An ionic receptor for Zn2+ metal ion using synthesised bis-formylpyrazole calix[4]arene and its computational study

Article abstract of DOI:10.1080/10610278.2017.1415437

Newly synthesised receptor Bis-(1,3-diphenyl-pyrazolyl methylene acetohydrazide)Calix[4]arene (DPPMACA) was evaluated for cation binding ability. The receptor DPPMACA selectively interact with Zn²⁺ metal ion as assessed through UV-visible spect

Full text of DOI:10.1080/10610278.2017.1415437

Supramolecular Chemistry
ISSN: 1061-0278 (Print) 1029-0478 (Online) Journal homepage: http://www.tandfonline.com/loi/gsch20
An ionic receptor for Zn2+ metal ion using
synthesised bis-formylpyrazole calix[4]arene and
its computational study
Brij Mohan, Krunal Modi, Pankaj Bhatia, H. K. Sharma, Divya Mishra, Vinod
K. Jain & Lakhbeer Singh Arora
To cite this article: Brij Mohan, Krunal Modi, Pankaj Bhatia, H. K. Sharma, Divya Mishra, Vinod
K. Jain & Lakhbeer Singh Arora (2017): An ionic receptor for Zn2+ metal ion using synthesised
bis-formylpyrazole calix[4]arene and its computational study, Supramolecular Chemistry, DOI:
10.1080/10610278.2017.1415437
To link to this article: https://doi.org/10.1080/10610278.2017.1415437
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Date: 19 December 2017, At: 11:48

Supramolecular chemiStry, 2017
https://doi.org/10.1080/10610278.2017.1415437
An ionic receptor for Zn2+ metal ion using synthesised bis-formylpyrazole calix[4]
arene and its computational study
Brij Mohana, Krunal Modib , Pankaj Bhatiaa, H. K. Sharmaa, Divya Mishrac, Vinod K. Jainc and Lakhbeer
Singh Arorad
aDepartment of chemistry, Kurukshetra university, Kurukshetra, india; bJ. heyrovsky institute of physical chemistry, academy of Sciences of
c
the czech republic, prague, czech republic; Department of chemistry, university School of Sciences, Gujarat university, ahmedabad, india;
dDepartment of chemistry, indian institute of technology Delhi, New Delhi, india
ABSTRACT
ARTICLE HISTORY
received 17 october 2017
accepted 5 December 2017
Newly synthesised receptor Bis-(1,3-diphenyl-pyrazolyl methylene acetohydrazide)Calix[4]arene
(DPPMACA) was evaluated for cation binding ability. The receptor DPPMACA selectively interact with
Zn2+ metal ion as assessed through UV-visible spectroscopy with a bathochromic shift of 14 nm but
gave negligible response for other metal cations used as their sulfates. The stoichiometry observed
as 1:1 with stability constant 6.438 × 103 M−1. Additionally, computational visions were concentrated
for studying the stability and spectroscopic analysis of the DPPMACA-Zn2+ complex using docking,
molecular dynamics simulations and density functional theory (DFT) along with time-dependent
density functional theory (TD-DFT). The calculations significantly supplement the findings and
elucidate the structural geometry and mode of interactions in supramolecular complexation.
Herein, we witnessed that DPPMACA was selectively stabilized by Metal-donor and Metal-acceptor
contacts with Zn2+ to generate a low-energy complex. These findings are of wide interest, especially
because Zn2+ is a well-known biological important cation.
KEYWORDS
Formylpyrazole; calixarene;
uV-vis; Zn2+ sensor; DFt
calculation
1. Introduction
molecular receptors for recognition systems capable of
sensing charged or neutral molecules (7–9). These recep-
tors reinforce theories on weak intermolecular interactions
for sensing, separation, catalysis and for many other appli-
cations of supramolecular technology (1–7). Mostly metals
of d block shows interactions with receptors and plays vital
The development of molecular receptors is very agile
research area as it provides substantial binding sites for
multiple ions (1–6). Calixarenes provide framework as
host molecules due to presence of cavity, functionaliza-
tion sites and efforts are continuously made to design
CONTACT Brij mohan
brizharry17@gmail.com
Supplemental data for this article can be accessed at https://doi.org/10.1080/10610278.2017.1415437.
© 2017 informa uK limited, trading as taylor & Francis Group

2
B. MOHAN ET AL.
role in functioning of a vast number of widely differing
bio-systems. When these metals are present in excess to
biological processes they cause excessive damage. Acute
poisoning occurs due to ingestion of copper, cadmium and
zinc salts. Further accumulation results in toxicity to liver,
kidneys, brain, lungs, heart and central nervous system
(10–12).
residual solvent (CDCl3) were taken as δ = 7.27 ppm for
1H-NMR and δ = 77.1 ppm for 13C-NMR. The multiplicities
for the coupled signals were designated using the follow-
ing abbreviations: s = singlet, d = doublet, m = multiplets
and are given in hertz. Mass spectra were recorded on a
Xevo G2-S Q-T of spectrometer (Waters, USA), capable of
recording high-resolution mass spectrum in the electros-
pray ionisation (ESI) modes.
Macrocyclic receptors are efficient for coordination
with alkali and alkaline earth metals. But the derivatives
of macrocyclic molecules (calix(aza-)crowns) are also
able to interact with softer di- and trivalent cations. The
schiff-base of calix[4]arenes are also investigated to form
complex with heavy transition metals and lanthanides.
Calixarenes have also been investigated to act as a phos-
phodiesterase enzyme models (13–15). Calixarenes with
group containing nitrogen and sulfur atoms are also found
as an ion-selective electrode sensitive to soft heavy metal
ions such as Ag+, Pb2+ and Hg2+ (16–22). Calixarene can be
functionalized with phosphines, amides and imines. They
come under attractive category that acts as host molecule
for transition metal ions and for the formation of supra-
molecular building blocks (23, 24). The bis-(8-oxyquino-
line)calix[4]arene, Di-aza-benzo crown ether derived from
p-tert-butyl calix[4]arenes species is known to be effective
receptor for Zn2+ ions (25, 26). Calix[6]arene-based receptor
with hydrophobic imidazole cavity displays a remarkable
set of biomimetic properties and binds with Zn2+ ion (27,
28).
2.2. Synthesis of receptor DPPMACA
4-formylpyrazole 4 was synthesised by the reported proce-
dure (29). The calix[4]arene hydrazone 5 was synthesised
by reported procedure (30, 31) (Scheme 1). The lower rim
substituted bis-formylpyrazole calix[4]arene derivative
DPPMACA was synthesised by refluxing 5 (0.8827 mmol)
with formylpyrazole (1.7654 mmol) as in 1:2 M ratio in eth-
anol with 2–3 drops of glacial acetic acid as catalyst for
30 h (Scheme 2). After product formation as observed by
TLC in methanol-chloroform solvent system; the reaction
mixture was cooled at room temperature and precipitated
with the yield of 70%. The solid obtained was recrystallized
with methanol-chloroform. The precipitate was filtered
with whatman filter paper 41, dried in vacuum oven and
subjected to spectral analysis (IR, 1H NMR (Figure S1, Figure
S2), 13C NMR (Figure S3) and mass spectroscopy (Figure
S4). Melting point 250 °C; IR(υmax, cm−1): 3257, 2958, 1699,
1598, 1544, 1485, 1444, 1357, 1296, 1209, 1055, 1H NMR:
δ (ppm) 11.37 (s, 2H, NH, D2O exchangeable), 8.79 (s, 2H,
pyrazole-H), 8.66–8.62 (d, 4H, Ar–H), 8.43 (s, 2H, CH=N),
Herein this paper, we report synthesis and metal cat-
ion binding properties of bis-formylpyrazole calix[4]arene
derivative. The lower rim functionalization of calixarene
with pyrazole has been chosen to design a moiety with the
effective electron density. Oxygen and nitrogen atoms in
calixarene are efficient to bind with Zn2+ ion.
CH3
NHN=C
NHNH2
COCH3
OHC
(i)
(ii)
+
N
N
2. Experimental
1
3
2
2.1. Chemicals and reagents
4
All reagents and solvents were obtained from CDH,
Spectrochem, Merck and Sigma Aldrich. The reagents and
solvents were used without further purification. Thin-layer
chromatography was performed on silica gel 60 F254 sili-
ca-aluminium plates, and the plates were visualized using
ultraviolet light.
Scheme 1. (i) ethanol-water acetic acid cat. (ii) poci3/DmF, 50–
60 °c, 5–6 h.
+
OHC
OH
OH
O
N
(iii)
O
OH
OH
O
O
N
2.1.1. Instruments
O
O
O
NH
N
O
NH
H2N
HN
N
The glasswares were dried overnight in an oven before use.
Open capillaries were used to determine melting point and
are thus uncorrected. IR spectra were recorded on ABB
MB 3000 IR Spectrophotometer. NMR data were recorded
on a Bruker AV(III)-400 MHz, with a BBFO probe. All sam-
ples were analysed in CDCl3. The reference values for the
HN
NH2
4
5
N
N
N
N
DPPMACA
Scheme 2. (iii) ethanol/acetic acid cat/refluxed, 30 h.

SUPRAMOLECULAR CHEMISTRY
3
8.22 (s, 2H, OH, D2O exchangeable), 7.84–7.73 (m, 4H, ArH),
7.66–7.64 (d, 2H, Ar–H), 7.54–7.44 (m, 6H, Ar–H), 7.40–7.31
(m, 4H, Ar–H), 7.14, (s, 4H, Ar–H), 6.92(s, 4H, Ar–H), 4.19 (s,
4H, –OCH2–), 3.86–3.82 (d, 4H, –Ar–CH2–Ar–), 3.39–3.35
(d, 4H, –Ar–CH2–Ar–), 1.33(s, 18H,-CH3), 1.05(s, 18H, –CH3).
13C NMR (75 MHz, CDCl3): δ(ppm); 182.75, 132.00, 129.57,
128.95, 128.81, 128.75, 128.81, 128.75, 125.190, 119.42,
119.34, 117.20, 78.12, 77.34, 76.71, 34.18, 31.62, 30.94.
MS-ESI-TOF (m/z) for C80H84N8O6 Calcd: 1252.6513 (M);
Found: 1253.2372 (M + 1)+ (Figure S4).
cut-off distance of 9.0 A (37), and long range electrostatic
interactions. For detailed analysis, 1000 frames were gen-
erated during 10 ns in the trajectory and captured every
10 ps time step. Furthermore, the structural changes and
dynamics behaviour of the complex were investigated by
estimating the root mean square deviation (RMSD), total
energy (E Total).
The Becke 3-parameter exchange functional together
with the Lee–Yang–Parr correlation functional (B3LYP) (38,
39) was used for all the calculations in the density functional
theory (DFT) method. In some previous reports, The B3LYP
functional has been successfully utilized for geometry opti-
misation of transition metal complexes (40–43). The general
basis sets were used for the complex DFT calculation. The
[B3LYP/6-31+G(d-p)/LANL2DZ] LANL2DZ relativistic pseu-
dopotential was used for the zinc metal ion, while the C, H, N,
O and S atoms were described by the 6-31+G(d-p) (43–45).
The DPPMACA and metal complexes were demonstrated
using Avogadro version 1.2.0 software (46). The gas phase
geometry optimizations were carried out without symmetry
constraint by using the Gaussian 09 W software (32).
The electronic structure calculations, thermodynamic
parameters were obtained from the geometry optimised
structure. The frontier molecular orbital (FMO) energies,
the energy of the lowest unoccupied molecular orbitals
(ELUMO) and the energy of the highest occupied molecular
orbital (EHOMO), of the studied metal complexes are calcu-
lated. The absorption spectra calculated usingTD-DFT level
of theory. The effect of solvent (THF) was systematically
monitored for all the steps via conductor-like Polarizable
Continuum Model (CPCM).
2.3. Computational methodology
The Geometry were optimised using Gaussian at den-
sity functional level (DFT) B3LYP/6-31G* of theory (32).
The Visualization of prior Geometry optimised structure
and Geometry optimised structure were done using
Schrodinger suite. The optimised structure was used as
starting host (DPPMACA) and Zn+2 as a guest for docking
in Hex 8.0 software (33).
The Fast Fourier transformation algorithm of rigid
DPPMACA approached with spherical polar Fourier basis
functions and grid sampling was accomplished to evolve
the 1D, 3D and 5D orientations. The computational anal-
ysis was carried out to emphasise the best pair wise inter-
actions between the host and guest molecules through
rotational correlation over angular terms in a constrained
search space approach. The inclusion complex of host and
guest was utilized for the superimposition to decipher the
3D knowledge based shapes energy scores calculation.
Thereafter, the best docked pose was retrieved from the
top ten scored clusters. The lowest energy pose was taken
as an input for Molecular dynamics stimulation using the
Desmond Program version (academic version) (34, 35).
To build the system, simple Point Charge water was
preferred as a solvent with optimisation potential for liq-
uid simulation, all atoms force field 2005 (36) in the cubic
periodic box (10 × 10 × 10) size followed by neutralisa-
tion process through Na+ and Cl− counter ions. The docked
host-guest complex was selected with 5036 atoms and
1619 water molecules proceeded by restraining steps
through system minimisation and pre-equilibrium to
relax the system initially. Ten nanosecond time interval was
chosen for the molecular dynamic (MD) simulations with
relaxation time of 2 ps at constant temperatures of 300 K,
pressure 1.03215 bar with Nose-Hoover thermostat and
Martyna-Tobias-Klein Barostat method having constant
volume and shape ensemble (NVT). In the simulation
process, Smooth Particle Mesh Ewald method (37) (with a
10−9 tolerance limit) was employed to decipher the long
range electrostatic interactions along with short-range
2.4. General procedure for the detection of cations
by spectrophotometry
Stock solutions of DPPMACA (10 μM) and the sulphate
salts (10 μM) of various metal ions [Zn2+, Y3+, Eu3+, Dy3+,
Na+, Nd3+, Fe2+, Cd2+, Al3+, Be2+, La3+, Cu2+ and K+ ions] were
prepared in THF-H2O (1:1 v/v) as the solvent system. In a
5-mL volumetric flask, 2.5 mL of the DPPMACA solution
and 2.5 mL of metal salt stock solutions were combined
so that the effective concentrations of both DPPMACA and
metal ions were same. Absorption studies were performed
using the as prepared solutions. A Job’s plot (Figure 4) and
Benesi–Hildebrand plot (Figure 5) were also performed
based on the absorption studies to establish the stoichi-
ometry and association constant of receptor-metal. UV/
VIS spectra (electronic spectra) of receptor and metal ions
with receptor were recorded on T 90 (PG Instruments Ltd)
UV/VIS spectrometer in the region 700–200 nm THF:H2O
solvent system.

4
B. MOHAN ET AL.
absorption spectra at 280 nm band due to π–π* transition
in both rings.
3. Result and discussion
3.1. Evaluation of DPPMACA for ionic recognition
The effect of different metal ions with respect to zinc
metal ion was also checked at the same concentration
(Figure 2) (47). The results showed that the presence of
other metal ions (Y3+, Eu3+, Dy3+, Na+, Nd3+, Fe2+, Cd2+, Al3+,
Be2+, La3+, Cu2+ and K+) with Zn2+ metal ions had a minimal
effect on the absorption spectra of DPPMACA + Zn2+ ions.
Also UV-vis titration was carried out; gradual addition
of Zn2+ ions (0–5 equivalent) led to a decrease in absorb-
ance of band at 280 and 230 nm with appearance of a new
band at 294 and 244 nm and an isosbestic points at 261
and 237 nm (Figure 3). The formation of inferred isosbestic
points indicated that a new species was formed and the
The synthesised molecular receptor DPPMACA was eval-
uated for cation binding ability by UV–visible spectros-
copy using THF-water as solvent. The titration of receptor
DPPMACA were carried out in THF:H2O (1:1 v/v) by add-
ing sulphate salts of Zn2+, Y3+, Eu3+, Dy3+, Na+, Nd3+, Fe2+,
Cd2+, Al3+, Be2+, La3+, Cu2+ and K+ metal ions (Figure 1). The
UV–Vis absorption spectrum of the receptor DPPMACA
(10 μM) exhibits absorption bands at λmax, 230 and 280 nm,
respectively (Figure 1). There was a negligible response
upon the addition of Y3+, Eu3+, Dy3+, Na+, Nd3+, Fe2+, Cd2+,
Al3+, Be2+, La3+, Cu2+ and K+ metal ions as their sulphate
salt. When Zn2+ ions was added to receptor DPPMACA
then a bathochromic shift was observed in absorption
spectra of receptor DPPMACA from 280 to 294 nm, 230 to
244 nm and a decrease in absorbance with isobestic point
261 and 237 nm. Upon addition of Zn2+ ions to a solu-
tion of receptor DPPMACA, a decrease in absorbance and
shifting in absorption maxima was noticed due to interac-
tion of Zn–O and Zn–N of lower rim calixarene (Table 1).
Phenolic and pyrazole group present in calixarene shows
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
1.5
1.4
200
250
300
350
400
450
1.3
1.2
1.1
1.0
Figure 2. (colouronline) observed interferencestudyof themetal
cations (y3+, eu3+, Dy3+, Na+, Nd3+, Fe2+, cd2+, al3+, Be2+, la3+, cu2+
and K+) with Dppmaca + Zn2+ ions (10 μm) in thF: h2o (1:1 v/v)
as solvent system at same concentration.
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
200 220 240 260 280 300 320 340 360 380 400 420 440
Figure 1. (colour online) uV-vis spectra of receptor Dppmaca
(10 μm) with Zn2+, y3+, eu3+, Dy3+, Na+, Nd3+, Fe2+, cd2+, al3+, Be2+
,
la3+, cu2+ and K+ used as their sulphates in thF:h2o (1:1 v/v) as
solvent system.
Table 1. Docking result analysis.
0.0
220 240 260 280 300 320 340 360 380 400 420
Interaction of
molecule
No
Name of interaction
Distance (Å)
1
2
3
4
5
Zn–o
Zn–o
Zn–o
Zn–o
Zn–N
metal-acceptor
metal-acceptor
metal-acceptor
metal-acceptor
metal-Donor
2.41
2.15
1.87
1.85
1.65
Figure 3. (colour online) uV-vis spectra of receptor Dppmaca
(10 μm) with increasing concentration of Zn2+ ions in thF: h2o
(1:1 v/v) as solvent system.

SUPRAMOLECULAR CHEMISTRY
5
transition between the free and the complexed species in
the solution. It was envisioned that the synthesised cavity
derived from diphenyl-pyrazolyl might be of 1:1 stoichi-
ometry of DPPMACA:Zn2+ ions, indicating an equilibrium
between DPPMACA and its Zn2+ complex THF: H2O (1:1
v/v) as solvent system (48). The Job’s plot (Figure 4) and
Benesi–Hildebrand plot (Figure 5) reveals the formation of
a complex between DPPMACA and Zn2+ ions with 1:1 sto-
ichiometry (49, 50). Also complexation of DPPMACA-Zn2+
was determined by MS-ESI spectroscopy DPPMACA
(MS-ESI-TOF (m/z) for C80H84N8O6 Calcd: 1252.6513 (M);
Found: 1253.2372 (M + 1)+ (Figure S4) and MS-ESI-TOF
(m/z) for DPPMACA-Zn2+ complex found 1314.1831and
m/z 1253.1522 for DPPMACA (Figure S5). Mass spectros-
copy is found to be in good agreement with the proposed
structures of receptor DPPMACA-Zn2+ complex. The mass
study of complexation is evident for 1:1 complexation of
the DPPMACA-Zn2+. The binding affinity, which was cal-
culated by the Benesi–Hildebrand using the absorption
spectra found to be 6.438 × 103 M−1.
3.2. Docking
Geometry optimisation (Figure 6) was carried out through
the Gaussian 09 program package and Figure 7 confirms
the optimisation steps with energy fluctuation. Molecular
docking was performed to evaluate the binding mecha-
nism of DPPMACA complex with zinc metal ion to corre-
late the quenching mechanism. Figure 8 shows the top
Figure 4. (colour online) Job plot for Dppmaca-Zn2+ complex
in thF-h2o (v/v = 1/1) solvent system. ([Dppmaca] + [Zn2+]) =
20 × 10−6 m at λmax = 280 nm.
Figure 6. (colouronline) Geometryoptimised imageof Dppmaca.
Figure 5. (colour online) B-h plot at 280 nm of receptor Dppmaca
and Zn2+ ion. using Benesi–hildebrand method employing 1/
(A− Ao) = 1/(A− Af) + 1/K(A− Af)[Zn2+] equation and observed
linearity in the plot which indicated the formation of a 1:1
complex with association constant 6.438 × 103 m−1
.
Figure 7. (colouronline) Dppmaca geometryoptimisation graph.

6
B. MOHAN ET AL.
Figure 8. (colour online) molecular docking posese of Dppmaca_Zn2+ complex.
view as well as front view of docked complex. The Zn2+
molecules were reacted as a guest which bound with the
host (DPPMACA). Five significant interactions (Table 1)
were identified by docking analysis and four of them were
metal acceptor while 1 was metal donor within the range
of 1.65–2.41 Å (Table 1). The docked compound remained
in the centre of the host compound which was the main
aspect of the binding with metal acceptor groups. So,
these results show the detection of metal ion with host
compound. Figure 4 Different views allowed to decipher
the binding affinity of Zn2+ compound with selected target
very deeply.
3.3. Molecular dynamics
Molecular dynamics (MD) simulations were implemented
to gauge the structural stability and integrity of host-
guest inclusion complex for 10 ns time trajectories. MD
simulations were executed in water solvent with constant
shape and volume at room temperature to understand
the behaviour and interactions of host-guest inclusion
complex during the whole event which reveals the total
energy, potential energy, temperature, volume, pressure,
RMSD, root mean square fluctuations, intramolecular
H-bond and radius of gyration (rGyr) at various time tra-
jectories (Figure S8).

SUPRAMOLECULAR CHEMISTRY
7
The average total energy value, potential energy value
was given in Table 2. Figure 9 shows the event analysis
of host-guest inclusion complex after the completion
of MD simulation event which clearly depicts the major
fluctuation in volume parameter within the range of
50,000–52,000 value while rest of all remained in between
−204.861 and 500 value range. Different types of energies
were obtained from event analysis, ranging from −200 to
500 kcal/mol which shows the changes occurred during
the whole event were consolidated by the aforesaid range
to make the complex stable. The most structural change
was notified in RMSD values which had not affected the
confirmation of host-guest inclusion complex and the
average range was 0.75 to 4.8 Å. After the 9 ns time inter-
val the drastic change was observed in the confirmation of
host-guest inclusion complex with the decreased numbers
of RMSD values. Intra-hydrogen bonds were found dur-
ing whole event that supports binding mechanism. Event
analysis energy value during 0–10 ns has been calculated.
Furthermore, a steady RMSD trajectory value with a small
change in the position in the Zn2+ atoms clearly specified
that the stability of the complex throughout the length
of the simulation run. No major fluctuations in the rGyr,
MolSA, SASA, and PSA plots were detected, which again
established the compactness and steady exposure of Zn2+
for a favourable conformational cavity of the DPPMACA
(Figure S9, Figure S10).
3.4. DFT calculation
Absorption spectra at the TD-DFT level of theory:
The nature of the absorption spectra was highlighted
via the quantum mechanical studies based on TD-DFT.
Experimental and theoretical lowest energy transitions
(λmax) were perceived by analysing the nature of these
transitions from the topologies of the Kohn–Sham orbit-
als. The FMO’s of DPPMACA can be found in Figure 8, and
the maximum wavelength absorption (λmax) is presented
in Table 3. It was clearly observed (Figure 10) that the UV
spectra emerged due to the electronic transitions from an
amalgam of higher energy orbitals (HOMO-19, HOMO-10,
HOMO-3, and HOMO) to lower energy orbitals (LUMO+1).
Note that HOMO and LUMO was distributed on moiety
substituents of DPPMACA. During the transitions, the distri-
butions of LUMOs were not considerably affected even for
other excited states. The significant electronic conjugation
Table 2. Simulation quality analysis result.
Average
SD
Slope (ps−1
)
total energy (kcal/mol)
potential energy (kcal/mol)
temp.(K)
−13014.535
−16032.925
298.793
−8.149
51429.914
47.058
36.867
1.732
127.687
137.616
−0.000
−0.000
0.000
0.001
0.001
pressure (bar)
Volume (cm3)
Figure 9. (colour online) root mean square deviation (rmSD), radius of gyration (rGyr), molecular surface srea (molSa), solvent accessible
surface area (SaSa), and polar surface area (pSa) of the complex over a time period of 10 ns.

8
B. MOHAN ET AL.
Table 3. main singlet vertical electron transition energies (ΔE), wavelengths (λ), oscillator strengths (f), and calculated at the tDDFt/
camB3lyp level.
Sr. no.
Name
Excitation (eV)
λexcitation
Oscillator strength
Key transitions
% Contribution
λexp
1
Dppmaca
4.3858
282.7
0.9379
homo-19→homo
homo-10→homo
homo-3→homo
homo-1→lumo+1
homo-5→lumo+6
homo-2→lumo
homo-2→lumo+1
homo-2→lumo+2
homo-2→lumo+3
homo-2→lumo+6
homo-2→lumo+15
homo→lumo+6
2.03
9.90
51.92
21.93
2.74
5.20
24.16
4.01
10.42
25.69
2.55
280
2
Dppmaca_Zn
4.1903
296.57
0.1033
294
2.02
Figure 10. (colour online) molecular orbital representation of receptor (Dppmaca) obtained at the cpcm-tD-cam-b3lyp/6-31+G(d-p)
level of approximation.
between calixarene and moiety (DPPMACA_Zn) is mainly
due to the shifting of the electron density from HOMO-1
to LUMO+1 in the first excited state. However, other tran-
sitions were also possible that originated from HOMO and
other lower energy orbitals. Also, the FMO of DPPMACA
complex with Zn metal ion depicted in Figure 11, maxi-
mum wavelength absorption (λmax) is presented in Table
1. It was perceived that the UV spectra emerged due to the
electronic transitions from an amalgam of higher energy
orbitals (HOMO-5, HOMO-2, and HOMO) to lower energy
orbitals (LUMO, LUMO+1, LUMO+2, LUMO+3, LUMO+6,
and LUMO+15) (Figure 11). It was clearly identified that
the UV-vis spectra of DPPMACA gives a bathochromic shift
of 14 nm with Zn2+ metal ion due to complexation. The
oscillator strength of these transitions was found to be
feeble due to the non-bonded nature of the complex.

SUPRAMOLECULAR CHEMISTRY
9
Figure 11. (colour online) molecular orbital representation of Dppmaca complexed with Zn metal obtained at the cpcm-tD-cam-
b3lyp/6-31+G(d-p) level of approximation.
Although many techniques are available for the determi-
nation of Zn2+ but due to easiness in handling, low cost,
good sensitivity, reliability and availability of instruments,
the spectrophotometry gains popularity over other tech-
niques. Computational discernments were provided to
understand the interaction behaviour/mechanism of
DPPMACA with Zn2+ ions via molecular docking followed
by dynamics studies. Zn2+ was stabilized by the non-co-
valent interaction achieved by the cavity of DPPMACA.
Importantly, the electronic transitions observed in the
excitation spectrum were generated from the shifting
of the electron density of HOMOs to LUMOs of Zn2+ to
4. Conclusion
In this paper an investigation was carried out to deter-
mine the probability of DPPMACA as a receptor for Zn2+
ions. The synthesised Bis-(1,3-diphenyl-pyrazolyl methyl-
ene acetohydrazide)Calix[4]arene (DPPMACA) has been
characterised by various spectral methods and it shows
strong recognition potential for Zn2+ ions on evaluation
with several metal sulphates. The stoichiometry was found
to be 1:1 with stability constant 6.438 × 103 M−1. The host
guest interaction was also determined by computational
methodology, molecular dynamics and DFT calculations.

10
B. MOHAN ET AL.
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The authors gratefully acknowledge the financial assistance
provided by UGC and CSIR, New Delhi, India to carry out this
work. Authors are thankful to Materials Research Centre, MNIT
Jaipur for providing spectral facilities. Access to computing and
storage facilities owned by parties and projects contributing
to the National Grid Infrastructure MetaCentrum provided un-
der the Programme ‘Projects of Large Research, Development,
and Innovations Infrastructures’ (CESNET LM2015042) Czech
republic, is greatly appreciated. Gratitude to acknowledge
DST-SERB, New Delhi through the project scheme SERB REF. No
EMR/2016/001958 for providing Dell Precision Tower 5810 has
been used for molecular dynamics stimulation. Configuration
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Disclosure statement
(21) Prodi, L.; Pivari, S.; Bolletta, F.; Hissler, M.; Ziessel, R. Eur. J.
Inorg. Chem. 1998, 1959–1965.
No potential conflict of interest was reported by the authors.
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Funding
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M.I. J. Chem. Soc., Chem. Commun. 1995, 929.
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This work was financially supported by by UGC and CSIR, New
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ORCID
Krunal Modi
Lakhbeer Singh Arora
http://orcid.org/0000-0002-1151-1207
http://orcid.org/0000-0001-7688-4947
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