Syntheses, characterization and molecular structures of calcium(II) and copper(II) complexes bearing O2-chelate ligands: DNA binding, DNA cleavage and anti-microbial study

Article abstract of DOI:10.1016/j.poly.2011.11.004

A new set of supramolecular complexes, [Cu(PMP)₂] [1], [Cu(MCPMP)₂] [2] and [Cu(PTPMP)₂] [3] (PMP = 5-methyl-4-(4-methyl-benzoyl)-2-phenyl-2,4-dihydro-pyrazol-3-one, MCPMP = 2-(3-chloro-phenyl)-5-methyl-4-(4-methyl-benzoyl))-2,4-dihydro-pyrazol-3-one and PTPMP = 5-methyl-4-(4-methyl-benzoyl)-2-p-tolyl-2,4-dihydro-pyrazol-3-one) have been synthesized and characterized by elemental analysis, metal estimation, molar conductivity, IR, UV-Vis and TG-DTA. The molecular geometry of one of these complexes has been determined by single crystal X-ray study. The X-ray diffraction analyses of the complexes show that the Cu(II) ion center is four-coordinated. The interaction of Cu(II) complexes with pET30a plasmid DNA was investigated by Viscosity and fluorescence spectroscopy. Results suggest that the copper complexes bind to DNA via an intercalative mode and can quench the fluorescence intensity of EB bound to DNA. The interaction between the complexes and DNA has also been investigated by agarose gel electrophoresis, interestingly, we found that the Cu(II) complexes can cleave circular plasmid DNA to nicked and super coiled forms. The complexes were screened for their anti microbial activity against Gram positive (Bacillus subtilis) and Gram negative (Escherichia coli). In the preparation of these complexes the acyl pyrazolone ligands are used and prepared by method suggested by Jensen. In contrast to conventional Claisen condensations, this method produces acyl derivative of the pyrazolone in good yield and is relatively easy to prepare. In these synthesis, condensations of acid chlorides with pyrazolones in dioxane, catalyzed by suspended calcium hydroxide results Ca(II) intermediate complex and then decomposition in 2 M hydrochloric acid to give acyl pyrazolone ligands. The intermediate Ca(II) complex, [Ca(PMP)₂(EtOH)₂], was isolated for the first time and its crystal structure is reported. The crystal structure of Ca(II) complex is stabilized by O-H...N, C-H...π and π-π stacking interactions.

Full text of DOI:10.1016/j.poly.2011.11.004

Polyhedron 31 (2012) 767–778
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Syntheses, characterization and molecular structures of calcium(II)
and copper(II) complexes bearing O2-chelate ligands: DNA binding,
DNA cleavage and anti-microbial study
a
b
c
c
R.N. Jadeja a, , Komal M. Vyas , Vivek K. Gupta , Rushikesh G. Joshi , C. Ratna Prabha
⇑
a Department of Chemistry, Faculty of Science, The M. S. University of Baroda, Vadodara 390 002, India
b Post-Graduate Department of Physics, Jammu University, Jammutawi 180 006, India
c Department of Biochemistry, Faculty of Science, The M. S. University of Baroda, Vadodara 390 002, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A new set of supramolecular complexes, [Cu(PMP)2] [1], [Cu(MCPMP)2] [2] and [Cu(PTPMP)2] [3] (PMP = 5-
methyl-4-(4-methyl-benzoyl)-2-phenyl-2,4-dihydro-pyrazol-3-one, MCPMP = 2-(3-chloro-phenyl)-5-
Received 16 September 2011
Accepted 2 November 2011
Available online 10 November 2011
methyl-4-(4-methyl-benzoyl))-2,4-dihydro-pyrazol-3-one and PTPMP = 5-methyl-4-(4-methyl-ben-
zoyl)-2-p-tolyl-2,4-dihydro-pyrazol-3-one) have been synthesized and characterized by elemental analy-
sis, metal estimation, molar conductivity, IR, UV–Vis and TG-DTA. The molecular geometry of one of these
complexes has been determined by single crystal X-ray study. The X-ray diffraction analyses of the com-
plexes show that the Cu(II) ion center is four-coordinated. The interaction of Cu(II) complexes with pET30a
plasmid DNA was investigated by Viscosity and fluorescence spectroscopy. Results suggest that the copper
complexes bind to DNA via an intercalative mode and can quench the fluorescence intensity of EB bound to
DNA. The interaction between the complexes and DNA has also been investigated by agarose gel electropho-
resis, interestingly, we found that the Cu(II) complexes can cleave circular plasmid DNA to nicked and super
coiled forms. The complexes were screened for their anti microbial activity against Gram positive (Bacillus
subtilis) and Gram negative (Escherichia coli). In the preparation of these complexes the acyl pyrazolone
ligands are used and prepared by method suggested by Jensen. In contrast to conventional Claisen conden-
sations, this method produces acyl derivative of the pyrazolone in good yield and is relatively easy to pre-
pare. In these synthesis, condensations of acid chlorides with pyrazolones in dioxane, catalyzed by
suspended calcium hydroxide results Ca(II) intermediate complex and then decomposition in 2 M hydro-
chloric acid to give acyl pyrazolone ligands. The intermediate Ca(II) complex, [Ca(PMP)2(EtOH)2], was iso-
lated for the first time and its crystal structure is reported. The crystal structure of Ca(II) complex is
Keywords:
O2-donor ligands
Ca(II) and Cu(II) complexes
Crystal structures
DNA studies
Anti-microbial activity
stabilized by O–HÁ Á ÁN, C–HÁ Á Á
p and p–p stacking interactions.
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
DNA conventional behavior and so that these transition metal
complexes possess a very broad application background in the field
of bio-inorganic chemistry [1–3].
DNA plays a fundamental role in the storage and expression of
genetic information in a cell. DNA is not only an important biolog-
ical material with a unique double helical rod like structure, but
also an interesting anionic polyelectrolyte. DNA is a particularly
good target for metal complexes as its base-pairs owns rich elec-
trons. Therefore, transition metal complexes can bind to DNA in
many modes such as electrostatic, groove and intercalative bind-
ing, etc. Among them, the intercalative mode is the most important
mode in which transition metal complexes can intercalate between
Studies pertaining to DNA cleavage by synthetic reagents are of
considerable interest because of their utility tools in molecular
biology. This has resulted in the development of both sequence
specific DNA cleavers [4] and DNA foot printing agents [5]. In most
of the cases, the cleavage of DNA was carried out by metal com-
plexes or organic dyes. Transition metal complexes with their var-
ied coordination environments and versatile redox and spectral
properties are multi-utility model nucleases that are capable of
cleaving DNA by both oxidative and hydrolytic cleavage pathways
[5,6].
the pair-bases of double helix DNA, forming p–p overlapping inter-
action. It is this interaction that greatly affects and/or damages
Pyrazolones constitute a group of organic compounds that have
been extensively studied due to their properties and applications.
Furthermore, 4-acyl-pyrazolone derivatives have the potential to
form different types of coordination compounds due to the several
⇑
Corresponding author. Tel.: +91 265 2795552.
E-mail address: rajendra_jadeja@yahoo.com (R.N. Jadeja).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.11.004

768
R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
electron-rich donor centers [7] and keto–enol tautomerism. The
flexibility and conformational freedom of 4-acyl-pyrazolone li-
gands give rise to a variety of interesting structural motifs. Current
interest in the coordination chemistry of b-diketones toward sev-
eral metal ions [8], particularly in the development of the relatively
new class of 4-acyl-5-pyrazolones, having a pyrazole ring fused to
a chelating carbonyl has emerged from several points of view.
4-Acylpyrazolones are well known for their strong affinity [9] for
alkali, alkaline and transition metal ions. Significant contemporary
interests in inorganic organic hybrid materials [10] reflect their po-
tential applications in areas, such as catalysis, molecular electron-
ics, magnetism, and photochemistry [11].
The chemistry of pyrazolone derivatives has been expanded
with the synthesis of their metal complexes, studies intended to
explain their biological activity which might be based on their
capacity to form complexes with some oligoelements. It has been
shown that the pyrazolone complexes with certain metal ions act
as antitumor agents [12]. However, in the latter half of 20th cen-
tury, antitumor, antiviral or antibacterial properties of several pyr-
azolone derivatives and their complexes have also been rereported
[13]. Recently, the chemistry of pyrazolonic metal complexes has
been reviewed [14].
Pvt. Ltd., Mumbai. Double distilled water was used for preparing
all the solutions. Purity of the ligands and its complexes was eval-
uated by thin layer chromatography.
Elemental analysis (C, H, N) of all the synthesized compounds
were performed on a model 2400 Perkin–Elmer elemental ana-
lyzer. Infrared spectra (4000–400 cmÀ1, KBr discs) of the samples
were recorded on a model RX 1 FTIR Perkin–Elmer spectrophotom-
eter. 1H and 13C NMR spectra were recorded with Bruker AV
400 MHz using CDCl3 as a solvent and TMS as an internal reference.
The electronic spectra (in DMF at room temperature) in the range
of 400–800 nm were recorded on a model Perkin Elmer Lambda 35
UV–VIS spectrophotometer. GC–MS spectra of all the ligands were
recorded on Trace GC ultra DSQ II. A simultaneous TG/DTA was re-
corded on EXSTAR6000 TG/DTA6300 model. Fluorescence spectra
were recorded on a model HITACHI, F-7000 fluorescence spectro-
photometer. Molar conductivity of 10À3 M solutions of the com-
plexes in DMF was measured at room temperature with a model
Elico CM 180 digital direct reading deluxe digital conductivity me-
ter. Copper and Calcium were determined by EDTA after decom-
posing the complexes with HNO3.
2.2. DNA binding and cleavage experiments
Amongst the metal ions chosen, we have opted for biocompat-
ible endogenous metal ion Cu, known for their essential role in bio-
logical living system. Copper has been recognized as an essential
trace metal for living organisms since the late 1930s [9]. Copper
is a bioessential element with relevant oxidation states +1 and
+2. Coordination compounds of copper, in both its oxidation states,
have been extensively used in metal mediated DNA cleavage
through the generation of hydrogen abstracting activated oxygen
species [15–17]. Due to their importance in biological processes,
Cu(II) complexes synthesis and activity studies have been the focus
from different perspectives. However, most of the Cu(II) complexes
break the DNA chain rely to the presence of H2O2. And owing to the
fact that all these complexes show their own selectivity for a cleav-
age mechanism or for DNA interaction, the design of new DNA
cleavage agents is of great interest.
Fluorescence quenching experiments were conducted by add-
ing Cu(II) complex solution at different concentrations (0–50
lM)
to the samples containing 40 M EB and 50 M DNA. All the sam-
l
l
ples were excited at 340 nm and emission was recorded at 550–
650 nm.
Viscosity experiments were carried out by using an Ostwald’s
capillary viscometer, immersed in a thermostated water bath with
the temperature setting at 30 0.1 °C for 15 min. DNA samples
with an approximate average length of 200 base pairs were pre-
pared by sonication in order to minimize complexities arising from
DNA flexibility [28]. The DNA concentration in nucleotide phos-
phate (NP) was 1 mM. The concentration changes of the Cu(II)
complexes was realized by adding different volume of Cu(II) com-
plex stock solution. Flow time was measured with a digital stop-
We are also interested in the chemistry of pyrazolones and we
have reported many complexes previously [18–22]. In this paper,
we report the synthesis of Cu(II) complexes derived from various
toluoyl pyrazolones. Among them, the interaction of Cu(II) com-
plexes with DNA has been carried out by employing fluorescence
and viscosity measurements. Furthermore, DNA cleavage activity
of the complexes with DNA has also been carried out. The interme-
diate Ca(II) complex, [Ca(PMP)2(EtOH)2], formed in the preparation
of ligands by following Jensen’s procedure [23] is also isolated and
its crystal structure is reported.
watch, and each sample was measured triply, and an average
1/3
flow time was obtained. Data were presented as (
the mole ratio of Cu(II) complex to DNA. Where
g
/
g0
)
versus
g
is the viscosity
of DNA in the presence of complex, and g0 is the viscosity of
DNA alone.
The cleavage of DNA by the Cu(II) complexes was monitored
using agarose gel electrophoresis. Reactions using 3
plasmid DNA in water was treated with the Cu(II) complexes and
M hydrogen peroxide. A loading buffer containing 0.25% bromo-
lM pET30a
5
l
phenol blue, 30% glycerol was added and the electrophoresis was
performed at 100 V in Tris–acetate–EDTA (TAE) buffer using 1%
agarose gel containing ethidium bromide. Agarose gel electropho-
resis of plasmid DNA was visualized by photographing the fluores-
cence of intercalated ethidium bromide under a UV illuminator at
360 nm.
2. Experimental
2.1. Materials and general physical measurements
The reagents and chemicals of analytical grade were procured
from commercial sources. Solvents used for electrochemical and
spectroscopic studies were purified using standard procedures
[24]. pET30a DNA (Bacterial expression vector) was isolated from
E. coli by using alkaline lysis method [25]. The stock solution of
DNA was prepared by dissolving appropriate amount of DNA in
H2O and stored at À20 °C. The ratio of the absorbance at 260 and
280 nm (A260/A280) was checked to be ꢀ1.86, indicating that the
DNA is sufficiently free from protein [26]. The concentration of
DNA was determined spectrophotometrically at 260 nm after
1:100 dilution using the known molar extinction coefficient value
of 6700 MÀ1 cmÀ1 [27]. Agarose (molecular biology grade) and
ethidium bromide (EB) were obtained from Hi-media laboratories
2.3. Antimicrobial study
The in vitro antimicrobial screening of the Cu(II) complexes
were tested for their effect on certain human pathogenic bacteria
by disc diffusion method [29]. The complexes were stored dry at
room temperature and dissolved in DMF. Both the Gram positive
(Bacillus subtilis) and Gram negative (Escherichia coli) bacteria were
grown in nutrient broth medium and incubated at 37 °C for 24 h
followed by frequent subculture to fresh medium and were used
as test bacteria. From this overnight grown culture, 1% inoculum
was added in soft agar and the mixture was poured in petriplates
containing base agar. After solidification, four wells were made.
To each well the test samples with different concentrations were

R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
769
added with a sterile micropipette. The plates were then incubated
2.6. Synthesis of Cu(TP)2
at 35 2 °C for 24 h for bacteria. Inhibition was recorded by mea-
suring the diameter of the inhibitory zone after the period of incu-
bation. All the experiments were repeated thrice and the average
values are presented.
Copper complexes were prepared with the following procedure:
an ethanolic solution (60 cm3, 0.2 mM) of the ligand was added to a
methanolic solution (10 cm3, 0.1 mM) of Cu(II) acetate monohy-
drate. A green precipitate was formed immediately. The reaction
mixture was set aside overnight and the solid product was filtered
off, washed with methanol and recrystallized from acetonitrile.
The reaction was carried out under a N2 stream [30]. Solvents were
dried by standard techniques.
2.4. Synthesis of 4-toluoyl pyrazolones [TP]
5-Methyl-4-(4-methyl-benzoyl)-2-phenyl-2,4-dihydro-pyrazol-3-
one (PMP) was prepared by the interaction of 5-methyl-2-phenyl-
2,4-dihydro-pyrazol-3-one in dioxane with calcium hydroxide and
benzoyl chloride by the procedure reported by Jensen [23]. Following
the same procedure, 2-(3-chloro-phenyl)-5-methyl-4-(4-methyl-ben-
zoyl))-2,4-dihydro-pyrazol-3-one [MCPMP] and 5-methyl-4-(4-
methyl-benzoyl)-2-p-tolyl-2,4-dihydro-pyrazol-3-one [PTPMP] were
prepared using 2-(3-chloro-phenyl)-5-methyl-2,4-dihydro-pyrazol-
3-one and 5-methyl-2-p-tolyl-2,4-dihydro-pyrazol-3-one, respec-
tively. 2-(3-Chloro-phenyl)-5-methyl-4-(4-methyl-benzoyl))-2,4-dih
ydro-pyrazol-3-one [MCPMP] and 5-methyl-4-(4-methyl-benzoyl)-
2-p-tolyl-2,4-dihydro-pyrazol-3-one [PTPMP] were prepared analo-
gously from 2-(3-chloro-phenyl)-5-methyl-2,4-dihydro-pyrazol-3-
one and 5-methyl-2-p-tolyl-2,4-dihydro-pyrazol-3-one, respectively.
PMP is cream crystals. Yield 80.85% m.p. 120 °C Anal. Calc. for
Complex 1 is green crystals. Yield 44.62%, m.p. >240 °C. Anal. Calc.
for C36H30CuN4O4 (M.W. 646.18): C, 66.91; H, 4.68; N, 8.67; Cu, 9.83.
Found: C, 66.81; H, 4.62; N, 8.59; Cu, 8.99%. IR (KBr, cmÀ1): 1571 (s)
(C@N, cyclic), 1215 (s) (C@N, azomethane), 1484 (m) (C–O), 479 (m)
(Cu–O); UV–Vis (DMF): kmax/nm 722 (
2B1g ? 2A1g
Square planar; Molar conductance (DMF,
À1 cm2 molÀ1): 7.00.
Complex 2 is green crystals. Yield 45.73%, m.p. >250 °C. Anal. Calc.
e
/dm3 molÀ1 cmÀ1 7368,
,
X
for C36H28CuN4O4Cl2 (M.W. 715.06): C, 60.47; H, 3.95; N, 7.83; Cu,
8.89. Found: C, 60.50; H, 3.93; N, 7.76; Cu, 8.78%. IR (KBr, cmÀ1):
1570 (s) (C@N, cyclic), 1220 (s) (C@N, azomethane), 1472 (m) (C–
O), 482 (m) (Cu–O); UV–Vis (DMF): kmax/nm 719 (
7004, 2B1g ? 2A1g
Square planar; Molar conductance (DMF,
À1 cm2 molÀ1): 11.00.
Complex 3 is also green crystals. Yield 41.04% m.p. >240 °C. Anal.
e
/dm3 molÀ1 cmÀ1
,
C18H16N2O2 (M.W. 292.33): C, 73.95; H, 5.52; N, 9.52. Found: C,
X
73.68; H, 5.21; N, 9.51%. 1H NMR (CDCl3): d 2.16 (s, 3H, PZ C–
CH3), 2.47 (s, 3H, N-TL C–CH3), 7.28–7.46 (m, 5H, Ph), 7.49–7.59
(m, 4H, TL), 7.88–7.90 (s, 2H, PZ ring). IR (KBr, cmÀ1): 1598 (s)
(C@N, cyclic), 1641 (m) (C@O, pyrazolone ring), 1225 (s) (C@N,
azomethane); 13C NMR (CDCl3) d: 16.04 [C–CH3, PZ], 21.70 [C–
CH3, TL], 103.56 [C@O], 120.73–129.14 [substituted benzene
rings]; MS: m/z = 292.07 [C18H16N2O]+, 214.05 [C12H11N2O2]+,
200.03 [C11H9N2O2]+, 119.04 [C8H7O]+, 91.06 [C7H7]+.
Calc. for C38H34CuN4O4 (M.W. 674.23): C, 67.69; H, 5.08; N, 8.31; Cu,
9.42. Found: C, 67.61; H, 5.05; N, 8.25; Cu, 8.78%. IR (KBr, cmÀ1):
1571 (s) (C@N, cyclic), 1217 (s) (C@N, azomethane), 1480 (m) (C–
O), 480 (m) (Cu–O); UV–Vis (DMF): kmax/nm 722 (
7580, 2B1g ? 2A1g
Square planar; Molar conductance (DMF,
À1 cm2 molÀ1): 10.00.
e
/dm3 molÀ1 cmÀ1
,
X
2.7. Crystal structure determination and refinement
MCPMP is brownish yellow crystals. Yield 81.20% m.p. 100 °C.
Anal. Calc. for C18H15N2O2Cl (M.W. 326.78): C, 66.16; H, 4.63; N,
8.57. Found: C, 66.20; H, 4.52; N, 8.51%. 1H NMR (CDCl3): d 2.15 (s,
3H, PZ C–CH3), 2.47 (s, 3H, N-TL C–CH3), 7.25–7.41 (m, 4H, Ph),
7.56–7.85 (m, 4H, TL), 7.87–7.98 (s, 2H, PZ ring). IR (KBr, cmÀ1):
1580 (s) (C@N, cyclic), 1635 (m) (C@O, pyrazolone ring), 1230 (s)
(C@N, azomethane); 13C NMR (CDCl3): d 16.13 [C–CH3, PZ], 21.72
[C–CH3, TL], 103.59 [C@O], 118.14–148.23 [substituted benzene
ring], 162.90 [C–Cl]; MS: m/z = 326.03 [C18H15N2O2Cl]+, 290.53
[C18H15N2O2]+, 214.07 [C11H8N2O2Cl]+, 200.05 [C11H9N2O2]+,
119.05 [C8H7O]+, 91.07 [C7H7]+
Crystals having good morphology were chosen for three-dimen-
sional intensity data collection. X-ray intensity data of the com-
plexes Ca(PMP)2(EtOH)2 and Cu(PMP)2 were collected at room
temperature on Bruker CCD area-detector diffractometer equipped
with graphite monochromated MoK
a radiation (a = 0.71073 Å).
The crystals used for data collection were of suitable dimensions.
The unit cell parameters were determined by least-square refine-
ments of all reflections in both cases. All the structures were solved
by direct method and refined by full-matrix least squares on F2.
Data were corrected for Lorentz, polarization and multi-scan
absorption correction [31]. The structures were solved by direct
methods using SHELXS97 [32]. All non-hydrogen atoms of the mole-
cule were located in the best E-map. Full-matrix least-squares
refinement was carried out using SHELXL97 [32]. Hydrogen atoms
were placed at geometrically fixed positions and allowed to ride
on the corresponding non-H atoms with C–H = 0.93–0.96 Å, and Ui-
so = 1.5 Ueq of the attached C atom for methyl H atoms and 1.2 Ueq
for other H atoms. Atomic scattering factors were taken from Inter-
national Tables for X-ray Crystallography (1992, Vol. C, Tables
4.2.6.8 and 6.1.1.4). An ORTEP [33] view of the both the complexes
with atomic labeling are shown in Figs. 1 and 2. The geometry of
the molecule has been calculated using the software PLATON
[34] and PARST [35]. The crystallographic data are summarized
in Table 1.
PTPMP is yellow crystals. Yield 80.25% m.p. 150 °C Anal. Calc. for
C
19H18N2O2 (M.W. 306.36): C, 74.49; H, 5.92; N, 9.14. Found: C,
74.39; H, 5.87; N, 9.03%. 1H NMR (CDCl3): d 2.19 (s, 3H, PZ C–
CH3), 2.46 (s, 3H, N-TL C–CH3), 7.27–7.33 (m, 4H, Ph), 7.56–7.76
(m, 4H, TL); IR (KBr, cmÀ1): 1543 (s) (C@N, cyclic), 1630 (m)
(C@O, pyrazolone ring), 1222 (s) (C@N, azomethane); 13C NMR
(CDCl3): d 16.00 [C–CH3, PZ], 21.69 [C–CH3, TL], 103.56 [C@O],
120.73–129.14 [substituted benzene rings]; MS: m/z = 306.08
[C19H18N2O2]+, 214.95 [C12H11N2O2]+, 185.12 [C11H11N2O]+,
123.82 [C5H4N2O2]+, 119.05 [C8H7O]+, 91.04 [C7H7]+.
2.5. Synthesis of Ca(PMP)2(EtOH)2
Ca(II) complex was prepared by the following method. The metal
salt was dissolved in ethanoland the solutionwas added to a hot eth-
anolic solution of the ligand. After the complete addition little
amount of sodium acetate was added and the mixture was refluxed
for 4 h. A crystalline solid was obtained, which was isolated by filtra-
tion and recrystallized from acetonitrile. Cream crystals; Yield
70.94% m.p. 200–205 °C. Anal. Calc. for C40H42N4O6Ca (M.W.
714.86): C, 67.20; H, 5.92; N, 7.83; Ca, 5.60. Found: C, 67.40; H,
5.86; N, 7.76; Ca, 5.55%. IR (KBr, cmÀ1): 1543 (s) (C@N, cyclic),
1210 (s) (C@N, azomethane), 1492 (m) (C–O), 429 (m) (Ca–O).
3. Results and discussion
3.1. Physicochemical properties of the synthesized ligands and their
complexes
The ligands and their complexes were synthesized in a very fac-
ile and essentially identical way. The Ligand acts as a bidentate O,

770
R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
Fig. 1. The molecular structure of the Ca(II) complex, showing the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are
shown as small spheres of arbitrary radii. The CaII cation lies on an inversion center.
Fig. 2. ORTEP view of the Cu(II) complex with displacement ellipsoids drawn at 50%. H atoms are shown as small spheres of arbitrary radii.
O donor towards the Metal(II) core. The complexes were obtained
from a refluxing mixture of the respective ligand and metal salt
precursors, taken in 1:2 molar proportions in purified solvent.
The complexes were found to be fairly soluble in most of the
common organic solvents. Molar conductance value of the com-
plexes soluble in DMF (10À3 M solution at room temperature),
indicates that the complexes have molar ratio of metal: ligand as
1:2. The lesser molar conductance values indicate that the

R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
771
Table 1
atoms of the three benzene rings exhibit signals in the range d
118.14–148.23 ppm and the number of signals varies from five to
ten. Nine signals were observed for ligand PTPMP, as expected
for all p-substituted benzene rings because of symmetry. However,
five signals were observed for ligand PMP. Some of the signals
might be overlapped as indicated by the intensity of a few signals.
The other ligand MCPMP, where one of the benzene rings is m-
substituted, show ten signals, respectively, as expected because
of the loss of symmetry. The data are presented in Section 2. All
the protons and carbons were found as to be in their expected
region.
Summary of crystallographic data.
Compound
[Ca(PMP)2(EtOH)2]
Cu(PMP)2
Chemical formula
Formula weight
Crystal description
a (Å)
b (Å)
c (Å)
C40H42CaN4O6
714.86
C36H30CuN4O4
646.18
yellow plate
9.2055(18)
10.146(2)
11.039(2)
109.522(3)
106.806(3)
100.840(3)
1
882.7(3)
4818
2661
0.0535
236
dark green rectangular
6.9189(3)
9.3336(4)
12.4621(6)
84.928(2)
83.774(2)
72.492(3)
1
761.65(6)
12841
2244
0.0324
207
a
(°)
b (°)
c
(°)
Z
V (Å3)
3.3. Mass spectra
Reflection collected
Independent reflections
Rint
Number of parameters
Crystal system
Space group
The mass spectra of all bidentate pyrazolonato ligands are in
good agreement with proposed structure. Melting point of each li-
gand is high, as a result of this; the mass spectra were carried out
by EI. The electronic impact mass spectra of PMP shows a molecu-
lar ion peak at m/z = 292 with a relative intensity near to 95%,
which is equivalent to its molecular weight. The other peaks ap-
peared in the mass spectrum (abundance range 1–100%) is attrib-
uted to the fragmentation of PMP molecule obtained from the
rupture of different bonds inside the molecule. The mass spectral
assignments for all the ligands are shown in the Section 2. Simi-
larly, the NMR spectra of another two ligands also show molecular
ion peaks equivalent to their molecular weight with high abun-
dance values. The data are presented in the Section 2.
triclinic
triclinic
ꢀ
ꢀ
P1
P1
q
calc(g cmÀ3
Absorption coefficient,
(cmÀ1
F (000)
)
1.345
0.232
1.409
0.764
l
)
378
23
1.014
0.0535/0.1321
0.0688/0.1422
335
23
1.002
0.0324/0.0877
0.0435/0.1017
Temperature (°C)
Goodness-of-fit (GOF) on F2
R1/wR2([I > 2
R1/wR2 (all data)
r
(I)]
complexes are electrically non-conducting in nature [36]. The ele-
mental analyses data concur well with the planned formulae for
the ligand and also recognized the [ML2(EtOH)2] composition of
the Ca(II) complex and [ML2] composition of Cu(II) complexes.
3.4. Description of crystal structures
3.4.1. [Ca(PMP)2(EtOH)2]
The molecular structure of [Ca(PMP)2Á(EtOH)2] together with
the atom-numbering scheme is illustrated in Fig. 1. The crystal
packing of the complex projected down the a axis is illustrated in
Fig. 3. Important bond lengths and angles for all the compounds
are listed in Table 2. The X-ray analysis revealed that the com-
pound was a 6-coordinate mononuclear Ca(II) complex with two
oxygen atoms of the ethanol molecules and four oxygen atoms of
two bidentate pyrazolonates. Taking into consideration that it usu-
ally adopts an octahedral conformation because of the large ligand
field stabilization energy, this configuration is quite ideal. The
coordination plane around Ca(1) ion is composed of O(1), O(2)
and O(3) atoms with normal bond distances of Ca(1)–O(1):
2.3215(15), Ca(1)–O(2): 2.3301(16) and Ca(1)–O(3): 2.3834(17).
In the equatorial plane, the trans angles in O(2)–Ca(1)–O(2) and
O(3)–Ca(1)–O(3) are exactly 180°, while 94.94(6)° for the angles
of O(3)–Ca(I)–O(2) and O(3)–Ca(I)–O(2) and 85.06(6)° for the an-
gles O(2)–Ca(I)–O(3) and O(2)–Ca(I)–O(3), add up to 360(24)°.
Bond angles show that the coordination geometry around the cal-
cium ion in the complex is slightly distorted octahedral. Atoms
O(1) and O(2) of both the ligand molecules occupy the equatorial
positions of the octahedron and O(3) atom of both the ligand mol-
ecules occupy two axial positions. Ca(II) is located in the center of
the octahedral.
In the complex, the bond length of O(1)–C(3) and O(2)–C(13)
are 1.255(3) and 1.251(3) Å, respectively, which are shorter than
1.43 Å for a C–O single bond and longer than 1.22 Å for a C@O dou-
ble bond length. Moreover, the C(3)–N(2) bond length is close to
the C–N double bond length, confirming that the keto form of
the ligand tautomerizes to the enol form. All atoms of the complex
and the pyrazolone rings are not in the same plane. As a result, the
compound is a non-plannar molecule. The complex contains two
ethanol molecules, which are bridged together through hydrogen
bond and connect one pyrazolone-ring N(1) atom with the neigh-
boring pyrazolone-ring N(1) atom through intermolecular hydro-
gen bonds [O(3)–H(3)Á Á ÁN(1)]. Thus, the molecules are stringed
3.2. IR Spectra
The ligands as well as its corresponding complexes show
absorption in the region 3000–2900 cmÀ1, which may be due to
m
C–H. The IR spectrum of the ligands has one prominent band
appearing between 1630–1641 cmÀ1 due to
v
C@O stretching modes.
This band disappeared on complexation and a new vC–O band at
1472–1492 cmÀ1 appeared [37]. Furthermore, comparison of the
IR spectra of the ligands with those of their metal(II) complexes,
indicates that the ligands are coordinated to metal(II) by two sites,
that is the ligands are bidentate. That the band due to vC@O is com-
pletely missing in the spectra of the complexes, suggests enoliza-
tion of the ligand on complexation. This is supported by the fact
that no band for vOH is observed in the infrared spectra of the li-
gands and their metal(II) complexes. Instead, a band due to vC–O
was observed for all the complexes, which supports the observa-
tion of their enolization during coordination. This fact suggests
that the ligand remains in the keto form in the solid state, but in
solution both the keto and enol forms remain in equilibrium.
Deprotonation occurs from the enol form on complexation. In addi-
tion, the new band at 429–482 cmÀ1 is assigned to M–O bond [22].
3.2.1. 1H and 13C NMR Spectra
The 1H spectra of all the ligands were recorded in CDCl3 at room
temperature. The signals due to methyl protons (two in the case of
PMP and MCPMP and three in the case of PTPMP) appeared as sin-
glet in the range d 2.15–2.47 ppm. In the aromatic region, a few
doublets and in few cases some overlapping doublets/multiplets
are observed in the range d 7.25–7.99 ppm in all the ligands. These
doublets/multiplets are due to aryl protons of two benzene rings.
We have not done any temperature dependent experiments. The
data are presented in Section 2.
In the 13C NMR spectra of the ligands, the carbon atoms of the
methyl groups appear in the range d 16.00–21.72 ppm. The carbon

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R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
Fig. 3. The crystal packing of Ca-complex projected down the a axis. Hydrogen atoms have been omitted for clarity.
Table 2
Important bond lengths and angles for the complexes.
Bond distances (Å) with esd’s in parentheses
Bond angles (°) with esd’s in parentheses
[Ca(PMP)2(EtOH)2]
Ca1–O1
Ca1–O2
Ca1–O3
O1–C3
O2–C13
O3–C21
C4–C13
C5–C12
C14–C19
C17–C20
N1–N2
2.3215 (15)
2.3301(16)
2.3834(17)
1.255(3)
1.251(3)
1.440(3)
1.433(3)
1.498(3)
1.395(3)
1.512(3)
1.405(2)
1.414(3)
O1–Ca1–O1
O1–Ca1–O2
O1–Ca1–O2
O2–Ca1–O2
O2–Ca1–O3
O1–Ca1–O3
O3–Ca1–O3
O1–Ca1–C3
O2–Ca1–C3
O1–Ca1–C3
C3–O1–Ca1
C13–O2–Ca1
180.0
78.96(5)
101.04(5)
180.0
94.94(6)
93.32(6)
180.00(9)
161.86(5)
118.64(6)
161.86(5)
126.70(14)
133.75(15)
N2–C6
Cu(PMP)2
Cu1–O1
Cu1–O2
C7–O1
1.9013(14)
1.9193(15)
1.271(2)
1.261(2)
1.397(2)
1.484(3)
1.363(3)
1.303(3)
O1–Cu1–O1
O2–Cu1–O2
O1–Cu1–O2
C7–O1–Cu1
C9–O2–Cu1
O1–C7–N1
O1–C7–C8
O2–C9–C8
180.00(9)
180.000(1)
93.18(6)
119.46(13)
129.29(14)
123.09(19)
130.86(19)
121.47(19)
C9–O2
N1–N2
C9–C10
C7–N1
C16–N2
together as shown in Fig. 4, and and three-dimensional non-planar
molecule structure supramolecule is formed. In above, H-bonding
interactions play an important role in forming the supramolecular
structure by self-assembly and stabilizing. A small portion of the
3D crystal structure of the complex due to hydrogen bonding inter-
actions (dashed lines) is shown in Fig. 4.
atoms of two bidentate pyrazolonates. The coordination plane
around Cu(1) ion is composed of O(1) and O(2) atoms with normal
bond distances of Cu(1)–O(1): 1.9013(14), and Cu(1)–O(2):
1.9193(15). In the equatorial plane, the trans angles in O(1)–
Cu(1)–O(1) and O(2)–Cu(1)–O(2) are exactly 180°, while
93.18(6)° for the angles of O(1)–Cu(I)–O(2) and O(1)–Cu(I)–O(2)
and 86.82(6)° for the angles O(1)–Cu(I)–O(2) and O(1)–Cu(I)–
O(2), add up to 360(24)°. Bond angles show that the coordination
geometry around the copper ion in the complex is slightly square
planer. Atoms O(1) and O(2) of both the ligand molecules occupy
the equatorial positions of the square plane and Cu(II) is located
in the center of the plane.
3.4.2. [Cu(PMP)2]
The molecular structure of [Cu(PMP)2] together with the atom-
numbering scheme is illustrated in Fig. 2. The crystal packing of the
complex projected down the a axis is illustrated in Fig. 5. Impor-
tant bond lengths and angles for all the compounds are listed in Ta-
ble 2. The X-ray analysis revealed that the compound was a 4-
coordinate mononuclear Cu(II) complex with the four oxygen
In the complex, the bond length of O(1)–C(7) and O(2)–C(9) are
1.271(2) and 1.261(2) Å, respectively, which are shorter than

R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
773
at 354 °C and the DTA peak is observed at 353 °C. The third stage
shows the mass loss at 470 °C corresponding to decomposition of
one ligand molecule. The observed mass loss is 40.73%, which is
consistent with the theoretical value of 40.66%. In this stage, DTG
peak is observed at 436 °C.
3.7. DNA binding studies
3.7.1. Viscosity studies
Optical photophysical probes provide necessary, albeit not suf-
ficient, insight to support a binding model. Hydrodynamic mea-
surements, i.e. viscosity and sedimentation that are sensitive to
length changes are regarded as the least ambiguous and most crit-
ical tests to a binding model in solution in the absence of crystal-
lographic structural data [39]. A classical intercalation model
usually results in lengthening of the DNA helix as base pairs are
separated to accommodate the bound ligand, leading to an in-
crease in the DNA viscosity. In contrast, semi-intercalation of a li-
gand could bend or kink the DNA helix, and thus reduce its
effective length and, concomitantly, its viscosity. A classical inter-
calation mode causes a significant increase in viscosity of DNA due
to an increase in separation of base pairs at intercalation sites and
hence an increase in overall DNA length [40].
The changes in the relative viscosity of rod-like DNA in the pres-
ence of Cu(II) complexes are shown in Fig. 6. The viscosity of DNA
increases greatly with increasing concentration of complex, which
is similar to that of the proven intercalator EtBr [41]. This observa-
tion suggests that the principal mode of DNA binding by complexes
involve base-pair intercalation, with one ligand intercalating into
the base pairs and the other ligand being left outside the helix
[42]. The intercalative interaction with DNA is related to the
molecular structure, as in this complex there is a little distorted
plane that may lead to the weak intercalative mode. This result
also parallels the pronounced emission enhancement of both com-
plexes, and is comparable with the proven classical intercalator
EtBr. On the basis of the viscosity results, the complexes bind with
DNA through the intercalation mode. The increased degree of vis-
cosity, which may depend on its affinity to DNA follows the order
of EB >3 > 2 > 1, which is consistent with the above results of Cu(II)
proposes to be bound to DNA by intercalation [43].
Fig. 4. A small portion of the 3D crystal structure of the Ca-complex due to
hydrogen bonding interactions (dashed lines). Hydrogen atoms have been omitted
for clarity. Color code: Ca-green; O-red; N-light blue; C-gray. (color online.)
1.43 Å for a C–O single bond and longer than 1.22 Å for a C@O dou-
ble bond length. Moreover, the C(7)–N(1) bond length is close to
the C–N double bond length, confirming that the keto form of
the ligand isomerizes to the enol form. All atoms of the complex
and the pyrazolone rings are in the same plane. As a result, the
compound is a planar molecule.
3.7.2. Competitive DNA-binding studies with EB
3.5. Electronic spectral studies
In order to further investigate the interaction mode between
the complexes and DNA, the fluorescence titration experiments
are performed. The fluorescence titration experiments, especially
the EB fluorescence displacement experiment, have been widely
used to characterize the interaction of complexes with DNA by fol-
lowing the changes in fluorescence intensity of the complexes. The
displacement technique is based on the decrease of fluorescence
resulting from the displacement of EB from a DNA sequence by a
quencher and the quenching is due to the reduction of the number
of binding sites on the DNA that is available to the EB. The intrinsic
fluorescence intensities of DNA and that of EB are low, while the
fluorescence intensity of EB will be enhanced on addition of DNA
as its intercalation into the DNA. Therefore, EB can be used to probe
the interaction of complexes with DNA. If the complexes can inter-
calate into DNA, the binding sites of DNA available for EB will be
decreased, and hence the fluorescence intensity of EB will be
quenched [44].
In our experiments, as depicted in Fig. 7 for complexes 1, 2 and
3, the fluorescence intensity of EB show a remarkable decreasing
trend with the increasing concentration of the complexes, indicat-
ing that some EB molecules are released from EB-DNA complex
after an exchange with the complex 1, 2 or 3 which result in the
fluorescence quenching of EB. This may be due either to the metal
complex competing with EB for the DNA-binding sites thus
Electronic spectra serve as a tool to distinguish between the
square-planar, octahedral, and tetrahedral geometries of the com-
plexes. The absorption regions, assignment and the proposed geom-
etry of the complexes are given in Section 2. Electronic absorption of
the copper complexes in the DMF solution show d–d transition band
between 719 and 722 nm, which can be assigned as the 2B1g ? 2A1g
transition, revealing that the Cu(II) complexes exist in the square-
planar geometry [38]. These results are the same as those found
for the crystallographically determined structure and spectoscopi-
cally confirmed.
3.6. TG-DTA studies
The TG curve of the complex [Ca(PMP)2(EtOH)2] follows the de-
crease in sample mass with increase in temperature. The decompo-
sition of the complex undergoes in three stages. The degradation of
one mole of EtOH molecule takes place in the first stage at 191 °C
with a mass loss of 6.41% (Calc.: 6.40%). The maximum rate of mass
loss is indicated by the DTG peak at 193 °C. One endotherm is ob-
served in the DTA trace at 194 °C. In second stage, the mass loss oc-
curred at 380 °C corresponds to decomposition of two EtOH
molecules with 12.82% (Calc.: 12.81%). The DTG peak is observed

774
R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
Fig. 5. The packing arrangement of molecules viewed down the a-axis.
increasing the complex concentration could be caused due to the
displacement of the DNA bound EB by the Cu(II) complexes. Such
a quenched fluorescence behavior of EB bound to DNA caused by
the interaction between the binuclear Cu(II) complexes and DNA
is also found in other copper complexes [45].
The quenching of EB bound to DNA by the test complexes is in
good agreement with the linear Stern–Volmer equation. The fluo-
rescence quenching curve of EB bound to DNA by the Cu(II) com-
plexes are shown in Fig. 8. The ratio of the slope to the intercept
obtained by plotting F0/F versus [Complex] yielded the value of
Kb corresponding to the three complexes as 1.14 Â 103,
5.54 Â 103 and 1.017 Â 104 MÀ1, respectively. These values sug-
gested that the complex 3 showed higher quenching efficiency
than the other complexes 1 and 2. Further, the figures also show
that the ratio of quenching of the intensities in all three complexes
is different, reflecting more binding of complex 3 with DNA to
leach out more number of EB molecules originally bound to DNA
than that of the complexes 1 and 2. Our results are consistent with
earlier reports on preferential binding to DNA in the Cu complexes
[46–48].All these results showed clearly that the complex 3 pos-
sesses strong tendency to bind with DNA which is consistent with
the viscosity results.
Fig. 6. Effect of increasing amounts of complex 1 (A), complex 2 (B) and complex 3
(C) on the relative viscosities of DNA at 30.0 0.1 °C. [DNA] = 1 mM, [Complex]/
[DNA] = 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, respectively.
3.8. DNA cleavage studies
The characterization of DNA recognition by transition metal
complex has been aided by the DNA cleavage chemistry that is
associated with redox-active or photoactivated metal complexes
[49]. DNA cleavage is controlled by relaxation of super coiled
displacing the EB (whose fluorescence is enhanced upon DNA bind-
ing) or it should be a more direct quenching interaction on the DNA
itself. We assume the reduction of the emission intensity of EB on

R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
775
Fig. 7. Emission spectra of EB bound to DNA in the absence (dash line) and presence (solid line) of complexes 1, 2 and 3, respectively. [EB] = 40 lM, [DNA] = 50 lM,
[Complex] = 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 lM, respectively; kex = 340 nm. The arrow shows the intensity changes on increasing the complex concentration.
circular form of pET30a DNA into nicked circular form and linear
form. When circular plasmid DNA is conducted by electrophoresis,
the fastest migration will be observed for the super coiled form
(Form I). If one strand is cleaved, the super coiled will relax to pro-
duce a slower-moving open circular form (Form II). If both strands
are cleaved, a linear form (Form III) will be generated that migrates
in between.
two bands was also observed indicating the formation of linear
DNA (form III).
As shown in Fig. 9, with the increase of the complex 1 concen-
tration, the intensity of the nicked (Form II) band was found de-
crease and simultaneously, the circular super coiled DNA (Form
I) band was also found decrease. When the complex concentration
was up to 50 lM (lane 8), the circular super coiled DNA (Form I)
Here we studied DNA cleavage on pET30a DNA isolated from E.
coli. The electrophoresis clearly revealed that all complexes act on
DNA as there was molecular weight difference between the control
and the treated DNA samples. The Cu(II) complexes in the presence
of H2O2 as an oxidizing agent show high nuclease activity with
DNA. As a sequel to find out whether any of these synthesized
compounds would exhibit DNA cleavage activities in vitro, their
band was extremely faint, while the nicked (Form II) band was al-
most disappeared. Fig. 10 shows that on increasing the concentra-
tion of complex 2, we found the result similar to complex 1. But the
difference was, when the complex concentration was up to 50 lM
(lane 8), the circular super coiled DNA (Form I) and nicked (Form II)
band were disappeared completely. Complex 3 shows different
cleavage than 1and 2. As shown in Fig. 11 with increase of complex
3 concentration, the super coiled DNA (Form I) apparently convert
to nicked (Form II). These results are similar to that observed for
some Cu-salen complexes as chemical nuclease [11]. It is likely
the generation of hydroxyl radical and/or activated oxygen
effect at concentrations of 10–50 lM (lanes 4–8) was studied using
pET30a DNA and the results are shown in Figs. 9–11, respectively.
In case of complexes 1 and 2, we found similar results, while
complex 3 gives different pattern. The difference between these

776
R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
Fig. 8. Fluorescence quenching curve of EB bound to DNA by (A) complex 1, (B) complex 2 and (C) complex 3. [EB] = 40
35, 40, 45, 60 M, respectively; kex = 340 nm.
lM, [DNA] = 50 lM, [Complex] = 0, 5, 10, 15, 20, 25, 30,
l
Fig. 9. Cleavage of DNA induced by complex 1: Lane 1, untreated DNA; lane 2, plasmid DNA + 3
complex + 3 l H2O2; lane 5, plasmid DNA + 20 M complex + 3 l H2O2; lane 6, plasmid DNA + 30
H2O2; lane 8, plasmid DNA + 50 M complex + 3 l H2O2.
l
l H2O2; lane 3, plasmid DNA + 50
l
M complex; lane 4, plasmid DNA + 10
lM
l
l
l
l
l
M complex + 3 l H2O2; lane 7, plasmid DNA + 40
l
lM complex + 3 ll
l
mediated by the copper complex results in DNA cleavage. Further
studies are undergoing to clarify the cleavage mechanism.
activity against Gram +ve bacteria. The test solutions were prepared
in DMF and the results of the antimicrobial activities are summa-
rized in Table 3 and Fig. 12. In our biological experiments, using
Cu(II) complexes, we have done antibacterial activity against Gram
+ve bacteria Bacillus subtilis and Gram Àve bacteria Escherichia coli.
The complexes have exhibited considerable activity against Gram
+ve B. subtilis, but inactive against Gram Àve E. coli. The results show
that complex 1 exhibits better activity than complexes 2 and 3.
3.9. Antimicrobial screening
The Cu(II) complexes were screened in vitro for its microbial
activity against certain pathogenic bacterial species using disc diffu-
sion method. The complexes were found to exhibit considerable

R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
777
Fig. 10. Cleavage of DNA induced by complex 2: Lane 1, untreated DNA; lane 2, plasmid DNA + 3
DNA + 10 M complex + 3 l H2O2; lane 5, plasmid DNA + 20 M complex + 3 l H2O2; lane 6, plasmid DNA + 30
complex + 3 l H2O2; lane 8, plasmid DNA + 50 M complex + 3 l H2O2.
l
l H2O2; lane 3, plasmid DNA + 50
l
M complex; lane 4, plasmid
l
l
l
l
lM complex + 3 ll H2O2; lane 7, plasmid DNA + 40 lM
l
l
l
Fig. 11. Cleavage of DNA induced by complex 3: Lane 1, untreated DNA; lane 2, plasmid DNA + 3
ll H2O2; lane 3, plasmid DNA + 50
lM complex; lane 4, plasmid
DNA + 10
lM complex + 3
l
l H2O2; lane 5, plasmid DNA + 20
lM complex + 3
ll H2O2; lane 6, plasmid DNA + 30
lM complex + 3
l
l H2O2; lane 7, plasmid DNA + 40 M
l
complex + 3 ll H2O2.
4. Conclusions
Table 3
Four new complexes containing pyrazolone have been synthe-
sized and thoroughly characterized. The molecular geometries of
two of these complexes have been determined by single crystal
X-ray study. The X-ray diffraction analyses of the complexes show
that the Ca(II) ion center is six-coordinated while the Cu(II) ion
center is four-coordinated. The crystal structure of Ca(II) complex
Antimicrobial activities of Copper(II) complexes against Gram +ve bacteria Bacillus
subtilis.
Complex
Diameter of inhibition zone (mm)
0.003 mM
0.03 mM
0.3 mM
3 mM
1
2
3
f
f
f
8
8
4
15
10
11
25
20
20
is stabilized by O–HÁ Á ÁN, C–HÁ Á Á
p and p–p stacking interactions.
The comparative in vitro binding studies of the Cu(II) complexes
with DNA were also investigated by fluorescence and viscosity
measurements. The results indicate that complex 3 has a greater
f = No inhibition zone is determined.
Fig. 12. Bacterial activity against Gram +ve bacteria (Bacillus subtilis) of (1) complex 1, (2) complex 2 and (3) complex 3.

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R.N. Jadeja et al. / Polyhedron 31 (2012) 767–778
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to DNA through intercalation, while 1 and 2 binds to DNA in a par-
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by gel electrophoretic mobility assay; the complexes display effi-
cient cleavage activity of plasmid pET30a DNA converting the Form
I to Form II and ultimately to leading to the formation of linearized
Form III with increasing concentrations of the complex. This work
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cleavage activity of the complexes. The results are of importance
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design of new useful DNA probes. They can also be considered
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