Bio active mixed ligand complexes of Cu(II), Ni(II) and Zn(II): Synthesis, spectral, XRD, DNA binding and cleavage properties

Article abstract of DOI:10.1016/j.inoche.2013.12.012

The paper presents the synthesis of complex combinations of Cu(II), Zn(II) and Ni(II) with Schiff bases obtained by the condensation reaction of diphenylglyoxal with 1-amino-4-nitrobenzene (L¹)/1-amino-4- chlorobenzene (L²)/p-anisidi

Full text of DOI:10.1016/j.inoche.2013.12.012

Inorganic Chemistry Communications 40 (2014) 157–163
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Feature article
Bio active mixed ligand complexes of Cu(II), Ni(II) and Zn(II): Synthesis,
spectral, XRD, DNA binding and cleavage properties
⁎
Natarajan Raman , Rajkumar Mahalakshmi
Research Department of Chemistry, VHNSN College, Virudhunagar 626 001, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The paper presents the synthesis of complex combinations of Cu(II), Zn(II) and Ni(II) with Schiff bases obtained
by the condensation reaction of diphenylglyoxal with 1-amino-4-nitrobenzene (L1)/1-amino-4-chlorobenzene
(L2)/p-anisidine (L3) as the main ligand and 1,10-phenanthroline as the co-ligand respectively. The characteriza-
tion of newly formed complexes has been done by spectral and molar conductivity studies. The bioefficacy of the
ligands and their complexes have been examined against the growth of bacteria and fungi in vitro to evaluate
their antimicrobial potential. The in vitro antibacterial and antifungal assay indicates that these complexes are
good antimicrobial agents against various pathogens. X-ray powder diffraction illustrates that the complexes
have crystalline nature. The effect of the metal complexes on DNA is carried out by pUC19 DNA agarose gel elec-
trophoresis at 50 V for 2 h. The results indicate that the complexes bind to DNA through intercalation and act as
efficient cleaving agents.
Received 25 October 2013
Accepted 9 December 2013
Available online 17 December 2013
Keywords:
XRD
Mixed ligand complexes
Antibacterial activity
DNA binding
DNA cleavage
1,10-Phenanthroline complexes
© 2013 Elsevier B.V. All rights reserved.
Contents
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162
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162
Appendix A.
References
Supplementary material
. . . . . . . . . . . .
.
Progress of a new chemotherapeutic Schiff bases is now attracting
the attention of medicinal chemist [1]. The area of inorganic chemistry,
which most widely developed in the last few decades is mainly due
to coordination chemistry and applies very particularly to the coordina-
tion compounds of transition metals. The chemistry of coordination
compounds has always been a challenge to the inorganic chemists.
Metal ion dependent processes are found throughout the life science
and vary tremendously in their function and complexity. In literature,
several reports linked the significance of biological activity of metal
complexes with the metal ions rather than with the ligands [2]. Transi-
tion metals are involved in numerous biological processes. The identifi-
cation of metal complex–DNA interaction is of fundamental importance
to the understanding of the molecular basis of therapeutic activity.
Metal complexes are well known to accelerate the drug action and
the efficiency of a therapeutic agent can often be enhanced upon coor-
dination with metal ions [3]. The pharmacological activity has also
been found to be highly dependent on the nature of the metal ion and
the donor sequence of the ligands as different ligands exhibit different
biological properties [4].
Diphenylglyoxal (benzil) is a diketone compound. Benzil and its re-
lated compounds have been extensively used as biologically active
complexing agents and analytical reagents [5]. 1,10-Phenanthroline
(phen) is a classic chelating bidentate ligand for transition metal ions
that has played an important role in the development of coordination
chemistry [6]. DNA binding of mixed ligand polypyridyl complexes (the
ligands employed include: 2,2-bipyridine (bpy), 1,10-phenanthroline
(phen), 4,7-diphenylphenanthroline (DIP), 5-nitrophenanthroline
(5-NO2-phen) and 9,10-phenanthrenequinonediimine (phi)) and the
factors (geometry, size, hydrophobicity, and hydrogen-bonding ability)
contribute to DNA binding affinity [7]. Taking advantages of these struc-
tural features (planarity, rigidity and hydrophobicity) phen derivatives
and their metal complexes have been used, for example, as intercalating
or groove binding agents for DNA [8,9]. Keeping the above facts in
our mind, we herein report the synthesis and structural characteriza-
tion, binding, cleavage and biological studies of few novel mixed
ligand Cu(II), Ni(II) and Zn(II) complexes with diphenylglyoxal and
1-amino-4-nitrobenzene/1-amino-4-chlorobenzene/p-anisidine as the
main ligand and 1,10-phenanthroline as the co-ligand (Scheme 1).
⁎
Corresponding author. Tel.: +91 9245165958; fax: +91 4562281338.
E-mail address: drn_raman@yahoo.co.in (N. Raman).
1387-7003/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.inoche.2013.12.012

158
N. Raman, R. Mahalakshmi / Inorganic Chemistry Communications 40 (2014) 157–163
Scheme 1. Schematic route for synthesis of Schiff base ligands and their mixed ligand metal complexes.
The metal ion is coordinated by six atoms, two nitrogen C_N from
diphenylglyoxal and 4N from co-ligand to form N6 type metal(II)
complexes.
The Schiff base ligand and its mixed ligand complexes were
prepared by a typical procedure [10–23]. The nature of bonding and
geometry of the transition metal complexes as well as ligands have
been deduced from elemental analysis, FT-IR, UV–vis, 1H NMR, EPR
spectral studies, magnetic susceptibility and molar conductance
measurements. All the instrumental details and their EPR spectral char-
acterization are given in Supplementary file. The analytical and physical
data of Schiff base ligands and its complexes are given in Supplementa-
ry file (Table S3).
The mode and propensity for binding of the complexes to calf
thymus DNA (CT-DNA) have been studied with the assist of different
techniques, like electronic absorption, viscosity and electrochemical
methods. DNA binding activities of metal complexes have been

N. Raman, R. Mahalakshmi / Inorganic Chemistry Communications 40 (2014) 157–163
159
Fig. 1. Absorption spectra of (a) [NiL1(phen)2] and (b) [CuL1(phen)2] complexes in buffer pH = 7.2 at 25 °C in the presence of increasing amount of DNA. Arrow indicates the changes in
absorbance upon increasing the DNA concentration.
Fig. 2. Absorption spectra of (a) [ZnL2(Phen)2] and (b) [CuL3(Phen)2]complexes in buffer pH = 7.2 at 25 °C in the presence of increasing amount of DNA. Arrow indicates the changes in
absorbance upon increasing the DNA concentration.
a clue of vital importance for the development of effective metal
based chemotherapeutic drugs. Any change in the UV–vis absorption
spectra of metal complexes upon the addition of DNA serves as a
proof for the existence of an interaction between them in particular,
hypochromism due to π–π* stacking interaction with a red-shift
(bathochromism) may appear in the case of an intercalative binding
leading to stabilization of DNA duplex. The extent of the hypochromism
commonly parallels the intercalative binding strength. The electronic
absorption spectra of [CuL1(phen)2] complex shows an intensive
absorption band at 385.0 nm, [CuL2(phen)2] complex at 267.0 nm
and [CuL3(phen)2] complex at 267.0 nm respectively. Further the
intense absorption bands with maxima of 383.0 nm, 269.0 nm
and 269.0 nm for [NiL1(phen)2], [NiL2(phen)2] and [NiL3(phen)2],
382.0 nm, 267.0 nm and 269.0 nm for [ZnL1(phen)2], [ZnL2(phen)2]
and [ZnL3(phen)2] respectively are obtained. On increasing concen-
tration of CT-DNA results in the bathochromic shift in the range
1.8–6.0 nm and significant hypochromicity lying in the range 17–31%.
The observed hypochromism could be credited to stacking interaction
between the aromatic chromophores of the complexes and DNA
base pairs consistent with the intercalative binding mode, while
the red-shift is an evidence of the stabilization of the CT DNA duplex.
UV–vis spectra of metal complexes in the absence or presence of CT
DNA values are shown representatively in Fig. 1 for (a) [NiL1(phen)2]
and (b) [CuL1(phen)2] complexes and in Fig. 2 for (a) [ZnL2(phen)2]
and (b) [CuL3(phen)2] complexes.
6.6 × 105, 4.9 × 105, 3.2 × 105 M−1 5.9 × 105, 4.2 × 105, and
,
2.8 × 105 M−1 respectively. The binding constant (Kb) values of these
complexes are compared to those observed for typical intercalators,
ethidium bromide and [Ru(bpy)2(dppz)]2+ whose binding constants
are in the order of 1.4 × 106 and N106 M−1 [24,25]. In order to compare
quantitatively the binding strength of the complexes with CT DNA, the
intrinsic binding constants (Kb) were obtained by monitoring the
changes in the absorbance for the complexes with increasing concen-
tration of DNA. Kb was obtained from the ratio of slope to the intercept
from the plot of [DNA] / (εa − εf) versus [DNA]. The Kb values are
shown in Table 1.
Table 1
Electronic absorption spectral properties of Cu(II), Ni(II) and Zn(II) complexes with DNA.
Compound
λmax
Δλ/nm
H%a
K × 105b
(M−1
)
Free
Bound
[CuL1(phen)2]
[NiL1(phen)2]
[ZnL1(phen)2]
[CuL2(phen)2]
[NiL2(phen)2]
[ZnL2(phen)2]
[CuL3(phen)2]
[NiL3(phen)2]
[ZnL3(phen)2]
385.0
383.0
382.0
267.0
269.0
267.0
267.0
269.0
269.0
375.0
378.5
377.8
264.0
267.2
265.0
264.2
266.6
267.0
6.0
4.5
4.2
3.0
1.8
2.0
2.8
2.4
2.0
31
19
23
28
17
20
18
20
24
7.5
5.6
3.8
6.6
4.9
3.2
5.9
4.2
2.8
The intrinsic binding constant values (Kb) for the complexes
[CuL1(phen)2], [NiL1(phen)2], [ZnL1(phen)2], [CuL2(phen)2],
[NiL2(phen)2], [ZnL2(phen)2], [CuL3(phen)2], [NiL3(phen)2], and
[ZnL3(phen)2] were found to be 7.5. × 105, 5.6 × 105, 3.8 × 105,
a
H% = [(Afree − Abound)/Afree] × 100%.
b
Kb = Intrinsic DNA binding constant determined from the UV–vis. absorption spec-
tral titration.

160
N. Raman, R. Mahalakshmi / Inorganic Chemistry Communications 40 (2014) 157–163
Fig. 3. Cyclic voltammograms of (a) [CuL1(phen)2] and (b) [NiL1(phen)2] in buffer (pH = 7.2) at 25 °C in the presence of increasing amount of DNA. Arrow indicates the changes in
voltammetric current upon increasing the DNA concentration.
Fig. 4. Cyclic voltammograms of (a) [CuL2(phen)2] and (b) [ZnL3(phen)2] in buffer (pH = 7.2) at 25 °C in the presence of increasing amount of DNA. Arrow indicates the changes in
voltammetric current upon increasing the DNA concentration.
The application of cyclic voltammetry to the studies of complexes
bound to DNA provides a useful complement to the formerly used
methods of investigation, such as UV–vis spectroscopy and viscosity
measurements. The cyclic voltammograms of (a) [CuL1(phen)2] and
(b) [NiL1(phen)2] complexes in the absence and in the presence of
varying amount of DNA are shown in Fig. 3 and (a) [CuL2(phen)2] and
(b) [ZnL3(phen)2] Fig. 4 respectively.
The incremental addition of CT DNA to the complex causes shift
in the potential of peak in cyclic voltammogram. This result shows
that complex stabilizes the duplex (GC pairs) by intercalating
way. Electrochemical parameters for the interaction of DNA
with [CuL1(phen)2], [NiL1(phen)2], [ZnL1(phen)2], [CuL2(phen)2],
[NiL2(phen)2], [ZnL2(phen)2], [CuL3(phen)2], [NiL3(phen)2] and
[ZnL3(phen)2] metal(II) complexes are shown in Table 2. Both the
cathodic and anodic peaks show positive or negative shift which in-
dicates intercalation of complex to DNA of base pairs. The incre-
ment addition of CT-DNA to the complexes causes a positive shift
in potential and a decrease in the current intensity. From these
data, it is understood that all the synthesized complexes interact
with DNA through intercalating way.
It is further evidence that the aspire of clarifying the binding of the
metal complexes to DNA, viscosity measurements were carried out on
Table 2
Electrochemical parameters for interaction of DNA with Cu(II), Ni(II) and Zn(II)
complexes.
⁎
Compound
E1/2 (V)
ΔEp(V)
Ipc/Ipa
Free
Bound
Free
Bound
[CuL1(phen)2]
[NiL1(phen)2]
[ZnL1(phen)2]
[CuL2(phen)2]
[NiL2(phen)2]
[ZnL2(phen)2]
[CuL3(phen)2]
[NiL3(phen)2]
[ZnL3(phen)2]
−0.471
−0.320
−0.288
−0.033
−0.083
−0.275
0.011
−0.248
−0.281
−0.239
−0.023
−0.018
−0.274
−0.195
0.223
0.933
0.768
0.874
0.186
1.20
0.657
0.333
0.572
0.874
0.991
0.840
0.795
0.212
1.269
0.687
0.235
0.605
0.795
0.7782
0.5632
0.6560
0.7432
0.5648
0.6342
0.7234
0.5653
0.6123
0.177
−0.288
−0.239
Fig. 5. Powder X-ray diffraction pattern of Cu(II) complex for L1.
⁎
Error limit: 5%.

N. Raman, R. Mahalakshmi / Inorganic Chemistry Communications 40 (2014) 157–163
161
Table 3
the viscosity of CT DNA are shown in Fig. S1 in supplementary file.
A significant increase in the viscosity of DNA on addition of complex
results due to the intercalation which leads to the separation among
the DNA bases to the increase in the effective size in DNA which
could be the reason for the increase in the viscosity [26].
X-ray diffraction data of [CuL1(phen)2].
2θ
d-Spacing
(hkl)
Intensity(%)
Observed
JCPDS
Observed
JCPDS
33.495
39.953
53.703
52.723
29.280
32.538
38.924
53.546
51.405
32.538
2.673
2.254
1.705
1.734
3.047
2.749
2.311
1.710
1.776
2.749
(110)
(200)
(020)
(112)
(110)
10.60
13.15
4.13
6.88
100
Single crystal X-ray crystallographic investigation is the most precise
source of information regarding the structure of the complexes, but the
difficulty of obtaining crystalline complexes in proper symmetric form
has rendered the powder X-ray diffraction method for such study.
To obtain further evidence about the structure of the metal complexes
X-ray diffraction was performed. In the powder X-ray diffraction analy-
sis, Cu(II) complex for L1 exhibited sharp peaks which are shown in
Fig. 5. All of these diffraction peaks in the XRD pattern indicate cubic
crystalline structure of Cu. The XRD pattern shows that the dominant
orientation of the sample was (110). XRD was able to confirm the char-
acteristic peaks for Cu when compared to the standard Joint Committee
Powder Diffraction System (JCPDS) number (89–1547). The JCPDS and
observed values are shown in Table 3. From the JCPDS value, the Cu
metal is present in coordination sphere. The XRD pattern indicates the
crystalline nature of the complex. Crystalline nature of complexes was
indicated by comparing the diffractograms of the ligands and complexes.
The minimum inhibitory concentration (MIC) of few selected com-
pounds, which showed significant activity against selected bacteria
and fungi species, were determined. The antibacterial studies inferred
that the Schiff bases (L1–L3) were highly active against both Gram-
positive and Gram-negative bacteria. All the Cu(II), Ni(II) and Zn(II)
metal complexes exhibited potential antibacterial activity against all
the bacterial strains (Table 4.) than the respective Schiff bases. Antimi-
crobial activity of the Schiff base complexes against bacterial pathogens
are shown in Fig. 6. In case of antifungal activity, the Schiff bases
and their Cu(II), Ni(II) and Zn(II) complexes were found to be highly
active and the values are shown in Table 5. All the metal complexes
possess higher antifungal activity than the Schiff bases. This higher
antimicrobial activity of the metal complexes compared to Schiff
bases may be due to the change in structure, due to coordination and
chelating tends to make metal complexes act as more powerful and
potent bactereostatic agents, thus inhibiting the growth of the microor-
ganisms [27,28]. Moreover, coordination reduces the polarity of the
metal ion mainly because of the partial sharing of its positive charge
with the donor groups within the chelate ring system formed during
Table 4
Minimum inhibitory concentration of the synthesized compounds against the growth of
bacteria (μg/mL).
Compound
S. aureus
K. pneumoniae
E. coli
P. aeruginosa
S. podity
L1
9.85
9.34
8.94
6.36
4.73
5.38
5.29
3.56
5.48
6.23
4.65
4.12
1.18
–
8.50
7.87
6.84
5.64
3.68
2.78
4.36
4.34
3.45
2.78
2.43
3.87
1.89
–
16.50
15.45
14.83
2.32
2.56
3.30
2.38
2.56
2.67
4.23
3.56
2.98
1.21
–
14.20
13.59
12.67
3.24
3.85
4.48
4.48
3.62
4.42
3.21
2.56
3.24
2.54
–
7.70
6.50
6.13
5.35
2.64
2.97
3.46
2.78
3.72
2.79
4.12
2.34
1.67
–
L2
L3
[CuL1(phen)2]
[NiL1(phen)2]
[ZnL1(phen)2]
[CuL2(phen)2]
[NiL2(phen)2]
[ZnL2(phen)2]
[CuL3(phen)2]
[NiL3(phen)2]
[ZnL3(phen)2]
Ciprofloxacin
DMSO
CT-DNA by varying the concentration of the complexes added. In the
absence of crystallographic structural data, hydrodynamic methods
that are sensitive to DNA length change are regarded as the least am-
biguous and the most critical tests of binding in solution. A classical
intercalation model results in the lengthening of the DNA helix as
the base pairs are separated to accommodate the binding molecule,
leading to an increase in the DNA viscosity. The plots of (η / ηo)1/3 vs
[Complex] / [DNA] = 1 / R (where η and ηo are the relative viscosities
of DNA in the presence and absence of complex respectively) give a
measure of the viscosity changes. The effects of all the complexes on
Fig. 6. Antimicrobial activity of the Schiff base complexes against bacterial pathogens.

162
N. Raman, R. Mahalakshmi / Inorganic Chemistry Communications 40 (2014) 157–163
Lane
1
2
3
4
5
Table 5
Minimum inhibitory concentration of the synthesized compounds against the growth of
fungi (μg/mL).
Compound
A. niger
F. solani
C. lunata
R. bataicola
C. albicans
L1
7.85
7.37
7.23
4.56
2.64
3.86
4.23
2.45
2.23
4.18
2.32
1.98
1.82
–
7.53
7.25
6.98
6.65
4.34
2.42
6.34
4.12
3.38
6.25
4.05
3.46
2.45
–
14.56
14.23
13.68
2.30
5.24
2.24
2.43
5.16
2.54
2.16
5.12
2.31
2.18
–
13.34
13.21
12.75
4.48
5.46
3.14
4.42
5.38
3.32
4.32
5.24
3.17
1.96
–
6.68
6.25
5.95
3.97
4.56
3.85
3.62
4.39
2.62
3.56
4.23
1.87
1.60
–
L2
Form II
Form II
Form I
L3
[CuL1(phen)2]
[NiL1(phen)2]
[ZnL1(phen)2]
[CuL2(phen)2]
[NiL2(phen)2]
[ZnL2(phen)2]
[CuL3(phen)2]
[NiL3(phen)2]
[ZnL3(phen)2]
Fluconazole
DMSO
Fig. 8. Gel electrophoresis diagram showing the cleavage of pUC19 DNA (10 μM) by the
complexes in a buffer containing 50 mM Tris–HCl and 50 mM NaCl in the presence of
ascorbic acid (AH2,10 μM) at 37 °C. Lane 1, DNA + Control; Lane 2, DNA + Ligand + AH2;
Lane 3, DNA + AH2 + [Cu(L2)(phen)2]; Lane 4, DNA + AH2 + [Ni(L2)(phen)2], Lane 5,
DNA + AH2 + [Zn(L2)(phen)2].
Lane
1
2
3
4
5
the coordination. This process, in turn, increases the lipophilic nature of
the central metal atom, which favors its penetration more efficiently
through the lipid layer of the microorganism, thus destroying them
more aggressively.
Form II
Form III
Form I
The ability of the complexes to cleave pUC19DNA was studied by
using gel electrophoresis technique. DNA cleavage is controlled by re-
laxation of super coiled circular form of pUC19 DNA into nicked circular
form and linear form. When pUC19 DNA was allowed to interact with
mixture of metal complexes and in the presence of ascorbic acid,
the mobility of the band was found to increase slightly as shown in
Figs. 7–9 for various types of (L1, L2 and L3) ligands and their metal(II)
complexes. The aptitude of the complexes in affecting DNA cleavage
has been investigated by gel electrophoresis using super coiled pUC19
DNA in 5 mM Tris–HCl/50 mM NaCl buffer solution (pH 7.2). When cir-
cular plasmid DNA is conducted by electrophoresis, the fastest migra-
tion will be observed for the supercoiled form (Form I). If one strand
is cleaved, the supercoils will relax to produce a slowly moving open cir-
cular from (Form II). If both strands are cleaved, a linear form (Form III)
will be generated that migrates in between [29,30]. All the complexes
are found to exhibit nuclease activity. Beneath the same conditions,
free ascorbic acid (AH2) produces no cleavage of pUC19 DNA. The result
of agarose gel electrophoresis indicates that the metal(II) complexes are
able to carry out an efficient cleavage of pUC19 DNA.
Fig. 9. Gel electrophoresis diagram showing the cleavage of pUC19 DNA (10 μM) by the
complexes in a buffer containing 50 mM Tris–HCl and 50 mM NaCl in the presence of
ascorbic acid (AH2,10 μM) at 37 °C. Lane 1, DNA + Control; Lane 2, DNA + Ligand + AH2;
Lane 3,DNA + AH2 + [Cu(L3)(phen)2], Lane 4, DNA + AH2+ [Ni(L3)(phen)2], Lane 5,
DNA + AH2+ [Zn(L3)(phen)2].
possess a broad spectrum of activity and open the possibilities of finding
new clinically effective antimicrobial compounds. The binding modes
were discussed and the experimental results showed that the entire
complex could be an applicant for DNA-binding reagents, as well as
laying the foundation for the rational design of new useful DNA probes
and effective inorganic complex nucleases.
In summary, a series of the mixed ligand metal complexes with
Schiff base ligand derived from diphenylglyoxal, and p-substituted ani-
line was synthesized and characterized. The binding behavior of metal
complexes with DNA was studied by UV spectra, viscosity and cyclic
voltammetery assay under various conditions. All the experimental
evidences indicate that all the three complexes of various ligands can
strongly bind to CT DNA via an intercalation mode. All the metal com-
plexes of various ligands show better DNA cleavage activity of pUC19
DNA in the presence of ascorbic acid. The Schiff base metal complexes
Acknowledgments
The authors express their heartfelt thanks to the College Managing
Board, Principal and Head of the Department of Chemistry, VHNSN
College, for providing necessary research facilities. SAIF, IIT Bombay
and CDRI, Lucknow, are gratefully acknowledged for providing instru-
mental facilities.
Appendix A. Supplementary material
Lane
1
2
3
4
5
Supplementary data to this article can be found online at http://dx.
doi.org/10.1016/j.inoche.2013.12.012.
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Form III
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dination chemistry of 1,3,5-triaza-7-phosphaadamantane (PTA) and derivatives.
Part II. The quest for tailored ligands, complexes and related applications zinc(II)
Fig. 7. Gel electrophoresis diagram showing the cleavage of pUC19 DNA (10 μM) by
the complexes in a buffer containing 50 mM Tris–HCl and 50 mM NaCl in presence of
ascorbic acid (AH2,10 μM) at 37 °C. Lane 1, DNA + Control; Lane 2, DNA + Ligand + AH2;
Lane 3, DNA + AH2 + [Cu(L1)(phen)2]; Lane 4,DNA + AH2 + [Ni(L1)(phen)2]; Lane 5,
DNA + AH2 + [Zn(L1)(phen)2].

N. Raman, R. Mahalakshmi / Inorganic Chemistry Communications 40 (2014) 157–163
163
carboxylates with/without N-donor organic ligands, Metal-Based Drugs 8 (2002)
269–274.
[5] N. Raman, S. Ravichandran, C. Thangraja, Copper(II), cobalt(II), nickel(II) and zinc(II)
complexes of Schiff base derived from benzil-2,4-dinitrophenylhydrazone with
aniline, J. Chem. Sci. 116 (2004) 215–219.
1,10 phenathroline, υ(M_N): 421. 1H NMR (δ, ppm): 6.9–7.4 (m, aromatic),
Molar conductance ×10−3, (S cm2 mol−1): 19.80; μeff (BM):Diamagnetic. λmax in
(DMSO), cm−1: 26,178, 13,576 cm−1
.
[18] Anal. Calc. for (L2)C50H34N6Cl2Cu: C, 70.4; H, 4.0; N, 9.9; Cl, 8.3;Cu, 7.4%. Found: C, 70.1;
H, 3.7; N, 9.6; Cl, 7.9;Cu, 7.1%. FT-IR (KBr), cm−1: υ(C_N): 1622, υ(C_N): 727–846
for 1,10 phenathroline, υ(M_N): 423. Molar conductance ×10−3, (S cm2 mol−1):
[6] P.G. Sammes, G. Yahioglu, 1,10-Phenanthroline: a versatile ligand, Chem. Soc. Rev.
23 (1994) 327–334.
14.70; μeff (BM):1.83. λmax in (DMSO), cm−1: 37,453, 35,568 cm−1
.
[7] F.H. Haghighi, F. Darabi, H. Farrokhpour, M. Daryanavard, H.A. Rudbari, Bis and
tris(2,3-dihydro-4a,12b-(epoxyethanooxy)[1,4]dioxino[2,3-f] [1,10]phenanthroline)
complexes of Ru(II): synthesis, structure and DNA binding properties, J. Mol. Struct.
1040 (2013) 98–111.
[8] K.E. Erkkila, D.T. Odom, J.K. Barton, Recognition and reaction of metallointercalators
with DNA, Chem. Rev. 99 (1999) 2777–2796.
[19] Anal. Calc. for (L2)C50H34N6Cl2Ni: C, 70.7; H, 4.0; N, 9.9; Cl, 8.4;Ni, 6.9%. Found:
C, 70.3; H, 3.6; N, 9.5; Cl, 8.0; Ni, 6.5%. FT-IR (KBr), cm−1: υ(C_N): 1634, υ(C_N):
724–846 for 1,10 phenathroline, υ(M_N): 421. Molar conductance ×10−3
,
(S cm2 mol−1): 16.20; μeff (BM):3.12. λmax in (DMSO), cm−1: 37,175, 11,967,
13,568 cm−1
.
[20] Anal. Calc. for (L2)C50H34N6Cl2Zn: C, 70.2; H, 4.0; N, 9.8; Cl, 8.3;Zn, 7.6%. Found:
C, 69.8; H, 3.7; N, 9.4; Cl, 7.9; Zn, 7.2%. FT-IR (KBr), cm−1: υ(C_N): 1623,
υ(C_N): 724–846 for 1,10 phenathroline, υ(M_N): 426. 1H NMR (δ, ppm):
6.9–7.4 (m, aromatic), Molar conductance ×10−3, (S cm2 mol−1): 20.95; μeff
[9] D.S. Sigman, R. Landgraf, D.M. Perrin, L. Pearson, Metal ions in biological systems,
in: A. Sigel, H. Sigel (Eds.), Probing of Nucleic Acids by Metal Ion Complexes of
Small Molecules, vol. 33, Marcel Dekker, NY, USA, 1996, p. 485.
[10] The Schiff base was prepared by the dropwise addition of an ethanolic solution
(50 mL) of diphenylglyoxal into a solution of 1-amino-4-nitrobenzene (L1)/1-
amino-4-chlorobenzene (L2)/p-anisidine (L3) (1:1 molar ratio of 10 mM) in etha-
nol. After completion of the addition, the solution was refluxed on a water bath
for 3 h and allowed to cool by standing at room temperature. The formed solid
product was removed by filtration and recrystallized from ethanol (yield: 75% for
L1; 70% for L2; 78% for L3).
(BM): Diamagnetic. λmax in (DMSO), cm−1: 37,453, 25,568 cm−1
.
[21] Anal. Calc. for (L3)C52H40N6O2Cu: C, 73.9; H, 4.8; N, 9.9; Cu, 7.5%. Found: C, 73.5;
H, 4.2; N, 9.6; Cu, 7.1%. FT-IR (KBr), cm−1: υ(C_N): 1664, υ(C_N): 724–846 for
1,10 phenathroline, υ(M_N): 424. Molar conductance ×10−3, (S cm2 mol−1):
13.75; μeff (BM):1.84. λmax in (DMSO), cm−1: 37,453, 33,654 cm−1
.
[22] Anal. Calc. for (L3)C52H40N6O2Ni: C, 74.7; H, 4.7; N, 9.8; Ni, 6.8%. Found: C, 74.3;
H, 4.3; N, 9.2; Ni, 6.5%. FT-IR (KBr), cm−1: υ(C_N): 1666, 727–852 for 1,10
phenathroline, υ(M_N): 422. Molar conductance ×10−3, (S cm2 mol−1): 15.20;
[11] Anal. Calc. for (L1)C26H18N4O4: C, 69.3; H, 4.0; N, 12.4%. Found: C, 68.9; H, 3.8;
N, 12.0%. FT-IR (KBr), cm−1: υ(C_N): 1593 1H NMR (DMSO-d6, 300 MHz, δ,
μeff (BM):3.20. λmax in (DMSO), cm−1: 37,174, 15,631, 13,568 cm−1
.
ppm): 6.8–7.7 (m, aromatic), λmax in (DMSO), cm−1: 37,251, 30,250 cm−1
.
[23] Anal. Calc. for (L3)C52H40N6O2Zn: C, 74.1; H, 4.6; N, 9.7; Zn, 7.6%. Found: C, 73.7;
H, 4.2; N, 9.3; Zn, 7.2%. FT-IR (KBr), cm−1: υ(C_N): 1664, υ(C_N): 724–846 for
1,10 phenathroline, υ(M_N): 421. 1H NMR (δ, ppm): 6.9–7.4 (m, aromatic),
Molar conductance ×10−3, (S cm2 mol−1): 22.14; μeff (BM): Diamagnetic. λmax
[12] Anal. Calc. for(L2)C26H18N2Cl2: C, 72.7; H, 4.2; N, 6.5;Cl,16.5%. Found: C, 70.1; H, 3.9;
N, 6.1;Cl,15.9%. FT-IR (KBr), cm−1: υ(C = N): 1664, 1H NMR (DMSO-d6, 300 MHz,
δ, ppm): 6.9–7.4 (m, aromatic), λmax in (DMSO), cm−1: 37,364, 31,260 cm−1
.
[13] Anal. Calc. for(L3)C28H24N2O2: C, 79.9; H, 5.7; N, 6.7; Found: C, 79.3; H, 5.4; N, 6.2%.
in (DMSO), cm−1: 37,174, 24,568 cm−1
.
FT-IR (KBr), cm−1: υ(C = N): 1668, 1H NMR (DMSO-d6, 300 MHz, δ, ppm): 6.9–7.4
[24] J.B. Lepecp, C. Paoletti, Fluorescent complex between ethidium bromide and nucleic
acids: physical–chemical characterization, J. Mol. Biol. 27 (1967) 87–106.
[25] A.E. Friedman, J.C. Chambron, J.P. Sauvage, N.J. Turro, J.K. Barton, Molecular
“Light Switch” for DNA: Ru(bpy)2(dppz)2+, J. Am. Chem. Soc. 112 (1990)
4960–4962.
[26] S. Satyanarayana, J.C. Dabrowiak, J.B. Chaires, Tris(phenanthroline)ruthenium(II)
enantiomer interactions with DNA: mode and specificity of binding, Biochemistry
32 (1993) 2573–2584.
[27] Z.H. Chohan, M. Arif, M.A. Akhtar, C.T. Supuran, Metal-based antibacterial and anti-
fungal agents: synthesis, aharacterization, and in vitro biological evaluation of Co(II),
Cu(II), Ni(II), and Zn(II) complexes with amino acid-derived compounds, Bioinorg.
Chem. Appl. 2006 (2006) 1–13.
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Schiff bases with antibacterial activity, J. Enzyme Inhib. Med. Chem. 18 (2003)
259–263.
(m, aromatic), λmax in (DMSO), cm−1: 37,254, 31,250 cm−1
.
[14] A solution of Schiff base and 1,10-phenanthroline in ethanol was added to a solution
of MCl2·2H2O (1:2:1 molar ratio of 10 mM) in ethanol and the mixture was stirred
for 1 h and the solution was refluxed on a water bath for 6 h. The solid product
so-formed was separated by filtration and washed thoroughly with ethanol
and dried in vacuo (yield: 62% for [CuL1(phen)2]; 59% for [NiL1(phen)2];
52% for [ZnL1(phen)2]; 58% for [CuL2(phen)2]; 56% for [NiL2(phen)2];
52% for [ZnL2(phen)2]; 60% for[CuL3(phen)2]; 57% for [NiL2(phen)2]; 53% for
[ZnL3(phen)2]).
[15] Anal. Calc. for (L1)C50H34N8O4Cu: C, 68.7; H, 3.9; N, 12.8; Cu, 7.3%. Found: C, 68.3;
H, 3.6; N, 12.6; Cu, 7.0%. FT-IR (KBr), cm−1: υ(C_N): 1654, υ(C_N): 721–850
for 1,10 phenathroline, υ(M_N): 422. Molar conductance ×10−3, (S cm2 mol−1):
15.75; μeff (BM):1.80. λmax in (DMSO), cm-1: 25,976, 13,568 cm−1
.
[16] Anal. Calc. for (L1)C50H34N8O4Ni: C, 69.1; H, 3.9; N, 12.9; Ni, 6.7%. Found: C, 68.7;
H, 3.5; N, 12.5; Ni, 6.3%. FT-IR (KBr), cm−1: υ(C_N): 1629, υ(C_N): 727–846 for
1,10 phenathroline, υ(M_N): 423. Molar conductance ×10−3, (S cm2 mol−1):
[29] D.S. Sigman, Nuclease activity of 1,10-phenanthroline-copper ion, Acc. Chem. Res.
19 (1986) 180–186.
[30] A.S. Sitlani, E.C. Long, A.M. Pyle, J.K. Barton, DNA photocleavage by
phenanthrenequinone diimine complexes of rhodium(III): shape-selective recogni-
tion and reaction, J. Am. Chem. Soc. 114 (1992) 2303–2312.
17.40; μeff (BM):3.10. λmax in (DMSO), cm−1: 26, 109, 15,593, 13,568 cm−1
.
[17] Anal. Calc. for (L1)C50H34N8O4Zn: C, 65.6; H, 3.9; N, 12.7; Zn, 7.4%. Found: C, 65.1;
H, 3.7; N, 12.3; Zn, 7.1%. FT-IR (KBr), cm−1: υ(C_N): 1627, υ(C_N): 727–846 for