Condensation product of 2-hydroxy-1-napthaldehyde and 2-aminophenol: Selective fluorescent sensor for Al3+ ion and fabrication of paper strip sensor for Al3+ ion

Article abstract of DOI:10.1016/j.ica.2017.09.025

The condensation product of 2-hydroxy-1-napthaldehyde and 2-aminophenol (L), in 1:1 (v/v) CH₃OH:H₂O acts as selective fluorescent sensor for Al³⁺. The fluorescence intensity of L at emission wavelength 517 nm, when excited with 360 nm photons, increases on interaction with Al³⁺ by ca. 7-fold. Under UV lamp, L shows light yellow fluorescence on interaction with Al³⁺ visible to bare eyes. Metal ions – Na⁺, K⁺, Ca²⁺, Mg²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Cd²⁺ and Hg²⁺do not interfere. The increase in fluorescence intensity is due to the quenching of photoinduced electron transfer (PET) process prevailing in L. The fluorescent and UV/Visible spectral data analysis showed a 1:1 complexation between L and Al³⁺ with logβ = 4.532 (β = binding constant) and detection limit 10^?5 M. DFT and TDDFT calculations also confirm 1:1 interaction between L and Al³⁺. L has been successfully applied in fluorescent imaging of Al³⁺ in live rat L6 myoblasts cells and as paper strip fluorescent sensor for Al³⁺ in aqueous medium.

Full text of DOI:10.1016/j.ica.2017.09.025

Inorganica Chimica Acta 469 (2018) 202–208
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Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
Condensation product of 2-hydroxy-1-napthaldehyde and
2-aminophenol: Selective fluorescent sensor for Al3+ ion and fabrication
of paper strip sensor for Al3+ ion
Smita Sarma a, Ananya Bhowmik b, Manas Jyoti Sarma a, Sofia Banu b, Prodeep Phukan a,
Diganta Kumar Das a,
⇑
a Department of Chemistry, Gauhati University, Guwahati 781 014, Assam, India
b Department of Bio-engineering and Technology, Institute of Science and Technology, Gauhati University, Guwahati 781 014, Assam, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 June 2017
Received in revised form 8 September 2017
Accepted 10 September 2017
Available online 18 September 2017
The condensation product of 2-hydroxy-1-napthaldehyde and 2-aminophenol (L), in 1:1 (v/v) CH3OH:
H2O acts as selective fluorescent sensor for Al3+. The fluorescence intensity of L at emission wavelength
517 nm, when excited with 360 nm photons, increases on interaction with Al3+ by ca. 7-fold. Under UV
lamp, L shows light yellow fluorescence on interaction with Al3+ visible to bare eyes. Metal ions – Na+,
K+, Ca2+, Mg2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+ and Hg2+do not interfere. The increase in fluores-
cence intensity is due to the quenching of photoinduced electron transfer (PET) process prevailing in L.
The fluorescent and UV/Visible spectral data analysis showed a 1:1 complexation between L and Al3+
with logb = 4.532 (b = binding constant) and detection limit 10À5 M. DFT and TDDFT calculations also
confirm 1:1 interaction between L and Al3+. L has been successfully applied in fluorescent imaging of
Al3+ in live rat L6 myoblasts cells and as paper strip fluorescent sensor for Al3+ in aqueous medium.
Ó 2017 Published by Elsevier B.V.
Keywords:
2-Hydroxy-1-napthaldehyde
2-Aminophenol
Fluorescence
Sensor
Aluminium
PET
DFT-TDDFT
L6 myoblasts cell
Paper sensor
1. Introduction
highly sophisticated techniques like atomic absorption and
emission spectroscopy, spectrophotometry, electrochemistry,
In the earth crust, lithosphere consists of Aluminium (Al) in
8.3% which is considered to be third most abundant element after
oxygen and silicon [1]. Aluminium compounds are widely used in
textile industries, paper industries, in making utensils, in alloys [2],
water purification, automobiles [3] etc. Due to its low density and
therefore low weight, high strength, superior malleability, easy
machining, excellent corrosion resistance, good thermal and
electrical conductivity Al is the second most widely used metal
after iron [4]. Although it is quite useful but it has got some adverse
effects too. Al3+ when consumed in surplus amount may lead to
neurodegenerative disease like Alzheimer disease, Parkinson
disease [5], bone abnormalities etc. Therefore the detection of
Al3+ is of great environmental as well as biological importance
[6]. Fluorescent sensors have attracted a lot of scientific interest
[7] due to their easy applicability, reasonable cost, higher
sensitivity, simple instrumentation etc in comparson to other
electrochemiluminescence etc [8,9].
As fluorescent sensor, simple Schiff base ligands, have gained
recent interest for different metal ions including Al3+. This is
basically due to their relatively easy one or two steps synthesis
[10–12]. Schiff bases recently reported as ‘‘off-on” fluorescent
sensor for Al3+ are based on – 2-Hydroxyacetophenone and
ethylenediamine [13], thiazoleand salicylaldehyde [14]; 2-hydrox-
yethylether-2-nitrophenol and salicylaldehyde [15], 8-hydroxyju-
lolidine-9- carboxaldehyde and benzohydrazide [16]; 2-
hydroxyaniline and 2 hydroxybenzaldehyde [17]; salicylhydrazide
and ortho-phthalaldehyde [18]; salicylaldehyde and 4,4-difluoro-
4-bora-3a,4adiaza-s-indacene [19]; thiophene-2-carboxylic acid
hydrazide [20]; 8-hydroxyquinoline-7-carbal-dehyde and 4-
aminopyrine [21]; 2-methyl quinoline-4-carboxylic hydrazide
and 8-formyl-7-hydroxyl-4-methyl coumarin [22]; perylenebisi-
mide and di(2-(salicylideneamino))ethylamine [23]; 4-aminoan-
tipyrine and salicylaldehyde, 4-aminoantipyrine and 2-hydroxy-1
naphthaldehydeantipyridine [24]; Rhodamineethylenediamine
and 1,8-naphthalic anhydride [25] etc.
⇑
Corresponding author.
E-mail address: diganta_chem@gauhati.ac.in (D.K. Das).
https://doi.org/10.1016/j.ica.2017.09.025
0020-1693/Ó 2017 Published by Elsevier B.V.

S. Sarma et al. / Inorganica Chimica Acta 469 (2018) 202–208
203
In this paper we have reported new fluorescent sensor for Al3+
derived from the condensation of 2-hydroxy-1-napthaldehyde
and 2-aminophenol in absolute alcohol. The sensor is selective
were done by pipetting out 2 mL of solution of L in 1 cm quartz cell
and by adding appropriate amount of metal ion using micro pip-
ette. For reversibility studies the concentration of EDTA2À was
made 0.1 M and added using micropipette.
for Al3+ while metal ions – Na+, K+, Ca2+, Mg2+, Mn2+, Co2+, Ni2+
,
Cu2+, Zn2+, Pb2+, Cd2+ and Hg2+ do not interfere. The interaction of
sensor with Al3+ results bare eye visible light yellow fluorescence
under UV lamp. The sensor is applicable to live rat L6 myoblasts
cells and has been used to obtain paper strip fluorescent sensor
for Al3+ in aqueous medium.
2.3. DFT calculations
From the available experimental data the structure of L:Al3+
complex was predicted and confirmed by DFT calculation. The L
and L:Al3+ complex were fully optimized using B3LYP [29] func-
tion. For L basis set 6-311G and for L:Al3+ metal complex basis
set LanL2DZ were used in the program Gaussian 09 [30]. The stabil-
ity of the complex was confirmed by the vibrational energy calcu-
lation with same level of theory. TD-DFT calculations were
performed to find out first three probable transitions of L:Al3+
complex.
2. Experimental
2-Hydroxy-1-napthaldehyde and DMSO-d6 are from Sigma
Aldrich, 2-aminophenol and metal salts were either from Merck
or Loba Chemie. The metal salts except Pb(NO3)2, CaCl2 and HgCl2
were sulphates. Metal salt solutions (0.01M) were prepared in dou-
bly distilled water obtained from quartz double distillation plant.
The FT-IR spectra were recorded in a Perkin Elmer RXI spec-
trometer as KBr pellets, NMR and 13C NMR spectra were recorded
on a Bruker Ultra Shield 300 MHz spectrophotometer using DMSO-
d6 as solvent. The fluorescence and UV/Visible spectra were
recorded in HITACHI 2500 and Shimadzu UV 1800 spectropho-
tometer respectively using quartz cuvette (1 cm path length).
2.4. Cytotoxicity studies
To test the cytotoxicity of the compound ‘A’,
a 3-(4,5-
dimethylthiazol-2-yl)-2,Sdiphenyl tetrazolium bromide (MTT)
assay was performed using the standard procedure. After treat-
ment of the L6 cells with concentration ranging from (10–300)
mM of compound A, 100 l
l of MTT solution (5 mg mlÀ1 phos-
phate-buffered saline (PBS) was added to each well of a 96-well
culture plate and incubated continuously at 37 °C for 4 h. All the
media was removed from the wells post incubation and replaced
2.1. Synthesis and characterization of the sensor (L)
L has been reported as an intermediate towards the synthesis of
a duel sensor for Al3+ and CNÀ [26]. 0.02 mol (0.035 g) of 2-
hydroxy-1-napthaldehyde and 0.02 mol (0.022 g) of 2-aminophe-
nol were dissolved in 10 mLC2H5OH in a 50 mL round bottom flask
and allowed to stir for 8 h. Yellowish precipitate was obtained, sol-
vent was evaporated in a rota evaporator to obtain the product
which was recrystallized from CH3OH. Yield: 70%.
with 100 ll of DMSO for solubilising the blue-violet intracellular
formazan crystals produced. Absorbance of the solution measured
at 595 nm using a microtiter plate reader. The values obtained
were the mean ( standard deviation) of three separate experi-
ments. The cytotoxicity was calculated as a percentage of cell via-
bility when compared to untreated control cells and expressed in
terms of IC50.
FTIR (KBr):1592 cmÀ1
aliphatic); 1512 cmÀ1
c=c).
HRMS: m/z 264.1.
(m (m (mc-H
c=N); 3444 cmÀ1 o-H); 2922 cmÀ1
(m
3. Results and discussion
1H NMR (300MHz, DMSO-d6, dppm, TMS): 15.69 (d,J = 9 Hz,1H);
10.38 (br,1H); 9.47 (d,J = 9.6 Hz,1H); 8.36 (d,J = 8.4 Hz,1H); 7.92 (d,
J = 7.5 Hz,1H); 7.79 (d,J = 9.6 Hz,1H); 7.66 (d,J = 7.8 Hz,1H); 7.49–
7.46 (m,1H); 7.27–7.25 (m,1H); 7.12–7.07 (m,1H); 6.99 6.93
(m,2H), 6.76 (d,J = 9.3 Hz,1H).
Scheme 1 A shows the chemical structure, based on different
spectral data, of the synthesised sensor 1-((2-hydroxyphenylim-
ino)methyl)naphthalene-2-ol (L). The DFT optimised structure of
L has been shown in Scheme 1B.
13CNMR (75 MHz, DMSO-d6, dppm, TMS): 177.9, 149.4, 148.4,
138.1, 134.0, 129.1, 128.5, 128.2, 126.8, 125.9, 125.2, 123.1,
119.9, 119.8, 117.6, 116.0, 107.7.
The fluorescent spectrum of L (2 Â 10À5 M) was recorded in 1:1
(v/v) CH3OH:H2O with excitation wavelength 360 nm. The maxi-
mum emission peak was observed at kmaxvalue 517 nm. The fluo-
rescence spectra of 2 Â 10À5 M solution of L was also recorded at
2.2. Preparation of solutions
different added concentrations of metal ions – Na+, K+, Al3+, Ca2+
,
Mg2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+ and Hg2+. Significant
enhancement in fluorescence intensity (ca. 7-fold) was observed
only in case of Al3+. Fig. 1 shows the fluorescence spectra of L in
presence of different metal ions when metal ion to L concentration
For sensing studies stock solution of
L was prepared as
2 Â 10À5 M in 1:1 (v/v) CH3OH:H2O. Metal ions solutions were also
prepared as 0.1 M in 1:1 (v/v) CH3OH:H2O. Fluorescent titrations
A
B
OH HO
N
1-((2-hydroxyphenylimino)methyl)naphthalen-2-ol
Scheme 1. Chemical structure of L (A) and DFT optimised structure of L (B).

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S. Sarma et al. / Inorganica Chimica Acta 469 (2018) 202–208
Fig. 3. Bar diagram comparing I/I0 values of L in presence of one equivalent of
different metal ions in 1:1 (v/v) CH3OH:H2O, kex = 360 nm. The height of the bar
corresponding to Al3+ is distinctive over the others.
Fig. 1. Effect of different metal ions at one equivalent concentration on the
fluorescence spectra of L in 1:1 (v/v) CH3OH:H2O with kex = 360 nm.
Fig. 4. Solutions of L each in presence of a metal ion (from left to right) – Na+, K+,
Al3+, Li+, Ca2+, Mg2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+ and Hg2+ when L is in one
equivalent to metal ion concentration in 1:1 (v/v) CH3OH:H2O, kex = 360 nm.
Fig. 2. Fluorescence spectra of L ((2 Â 10À5 M) in 1:1 (v/v) CH3OH:H2O at different
added concentration of Al3+, kex = 360 nm.
ratio is 1:2. Fig. 2 shows the fluorescence spectra of L in presence of
different added concentrations of Al3+. Inset of Fig. 2 is the plot of I/
I0 values for L versus concentration of added Al3+ which attains
maximum when Al3+:L ratio became 1:1 indicating that one L
binds per Al3+. Here I and I0 are the fluorescence intensity of L at
two equivalent concentrations of a particular metal ion and in
Fig. 5. Plot of log[(I0ÀIs)/(IsÀI )] versus log[Al3+] for fluorescence spectral titration
a
of L against Al3+ in 1:1 (v/v) CH3OH:H2O, kex = 360 nm.
absence of Al3+
, respectively. The I/I0 values for interaction
one equivalent to metal ion concentration. The solution containing
Al3+ fluoresces brightly under UV radiation of 360 nm wavelength
while the other solutions do not.
The binding constant and stoichiometry of binding was deter-
mined by plotting log[(IoÀIs)/(IsÀImax)] versus log[Al3+] (Fig. 5)
[27]. The slope of the plot was 1.2 indicating 1:1 binding ratio
between L and Al3+. The binding constant (b) has been calculated
as logb = 4.5. The binding stoichiometry as well as the binding con-
stant was further confirmed by recording UV–visible spectra of L
recorded at different added concentration of Al3+ (Fig. 6) [27].
between L and different metal ions mentioned above have been
compared through a bar diagram in Fig. 3. Results shown in
Fig. 1 and Fig. 3 clearly prove that L acts as a selective fluorescent
sensor for Al3+ over the other metal ions.
The enhancement in the fluorescence intensity of L on interac-
tion with Al3+ can be explained on the basis of Photo induced Elec-
tron transfer (PET) mechanism. The lone pairs of electrons in N and
O atoms present on L are involved in PET causing quenching of flu-
orescence in it. When Al3+ ion binds to L involving lone pairs on the
N and O the PET was quenched and enhancement in the fluores-
cence intensity was observed.
The two absorption peaks at 345 nm and 246 nm are due to
p-
p⁄
transitions. Upon addition of Al3+ absorption of both of these two
peaks increases with the formation of three isosbestic points at
245 nm, 290 nm and 390 nm respectively. Inset of Fig. 6 is the plot
of log[(AoÀAs)/(AsÀAmax)]versus log[Al3+]. The slope 1.15 supports
The bare eye fluorescent recognition of Al3+ by L was also pos-
sible when illuminated with UV radiation of 360 nm. Fig. 4 shows
different solutions of L each in presence of a metal ion when L is in

S. Sarma et al. / Inorganica Chimica Acta 469 (2018) 202–208
205
Fig. 6. UV/Visible spectra of L at different added concentration of Al3+ in 1:1 (v/v)
CH3OH:H2O.
Fig. 8. I/I0 response of L in presence of (i) Al3+ (grey bars); (ii) Al3+ and another
metal ion (black bars) in 1:1 (v/v) CH3OH:H2O. Similar heights of black and grey
bars confirm selectivity of L towards Al3+ over other metal ions.
the 1:1 interaction between L and Al3+, the binding constant value
has been calculated as logb = 4.5 which is also in close proximity to
the value calculated from fluorescence data. Here I0 (A0) is the flu-
orescence intensity (absorbance) of L in absence of metal ion, Is (As)
is the fluorescence intensity (absorbance) of L in presence of a par-
3.1. Effect of pH on fluorescence of L in absence and presence of Al3+
ticular concentration of metal ion while Imax (A ) is the maximum
a
Fluorescence spectra of L as well as L in presence of one equiv-
alent of Al3+ were recorded varying the pH in the range 2.0–10.0
(Fig. 9). In case of L the fluorescence intensity remains almost same
in the entire pH range. pH titration in presence of Al3+ shows a
gradual enhancement in fluorescence intensity till pH 6.0, remain
constant until pH 8.0 is reached and then shows a gradual declina-
tion till pH 10.0. At pH lower than 6.0 the L:Al3+ complex slowly
breaks down due to the protonation of the two hydroxyl groups
in L. Similarly above pH 8.0 the complex breaks down due to for-
mation of aluminium hydroxide and declining fluorescence inten-
sity is observed. Hence the L:Al3+ complex remains stable in the pH
range 6.0–8.0.
fluorescence intensity (absorbance) of L in presence of metal ion.
The detection limit was calculated to be 10À5 M from the plot of (Is-
ÀIo) versus log[Al3+] as per reported procedure [28]. The Job’s plot
was also recorded to prove the 1:1 interaction between L and Al3+
as shown in Fig. 7. The maximum absorbance at mole fraction 0.5
supports the 1:1 interaction.
The interference from other metal ions towards the sensing
ability of L towards Al3+ was verified. For this purpose, fluorescence
spectra were recorded for L in presence of one equivalent of Al3+
along with two equivalents of another metal ion. Fig. 8 compares
I/I0 values, through bar diagram, for L in presence of Al3+ (black
bars) along with L in presence of Al3+ and another metal ion (grey
bars). Here, I0 is the fluorescence intensity of L in absence of any
metal ion while I is the fluorescence intensity of L. The comparable
heights of the black and grey bars indicate that L can detect Al3+
even in presence of two equivalents of another metal ion.
3.2. Reversibility with Na2EDTA
The enhancement in the fluorescent intensity of L on interaction
with Al3+ was found to be reversible. When Na2EDTA was added
Fig. 7. Job’s method of continuous variation for determining the stoichiometric
Fig. 9. Effect of pH on the fluorescent intensity of L (r) and Al3+:3 L (N) in 1:1 (v/v)
CH3CN:H2O.
binding ratio between L and Al3+
.

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S. Sarma et al. / Inorganica Chimica Acta 469 (2018) 202–208
its secondary valence. From optimized DFT structure it could be
observed that, in the L:Al3+ complex the
-electron cloud of naph-
thylene ring have been extended to the –C@N– imine bond
through, the –CH link. Due to this extended delocalization of
p
p-
electron, fluorescence intensity might be enhanced in the L:Al3+
complex compare to L. Moreover from DFT, optimized HOMO-
LUMO of L and L:Al3+ complex was calculated and it is observed
that for L:Al3+ complex HOMO is totally L centric (Fig. 12).
TD-DFT studies show that there are mainly three transitions
(Hartree/Particle) for L:Al3+ complex. The first transition is from
HOMO (À0.24294) to LUMO (À0.13059), second one is from
HOMO-1 (À0.25909) to LUMO and the third one is from HOMO
to LUMO + 1 (À0.09821) and the last transition due to ligand to
metal charge transfer.
Fig. 10. Effect of EDTA2- anion at different added concentration on the fluorescence
spectra of
L . The gradual decrease in
in presence of one equivalent of Al3+
fluorescence intensity proves the reversibility of Al3+ to L binding.
gradually to an already fluorescent 1:1 equivalent solution of L and
Al3+, decrease in the fluorescence intensity was observed till it
became equal to the original fluorescence intensity of L (Fig. 10).
Here the strong chelator EDTA2- removes Al3+ from L:Al3+ complex
as [(EDTA)Al]- and free L leaves behind.
3.3. DFT calculations
From the DFT optimized structure it has been seen that L is not
fully planner, it has a twisted structure in the optimized form. Cal-
culations show that L:Al3+ complex has trigonal planner structure
with Al3+ at its centre (Fig. 11). In the optimized structure Al3+ is
bonded with two oxygen atoms and a nitrogen atom to complete
Fig. 11. DFT optimised structure of L:Al3+ complex. Al3+ binds to one N and two O
atoms in a trigonal planar mode.
Fig. 12. DFT optimised shapes of HOMO & LUMO of L; HOMO, LUMO, HOMO-1 &
LUMO + 1 of L:Al3+
.

S. Sarma et al. / Inorganica Chimica Acta 469 (2018) 202–208
207
Fig. 13. Fluorescence image of (A) rat L6 myoblasts cells (B) Rat L6 myoblasts cells in presence of Al3+ (C) Rat L6 myoblasts cells in presence of L (D) Rat L6 myoblasts cells in
presence of L and Al3+
.
the concentration selected for our study was 50 mM which indi-
cated 70 percent survival.
3.4.2. Fluorescent paper sensor for Al3+
1 mM solution of L prepared by dissolving appropriate amount
of L in 1:1 (v/v) CH3OH:H2O. Whatmann 42 filter paper was cut in
as 0.5 cm by 3 cm paper strip and placed on a clean and dry glass
surface. The above solution of L was spread on 0.5 Â 2 cm area of
the paper strip carefully and allowed to dry normally. The process
was repeated three times to obtain the paper strip fluorescent sen-
sor for Al3+. The coated portion of the paper strip was dip for 3 s
into a solution of 10À5 M Al3+ containing all the other metal ions
studied above for interference keeping the concentration of each
of them at 10À3 M. The strip is then dried under normal environ-
ment and placed under UV lamp to observed bright yellow-green
fluorescence (Fig. 14).
Fig. 14. Paper sensors for Al3+ under UV light after interaction with Al3+ (Left) and
Acknowledgements
without interaction with Al3+ (Right).
The DST, New Delhi and UGC, New Delhi are thanked for finan-
cial assistance to the Department through FIST and SAP respec-
tively. IIT-Guwahati is thanked for HRMS. DST-SERB is thanked
for financial assistance vide project No. EMR/2016/001745.
3.4. Living biological cell imaging studies
The biological application in case of L for sensing Al3+ was done
in rat L6 myoblasts which were grown in DMEM (Dulbecco’s mod-
ified eaglemedium) supplemented with 10% Fetal Bovine Serum
(FBS), 1% penicillin–streptomycin and maintained at 37 °C in a
Appendix A. Supplementary data
humidified atmosphere with 5% CO2. 10 l
L of aqueous Al3+ was
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.ica.2017.09.025.
added and the cells were incubated for another 3 h. After comple-
tion of the incubation, the excess Al3+ was washed with phosphate
buffer saline (PBS). Then the fluorescence microscopy images were
recorded for (A) Cells; (B) Al3+ + Cells; (C) L+ Cells and (D) L
+ Al3+ + Cells which were shown in (Fig. 13). The plate for L
+ Al3+ + Cells shows bright spots which were not observed in case
of other plates. This result confirms the applicability of L for fluo-
rescence imaging of Al3+ in live cells.
Reference
[1] B.K. Datta, C. Kar, A. Basu, G. Das, Tetrahedron Lett. 54 (2013) 771.
[2] Y.W. Choi, G.J. Park, Y.J. Na, H.Y. Jo, S.A. Lee, G.R. You, Sens. Actuator B 194
(2014) 343.
[3] N. Mergu, A.K. Singh, V.K. Gupta, Sensors 15 (2015) 9097.
[4] S.V. Verstraeten, L. Aimo, P.I. Oteiza, Arch. Toxicol. 82 (2008) 789.
[5] V. Kumar, A. Kumar, U. Diwan, Shweta Ramesh, S.K. Srivastava, K.K. Upadhyay,
Sens. Actuator B 207 (2015) 650.
[6] S. Sarma, P.K. Bhattacharyya, D.K. Das, J. Fluoresc. 25 (2015) 1537.
[7] A. Sahana, A. Banerjee, S. Das, S. Lohar, D. Karak, B. Sarkar, S.K. Mukhopadhyay,
A.K. Mukherjee, D. Das, Org. Biomol. Chem. 9 (2011) 5523.
[8] D. Brian, M.S. Brooks, M.M. Richter, Anal. Chem. 75 (2003) 1102.
3.4.1. Cytotoxicity Results
The MTT assay data signified that compound A was not greatly
cytotoxic, with IC50 values of 300 0.0015 mM in L6 cells. Hence,

208
S. Sarma et al. / Inorganica Chimica Acta 469 (2018) 202–208
[9] V.K. Gupta, A.K. Jain, G. Maheshwari, Talanta 72 (2007) 1469.
[25] S. Paul, A. Manna, S. Goswami, Dalton Trans. 44 (2015) 11805.
[26] Chang Ya-Ju, Wu Shih-Sheng, Hu Ching-Han, Cho Chien, Kao Min Xiu, Wu An-
Tai, Inorg. Chim. Acta 432 (2015) 25.
[27] K. Dutta, R.C. Deka, D.K. Das, Spectrochim. Acta. A 124 (2014) 124.
[28] S. Sarma, P.K. Bhattacharyya, D.K. Das, J. Fluoresc. 26 (2016) 899.
[29] (a) A.D. Becke, J. Chem. Phys. 98 (1993) 5648;
[10] K. Dutta, R.C. Deka, D.K. Das, J. Lumin. 148 (2014) 325.
[11] J. Kumar, M.J. Sarma, P. Phukan, D.K. Das, Dalton Trans. 44 (2015) 4576.
[12] J. Kumar, P. Bhattacharyya, D.K. Das, Spectrochim. Acta A 138 (2015) 99.
[13] D.K. Das, J. Kumar, A. Bhowmick, P.K. Bhattacharyya, S. Banu, Inorg. Chim. Acta
462 (2017) 167.
[14] V.K. Gupta, A.K. Singh, L.K. Kumawat, Sens. Actuators B 195 (2014) 98.
[15] C.H. Chen, D.J. Liao, C.F. Wan, A.T. Wu, Analyst 138 (2013) 2527.
[16] S.A. Lee, G.R. You, Y.W. Choi, H.Y. Jo, A.R. Kim, I. Noh, S.J. Kim, Y. Kim, C. Kim,
Dalton Trans. 43 (2014) 6650.
[17] S. Kim, J.Y. Noh, K.Y. Kim, J.H. Kim, H.K. Kang, S.W. Nam, S.H. Kim, S. Park, C.
Kim, J. Kim, Inorg. Chem. 51 (2012) 3597.
[18] L. Wang, W. Qin, X. Tang, W. Dou, W. Liu, Q. Teng, X. Yao, Org. Biomol. Chem. 8
(2010) 3751.
[19] R. Kang, X. Shao, F. Peng, Y. Zhang, G.T. Sun, W. Zhaoa, X.D. Jiang, RSC Adv. 3
(2013) 21033.
(b) C. Lee, W. Yang, R.G. Parr, Phys. Rev. B 37 (1988) 785.
[30] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
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. Sonnenberg, M.
Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y.
Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J.E. Peralta, F.
Ogliaro, M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, T. Keith,
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, O.
Farkas, J.B. Foresman, J.V. Ortiz, J. Cioslowski and D.J. Fox, Gaussian Inc,
Wallingf, Gaussian 09, Revision B.01.
[20] K. Tiwari, M. Mishra, V.P. Singh, RSC Adv. 3 (2013) 12124.
[21] L. Fan, X. Jiang, B. Wang, Z. Yang, Sens. Actuators B 205 (2014) 249.
[22] J. Qin, T. Li, B. Wang, Z. Yang, L. Fan, Spectrochim. Acta A 133 (2014) 38.
[23] S. Malkondu, Tetrahedron 70 (2014) 5580.
[24] V.K. Gupta, A.K. Singh, N. Mergu, Electrochim. Acta 117 (2014) 405.