ma, Z. Tan, G. Wei, D. Wei, Y. Du, Solvent controlled sugar–rhodamine
2
+
fluorescence sensor for Cu detection, Analyst, 2012, 137, 1436–1439;
h) C. Yu, L. Chen, J. Zhang, J. Li, P. Liu, W. Wang, B. Yan, “Off–on” based fluorescent
(
2
+
chemosensor for Cu in aqueous media and living cells, Talanta, 2011, 85, 1627–1633.
8] a) T. G. Jo, Y. J. Na, J. J. Lee, M. M. Lee, S. Y. Lee and C. Kim, A diaminomaleonitrile
based selective colorimetric chemosensor for copper(II) and fluoride ions, New J.Chem., 2015,
9, 2580
[
3
b) S. Goswami ,S. Maity, A. K.Das, A. C. Maity, Single chemosensor for highly selective
colorimetric and fluorometric dual sensing of Cu(II) as well as ‘NIRF’ to acetate ion,
Tetrahedron Letters, 2013, 54, 6631–6634
c) H. Zhou, J. Wang, Y. Chen, W. Xi, Z. Zheng, D. Xu, Y. Cao, G. Liu, W. Zhu, J. Wu, Y. Tian,
New diaminomaleonitrile derivatives containing azaꢀcrown ether: Selective, sensitive and
colorimetric chemosensors for Cu(II), Dyes and Pigments, 2013, 98, 1ꢀ10

RSC Advances
Page 18 of 21
View Article Online
DOI: 10.1039/C6RA01269H
d) M.X Liu, T.B Wei, Q.Lin, Y.M Zhang, A novel 5ꢀmercapto triazole Schiff base as a selective
2
+
chromogenic chemosensor for Cu , Spectrochimica Acta Part A: Molecular and Biomolecular
Spectroscopy, 2011, 79, 1837– 1842
e) A. Kumar, V. Kumar, U. Diwan, K.K. Upadhyay, Highly sensitive and selective nakedꢀeye
2
+
detection of Cu in aqueous medium by a ninhydrin–quinoxaline derivative, Sens. Actuat. B,
013, 176, 420– 427.
2
f) U. Diwan, A. Kumar , V. Kumar , K.K. Upadhyaya, P.K. Roychowdhury, A water compatible
turn ‘on’ optical probe for Cu2+ based on a fluorescein–sugar conjugate, Sensors and Actuators
B, 2014, 196, 345–351.
[
9] A.Bremer, C.M. Ruff, D.Girnt, U.Müllich, J.Rothe, P.W.Roesky,P.J.Panak, A.Karpov, T.J.J.
Müller, M.A.Denecke, A.Geist, 2,6ꢀBis(5ꢀ(2,2ꢀdimethylpropyl)ꢀ1Hꢀpyrazolꢀ3ꢀyl)pyridine as a
Ligand for Efficient Actinide(III)/Lanthanide(III) Separation, Inorg. Chem., 2012, 51,
5199−5207.
[
10] R.M. Duke, T. McCabe, W. Schmitt, and T. Gunnlaugsson, Recognition and Sensing of
Biologically Relevant Anions in Alcohol and Mixed Alcohol−Aqueous Solutions Using Charge
Neutral CleftLike GlycolꢀDerived Pyridyl−Amidothiourea Receptors, J. Org. Chem., 2012, 77,
3115−3126.
[
11] A. Kumar, V. Kumar, U. Diwan, K.K. Upadhyay, Highly sensitive and selective nakedꢀeye
2
+
detection of Cu in aqueous medium by a ninhydrin–quinoxaline derivative, Sens. Actuat. B,
013, 176, 420– 427.
12] V. K. Gupta, A.K. Singha, M.R. Ganjalic, P. Norouzic, F. Faridbodc, N. Mergua,
2
[
Comparative study of colorimetric sensors based on newly synthesized
Schiff bases, Sens. Actuators. B, 2013, 182, 642– 651.

Page 19 of 21
RSC Advances
View Article Online
DOI: 10.1039/C6RA01269H
[
[
13] IUPAC, Spectrochim. Acta Part B, 1978, 33, 241–245.
14] M.J. Frisch, et al., GAUSSIAN 03, Revision D.01, Gaussian, Inc., Wallingford, CT,
004.
2
[
15] (a) V. K. Gupta, A.K. Singha, M.R. Ganjalic, P. Norouzic, F. Faridbodc, N. Mergua,
Comparative study of colorimetric sensors based on newly synthesized
Schiff bases, Sens. Actuat. B, 2013, 182, 642– 651
(b) N. Mergua, V.K. Gupta, A novel colorimetric detection probe for copper(II) ions based on a
Schiff base, Sens. Actuat. B, 2015, 210, 408–417
2
+
(
c) D.Maity and T. Govindaraju, Highly Selective Colorimetric Chemosensor for Co , Inorg.
Chem., 2011, 50, 11282–11284
2
+
[
16] D. Maity, T. Govindaraju, Highly selective visible and nearꢀIR sensing of Cu
based on thiourea–salicylaldehyde coordination in aqueous media, Chem.
A Eur. J., 2011, 17, 1410–1414
–
[
17] S.Prabhu, S.Saravanamoorthy, M.Ashok , SivanVelmathi, Colorimetric and fluorescent
sensing of multi metal ions and anions by salicylaldimine based receptors, J. Lumin., 2012, 132,
79–986
9
[
18] Y.J. Zhang, X.P.He, M.Hu, Z. Li , X.X Shi , G.R. Chen, Highly optically selective and
electrochemically active chemosensor for copper (II) based on triazoleꢀlinked glucosyl
anthraquinone, Dyes Pigments, 2011, 88, 391ꢀ395

RSC Advances
Page 20 of 21
View Article Online
DOI: 10.1039/C6RA01269H
[
19] A.Kumar, V. Kumar, U. Diwan, K.K. Upadhyay, Highly sensitive and selective nakedꢀeye
detection of Cu2+ in aqueous medium by a ninhydrin–quinoxaline derivative, Sens. Actuat. B,
013, 176, 420– 427
20] H.H Wang, L.Xue, ZhangꢀJian Fang, G.P. Li and H. Jiang, A colorimetric and fluorescent
chemosensor for copper ions in aqueous media and its application in living cells, New J. Chem.,
010, 34, 1239–1242
21] N.Mergu, V.K. Gupta, A novel colorimetric detection probe for copper(II) ions based on a
Schiff base, Sens. Actuat. B, 2015, 210, 408–417
22] M.X.Liu, T.B.Wei, Q.Lin, Y.M.Zhang, A novel 5ꢀmercapto triazole Schiff base as a
2
[
2
[
[
2
+
selective chromogenic chemosensor for Cu , Spectrochim. Acta. A, 2011, 79, 1837– 1842
23] K.B.Kim, H.Kim, E.J.Song, S.Kim,I.Noh and C.Kim, A capꢀtype Schiff base acting as a
[
fluorescence sensor for zinc(II) and a colorimetric sensor for iron(II),copper(II), and zinc(II) in
aqueous media, Dalton Trans., 2013, 42, 16569
[
24] N.Narayanaswamy, T.Govindaraju, Aldazineꢀbased colorimetric sensors for Cu2+ and
Fe3+, Sens. Actuat. B, 2012, 161, 304– 310
25] R.Sheng, P.Wang,Y. Gao, Y.Wu, W.Liu,J.Ma, H.Li,, S.Wu, Colorimetric Test Kit for Cu2+
Detection, Org. Lett., 2008, 10, 21
26] X. Baoa, J. Yua, Y. Zhoub,Selective colorimetric sensing for F− by a cleftꢀshaped anion
receptor containing amide and hydroxyl as recognition units, Sens. Actuat. B, 2009, 140, 467–
72.
[
[
4

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DOI: 10.1039/C6RA01269H
Graphical Abstract
Highly sensitive and selective “naked eye” sensing of Cu (II) by a novel amido-imine based
receptor: a spectrophotometric and DFT study with practical application
Arghyadeep Bhattacharyya, Soumen Ghosh, Nikhil Guchhait*
Department of Chemistry, University of Calcutta, 92, A.P.C. Road, Kolkataꢀ700009, India
*Corresponding author. Tel.: +913323508386; fax: +913323519755.
Eꢀmail address: nguchhait@yahoo.com (N. Guchhait).