Exploration of synthesis, structural aspects, DFT studies and bio-efficacy of some new DHA-benzohydrazide based copper(II) complexes

Article abstract of DOI:10.1016/j.molstruc.2020.129460

A copper (II) complex with ligand obtained by the dehydrative condensation of 3-acetyl-6-methyl-2H-pyran-2,4(3H)?dione (DHA) and benzohydrazide has been synthesized (4). This species was additionally coordinated by various solvent molecules, namely ethano

Full text of DOI:10.1016/j.molstruc.2020.129460

Journal Pre-proof
Exploration of synthesis, structural aspects, DFT studies and
bio-efficacy of some new DHA-benzohydrazide based copper(II)
complexes
Richa , Sunil Kumar , Jayant Sindhu , Poonam Choudhary ,
Sundeep Jaglan , Ennio Zangrando , Rakesh Kumar ,
Subash C. Sahoo , Vinod Kumar , Surinder K. Mehta ,
Ramesh Kataria
PII:
S0022-2860(20)31775-0
DOI:
Reference:
https://doi.org/10.1016/j.molstruc.2020.129460
MOLSTR 129460
To appear in:
Journal of Molecular Structure
Received date:
Revised date:
Accepted date:
18 August 2020
13 October 2020
14 October 2020
Please cite this article as: Richa , Sunil Kumar , Jayant Sindhu , Poonam Choudhary ,
Sundeep Jaglan , Ennio Zangrando , Rakesh Kumar , Subash C. Sahoo , Vinod Kumar ,
Surinder K. Mehta , Ramesh Kataria , Exploration of synthesis, structural aspects, DFT studies
and bio-efficacy of some new DHA-benzohydrazide based copper(II) complexes, Journal of Molecular
Structure (2020), doi: https://doi.org/10.1016/j.molstruc.2020.129460
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Highlights

Solvent coordinated Cu(II) complexes (5a-5g) have been synthesized and characterized by X-ray diffraction
analysis.


Copper is tetra-coordinated by chelating carbohydrazide ligand and coordinated solvent.
The intermolecular interactions revealed the importance of O-H interactions in self-assembly and the higher
chemical stability of 5c was established by DFT studies.

Compound 5f shows potent antibacterial activity against B. subtilis with MIC and MBC value of 32 M.

Exploration of synthesis, structural aspects, DFT studies and bio-efficacy of some new
DHA-benzohydrazide based copper(II) complexes
Richaa, Sunil Kumarb, Jayant Sindhuc, Poonam Choudharyd, Sundeep Jagland, Ennio Zangrandoe,
Rakesh Kumara, Subash C. Sahooa, Vinod Kumar f, Surinder K. Mehta a, Ramesh Katariaa*
aDepartment of Chemistry and Centre for Advance Studies in Chemistry, Panjab University, Chandigarh-160014, India
bDepartment of Chemistry, School of Basic and Applied Sciences, Maharaja Agrasen University, Baddi, Solan-174103,
India
cDepartment of Chemistry, COBS & H, CCS Haryana Agricultural University, Hisar-125004, India
dMicrobial Biotechnology Division, CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu-180001, India
eDepartment of Chemical and Pharmaceutical Sciences, University of Trieste, Trieste 34127, Italy
fDepartment of Chemistry, C. U. Haryana, Mahendergarh-123031, India
Email: rkataria@pu.ac.in
ABSTRACT
A copper (II) complex with ligand obtained by the dehydrative condensation of 3-acetyl-6-methyl-2H-pyran-
2,4(3H)-dione (DHA) and benzohydrazide has been synthesized. The complex species are additionally
coordinated by various solvent molecules, namely ethanolamine, methanol, DMF, dimethyl amine, isopropyl
amine, diisobutylamine, and ethylenediamine (5a-5g) have been synthesized. All the complexes were
characterized by single crystal X-ray diffraction analysis and other analytical techniques. In each case, the
copper atom is tetra-coordinated by chelating carbohydrazide ligand through O, N, O donor atoms and the
N/O heteroatom from the coordinated solvent (except for ethylenediamine, where Cu is pentacoordinated).
The intermolecular interactions present in each complex have been quantified using Hirshfeld surface
analysis, and the electrostatic properties associated with these complexes were calculated using DFT studies.
Considering the expected bioactivity of carbohydrazide derivatives, the antibacterial activity of ligand and
copper complexes was tested against pathogenic Gram-positive and Gram-negative bacteria using
ciprofloxacin as positive control. Compound 4 and 5f shows potent antibacterial activity against B. subtilis
with MIC and MBC value of 32 M
Keywords: Antibacterial, Copper complex, Carbohydrazide, DFT, X-ray crystal structure
1
INTRODUCTION
Design and synthesis of bioinorganic compounds of biological interest has attracted considerable interest in
past few years. The pharmacokinetic and pharmacodynamic properties of an agent are dependent upon
solubility and bio-availability, which can be significantly enhanced by complexation. [1,2] It has been well
evident in the literature that the bioactivity of metal complexes surpasses organic ligands. Choosing proper
ligand and its chelation with suitable metal complex are some of the key factors for controlling the biological

efficacy of compounds. Copper complexes have also been explored as catalyst in asymmetric photoredox
reactions [3], hydroalkylation of alkynes [4], alcohol oxidation [5] and C-H activation in the Henry reaction
[6]. In addition, many sensing applications have utilized copper complexes for the detection of hydrogen
peroxide and nitrite [7], adrafinil [8] and dissolved oxygen in water.[9] In addition to this a wide range of
biological activity has been associated with copper complexes [10–12] which have attracted scientific
community to develop novel, selective and less toxic copper compounds with promising biological
properties.
Similarly, pyrones consist of a diverse group of bioactive metabolites, viz. cytotoxic, antialgal, antibacterial,
and antifungal activity.[13–16] Recently, Marc Stadler and his coworkers isolated new α-pyrone derivatives
(Ia-Ib), udagawanones A and B, isolated from cultures of the endophyte Neurosporaudagawae, which were
moderately active against fungi and mammalian cells[17]. Li et al. isolated two new Pleospyrones analogues
(chlamydosporol derivatives) from the culture of the endophytic fungus Pleosporales sp. Sigrf05. [18] These
analogues (IIa and IIb) exhibited good cytotoxicities against various cancer cell lines. Analogues of Maltol,
a natural product that exhibits in vitro antiproliferative activity against cancer cell lines have been
synthesized [19,20]. A copper complex (III) of Maltol a natural product exhibits in vitro antineoplastic
activity against HeLa cell lines when performed using MTT assay. [21]
Figure 1: Structures of some bioactive compounds
Non-covalent interactions have extensive applications in different fields of science.[22] Since the
physiological properties associated with a material greatly differ due to the presence of some peculiar non-
covalent interactions. [23] The biological function associated with a bio-macromolecule can be qualitative
explored in order to identify the existence of non-covalent interactions. [24–26] In addition, molecular
recognition, being one of the fundamental biological step, is also governed largely by non-covalent
interactions. Exploration of non-covalent interactions will help in fine-tuning the biological role associated
with a molecule and opens new horizons for developing new generation of biologically significant
molecules.[27] In continuation of our interest in the field of metal complex chemistry [28–30] we herein,
explored the synthesis, non-covalent interactions, electrostatic properties and antibacterial potential of copper

complexes of carbohydrazide of pyrone (DHA) through solvent binding/complexation. The study was aimed
at exploring the biological potential of newly synthesized solvent coordinated copper complexes and their
comparison with the initially formed copper complex.
2
Experimental
2.1 General methods and materials
Dehydroacetic acid (DHA) and ethyl benzoate were purchased from Sigma Aldrich and used without further
purification. Methanol and N,N-dimethylformamide were obtained from Fischer Scientific Pvt. Ltd.
Isopropylamine, ethylene diamine, ethanol amine, di-isobutylamine, dimethylamine and anhydrous copper
acetate were purchased from Avra chemicals and used as supplied.
2.2 Instrumentation
Elemental analysis was performed on FLASH EA 1112 Series CHNS Analyzer. The FTIR spectra were
recorded on Perkin-Elmer FTIR 2000 spectrometer. The thermal gravimetric analysis (TGA) was carried out
on SDT Q600 (V20.9 Build 20) instrument (Artisan Technology Group, Champaign, IL) under N2
atmosphere. Single crystal X-ray diffraction data were collected using a Super-Nova diffractometer equipped
with a micro-focus sealed tube. HRMS of all synthesized solvated complexes (5a-5g) was recorded on LC-
MS Spectrometer Model Q-ToF (Figure 6S-12S, Table 15S). Antibacterial activity of the title compounds
was carried out at IIIM-CSIR, Research Institute in Jammu, India.
2.3 Synthesis of ligand and complexes
2.3.1 Synthesis of benzohydrazide (1)
To a stirred solution of ethyl benzoate in ethanol, an ethanolic solution of hydrazine hydrate was added
dropwise. The reaction mixture was then refluxed for 7-8 h and the precipitate thus formed was allowed to
cool at room temperature and collected through filtration, washed thoroughly with cold ethanol to give pure
benzohydrazide. Yield: 87%; melting point: 112-114°C (lit. mp [31]: 115 °C); IR (max, cm-1): 3353, 3325,
1643, 1590.
2.3.2 Synthesis of ligand DHB (3)
The benzohydrazide (1) formed was dissolved in a 50 mL round bottom flask using ethanol. To this an
ethanolic solution of dehydroacetic acid (2) was added and the resulting reaction mixture was refluxed for 3 h
at 80 °C and then stirred for 24 h at room temperature. The yellow solid thus obtained was filtered and
recrystallized from hot ethanol. The precipitate thus formed was filtered under vacuum, washed with cold
ethanol, and dried in vacuum as per the literature reported method. [32] Yield 91%; IR(νmax, cm-1): 3153

(NH),1639 (C=N); Elemental analysis calculated for C15H14N2O4: C, 62.93; H, 4.93; N, 9.79. Found C,
62.85; H, 4.98; N, 9.84.
2.3.3 Synthesis of metal complex 4
To an ethanolic solution of (E)-N-(1-(2-hydroxy-6-methyl-4-oxo-4H-pyran-3-yl)benzohydrazide (3) a hot
ethanolic solution of [Cu(OAc)2].H2O was added with constant stirring (metal-ligand ratio of 1:1). The
reaction mixture was refluxed for 1 h and further stirred for 24 h at room temperature. The resulting green
precipitates were filtered and then dried in an oven. The resulted precipitate in ethanolic solution kept at
room temperature for evaporation, afforded rod shaped blue crystals after 2 days.
2.3.3.1 Synthesis of solvated metal complex 5a
Ethanolamine was added dropwise to a hot methanolic solution of copper complex (4). Clear solution of the
reaction mixture was obtained after heating at 60°C. The solution was kept at slow evaporation at room
temperature, and needle shaped crystals were obtained after one week. Yield 60%; IR (νmax, cm-1): 3372,
3280, 2941, 1674, 1639, 1557, 1515, 1442, 1348, 1255; Elemental analysis calculated for C17H19CuN3O5: C,
49.94; H, 4.68; N, 10.28. Found C, 49.90; H, 4.62; N, 10.23; HRMS (m/z): Calcd:408 Found:409.06[M+H]+
2.3.3.2 Synthesis of solvated metal complex 5b
A clear solution was formed when methanol (20 mL) was added dropwise to the conical flask containing
copper complex (4). The content of the flask was heated gently at 60°C. Block shape crystals suitable for
single-crystal X-ray diffraction were obtained by evaporating the solution at room temperature for five days.
Yield 70%; IR (νmax, cm-1): 3542, 3399, 3056, 1671, 1615, 1585, 1557, 1445, 1350, 1239; Elemental analysis
calculated for C16H16CuN2O5: C, 50.59; H, 4.25; N, 7.37. Found C, 50.51; H, 4.15; N, 7.29; HRMS (m/z):
Calcd: 379 Found: 380.04 [M+H]+
2.3.3.3 Synthesis of solvated metal complex 5c
DMF was added dropwise to a hot methanolic solution of copper complex (4) till the solution became clear
and then gently warm the mixture at 60°C. Needle shaped crystals suitable for single crystal X-ray diffraction
were obtained on slow evaporation for 10-11 days. Yield 58%; IR(νmax, cm-1): 3546, 3403, 3051, 1671, 1617,
1557, 1523, 1445, 1351, 1239; Elemental analysis calculated forC18H19CuN3O5: C, 51.36; H, 4.55; N, 9.98.
Found C, 51.31; H, 4.52; N, 9.94; HRMS (m/z): Calcd: 420 Found: 421.53 [M+H]+
2.3.3.4 Synthesis of solvated metal complex 5d
To the hot methanolic solution (10 mL) of copper complex (4), dimethyl amine was added dropwise till the
solution becomes and heat the solution at 60°C. Needle shaped crystals were obtained on slow evaporation of
the solvent at room temperature after 20 days. Yield 65%; Elemental analysis calculated for C17H19CuN3O4:

C, 51.97; H, 4.87; N, 10.70; Found C, 51.91; H, 4.80; N, 10.66; HRMS (m/z): Calcd: 392 Found: 393.08
[M+H]+
2.3.3.5 Synthesis of solvated metal complex 5e
To a conical flask containing 10 mL of methanolic solution of copper complex (4), isopropyl amine was
added dropwise till the solution becomes clear and heated the solution at 60°C. Needle shape crystals suitable
for single-crystal X-ray diffraction were obtained by evaporating the solution at room temperature for two
weeks. Yield 76%; IR (νmax, cm-1): 3325, 3272, 2978, 1679, 1645, 1562, 1515, 1444, 1351, 1189; Elemental
analysis calculated for C18H21CuN3O4: C, 53.13; H, 5.20; N, 10.33; Found C, 53.06; H, 5.15; N, 10.30;
HRMS (m/z): Calcd: 406 Found:407.09 [M+H]+
2.3.3.6 Synthesis of solvated metal complex 5f
To a hot methanolic solution (10 mL) of copper complex (4), di-isobutylamine was added dropwise till the
solution become clear and heated the solution at 60°C. The solution was kept for slow evaporation at room
temperature. Needle shaped crystals were obtained after two weeks. IR (νmax, cm-1): 3348, 2958, 1684, 1662,
1557, 1518, 1445, 1347, 1230; Elemental analysis calculated for C23H31CuN3O4: C, 57.91; H, 6.55; N, 8.81.
Found C, 57.87; H, 6.50; N, 8.78; HRMS (m/z): Calcd: 476 Found: 477.16 [M+H]+
2.3.3.7 Synthesis of solvated metal complex 5g
Ethylene diamine was dropwise added to the hot methanolic solution of the copper complex (4) till it became
clear and heated the solution at 60°C. The solution was allowed to kept at slow evaporation at room
temperature. Needle shaped crystals suitable for single crystal X-ray diffraction was obtained after two
weeks. IR (νmax, cm-1): 3390, 3248, 3158, 2864, 1683, 1561, 1513, 1444, 1348, 1168; Elemental analysis
calculated for C17H20CuN4O4: C, 50.06; H, 4.94; N, 13.74. Found C, 50.02; H, 4.90; N, 13.69; HRMS (m/z):
Calcd: 407 Found: 407.96 [M+H]+
2.4 Antimicrobial activity
The compounds (3,4 and 5) were evaluated for their antibacterial and antifungal activity against four
bacterial lines, Gram-positive Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, and Gram-
negative Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853) and two fungal strains
(Aspergillus niger ATCC 16404, Candida albicans ATCC 24433). The antibacterial and antifungal assays
were performed in accordance with the procedures outlined by Clinical and Standards Institute (CLSI) [33–
35]. Mueller-Hinton Agar (MHA) and Mueller-Hinton Broth (MHB) was prepared as per the manufacturer’s
instructions (HiMedia Laboratories, India). The pre-cultures of the bacterial strains were prepared in MHB
by fresh inoculums of the cultures incubated at 37°C for 18-24 h, at 100 rpm shaking, to obtain
concentrations of approximately 5 to 6 log CFU/mL (evaluated and adjusted photometrically at 625 nm). The

bacterial suspensions were further diluted with MHB to obtain a final inoculum of 5 × 105 CFU/mL. The
assays were performed in clear 96 well microtiter plates. The compounds were dissolved in DMSO to make a
stock solution of 10 mM. Initially the compounds were screened for antibacterial/antifungal activity at slight
higher concentration (128 µM), and those showing inhibition in primary screening were further tested at
different concentrations to obtain MIC and MBC values (Table 2). Each experiment was accompanied by a
positive control containing broth, pathogen and a known inhibitory compound (Ciprofloxacin); a negative
control containing broth and pathogen. Amphotericin B was used as positive control during antifungal
screening of compounds. The plates were incubated for 24 h at 37°C with agitation and then observations
were recorded visually. The minimum concentration of the compound at which there is no visual growth was
observed is considered as MIC. A loopful inoculum from the wells containing no visual growth was streaked
on the Tryptic Soya Agar media and incubated for 24 h at 37°C to record MBC. In case of fungi, the test was
done in Saubroud Dextrose Broth (SDB) for MIC and Saubroud Dextrose Agar (SDA) for MFC and plates
were kept for 48 h (instead of 24 h as for bacteria). All the experiments were performed in triplicate and the
results were described as their mean.
2.5 X-ray crystallographic analyses
All the crystals were mounted on Hampton cryoloops. Geometric and intensity data for all the crystals were
collected at room temperature using a Rigaku Super-Nova diffractometer equipped with a micro-focus sealed
X-ray tube with Mo-Kα radiation (λ=0.71073 Å), and CCD HyPix3000 detector. The CrysAlisPro software
[36] was used for data acquisition and reduction. The absorptions were corrected by SCALE3 ABSPACK
multi-scan method. Using Olex2 package [37], all the structures were solved with direct methods [38] and
refined by the full-matrix least-squares methods based on F2 implemented in ShelXL. [39] The structural
analysis of complexes 5b, 5c and 5g shows the presence of a lattice methanol molecule. Hydrogen atoms
were fixed at geometrical calculated positions except those of alcohol molecules in complex 5b, which were
detected on the difference Fourier map. All the non-hydrogen atoms were refined with anisotropic thermal
parameters. Crystallographic data and details of structural refinements, bond lengths, angles and hydrogen
bond geometric parameters of all complex are summarized in Table S1-S7.
Crystallographic data have been deposited with the Cambridge Crystallographic Data Centre as
supplementary publication no. CCDC-1948211 for complex 4, 1992007, 1992010-13, 1992017, and 1992020
for complexes 5d, 5e, 5a, 5c, 5f, 5b and 5g, respectively. Copies of the data can be obtained free of charge on
application to The Director, CCDC, 12 Union Road, Cambridge CB21EZ, UK (fax: Int. code +(1223)336-
033; e-mail: deposit@ccdc.cam.ac.uk).

2.6 Computational Details
The single point energy calculations were done for all the metal complexes by using Gaussian 09 program
and the coordinates from crystallographic analyses. DFT based method Becke's three parameter hybrid
functional (B3) for the exchange part and the Lee-Yang-Parr (LYP)[40] correlation function at 6-311+G(d)
level was used all C, H, N and O atoms, while LANL2DZ basis set was used for Cu metal.[41] The
visualization of optimized geometry was performed using Avogadro 1.2 package. Crystal explorer program
was used for Hirshfeld surfaces analysis and generating fingerprint plots.
3
Results and Discussion
3.1 Synthesis and characterization
The carbohydrazide ligand
(Z)-N-((E)-1-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)ethylidene)
benzohydrazonic acid (3) was synthesized by the reaction of DHA (2) and benzohydrazide (1) in refluxing
methanol. The benzohydrazide was firstly synthesized from the condensation of ethyl benzoate with
hydrazine hydrate in refluxing ethanol. Ligand 3, thus formed was reacted with copper acetate in the
presence of ethanol to afford the trigonal bipyramidal copper complex 4, showing coordination with two
molecules of ligand and one molecule of water, and their detail structural description reported earlier by our
group. [28] Moreover, the related crystallographic parameters are listed in Tables 1S-2S and X-ray structure
is shown in Figure 1S. Then complex 4 was reacted with equimolar amount of ethanolamine, and it was
observed that the new incoming nucleophilic solvent (characterized by X-ray structural analysis, Figure 2)
replaced the monodentate ligand molecule and aqua species. The structure of all the metal complex
alongwith their synthetic route is shown in Scheme 1.

Scheme 1: Synthetic outline for the synthesis of solvated complexes 5a-5g
Possibly the mono-coordinated carbohydrazide ligand was a labile leaving group which was easily replaced
by the incoming nucleophilic solvent. Then, to generalize the concept of solvation of complex with co-
solvent, an attempt was made to explore the reaction with various amines and other nucleophiles such as
isopropylamine, di-isobutylamine, ethylenediamine, dimethylformamide, and dimethylamine. The structure
of all the synthesized complexes (5a-5g) was confirmed by single crystal X-ray diffraction analysis.
3.1.1 Description of crystal structures
All the complexes have been synthesized with copper (II) salt, doubly deprotonated tridentate ligand H2L
(H2L = N'-(1-(2-hydroxy-6-methyl-4-oxo-4H-pyran-3-yl)ethylidene)benzohydrazide and various amines,
methanol or dimethylformamide and characterized by single crystal diffraction analysis. At our knowledge,
none of the reported copper complexes with this ligand using different solvent have been structurally
reported.
3.1.1.1 Complexes
[Cu(L)(NH2CH2CH2OH)]
(5a),
[Cu(L)(NH(CH3)2)]
(5d),
and
[Cu(L)(NH(CH2CH(CH3)2)2] (5f)
The X-ray structural analysis shows that the complex 5a crystallizes in monoclinic system with space group
C2/c, while 5d and 5f crystallize in triclinic of P-1 space group. In the complexes 5a, 5d and 5f the copper
(II) center exhibits a square planar coordination geometry, realized by the tridentate ligand through the imino

N, the deprotonated OH of pyranone ring and the amide carboxyl oxygen donors, and by a neutral molecule
bound with the primary (in 5a) or secondary amine (5d, 5f) nitrogen donor (Figure 2).
Figure 2: Molecular structure of the complexes 5a, 5d and 5f (ORTEP diagram with 50% probability thermal ellipsoids, 35% for
5f)
The Cu-O bond distances vary from 1.868(2) to 1.907(3) Å, with about 0.02 Å shorter for the lactone
oxoanion O2 and the Cu-N(imino) ones vary from to 1.913(3) to 1.9265(16) Å. On the other side, the Cu-
N(amine) bond lengths appear slightly shorter in 5a, of 1.9882(16) Å, with respect to the values measured in
5d and 5f (2.012(2) and 2.008(3) Å), thus steric effects are prevailing over basicity. The coordination bond
distances reported in Table 4S are indicative of the deviations from ideal values and the O1-Cu-N2 angle in
the five membered ring shows the narrow value of ca. 83°.
In the crystal packing of 5a the complexes are arranged in pair about a center of symmetry where the
ethanolamine alcoholic group of each complex forms a hydrogen bond with oxygen O4 of the symmetry
related species (O5…O4 = 2.773(3) Å). In addition, these dimers are weakly connected through N3-H…O5’’
hydrogen bond (N3…O5’’ = 3.066(3) Å) to give rise to a polymeric arrangement (Figure 3). Complexes 5d
are also connected to form a polymeric arrangement realized by weak N3-H…O4’ hydrogen bonds (Figure 4,
N3…O4’ = 3.166(4) Å). Conventional hydrogen bond parameters for all structures reported are listed in
Table 7S.
Figure 3: Complexes 5a arranged about a crystallographic symmetry center connected by O5-H…O4’ hydrogen bonds and further
by N3-H…O5’’ interactions to form a polymeric arrangement.

Figure 4: Crystal packing of complexes 5d connected by weak N3-H…O4’ hydrogen bonds to form a polymeric chain
3.1.1.2 Complexes
[Cu(L)(CH3OH)]‧(CH3OH)
(5b),
[Cu(L)(dmf)](CH3OH)
(5c),
and
[Cu(L)(NH2CH(CH3)2] (5e)
Complexes 5b and 5c crystallize in triclinic system of P-1space group, both with a lattice methanol molecule,
while complex 5e crystallizes in monoclinic system with P21/c space group. The coordination geometry of
copper ion in all cases is square pyramidal where the basal plane is occupied by the tris-chelating ligand L
through the ONO donor set and one methanol in 5b, a dmf molecule in 5c, an iPr-amine in 5e. Oxygen atom
O4’ (in 5b and 5e) and O1’ (in 5c), of a symmetry related molecule, resides at the apex of the pyramidal
environment (Figure 5), so that in solid state the complexes are centrosymmetric dinuclear species (Figures
2S-4S of supplementary material).
Figure 5: ORTEP diagram of complexes 5b, 5c and 5e with thermal ellipsoids set at 50% probability level
The coordinated bond distances and angles are reported in Table 5S. The Cu-O and Cu-N bond lengths
involving ligand L show comparable trend as that observed in complexes described above, while the Cu-
OCH3 and Cu-O(dmf) are of 1.943(3) and 1.9757(17) Å for 5b and 5c, respectively, which are likely affected
by the H bond with a lattice methanol molecule. The Cu-N3 in 5e is 1.992(2) Å, in accord with the value in
5a (1.9882(16) Å) for a primary amine. The apical Cu-O distances are longer for Jahn-Teller effect, of
2.881(4), 2.6221(18), and 2.678(2) in 5b, 5c and 5e, respectively. Although the former distance appears
rather long, the interaction is apparent by O4 displacement of 0.23 Å from the lactone mean plane towards
the copper atom of the symmetry related complex.

Complexes 5b and 5c crystallize with a lattice methanol molecule, a feature affecting the crystal packing of
both. In 5b the methanol molecule acts as acceptor from the alcoholic coordinated group and as donor
towards oxygen O4’ of a symmetry related molecule (O5…O6 = 2.616(5) Å; O6...O4’ = 2.741(5) Å, Figure
6), thus connecting the complex dimers and forming a polymeric chain, elongated in the direction of axis b.
On the other hand in crystal packing of 5c the methanol molecule is H-bound to oxygen O4 as indicated in
Figure 5 (O6…O4 = 2.803(4) Å).
Figure 6: Polymeric chain built by H-bond in the crystal packing of 5b with indication of the complex dimers connected by Cu-
O4’ bonds. (O4’ at 1+x, -1+y, z; only H atoms involved in interactions are shown)
3.1.1.3 Complex [Cu(L)(en)](CH3OH) (5g)
Complex 5g crystallizes in triclinic system of space group P-1 with a lattice methanol molecule. Figure 7
depicts an Ortep view, while a selection of bond distances and angles are listed in Table 6S.
Figure 7: Molecular structure of complex5g (ORTEP diagram, with 50% probability thermal ellipsoids).
The metal centre is five coordinated in a highly distorted square pyramidal environment realized by the ONO
donor set of tridentate ligand L and by a chelating ethylendiamine. The coordination geometry is confirmed
by the trigonality τ index of 0.03 (being = 0 or 1 for a perfect square pyramidal and trigonal bipyramidal
geometry, respectively).[42] The Cu‒O1, Cu‒O2 and Cu-N2 bond distances of chelating ligand (1.9505(13),
1.9126(14) and 1.9335(17) Å, respectively) follow a trend similar to previous complexes, but all appear
slightly longer. The Cu-N(en) bond lengths of ethylenamine are of 2.0357(17) and 2.2969(17) Å,
significantly different as expected for a square pyramidal copper (II) complex. The bond angles N2-Cu-N4

and N(3) Cu-N(4), of 114.51(6) and 81.62(6)°, are indicative of deviation from an ideal apical position of N4
in the square pyramidal geometry.
The lattice methanol molecule and amine groups generate a one-dimensional hydrogen bonding scheme
forming a polymer developed in the [101] crystallographic direction. The O5…O1 distance is 2.776(2) Å,
while the N-O interactions are weaker, of about 3.0 Å (Figure 8).
Figure 8: 1D polymeric arrangement of complexes 5g connected by H-bonds involving the bridging methanol and amine N3/N4
groups.
The crystal structures of all the complexes do not show any significant π-π interaction among phenyl rings,
and the packing is mainly dominated by H-bonds as described. The coordinated bond distances and angles of
complexes reported are in good agreement with values measured in the two copper complexes comprising an
analogous ligand [43,44].
3.1.2 Hirshfeld surface analysis
In a crystal structure, hydrogen bond donors and acceptors result into intermolecular interactions of variable
range that are responsible for molecular assembly in solid state. These interactions can be explored in a
quantitative manner using Hirshfeld Surface (HS) analysis.[45] In addition to short contacts, the surface
characteristic of molecular systems can also be visualized using HS analysis. The presence of solvent in the
crystal structure effect various intramolecular interactions operative in case of compound. HS were used to
investigate the solvates and voids. In some cases, solvents have a stabilizing effect on the crystal structure of
the compounds. On the other hand, the various intramolecular interactions are also effected by the presence
of a solvent molecule. The total percentage contribution of interaction is larger in the presence of a solvent
that represent the presence of disorder. Cruz Cabeza et al. have demonstrated the role of solvents in
stabilizing crystal structures by computational methods.[46] The phenomenon of formation of isomorphic
desolvates of organic compounds is well-documented in the literature. For example, hydrates that desolvate
yet retain their original crystal lattice, which is less stable than its solvated form, are known for cephalexin,
cefaclor, erythromycin A and spirapril hydrochloride hydrates, to name but a few.[47]

Void refers to isolated cavity filled with solvent or guest molecule and resulted into permanent channels by
their linking in different dimensions. This feature is associated with the porosity of crystals and used for the
transportation of small molecules. The mapping of the procrystal isosurface within a unit cell has been
implemented in Crystal Explorer, volumes within the voids defined in this manner, and their surface areas,
are computed trivially and routinely. The exact isovalues of the procrystal electron density provide physically
meaningful volumes and surface areas of voids in molecular crystals. HS are mapped using color-coded
surfaces with red, blue, and white color. The intermolecular contacts are visualized using dnorm value, where
intermolecular contacts shorter than vdW are associated with a negative dnorm value and represented by red
color, larger with positive dnorm by blue color, while contacts equal to vdW distance are shown by white color
and associated to zero dnorm value. The related π-π interactions among aromatic regions are obtained along a
specific axis by shape index with blue, red, and white colored zones. The curvedness provides information
about the curvature of the surface, where low and large values are associated to flat surface and sharp
curvature, respectively. The larger flat regions have a boundary of blue color. The Hirshfeld surface for 5a
are over di (0.720 to 2.599 Å), de (0.720 to 2.488 Å), dnorm (-0.632 to 1.387 Å), shape index (-0.994 to 0.997
Å) and curvedness (-3.711 to 0.526 Å). The voids present on the surface have volume 419.40 ų with area of
393.95 Ų. The Hirshfeld surface for 5d are over di (0.922 to 2.836 Å), de (0.923 to 2.544 Å), dnorm (-0.325 to
1.484 Å), shape index (-0.998 to 0.995 Å) and curvedness (-3.350 to 0.457 Å). The voids present on the
surface have volume 414.10 ų with area of 385.63 Ų. For compound 5f, HS are over di (1.037 to 2.609 Å),
de (1.037 to 2.501 Å), dnorm (-0.097 to 1.479 Å), shape index (-0.998 to 0.995 Å) and curvedness (-4.477 to
0.748 Å). The voids present on the surface have volume 583.33 ų with area of 488.62 Ų (Figure 9).
Figure 9: Hirshfeld surface analysis of 5a, 5d and 5f

The Hirshfeld surface decomposed into 2D fingerprint to quantify the intra and intermolecular interactions
present in case of 5a, 5d and 5f. It was observed that in all the three cases the major contribution was from
H-H interaction that makes 53.1%, 52.3% and 58.2% of the total contribution made by different interactions
in 5b, 5c and 5e, respectively. The contribution of O-H interaction in case of 5b, 5c and 5e is 22.0%, 18.3%
and 15.7% respectively. The other minor contributions are shown in Figure 10.
Figure 10: 2D fingerprint plot for 5a, 5d and 5f
The Hirshfeld surface for 5b are over di (0.743 to 2.651 Å), de (0.743 to 2.507 Å), dnorm (-0.599 to 1.314 Å),
shape index (-0.995 to 1.000 Å) and curvedness (-4.726 to 0.365 Å).The voids present on the surface have
volume 428.00 ų with area of 401.67 Ų. The Hirshfeld surface for 5c are over di (0.751 to 2.693 Å), de
(0.753 to 2.601 Å), dnorm (-0.583 to 1.283 Å), shape index (-0.997 to 0.996 Å) and curvedness (-3.749 to
0.376 Å).The voids present on the surface have volume 492.50 ų with area of 457.59 Ų. For compound 5e
HS are over di (0.995 to 2.547 Å), de (0.994 to 2.499 Å), dnorm (-0.208 to 1.295 Å), shape index (-0.999 to
0.999 Å) and curvedness (-3.462 to 0.466 Å).The voids present on the surface have volume 449.70 ų with
area of 409.32 Ų (Figure 11).

Figure 11: Hirshfeld surface analysis of 5b, 5c and 5e
The Hirshfeld surface decomposed into 2D fingerprint to quantify the intra and intermolecular interactions
present in case of 5b, 5c and 5e. It has been observed that in all the three cases the major contribution was
from H-H interaction, which makes 69.6%, 51.7% and 55.7% of the total contribution made by different
interactions in 5b, 5c and 5e, respectively. The contribution of O-H interaction in case of 5b, 5c and 5e is
9.8%, 18.9% and 18.3% respectively. The other minor contributions are shown in Figure 12.
Figure 12: 2D fingerprint plot for 5b, 5c and 5e
Finally, the Hirshfeld surface for 5g are over di (0.854 to 2.544 Å), de (0.854 to 2.590 Å), dnorm (-0.431 to
1.738 Å), shape index (-0.999 to 0.998 Å) and curvedness (-3.944 to 0.315 Å). The voids present on the
surface have volume 482.09 ų with area of 424.68 Ų (Figure 13).

Figure 13: Hirshfeld surface analysis of 5g
The HS was further decomposed into fingerprint region where H-H interactions contributes to a maximum of
54.0%. In addition to this, other significant contributions are from O-H and C-H contacts with overall
contribution of 16.0% and 14.8%. The minor contribution of Cu-O, C-C, and N-H contact are recorded with
1.6%, 2.1%, and 1.2%, respectively (Figure 14).
Figure 14: 2D fingerprint plot for 5g
The supramolecular interactions discussed in crystallographic description are responsible for various
polymeric forms in case of all the crystals. Hirshfeld surface analysis was done to explore atom based
interactions present in case of all the complexes. It has been observed that the polymeric forms of all these
crystals are mainly due to potential hydrogen bonding interaction. The higher percentage of O-H type
interaction observed by the decomposition of Hirshfeld surface into 2D fingerprint region supports the
formation of various polymeric arrangement due to potential O-H bonding in all the crystals. Moreover,
various inter and intramolecular interactions present in case of all the metal complexes was calculated using
PARST incorporated in Wingx. The self-assembly of all the metal complexes is primarily due to H-H and O-
H type of interactions. The main D-H---A type interactions present in case of all the metal complexes has
been listed in Table 8S-14S.
3.2 DFT studies
Frontier molecular orbitals HOMO and LUMO and their gap play a significant role in investigating the
kinetic stability and chemical reactivity of a molecule.[48] The ability of a molecule to act as electron donor
and acceptor solely depends upon the distribution of electrons and their energy in HOMO and LUMO.

Materials associated with large HOMO-LUMO gap have large kinetic stability, because it is difficult to add
electrons into high energy lying LUMO orbitals.[49] Thus, compounds associated with large energy gap are
associated with low chemical reactivity. Moreover, the electronic transitions associated with a molecule can
also be explored using the time dependent approach. In order to investigate the electrostatic parameters
associated with the present metal complexes (5a-5g), single point energy was calculated for all of these in
gas phase using by taking the atomic coordinates from crystallographic analyses. In order to formulate a
relationship within electrostatic properties, all the metal complexes have been grouped similarly as done in
crystal studies. In case of compound 5a, the energy of HOMO and LUMO is -5.659 and -1.733 eV,
respectively with an energy gap of 3.926 eV. The energy of frontier molecular orbitals for all other
compounds has been summarized in Figure 15, which reveals that within 1st group, compound 5a has high
chemical stability with an energy difference of 3.926 eV in comparison with 3.845 and 3.895 eV for 5d and
5f, respectively. Similarly, in 2nd group compound 5c is more stable with an energy difference of 3.976 eV in
comparison with 3.221 and 3.923 eV for 5b and 5e, respectively. Among all seven metal complexes,
compound 5c shows the higher chemical stability based on HOMO-LUMO energy difference.
Koopman’s theorem proposed several electrostatic parameters for molecular systems which can be assessed
to determine the site selectivity and chemical reactivity of a molecule.[48] Various aspects of chemical
reactivity associated with a molecule can be assessed directly by utilizing the information related with
frontier molecular orbitals. Over the years, these reactivity indices have been utilized extensively for
studying different facets of medicinal chemistry. Moreover, the dynamics of a reaction can also be studied by
exploring the time dependent profile of these global descriptors. Chemical hardness (η), softness (s), chemical
potential (µ), electronegativity (χ) and electrophilicity index (ω) are important global reactivity descriptors
which could explain most of the physiochemical properties associated with a molecule.[49] Electrophilicity
index (ω) is a definite and positive quantity that measures the stabilization energy when extra electronic
charge is added to the system. Moreover, this descriptor also explains the transfer of charge in a chemical
reaction, lower the value, lower will be the electrophilicity. The global reactivity descriptors calculated for all
the metal complexes are listed in Table 1. The compound 5b appears to be the most electrophilic, and
compound 5g the least among all complexes.

Figure 15: Frontier molecular orbitals for compounds 5a-5g
Table 1: Electrostatic parameters for compounds 5a-5g calculated in gas phase
Complex HOMO LUMO Electronegativity
Chemical
potential
(µ)
Chemical
hardness
η= (I-A)/2
Chemical
softness (s)
Electrophilicity
χ = (I+A)/2
Index (ω)
-5.6590 -1.7330
-5.0830 -1.8620
-5.4280 -1.4520
-5.4950 -1.6500
-5.5420 -1.6190
-5.5130 -1.6180
-5.2400 -1.3810
3.6960
3.4725
3.4400
3.5725
3.5805
3.5655
3.3105
-3.6960
-3.4725
-3.4400
-3.5725
-3.5805
-3.5655
-3.3105
1.9630
1.6105
1.9880
1.9225
1.9615
1.9475
1.9295
0.2547
0.3105
0.2515
0.2601
0.2549
0.2567
0.2591
3.4795
3.7436
2.9763
3.3193
3.2679
3.2639
2.8400
5a
5b
5c
5d
5e
5f
5g
3.3 TGA data
Thermogravimetric analysis is a useful technique to evaluate the stability of a complex. The synthesized
solvated metal complexes undergone thermal decomposition over temperature range 25-1000°C under
nitrogen atmosphere. The data strongly suggested that proposed formulas were correct for these complexes
(Figure 5S). Thermogram of complex 5a shows three degradation steps within the temperature range of 50-
200, 200-445 and 445-950°C, which correspond to mass loss of 20.02, 50.60 and 18.20% respectively.

Thermogram of complex 5b shows weight loss of 16.78, 35.62 and 31.14% in the temperature ranges 70-140,
300-440 and 440-920°C. While the TGA profile of complex 5c shows a first decomposition stage between
70-140°C with weight loss of 15.57%, second occurred at 300-415°C with weight loss of 34.34% and third
stage in between 415-920°C. The decomposition step for complex 5f started in the temperature range 70-
170°C with mass loss of 31.51%, then in range between 170-410°C with weight loss of 27.93% and third
degradation stage between 410-915°C.
3.4 Antimicrobial activity
In the preliminary screening none of the synthesized complexes were found to have antifungal activity.
Moreover, no antibacterial activity was observed against Gram-negative bacteria. The complex outer
membrane (OM) in Gram-negative bacteria makes them tough to combat as compared to Gram-positive
pathogens. The complex OM in Gram-negative bacteria acts as a selective barrier; they can modify their
permeability properties, which have a major impact on the susceptibility to the antibiotics/molecules. [50]
Synthesized complexes were found to be active against the Gram-positive Bacteria Staphylococcus aureus
and Bacillus subtilis. All the compounds showed very good minimum inhibitory concentration and minimum
bactericidal concentration against B. subtilis. Carbohydrazide ligand 3 didn’t exhibited any type of activity
against both the Gram-positive bacteria at the concentration 128 μM. On the basis of minimum inhibitory
activity shown against bacteria, complex 4 and 5f was found to be the most effective against B. subtilis with
32 M MIC and MBC values. Compound 5f also showed good MIC values against S. aureus (Table 2). It is
noteworthy that the Cu2+ was inactive at 128 μM concentration when tested for antimicrobial activity.
Table 2: MIC and MBC of compounds 5a-5g against S. aureus and B. subtilis
Staphylococcus aureus
Bacillus subtilis
(ATCC 25923 )
(ATCC 6633)
Primary
screening at Inhibitory
128 µM
Minimum
Minimum
Primary
screening at Inhibitory
128 µM
Minimum
Minimum
Complex/Co
mpound
Bactericidal
Concentration
(MBC) µM
Bactericidal
Concentration
(MBC) µM
Concentration
(MIC) µM
Concentration
(MIC) µM
NA
+
-
-
NA
+
-
-
3
64
64
32
64
64
64
64
64
32
64
32
64
64
64
64
128
32
64
4
+
128
128
128
128
128
64
128
128
128
128
128
128
128
+
5a
5b
5c
5d
5e
5f
5g
+
+
+
+
+
+
+
+
+
+
+
128
+

+
0.016
0.016
+
0.016
0.016
Ciprofloxacin
+ Samples shows antibacterial activity in primary screening; NA: Not active
4
Conclusion
In conclusion, an efficient and mild synthetic approach metal complexes of (Z)-N-((E)-1-(4-hydroxy-6-
methyl-2-oxo-2H-pyran-3-yl)ethylidene)benzohydrazonic acid coordinated with solvated with various
solvent molecules such as isopropylamine, di-isobutylamine, ethylenediamine, dimethylformamide,
dimethylamine and methanol has been developed. The complexes were characterized extensively with the
help of IR, TGA and single crystal X-ray analysis. The intermolecular interactions exist in case of all the
complexes have been quantified using Hirshfeld surface analysis. The electrostatic properties associated with
all these complexes was calculated using DFT studies. The synthesized copper complexes exhibited
significant activity against the Gram-positive bacteria specifically against B. subtilis. Complex 4 and 5f was
found to be the most effective against B. subtilis with 32 M MIC and MBC values. On the other hand, the
complexes did not exhibit antifungal activity against the fungal strains Candida albicans and Aspergillus
niger. Therefore, the synthesized metal complexes can act as selective antibacterial agents, since they exhibit
activity only against Gram-positive bacteria.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that
could have appeared to influence the work reported in this paper.
Acknowledgments
Authors thanks DST-FIST for single crystal facility, DST-PURSE and UGC-CAS for departmental support.
Richa thanks CSIR for financial support in the form of JRF.

Credit author statement
Conceptualization
Methodology
Software
Ramesh Kataria, Ennio Zangrando, Jayant Sindhu, Vinod Kumar, SK Mehta
Richa, Poonam Choudhary, Sundeep Jaglan, Rakesh Kumar
SC Sahoo, Ramesh Kataria, Jayant Sindhu, Ennio Zangrando
Ramesh Kataria, Jayant Sindhu, Vinod Kumar, SK Mehta, SC Sahoo
Richa, Rakesh, Jayant, Ramesh Kataria, Poonam Choudhary, Sundeep Jaglan
Richa, Rakesh, Poonam Choudhary, Sundeep Jaglan
Validation
Formal analysis
Investigation
Resources
Ramesh Kataria, SK Mehta
Data Curation
Richa, SC Sahoo, Ramesh Kataria, Jayant Sindhu, Ennio Zangrando, Sunil Kumar
Richa, Ramesh Kataria, Jayant Sindhu, Ennio Zangrando, Sunil Kumar, SK Mehta,
Rakesh Kumar, Vinod Kumar
Writing Original Draft
Richa, Ramesh Kataria, Jayant Sindhu, Ennio Zangrando, Sunil Kumar, SK Mehta,
Writing Review & Editing Rakesh Kumar, Vinod Kumar, Poonam Choudhary, Sundeep Jaglan, SC Sahoo
Visualization
Ramesh Kataria, SK. Mehta, Ennio Zangrando, Sunil Kumar, Vinod Kumar
Supervision
Ramesh Kataria
Project administration
Funding acquisition
Ramesh Kataria
Ramesh Kataria, SK Mehta
References:
[1] C.R. Culy, D. Clemett, L.R. Wiseman, Oxaliplatin: A review of its pharmacological properties and
clinical efficacy in metastatic colorectal cancer and its potential in other malignancies, Drugs. 60
(2000) 895–924. https://doi.org/10.2165/00003495-200060040-00005.
[2] J.R. Eckardt, D.L. Bentsion, O.N. Lipatov, I.S. Polyakov, F.R. MacKintosh, D.A. Karlin, G.S. Baker,
H.B. Breitz, Phase II study of picoplatin as second-line therapy for patients with small-cell lung
cancer, J. Clin. Oncol. 27 (2009) 2046–2051. https://doi.org/10.1200/JCO.2008.19.3235.
[3] Y. Li, K. Zhou, Z. Wen, S. Cao, X. Shen, M. Lei, L. Gong, Copper(II)-Catalyzed Asymmetric
Photoredox Reactions: Enantioselective Alkylation of Imines Driven by Visible Light, J. Am. Chem.
Soc. 140 (2018) 15850–15858. https://doi.org/10.1021/jacs.8b09251.
[4] A.M. Suess, M.R. Uehling, W. Kaminsky, G. Lalic, Mechanism of Copper-Catalyzed Hydroalkylation
of Alkynes: An Unexpected Role of Dinuclear Copper Complexes, J. Am. Chem. Soc. 137 (2015)
7747–7753. https://doi.org/10.1021/jacs.5b03086.

[5] Z. Ma, Q. Wang, E.C.B.A. Alegria, M.F.C.G. Da Silva, L.M.D.R.S. Martins, J.P. Telo, I. Correia,
A.J.L. Pombeiro, Synthesis and structure of copper complexes of a N6O4 macrocyclic ligand and
catalytic application in alcohol oxidation, Catalysts. 9 (2019). https://doi.org/10.3390/catal9050424.
[6] Z. Ma, A. V. Gurbanov, A.M. Maharramov, F.I. Guseinov, M.N. Kopylovich, F.I. Zubkov, K.T.
Mahmudov, A.J.L. Pombeiro, Copper(II) arylhydrazone complexes as catalysts for C[sbnd]H
activation in the Henry reaction in water, J. Mol. Catal. A Chem. 426 (2017) 526–533.
https://doi.org/10.1016/j.molcata.2016.05.030.
[7] R.R. Zhuang, F.F. Jian, K. Wang, An electrochemical sensing platform based on a new copper
complex for the determination of hydrogen peroxide and nitrite, Sci. Technol. Adv. Mater. 10 (2009).
https://doi.org/10.1088/1468-6996/10/4/045001.
[8] M.G. Caglayan, S. Sheykhi, L. Mosca, P. Anzenbacher, Fluorescent zinc and copper complexes for
detection of adrafinil in paper-based microfluidic devices, Chem. Commun. 52 (2016) 8279–8282.
https://doi.org/10.1039/c6cc03640f.
[9] S.G. Leonardi, M. Bonyani, K. Ghosh, A.K. Dhara, L. Lombardo, N. Donato, G. Neri, Development
of a novel Cu(II) complex modified electrode and a portable electrochemical analyzer for the
determination of dissolved oxygen (DO) in water, Chemosensors.
https://doi.org/10.3390/chemosensors4020007.
4
(2016).
[10] E.K. Efthimiadou, H. Thomadaki, Y. Sanakis, C.P. Raptopoulou, N. Katsaros, A. Scorilas, A.
Karaliota, G. Psomas, Structure and biological properties of the copper(II) complex with the quinolone
antibacterial drug N-propyl-norfloxacin and 2,2′-bipyridine, J. Inorg. Biochem. 101 (2007) 64–73.
https://doi.org/https://doi.org/10.1016/j.jinorgbio.2006.07.019.
[11] A.H. Calvert, S.J. Harland, D.R. Newell, Z.H. Siddik, A.C. Jones, T.J. McElwain, S. Raju, E.
Wiltshaw, I.E. Smith, J.M. Baker, M.J. Peckham, K.R. Harrap, Early clinical studies with cis-
diammine-1,1-cyclobutane dicarboxylate platinum II, Cancer Chemother. Pharmacol. 9 (1982) 140–
147. https://doi.org/10.1007/BF00257742.
[12] K.S. Egorova, V.P. Ananikov, Toxicity of Metal Compounds: Knowledge and Myths,
Organometallics. 36 (2017) 4071–4090. https://doi.org/10.1021/acs.organomet.7b00605.
[13] L. Jin, C. Quan, X. Hou, S. Fan, Potential Pharmacological Resources: Natural Bioactive Compounds
from Marine-Derived Fungi, Mar. Drugs. 14 (2016). https://doi.org/10.3390/md14040076.
[14] K. Trisuwan, V. Rukachaisirikul, Y. Sukpondma, S. Preedanon, S. Phongpaichit, J. Sakayaroj, Pyrone
derivatives from the marine-derived fungus Nigrospora sp. PSU-F18, Phytochemistry. 70 (2009) 554–
557. https://doi.org/10.1016/j.phytochem.2009.01.008.
[15] T. Zhao, L.L. Xu, Y. Zhang, Z.H. Lin, T. Xia, D.F. Yang, Y.M. Chen, X.L. Yang, Three new α-pyrone
derivatives from the plant endophytic fungus Penicillium ochrochloronthe and their antibacterial,
antifungal, and cytotoxic activities, J. Asian Nat. Prod. Res. 21 (2019) 851–858.
https://doi.org/10.1080/10286020.2018.1495197.
[16] C. Yuan, H.X. Yang, Y.H. Guo, L. Fan, Y.B. Zhang, G. Li, New α-pyrones from an endophytic
fungus,:
Hypoxylon
investiens
J2,
RSC
Adv.
9
(2019)
27419–27423.
https://doi.org/10.1039/c9ra05308e.
[17] A.P.G. Macabeo, A.J.C. Cruz, A. Narmani, M. Arzanlou, A. Babai-Ahari, L.A.E. Pilapil, K.Y.M.

Garcia, V. Huch, M. Stadler, Tetrasubstituted α-pyrone derivatives from the endophytic fungus,
Neurospora udagawae, Phytochem. Lett. 35 (2020) 147–151.
https://doi.org/10.1016/j.phytol.2019.11.010.
[18] D. Lai, Z. Mao, Z. Zhou, S. Zhao, M. Xue, J. Dai, L. Zhou, D. Li, New chlamydosporol derivatives
from the endophytic fungus Pleosporales sp. Sigrf05 and their cytotoxic and antimicrobial activities,
Sci. Rep. 10 (2020) 8193. https://doi.org/10.1038/s41598-020-65148-0.
[19] S. Amatori, G. Ambrosi, M. Fanelli, M. Formica, V. Fusi, L. Giorgi, E. MacEdi, M. Micheloni, P.
Paoli, R. Pontellini, P. Rossi, Synthesis, basicity, structural characterization, and biochemical
properties of two [(3-hydroxy-4-pyron-2-yl)methyl]amine derivatives showing antineoplastic features.,
J. Org. Chem. 77 (2012) 2207–2218. https://doi.org/10.1021/jo202270j.
[20] S. Amatori, I. Bagaloni, E. MacEdi, M. Formica, L. Giorgi, V. Fusi, M. Fanelli, Malten, a new
synthetic molecule showing in vitro antiproliferative activity against tumour cells and induction of
complex
DNA
structural
alterations,
Br.
J.
Cancer.
103
(2010)
239–248.
https://doi.org/10.1038/sj.bjc.6605745.
[21] A. Barve, A. Kumbhar, M. Bhat, B. Joshi, R. Butcher, U. Sonawane, R. Joshi, Mixed-ligand
copper(II) maltolate complexes: Synthesis, characterization, DNA binding and cleavage, and
cytotoxicity, Inorg. Chem. 48 (2009) 9120–9132. https://doi.org/10.1021/ic9004642.
[22] A. Otero-De-La-Roza, E.R. Johnson, A benchmark for non-covalent interactions in solids, J. Chem.
Phys. 137 (2012). https://doi.org/10.1063/1.4738961.
[23] E. Stoler, J.C. Warner, Non-Covalent derivatives: Cocrystals and eutectics, Molecules. 20 (2015)
14833–14848. https://doi.org/10.3390/molecules200814833.
[24] A. Karshikoff, Non-covalent interactions in proteins, 2006. https://doi.org/10.1142/P477.
[25] J. Černý, P. Hobza, Non-covalent interactions in biomacromolecules, Phys. Chem. Chem. Phys. 9
(2007) 5291–5303. https://doi.org/10.1039/b704781a.
[26] S.U. Rehman, T. Sarwar, M.A. Husain, H.M. Ishqi, M. Tabish, Studying non-covalent drug-DNA
interactions, Arch. Biochem. Biophys. 576 (2015) 49–60. https://doi.org/10.1016/j.abb.2015.03.024.
[27] K.D. Patel, U.H. Patel, Quantitative analysis of weak interactions by Lattice energy calculation,
Hirshfeld surface and DFT studies of sulfamonomethoxine, J. Mol. Struct. (2017).
https://doi.org/10.1016/j.molstruc.2016.08.046.
[28] D. Vashisht, S. Sharma, R. Kumar, V. Saini, V. Saini, A. Ibhadon, S.C. Sahoo, S. Sharma, S.K.
Mehta, R. Kataria, Dehydroacetic acid derived Schiff base as selective and sensitive colorimetric
chemosensor for the detection of Cu(II) ions in aqueous medium, Microchem. J. 155 (2020) 104705.
https://doi.org/10.1016/j.microc.2020.104705.
[29] R. Kumar, V. Mutreja, G. Sharma, S. Kumar, A. Ali, S.K. Mehta, P. Venugopalan, R. Kataria, S.C.
Sahoo, The role of a weakly coordinating thioether group in ligation controlled molecular self-
assemblies and their inter-conversions in Ni(ii) complexes of l-methionine derived ligand, New J.
Chem. 43 (2019) 11222–11232. https://doi.org/10.1039/c9nj02573a.
[30] G. Singh, J. Sindhu, Manisha, V. Kumar, V. Sharma, S.K. Sharma, S.K. Mehta, M.H. Mahnashi, A.
Umar, R. Kataria, Development of an off-on selective fluorescent sensor for the detection of Fe3+ ions

based on Schiff base and its Hirshfeld surface and DFT studies, J. Mol. Liq. 296 (2019).
https://doi.org/10.1016/j.molliq.2019.111814.
[31] X. Wang, H. Wang, P. Chen, Y. Pang, Z. Zhao, G. Wu, Synthesis and Biological Activities of Some
Novel (E)-Alpha-(methoxyimino)benzeneacetate Derivatives with Modified 1,2,4-Triazole Moiety, J.
Chem. 2014 (2014) 1–10. https://doi.org/10.1155/2014/681364.
[32] M.R. Maurya, N. Saini, F. Avecilla, Liquid phase versus microwave assisted selective oxidation of
volatile organic compounds involving dioxidomolybdenum(VI) and oxidoperoxidomolybdenum(VI)
complexes as catalysts in the presence/absence of an N-based additive, Polyhedron. 90 (2015) 221–
232. https://doi.org/10.1016/j.poly.2015.01.030.
[33] A.L.S.I. Clinical, Document M27-A4, Ref. Method Broth Dilution Antifung. Suscetibility Test.
Yeasts. (2012).
[34] CLSI, M38-A2 Reference Method for Broth Dilution Antifungal Susceptibility Testing of Filamentous
Fungi; Approved Standard—Second Edition, Clin. Lab. Stand. Inst. 28 (2008) 29.
[35] B.L.Z. F. R. Cockerill, M. A. Wiker, J. Alder, M. N. Dudley, G. M. Eliopoulos, M. J. Ferraro, D. J.
Hardy, D. W. Hecht, J. A. Hindler, J. B. Patel, M. Powell, J. M. Swenson, R. B. Thomson, M. M.
Traczewski, J. D. Turnidge, M. P. Weinstein, Methods for Dilution Antimicrobial Susceptibility Tests
for Bacteria That Grow Aerobicallyꢀ; Approved Standard — Ninth Edition, 2012.
[36] Agilent, CrysAlisPro Data Collection and Processing Software for Agilent X-ray Diffractometers,
Technol. UK Ltd, Yarnton, Oxford, UK. 44 (2014) 1–53.
[37] O. V. Dolomanov, L.J. Bourhis, R.J. Gildea, J.A.K. Howard, H. Puschmann, OLEX2: A complete
structure solution, refinement and analysis program, J. Appl. Crystallogr. 42 (2009) 339–341.
https://doi.org/10.1107/S0021889808042726.
[38] M.C. Burla, R. Caliandro, M. Camalli, B. Carrozzini, G.L. Cascarano, L. De Caro, C. Giacovazzo, G.
Polidori, D. Siliqi, R. Spagna, IL MILIONE: A suite of computer programs for crystal structure
solution
of
proteins,
J.
Appl.
Crystallogr.
40
(2007)
609–613.
https://doi.org/10.1107/S0021889807010941.
[39] G.M. Sheldrick, Crystal structure refinement with SHELXL, Acta Crystallogr. Sect. C Struct. Chem.
71 (2015) 3–8. https://doi.org/10.1107/S2053229614024218.
[40] A.D. Becke, Density‐functional thermochemistry. I. The effect of the exchange‐only gradient
correction, J. Chem. Phys. 96 (1992) 2155–2160. https://doi.org/10.1063/1.462066.
[41] A.C. Ekennia, A.A. Osowole, L.O. Olasunkanmi, D.C. Onwudiwe, O.O. Olubiyi, E.E. Ebenso,
Synthesis, characterization, DFT calculations and molecular docking studies of metal (II) complexes,
J. Mol. Struct. 1150 (2017) 279–292. https://doi.org/10.1016/j.molstruc.2017.08.085.
[42] A.W. Addison, T.N. Rao, Synthesis, Structure, and Spectroscopic Properties, Dalt. Trans. (1984)
1349–56.
[43] U. Kendur, G.H. Chimmalagi, S.M. Patil, K.B. Gudasi, C.S. Frampton, Synthesis, structural
characterization and biological evaluation of mononuclear transition metal complexes of zwitterionic
dehydroacetic acid N-aroylhydrazone ligand, Appl. Organomet. Chem. 32 (2018) 1–21.
https://doi.org/10.1002/aoc.4278.

[44] U. Kendur, G.H. Chimmalagi, S.M. Patil, K.B. Gudasi, C.S. Frampton, C. V. Mangannavar, I.S.
Muchchandi, Mononuclear late first row transition metal complexes of ONO donor hydrazone ligand:
Synthesis, characterization, crystallographic insight, in vivo and in vitro anti-inflammatory activity, J.
Mol. Struct. 1153 (2018) 299–310. https://doi.org/10.1016/j.molstruc.2017.10.022.
[45] M.A. Spackman, D. Jayatilaka, Hirshfeld surface analysis, CrystEngComm. (2009).
https://doi.org/10.1039/b818330a.
[46] F.P.A. Fabbiani, L.T. Byrne, J.J. McKinnon, M.A. Spackman, Solvent inclusion in the structural voids
of form II carbamazepine: single-crystal X-ray diffraction, NMR spectroscopy and Hirshfeld surface
analysis, CrystEngComm. 9 (2007) 728–731. https://doi.org/10.1039/B708303N.
[47] G.A. Stephenson, E.G. Groleau, R.L. Kleemann, W. Xu, D.R. Rigsbee, Formation of Isomorphic
Desolvates: Creating
a
Molecular Vacuum, J. Pharm. Sci. 87 (1998) 536–542.
https://doi.org/https://doi.org/10.1021/js970449z.
[48] P.W. Ayers, M. Levy, Perspective on “Density functional approach to the frontier-electron theory of
chemical reactivity,” Theor. Chem. Acc. 103 (2000) 353–360. https://doi.org/10.1007/s002149900093.
[49] P.K. Chattaraj, Chemical Reactivity and Selectivity:ꢀ Local HSAB Principle versus Frontier Orbital
Theory, J. Phys. Chem. A. 105 (2001) 511–513. https://doi.org/10.1021/jp003786w.
[50] A.H. Delcour, Outer membrane permeability and antibiotic resistance, Biochim. Biophys. Acta -
Proteins
Proteomics.
1794
(2009)
808–816.
https://doi.org/https://doi.org/10.1016/j.bbapap.2008.11.005.

Graphical Abstract
A series of novel solvent coordinated copper(II) complex with hydrazone of 3-acetyl-6-methyl-2H-pyran-
2,4(3H)-dione (DHA) have been synthesized. Structural aspects, electrostatic and biological properties
related with these complexes have been studied.