Synthesis, XRD and spectroscopic characterization of pharmacologically active Cu(II) and Zn(II) complexes

Article abstract of DOI:10.1016/j.molstruc.2017.03.053

The present contribution accounts for the synthesis and structural elucidation of a newly synthesised copper and zinc containing schiff base compounds obtained by the condensation of 1, 2-diphenylethane-1, 2-dione and dinitrophenyl hydrazine as main ligand and benzene-1,2-diamine as co-ligand respectively. The synthesised compounds were characterized by several techniques, including elemental analysis, molar conductance and electronic, FT-IR, XRD, mass and ¹H NMR spectral studies. The analytical and molar conductance values indicated that the complexes have square planar and tetrahedral geometry respectively. X-ray powder diffraction illustrates that they are crystalline in nature. The copper and zinc complexes were screened for their antimicrobial potential against some bacterial and fungi strains and the assay indicate that these complexes are good antimicrobial agents against these tested pathogens.

Full text of DOI:10.1016/j.molstruc.2017.03.053

Journal of Molecular Structure 1139 (2017) 264e268
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Synthesis, XRD and spectroscopic characterization of
pharmacologically active Cu(II) and Zn(II) complexes
Parveez Gull*, Athar Adil Hashmi**
Department of Chemistry, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The present contribution accounts for the synthesis and structural elucidation of a newly synthesised
copper and zinc containing schiff base compounds obtained by the condensation of 1, 2-diphenylethane-
1, 2-dione and dinitrophenyl hydrazine as main ligand and benzene-1,2-diamine as co-ligand respec-
tively. The synthesised compounds were characterized by several techniques, including elemental
analysis, molar conductance and electronic, FT-IR, XRD, mass and 1H NMR spectral studies. The analytical
and molar conductance values indicated that the complexes have square planar and tetrahedral geom-
etry respectively. X-ray powder diffraction illustrates that they are crystalline in nature. The copper and
zinc complexes were screened for their antimicrobial potential against some bacterial and fungi strains
and the assay indicate that these complexes are good antimicrobial agents against these tested
pathogens.
Received 5 January 2017
Received in revised form
12 March 2017
Accepted 13 March 2017
Available online 16 March 2017
Keywords:
Schiff base
Schiff base metal complexes
Synthesis
© 2017 Elsevier B.V. All rights reserved.
Spectroscopic studies
Powder XRD
Antimicrobial activities
1. Introduction
drug design, biological applications [5], in the field of optics [6] and
chemical sensors [7]. Additionally, the metal complexes of the schiff
The development of new Schiff base chemotherapeutic agents
has attracted the attention of medicinal chemist [1]. In the last few
decades the field of bioinorganic chemistry has developed exten-
sively mainly because of the coordination chemistry and predom-
inantly of coordination behaviour of transition metals. The
stimulating coordination chemistry of metal ions has fascinated the
inorganic chemists because of the varying behaviour in their
function and complexity. The transition metals are involved in
several biological processes and have been abundantly stated in the
literature as compared to the ligand systems [2]. Schiff bases
represent a significant family of ligands in coordination chemistry
because of their synthetic flexibility and selectivity towards a
particular central metal atom. Schiff base ligands are synthesised by
the condensation reaction of primary amines and an aldehyde thus
considered as the ‘privileged’ ligands in the coordination chemistry
[3,4]. The azomethine group present in the schiff base ligands is
best suited for the chelation of metal ions through the nitrogen
having a lone pair of electrons. Nowadays the schiff base ligands
have received great attention because of their wide applications in
bases have shown versatile biological applications ranging from
antibacterial, antifungal, herbicidal, antitumor, medicinal imaging
and bio-modeling techniques [8e10]. Since the function of storage
and transport of genetic information in a cell is performed by the
DNA and also acts as a target of anticancer drugs [11,12]. The DNA
sequences regulate the gene expression, gene transcription carci-
nogenesis and mutagenesis etc. [13] These DNA progressions can be
altered by combining the synthesised metal complexes with the
DNA which damage the DNA, hence its proper functioning. In
recent times, Shahabadi et al., have reported that the DNA inter-
action between the DNA and some molecules hence cause DNA
damage. Further, it stops the cell division of cancerous cells and
caused death of cells [14,15]. Therefore the synthesis and designing
of new metal complexes capable of DNA interaction is the need of
the hour. Since the small metal containing complexes form majorly
non-covalent interactions (non-specific/directional) with the DNA
and due to this small metal containing complexes have several
applications in anti-tumor and molecular biology [16,17].
Based on the above facts, the synthesis of new Schiff base by the
condensation of 1, 2-diphenylethane-1, 2-dione and dinitrophenyl
hydrazine has been reported. The Schiff base ligand has been co-
ordinated to bio essential transition metal ions Cu(II) and Zn(II) to
form the mixed ligand complexes using benzene-1,2-diamine as
* Corresponding author.
** Corresponding author.
E-mail address: dr.aahashmi@yahoo.co.in (A.A. Hashmi).
http://dx.doi.org/10.1016/j.molstruc.2017.03.053
0022-2860/© 2017 Elsevier B.V. All rights reserved.

P. Gull, A.A. Hashmi / Journal of Molecular Structure 1139 (2017) 264e268
265
ancillary ligand. Further, the synthesised ligand and the complexes
were characterized by various physical and spectroscopic tech-
niques. The bio-relevancy of these complexes have been profes-
sionally studied and explored by anti-microbial studies.
n
(NO) 1610, ʋ(MeN) 446. 1H NMR (d-CDCl3): 9.0 (s, NH); 3.92 (s,
eNH2); 7.10e8.0 (m, Ar-H) ppm. UV/Vis (DMSO, lmax (nm): 642,
508. MS (m/z): 561 [M]þ.
[Zn(L)]: Yield: 69%. Anal. Calc. (%) for (C26H22ZnN6O5):
(563.88 g molꢀ1): C, 55.38; H 3.93; N, 14.90. Found: C, 55.15; H,
3.75; N, 14.80. FT-IR (KBr), cmꢀ1: ʋ(NeH) 3343, ʋ(C]N) 1620, ʋ(C]
2. Experimental protocols
O) 1705, n
(NO) 1610, ʋ(MeN) 435. 1H NMR (d-CDCl3): 9.0 (s, 1H);
4.20 (s, for eNH2); 7.10e8.75 (m, Ar-H) ppm. UV/Vis (DMSO, lmax
2.1. Reagents and instruments
(nm): 320. MS (m/z): 562 [M]þ
The chemicals and solvents of analytical grade were purchased
directly from Aldrich and Fluka and used without any further pu-
rification. Elemental analyses (C, H, and N) were performed with a
PerkineElmer 2400 series II analyzer. 1H NMR spectroscopic mea-
surements were performed on a Varian 500 MHz spectrometer in
d-CDCl3, using TMS (SiMe4) as an internal reference at room tem-
perature. Infrared spectra (4000-400 cmꢀ1) were collected on a
Perkin Elmer 100/ATR spectrophotometer at 25 ꢁC using KBr plates.
UVeVis spectra were recorded with a Perkin Elmer double-beam
spectrophotometer using a quartz glass cell with a path length of
10 mm. The molar conductance values (10ꢀ3 mol Lꢀ1) of the com-
plexes, in DMSO, were measured using a Systronic Conductivity
Bridge 304. X-ray diffraction spectra of copper and zinc complexes
are carried out with powdered compounds using RIGAKU ULTIMA
IV diffractometer system at 25 ꢁC in Cu anode source and the
generator settings as 30 mA, 40 kV.
2.4. Antimicrobial activity
The synthesised metal complexes were evaluated for their
antimicrobial potential against some strains of bacteria and fungi
like Escherchia coli, Bacillus subtilis and Staphylococcus aureus and
Aspergillus niger, Aspergillus flavus and candida albicans respectively.
The compounds were dissolved in DMSO to get the required test
solutions.
3. Results and discussions
All complexes gave satisfactory elemental analyses results
which were in good agreement with those calculated for the sug-
gested formulae and shown in Table 1. The complexes are insoluble
in water or in nonpolar organic solvents (CCl4, Cyclohexane) and
soluble in DMSO or DMF solutions. The molar conductance of the
solid complexes measured by Systronic Conductivity Bridge 304
indicated the non-electrolytic nature of the complexes [18]. Various
crystallization attempts using mixtures of solvents and low tem-
peratures, were unsuccessful for the growth of a single crystal
suitable for X-ray crystallography. However, the analytical, spec-
troscopic and magnetic data facilitated the possible structure of the
synthesised complexes to be proposed.
2.2. Synthesis of Schiff base (E)-2-(2-(2,4-dinitrophenyl)
hydrazono)-1,2-diphenylethanone (L)
A hot ethanoic solution (20 mL) of 1, 2-diphenylethane-1, 2-
dione and (1 g, 0.005 mol), and a hot ethanolic solution (20 mL)
of Dinitrophenyl hydrazine (0.93 g, 0.005 mol) are mixed slowly
with constant stirring. The mixture is refluxed at 75 ꢁC for 6e7 h in
presence of few drops of concentrated HCl (pH 3e4). On cooling, a
solid yellow coloured precipitate is formed, which was filtered,
washed with cold EtOH, and dried under vacuum over P4O10
(Scheme 1).
3.1. Molar conductance and elemental analysis measurements
The molar conductivities of 10ꢀ3 M solutions of the synthesised
metal Complexes in DMF solution showed values in the range of
L: Yield: 67%. Anal. Calc. (%) for C20H14N4O5 (390 g molꢀ1): C,
61.54; H 3.62; N, 14.33. Found: C, 61.50; H, 3.58; N, 14.29. FT-IR
2e5
U
ꢀ1cm2molꢀ1 representing the non-electrolytic nature of the
(KBr), cmꢀ1: ʋ(NeH) 3336, (C]N) 1625, ʋ(C]O) 1710,
n(NO)
metal complexes [19,20]. The elemental analysis results of the
metal complexes also agree with the calculated values. The molar
conductance and elemental analysis data (as shown in Table 1)
shows the formula for metal complexes as [M(C26H22N6O5)] where
M ¼ Cu(II) and Zn(II).
1610. 1H NMR (d-CDCl3): 9.01 (s, 1H); 7.18e8.76 (m, Ar-H) ppm. MS
(m/z): 391 [MþH]þ.
2.3. Synthesis of metal complexes
An ethanolic solution of metal (II) chloride (1 mmol) was stirred
with an ethanolic solution of the Schiff base (L) (1 mmol) and
ethanolic solution of benzene-1,2-diamine (1 mmol) for 1 h and the
mixture was then refluxed for 3 h on a water bath. The solid
complexes were precipitated and the precipitate was filtered off,
washed thoroughly with ethanol and dried in vacuo (Scheme 2).
[Cu(L)]: Yield: 69%. Anal. Calc. (%) for (C26H22CuN6O5)
(562 g molꢀ1): C, 55.56; H 3.95; N, 14.95. Found: C, 54.10; H 3.88; N,
13.90. FT-IR (KBr), cmꢀ1: ʋ(NeH) 3342, ʋ(C]N) 1610, ʋ(C]O) 1710
3.2. IR spectra
The IR Spectra of ligand and its metal complexes were obtained
on
a
Perkin-Elmer Series 2000 apparatus in the range
4000e200 cmꢀ1. The infrared spectra of the synthesised primary
Schiff base ligand (Fig. S1) shows the absorption band at 1625 cmꢀ1
corresponds to the imine (>C]N) group [21] and a strong band at
1710 cmꢀ1 corresponding to the >C]O group which confirms the
complete condensation of the two reacting moieties. In addition to
Scheme 1. Structure of the Schiff base ligand.

266
P. Gull, A.A. Hashmi / Journal of Molecular Structure 1139 (2017) 264e268
Scheme 2. Structure of the metal Schiff base complexes.
Table 1
Analytical data of the Cu(II), and Zn(II) complexes.
Complexes
Elemental analysis calculated (found) (%)
Molar conductivity (Uꢀ1 cm2 molꢀ1
)
Mol. wt.
C
H
N
[Cu(C26H22N6O5)]
[Zn(C26H22N6O5)]
562
563.88
55.56 (54.10)
55.38 (55.15)
3.95 (3.88)
3.93 (3.75)
14.95 (13.90)
14.90 (14.80)
2.5
3.3
these peaks an absorption bands observed in the region of
3340e3330 cmꢀ1 and 1500-1630 cmꢀ1 are assigned to the eNH
group and eNO group present in the ligand. While as in case of
metal complexes (Fig. S2) the strong band at 1625 cmꢀ1 is shifted to
lower frequency numbers by 15e5 cmꢀ1 leading to the confirma-
tion of coordination through the imino (>C]N) group to the metal
atom in complexes. Also there is an occurrence of new bands in the
region 460e420 cmꢀ1 which has been attributed to MeN bonds
respectively [22]. The IR spectral bands of metal complexes are
summarized in Table 2.
in the region of 9.0 ppm and 3.92 ppm corresponds to the sec-
ondary amide proton (NH) [23] and amine group (NH2) respectively
(Fig. S5). The aromatic protons of the ligand were observed as a
multiplet in the region of 7.18e8.0 ppm [24,25].
3.5. Electronic spectral
The
electronic
spectra
of
[Cu(C26H22N6O5)]
and
[Zn(C26H22N6O5)] complexes were recorded at room temperature
in DMSO-d6. The transitions and assignments are given in Table 3.
The electronic spectra of the [Cu(C26H22N6O5)] complex in 10ꢀ3
M
DMSO showed two bands at 642, 508 nm, which are assigned to
2B1g/2A1g and 2B1g /2Eg transitions respectively [26e29], and the
magnetic moment of Cu(L) complex was 1.79 B M. Both the elec-
tronic spectra and the magnetic values proposed the presence of
the square planar geometry for [Cu(C26H22N6O5)] complex. The
electronic absorption spectra of the [Zn(C26H22N6O5)] complexe in
DMSO, are dominated by the broad band in the region 320 nm
corresponding to the intra-ligand transition or/and a charge-
transfer transition. No ded transition is expected for d10 Zn (L)
complexes.
3.3. Mass spectra
The ESI mass spectra of the schiff base ligand and its metal
complexes were recorded. The mass spectrum of primary ligand
shows a distinct molecular ion peak at m/z ¼ 391 which confirms
the molecular formula and the structure of the ligand. The mass
spectra of the synthesised metal complexes displayed molecular
ion peak [M]þ, m/z at 561 and 562 a.m.u corresponding to their
molecular formulae [Cu(C26H22N6O5)]and [Zn(C26H22N6O5)]
respectively (Figs. S3 and S4). This information obtained from the
mass spectroscopy confirms the proposed structures and molecular
formulae adequately. There are various other peaks in the spectra
which are due to the thermal cleavage of the complexes assigned to
various fragments of the dissociated molecule.
3.6. X-ray diffraction analysis
X-ray diffraction is an important instrumental technique that is
employed to identify the crystalline materials. It can be easily
realised that the design of the Schiff base varies from the metal
complexes, which may be credited to the development of a definite
crystalline structure. The X-ray diffraction patterns of the syn-
thesised complexes revels the crystalline nature of the metal
complexes (Figs. 1 and 2) and are worked out by using trial and
3.4. 1H NMR
The NMR spectroscopy is the main technique used for estab-
lishing the structure of many schiff base ligands and their metal
complexes. In 1H NMR spectra of all the metal complexes a singlet
Table 3
Table 2
UV absorption bands of schiff base ligand and its metal complexes.
IR spectral data (cmꢀ1) of Cu(II) and Zn(II) complexes.
Compound
lmax (nm)
Assignment
Geometry
Compound
ʋ(NeH)
ʋ(C]N)
ʋ(C]O)
ʋ(MeN)
[Cu(C26H22N6O5)]
642
508
320
2B1g
2B1g
LMCT
/
/
2A1g
2Eg
Square planar
[Cu(C26H22N6O5)]
[Zn(C26H22N6O5)]
3342
3343
1610
1620
1710
1705
446
435
[Zn(C26H22N6O5)]
Tetrahedral

P. Gull, A.A. Hashmi / Journal of Molecular Structure 1139 (2017) 264e268
267
Table 4
In vitro Antibacterial activity of the compounds (MIC, m
g mlꢀ1).
Compounds
Bacterial species
B. subtilis
S. aureus
E. coli
[Cu(C26H22N6O5)]
[Zn(C26H22N6O5)]
Amikacina
10
11
04
08
10
05
09
12
06
Table 5
In vitro Antifungal activity of the compounds (MIC,
m
g mlꢀ1).
Compounds
Fungal species
A. flavus
c. albicans
A. niger
[Cu(C26H22N6O5)]
[Zn(C26H22N6O5)]
Nystatin
14
11
06
13
14
04
10
10
07
Staphylococcus aureus and Escherchia coli and antifungal activities
against Aspergillus flavus, candida albicans and Aspergillus niger by
disc diffusion method. Amikacin and Nystatin were used as stan-
dards drugs for the comparison of the results. MIC values are
determined by the serial dilution technique [30]. The nutrient broth
test tubes were incubated with bacteria and fungi cultures which
were 24 h old. The test tubes were incubated at 37 ꢁC and at room
temperature for bacteria and fungi respectively. The test tubes
containing the organisms were incubated and observed for 24 h
and 48 h respectively for the presence of turbidity (Tables 4 and 5).
The outcome in the above studies shows that the metal con-
taining moieties exhibit enhanced inhibition potential (Figs. 3 and
4). This enhanced anti-microbial potential of these compounds
can be explained on the basis of the chelation of the metal ion with
the azomethine group of the primary ligand system which helps in
explaining the mechanism of transamination reactions of the bio-
logical systems [31]. According to Tweedy's theory [32,33] chela-
tion could enhance the lipophilic character of the central metal
atom, which subsequently favors its permeation through the lipid
layers of the cell membrane and blocking the metal binding sites on
enzymes of microorganism. On chelation, the polarity of the metal
ion gets decreased to a greater extent, due to the overlap of the
ligand orbital and partial sharing of its positive charge with donor
Fig. 1. X-Ray diffractogram of [Cu(C26H22N6O5)].
groups. In addition, it improves the
p
-electron delocalization on the
Fig. 2. X-Ray diffractogram of [Zn(C26H22N6O5)].
B. subtilis
S. aureus
E. coli
error method for finding the best fit between observed and calcu-
lated values. The diffractogram of Cu (II) complex shows 25 re-
flections with maxima at 2
q
¼ 19.510. The observed unit cell
parameters are as follows a ¼ 20.54 Å, b ¼ 20.54 Å, c ¼ 2.56 Å and
a
¼ 90ꢁ,
b
a
¼ 90ꢁ,
g
l
¼ 90ꢁ. The complex satisfies the condition a ¼ b
¼ 90ꢁ and the compound to be tetragonal. The
s c and
¼
b
¼
diffractogram pattern of Zn (II) complex shows 27 reflections with
maxima at 2
q
¼ 16.98. The observed unit cell parameters are as
follows a ¼ 15.10 Å, b ¼ 7.05 Å, c ¼ 18.33 Å and
a
¼ 90ꢁ,
b
¼ 90ꢁ,
g
a
¼ 90ꢁ. The complex satisfies the condition a s b s c and
¼
b
¼
g
¼ 90ꢁ and the compound to be orthorhombic. All the
peaks were matched with the JCPDF.
3.7. Biological activity
3.7.1. Antimicrobial activity
The synthesised compounds of copper and zinc complexes were
screened for antibacterial activities against Bacillus subtilis,
Fig. 3. Antibacterial activities of metal complexes (MIC, m
g mlꢀ1).

268
P. Gull, A.A. Hashmi / Journal of Molecular Structure 1139 (2017) 264e268
Appendix A. Supplementary data
A. flavus
c. albicans
A. niger
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.molstruc.2017.03.053.
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The analytical data revealed a single metal ion mononuclear
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tetrahedral for the [Zn(C26H22N6O5)]. The primary ligand and
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Acknowledgments
The authors are grateful to the University Grants Commission,
New Delhi for providing UGC-BSR Meritorious research fellowship
to P. Gull.
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