Spectral, Electrochemical and DNA binding properties of some Macroacyclic Transition metal complexes using diverse spectral methods

Abstract

The DNA binding capability of the four novel transition metal complexes containing macroacyclic Schiff base ligand of the type N 1 ,N 8-bis(9-(benzylimino)phenanthren-10-ylidene)naphthalene-1,8-diamine were synthesized and structurally characterized by elemental analysis, IR and 13 C NMR and mass spectral studies. Spectroscopic data suggested the square planar geometry for all the complexes. Binding studies of these complexes with double-stranded (ds) DNA were analysed by absorption spectra, emission spectra, CD spectra and viscosity studies. The results revealed that the metal complex intercalates into the DNA base stack as intercalator. The intrinsic binding constant Kb and the apparent binding constant Kapp has been estimated at room temperature. These binding constant values for all the complexes obtained from absorption spectra and fluorescence spectra indicate that the complexes intercalate between the base pairs of the CT-DNA tightly.

Full text

14
International Journal of Research in Inorganic Chemistry 2015; 5(3): 14-20
Original Article
Spectral, Electrochemical and DNA binding properties of some Macroacyclic
Transition metal complexes using diverse spectral methods
C. Joel1, *S. Theodore David1, R. Biju Bennie1, S. Daniel Abraham1, S. Iyyam Pillai2, S.Magala Sathyasheeli3
1P.G. Department of Chemistry, St. John’s College, Tirunelveli-627002, India.
2P G and Research Department of Chemistry, Pachaiyappa’s College, Chennai-600030, India.
3Infant Jesus college of Engineering, Keelavallanadu, Thoothukudi, India
Corresponding author: Dr. S. Theodore David
Phone No. 09366705118,
E-mail: s.theodore.david@gmail.com
Received 01 August 2015; accepted 29 August 2015
Abstract
The DNA binding capability of the four novel transition metal complexes containing macroacyclic Schiff base ligand of
the type N1,N8-bis(9-(benzylimino)phenanthren-10-ylidene)naphthalene-1,8-diamine were synthesized and structurally
characterized by elemental analysis, IR and 13C NMR and mass spectral studies. Spectroscopic data suggested the square
planar geometry for all the complexes. Binding studies of these complexes with double-stranded (ds) DNA were analysed
by absorption spectra, emission spectra, CD spectra and viscosity studies. The results revealed that the metal complex
intercalates into the DNA base stack as intercalator. The intrinsic binding constant Kb and the apparent binding constant
Kapp has been estimated at room temperature. These binding constant values for all the complexes obtained from absorption
spectra and fluorescence spectra indicate that the complexes intercalate between the base pairs of the CT-DNA tightly.
© 2015 Universal Research Publications. All rights reserved
Key Words: Acyclic ligand, Transition metals, CT-DNA, Hypochromism, Intercalation
1. Introduction
In spite of the rapid development of novel
anticancer drugs, it remains the major cause of death in the
world due to drug resistance or undesirable side effects [1].
Metal-based pharmaceuticals are of considerable interest
due to their application in DNA molecule probes and
chemotherapeutic reagents for the confrontation against
cancer [2-4]. Cisplatin, one of the world’s most important
metal-based drugs, acts mainly through induction of DNA
unwinding and DNA-protein binding, which is introduced
in 1970s [5-7]. But the serious side effects such as asneuro-
, hepato- and nephrotoxicity and the insurmountable
frequent development of resistance had limited its
effectiveness [8-11]. Therefore, numerous attempts have
been devoted to develop alternative strategies, based on
different metals, with improved pharmacological properties
and aimed at different targets. Acyclic compounds are
important and powerful ligands, ubiquitous in transition
metal coordination chemistry. They mimic important
biological ligands. The chemistry of compartmental ligands
capable of forming acyclic complexes with similar or
dissimilar metal ions has grown rapidly. Acyclic ligands
can impose high degree of preorganization on metal
complex formation and are used as models for protein–
metal binding sites in biological systems, as synthetic
ionophores, as therapeutic reagents in chelate therapy for
the treatment of metal toxication, in catalysis, and to
investigate the mutual influence of metal centers on their
physicochemical properties [12]. Use of transition metals
by nature in different biological processes drive the quest
of the scientist to understand the underlying principles of
its functionality which eventually helps to develop different
structural and more importantly functional model systems.
Apart from studying different biological processes induced
by metal ions many new molecules have been also
developed over the years showing interesting properties
like antibacterial, antifungal, antimicrobial and
anticancer/antiproliferative activity where the transition
metal ion performs a pivotal role in terms of structural
organisation and overall functionality [13]. Recently, our
group has continuously been interested in preparing the
N2O2 based macroacycles into complex systems. For
examples, we have reported the synthesis, characterisation
and DNA binding studies of NNOO or NNNN containing
Co(II), Ni(II), Cu(II) and Zn(II) complexes.. Here in, we
report the synthesis, spectral characterization, DNA binding
properties of transition metal complexes of macroacyclic
ligands.
Available online at http://www.urpjournals.com
International Journal of Research in Inorganic Chemistry
Universal Research Publications. All rights reserved

15
International Journal of Research in Inorganic Chemistry 2015; 5(3): 14-20
2. Experimental section
9,10-Phenanthrenequinone, 1,8-diaminonaphthal-
-ene and benzylamine were obtained from Sigma-Aldrich,
all other reagents and solvents were purchased from Merck
and used as received. CT DNA (calf thymus) was
purchased from Bangalore Genei (India). Ethidium
bromide (EB) was obtained from Sigma (USA).
Tris(hydroxymethyl)aminomethane–HCl (Tris–HCl) buffer
solution were prepared by using triple distilled water. All
the reactions were performed under aerobic conditions.
2.1. Characterization
The infrared spectra of the solid samples were
recorded in JASCO/FT-IR 410 spectrometer in the range of
4000-400 cm-1. Electronic spectra were recorded using
Perkin Elmer Lambda-35 UV-Vis. spectrometer using
DMSO as solvent in the range of 200-800 nm. The molar
conductivity measurements of the metal complexes were
carried out in ~10-3M DMSO solutions using a Coronation
digital conductivity meter. The 13C NMR was recorded on a
JEOL GSX-400 spectrometer employing CDCl3 as solvent
at ambient temperature. The mass spectral study was
carried out using JEOL D-300 (EI) mass spectrometer. EPR
measurements of Cu(II) complexes of all the studied
ligands were recorded at liquid nitrogen temperature on a
Varian E-4 X-band spectrometer using DPPH as the g-
marker.
2.2. DNA binding experiments
2.2.1. Absorption spectral studies
Electronic absorption spectrum of the complex
was recorded before and after addition of CT-DNA in the
presence of 50 mM Tris-HCl buffer (pH 7.5). A fixed
concentration of metal complexes (10 μM) was titrated
with incremental amounts of CT-DNA over the range (0 –
200 μM). The equilibrium binding constant (Kb) values for
the interaction of the complex with CT-DNA were obtained
from absorption spectral titration data using the following
equation 1 [14].
[DNA]/ (εa - εf) = [DNA]/ (εb - εf) + 1/Kb (εb - εf) (1)
Where εa is the extinction coefficient observed for the
charge transfer absorption at a given DNA concentration, εf
the extinction coefficient at the complex free in solution, εb
the extinction coefficient of the complex when fully bound
to DNA, Kb the equilibrium binding constant, and [DNA]
the concentration in nucleotides. A plot of [DNA]/(εa - εf)
versus [DNA] gives Kb as the ratio of the slope to the
intercept. The non-linear least square analysis was
performed using Origin lab, version 6.1.
2.2.2. Fluorescence spectral studies
The fluorescence spectral method using ethidium
bromide (EB) as a reference was used to determine the
relative DNA binding properties of the complexes to calf
thymus (CT- DNA in 50 mM Tris HCl / 1 mM NaCl
buffer, pH 7.5). Fluorescence intensities of EB at 610 nm
with an excitation wavelength of 510 nm were measured at
different complex concentrations. Reduction in the
emission intensity was observed with addition of the
complexes. The relative binding tendency of the complexes
to CT DNA was determined from a comparison of the
slopes of the lines in the fluorescence intensity versus
complex concentration plot.
Io/I=1 + Ksvr(2)
Where I0, is the ratio of fluorescence intensities of the
complex alone, I is the ratio of fluorescence intensities of
the complex in the presence of CT-DNA. Ksv is a linear
Stern–Volmer quenching constant and r is the ratio of the
total concentration of quencher to that of DNA, [M] /
[DNA].A plot of I0 / Ivs. [Complex]/ [DNA], Ksv is given by
the ratio of the slope to the intercept. The apparent binding
constant (Kapp) was calculated using the equation KEB[EB] /
Kapp[complex], where the complex concentration was the
value at a 50% reduction of the fluorescence intensity of
EB and KEB = 1.0 x 107 M-1 ([EB] = 3.3 μM) [15].
2.2.3. CD spectral studies
Circular dichroic spectra of CT DNA in the
presence and absence of metal complexes were obtained by
using a JASCO J-715 spectropolarimeter equipped with a
Peltier temperature control device at 25 ± 0.1 °C with a 0.1
cm path length cuvette. The spectra were recorded in the
region of 220–320 nm for 200 μM DNA in the presence of
100 μM of the complexes.
2.2.4 Viscosity measurements
The binding mode of the complexes to CT-DNA
by viscosity measurements, were carried out on CT-DNA
(0.5 mM) by varying the concentration of the complex
(0.01 mM, 0.02 mM, 0.03 mM, 0.04 mM, 0.05 mM). Data
were presented as (η/ηo) versus binding ratio of
concentration of complex to that of concentration of CT-
DNA , where η is the viscosity of DNA in the presence of
complex and ηo is the viscosity of DNA alone. Viscosity
values were calculated after correcting the flow time of
buffer alone (to), ŋ= (t−to)/to[16].
2.3. Synthesis Procedures
2.3.1. Synthesis of macroacyclic ligand (L)
To 2 mmol of 9,10-phenanthrenequinone (0.42 g)
in methanol (100 ml), 1 mmol 1,8-diaminonaphthalene
(0.16 g) was added.. The solution was stirred under reflux
for 3h, reduced in volume and the precipitate filtered,
washed with methanol and dried in vacuo. The compound,
partially dissolved in methanol, was treated with 2 mmol
benzylamine (0.22 ml). The mixture was stirred under
reflux for 3h, then reduced in volume and the precipitate
collected by filtration, washed with methanol and dried in
vacuo. (Scheme.1)
(L): Yield: 74%, Black compound, m.p: 239 0C, Anal.
Found.(%): C, 87.06; H, 5.01; N, 7.75; Calc.(%): C, 87.12;
H, 5.06; N, 7.82; EI-MS: m/z, 716.38; IR (KBr, cm-1):
ν(C=N), 1648 cm-1, ν(-C=C-), 1596 cm-1, ν(C-H), 2904; 13C NMR
(δ, ppm in CDCl3) 166.81 (C=N).
2.3.2. Synthesis of macroacyclic Schiff base complexes
[ML] A solution of hydrated metal chloride
CoCl2·6H2O/NiCl2·6H2O/CuCl2·2H2O and ZnCl2 (1 mmol)
in methanol (25 ml) was added slowly to a hot solution of
(L) (1 mmol) dissolved in 25 ml of methanol. The resulting
solution was magnetically stirred under reflux for 8 h at
room temperature resulting in the isolation of solid product.
The product thus formed was filtered, washed with

16
International Journal of Research in Inorganic Chemistry 2015; 5(3): 14-20
methanol and dried in vacuum over anhydrous calcium
chloride.
[Co(L)]Cl2: Yield: 78%; Black compound; Anal.
Found.(%): C, 80.47; H, 4.61; N, 7.18 and Co, 7.53;
Calc.(%): C, 80.50; H, 4.68; N, 7.22 and Co, 7.60; IR (KBr,
cm-1): ν(C=N), 1612 cm-1, ν(C-H), 2944 cm-1, ν(C=C), 1567 cm-
1, ν(M-N), 477 cm-1; ʌm(Smol-1cm2) 129.65; UV-Vis. in
DMSO, nm (transition): 240 (π-π* ligand), 355 (MLCT)
and 575(4A2g →4T1g ).
[Ni(L)]Cl2: Yield: 82%; Pale Brown compound; Anal.
Found.(%): C, 80.47; H, 4.61; N, 7.18 and Ni, 7.54;
Calc.(%): C, 80.53; H, 4.68; N, 7.22 andNi, 7.57; IR (KBr,
cm-1): ν(C=N), 1599 cm-1, ν(C-H), 2898 cm-1, ν(C=C), 1557 cm-1,
ν(M-N), 486; ʌm(Smol-1cm2) 123.68; UV-Vis. in DMSO, nm
(transition): 237 (π-π* ligand), 430 (MLCT) and 608 (1A1g
→ 1B1g).
[Cu(L)]Cl2: Yield: 79%; Dark brown compound; Anal.
Found.(%): C, 80.01; H, 4.61; N, 7.13 and Cu, 8.09;
Calc.(%): C, 80.03; H, 4.65; N, 7.18 and Cu, 8.14; IR (KBr,
cm-1): ν(C=N), 1608 cm-1, ν(C-H), 2891 cm-1, ν(C=C), 1561 cm-1,
ν(M-N), 479; ʌm(Smol-1cm2) 133.19; UV-Vis. in DMSO, nm
(transition): 266 (π-π* ligand), 419 (MLCT) and 696 (2B1g
→ 2Eg).
Zn(L)]Cl2: Yield: 82%; Black compound; Anal.
Found.(%): C, 79.76; H, 4.57; N, 7.14 and Zn, 8.29;
Calc.(%): C, 79.84; H, 4.64; N, 7.16 and Zn, 8.36; IR (KBr,
cm-1): ν(C=N), 1605 cm-1, ν(C-H), 2909 cm-1, ν(C=C), 1561 cm-
1,ν(M-N), 443; ʌm(Smol-1cm2) 130.08.
Schematic representation for the synthesis of ligand and its
complexes
3. Results and discussion
3.1. 13C NMR spectral analysis
The 13C NMR spectrum of the macroacyclic
ligand exhibited signals at  117.08, 120.04, 123.31,
124.90, 126.65, 127.24, 127.51, 127.83, 128.30, 129.08,
131.76, 133.43, 136.67, 138.20, 153.64 were due to
aromatic carbons (Ar-C). The imino carbon (C=N) atoms
are observed at  166.81. The peak observed at  59.74 was
due to methylene carbon (-CH2-) of the benzylamine
moiety. The 13C NMR spectrum confirms the formation of
Schiff base ligand by the condensation of 9,10-
phenanthrenequinone, 1,8-diaminonaphthalene and
benzylamine.
Fig. 1. 13C NMR spectra of the ligand
3.2. EI-Mass spectral analysis
The EI mass spectrum of the ligand shows the
molecular ion peak at m/z = 716 [M]+ (C52H36N4)+ confirms
the formation of the macroacyclic Schiff base ligand. The
peaks at m/z = 706, 661, 588, 558, 522, 435, 370, 355, 330,
320, 281 and 178 corresponds to the fragments C51H35N4,
C48H32N4, C42H26N4, C40H26N4, C38H22N3, C31H21N3,
C27H18N2, C25H22N2, C24H14N2, C23H16N2, C21H15N, and
C12H6N2 respectively. This confirms the molecular
structure of the macroacyclic Schiff base ligand.
Fig 2. EI mass spectrum of the ligand
3.3. Vibrational spectroscopy
The FT-IR spectrum of the ligand, formed by the
condensation of 9,10-Phenanthrenequinone, 1,8-diamino-
-naphthalene and benzylamine, is given in Figure 3. The
υ(C=O) band of the 9,10-Phenanthrenequinone expected at
1675 cm-1, as well as the –NH2 stretching vibrations of 1,8-
diaminonaphthalene and benzylamine (likely at 3432 and
3328 cm-1), are absent in the IR spectrum of the ligand.
However, a new significant band at 1648cm-1 has emerged,
and this can be assigned to the absorption due to the imino
group [17]. The spectrum also shows the strong band in the
1596 cm-1 region, which is assigned to aromatic ring -C=C-
stretching vibration. The other strong band at 2904 cm-1 is
related to (-C-H) modes of vibrations. The infrared spectra
of the complexes CoL, NiL, CuL and ZnL are provided

17
International Journal of Research in Inorganic Chemistry 2015; 5(3): 14-20
Fig.3. FT-IR spectra of the ligand Fig.4. FT-IR spectra of the CoL complex
respectively in Figures 4, S1, S2 and S3. In order to study
the binding mode of the ligand to the metal in the
complexes, the IR spectrum of the free ligand was
compared with those of the complexes. The band at 1648
cm-1 for the imino group of the ligand has been shifted to
lower frequencies 1612 cm-1, 1599 cm-1, 1608 cm-1 and
1605 cm-1 respectively in CoL, NiL, CuL and ZnL
complexes. This evidently indicates the coordination of the
imino nitrogen to metal centers, viz. Co(II), Ni(II), Cu(II)
and Zn(II) [18]. Further, the IR spectra of metal complexes
also show some new sharp bands in the region 477cm-1,
486 cm-1, 479 cm-1
and 443 cm-1 for Co(II), Ni(II), Cu(II) and Zn(II)
complexes respectively which is due to the formation of
coordinate bond between the imino nitrogen and the metal
ions [19].
3.4 Electronic spectroscopy
The electronic spectra of the complexes have been
measured in the range 200-800 nm in DMSO. The UV-Vis
absorption bands of the complexes CoL, NiL and CuL are
presented in Figure 5. The ligand shows absorption
between 200-300 nm which is intra-ligand charge transfer
transitions. The absorption band in the region 350-430 nm
is attributed to the metal - ligand charge transfer. The
Co(II) complex shows a low intensity band at 575 nm
corresponding to 4A2g → 4T1g transition, which reveals that
Co(II) complex exists in square-planar geometry [20]. The
Ni(II) complex shows a low intensity band at 608 nm,
which is assigned to 1A1g → 1B1g transition, arising from
the square planar environment around the Ni(II) ion [21].
The observed square-planar environment for the nickel(II)
complex in conformity with the fact that all known square-
planar complexes of nickel(II) are diamagnetic. In the
electronic absorption spectrum of the present Cu(II)
complex, it shows
one d–d transition at 696 nm which can be assigned to 2B1g
→ 2Eg transition [22]. It confirms that the copper(II)
complex exists in square planar geometry. Zn(II) ion which
has a completely filled d10 electronic configuration is not
expected to show any d-d electronic transition, and the
complex is expected to have tetrahedral geometry with sp3
configuration.
Fig.5. Electronic spectrum of CoL, NiL & CuL complexes

18
International Journal of Research in Inorganic Chemistry 2015; 5(3): 14-20
3.5. Electrochemical studies
The cyclic voltammogram of the mononuclear copper(II)
complex CuL is shown in Figure 6. The cyclic
voltammogram of Cu(II) complex exhibits more negative
cathodic response at Epc = -1.1 V which represent the redox
property of the macroacyclic ligand. The quasi-reversible
cathodic peak at Epc = -0.12 V with corresponding anodic
peak at Epa = -0.4 V is assigned to the formation of
Cu(II)/Cu(I) couple. The quasi-reversible anodic peak at
Epa = 1.09 V with the corresponding cathodic peak is
attributed to the oxidation process Cu(II) to Cu(III).
Fig. 6. Cyclic voltammogram of CuL
3.6. DNA binding studies
3.6.1. Absorption spectral studies
The interactions of complexes CoL, NiL, CuL and
ZnL in the absence and presence of increasing amount CT-
DNA (at a constant concentration of complexes) are
represented in Figures 7, S4. S5 and S6 respectively. The
electronic absorption spectroscopy is one of the most
common method to study the DNA-binding properties of
metal complexes, since there are strong MLCT (metal-to-
ligand) and charge transfer (intraligand) features were
observed in the absorption spectra of these complexes. In
general, Hypochromism is suggested to occur due to an
intercalative mode of binding involving a tough stacking
interaction between an aromatic chromophore and the base
pairs of DNA [23]. Upon addition of CT-DNA, the
observed absorption bands of complexes exhibited
hypochromism showing with a slight bathochromism of
about 2 nm suggesting of stabilization of the DNA Helix.
Further, a plot of DNA]/(єa-єf) versus [DNA] was
drawn to elucidate the DNA binding affinities of the
complexes, and is provided in Figure 8. In order to
quantitatively compare the binding affinity of complexes
with CT-DNA the intrinsic binding constants Kb of the
complexes were determined and which are comparable to
that observed for typical classical intercalators, it suggests a
mode of intercalative binding that involves a stacking
interaction between the complexes and the base pairs of
DNA. The binding Constants (Kb) of the metal complexes
were given in Table 1.
Fig. 7. Absorption spectra of complex CoL (1 x 10-5 M) in
the absence and presence of increasing amounts of CT-
DNA (0-25 x 10-5 M) at room temperature in 50 mM Tris-
HCl/NaCl buffer (pH = 7.5). Arrow shows the absorbance
changing upon increasing DNA concentrations
Fig. 8. The plots of [DNA]/(єa-єf) versus [DNA] for the
titration of DNA with mononuclear CoL, NiL, CuL and
ZnL complexes

19
International Journal of Research in Inorganic Chemistry 2015; 5(3): 14-20
3.6.2. Emission spectral studies
In order to further investigate the interaction mode
of complex with DNA, a competitive binding experiment
using EB as a probe was carried out. EB does not show any
appreciable emission in the buffer solution due to
fluorescence quenching of the free EB by solvent
molecules, while in the presence of CT DNA, the
fluorescence intensity of EB is highly enhanced due to its
strong intercalation between the adjacent DNA base pairs
[24]. EB shows an increase in the emission intensity due to
its intercalative binding to CT-DNA. The changes in the
fluorescence intensity at 613 nm (excitation at 545 nm) of
EB-CT-DNA were measured with respect to the
concentration of the complexes CoL, NiL, CuL and ZnL.
On addition of complexes to CT-DNA, the fluorescence
intensity decreased with increasing the concentration of
complexes without any change in the shape and position of
the fluorescence peaks as depicted in Figures 9, S7, S8 and
S9. According to the classical Stern–Volmer equation, the
quenching plot illustrates that the quenching of EB bound
to CT-DNA by complex is in agreement with the linear
Stern–Volmer equation, which also indicates the complexes
bind to DNA as shown in Figure 10. The apparent binding
constants (Kapp) of the complexes were calculated and
given in Table 1.
Fig. 9.Emission spectrum of EB bound to DNA in the
presence of CoL ([EB] = 3.3 μM, [DNA] = 40 μM,
[complex] = 0-30 μM, λex= 430 nm). Arrow shows the
absorbance changing upon increasing complex
concentrations.
Fig. 10. The plots of emission intensity Io / I vs [DNA] /
[complexes]
Table 1 Binding constant and Apparent Binding constant
(Kapp) of the complexes
Complexes
Binding constant
(Kb) M-1
Apparent binding
constant (Kapp) M-1
CoL
9.91 x 104
1.7 x 105
NiL
4.16 x 105
4.9 x 105
CuL
1.19 x 106
8.9 x 105
ZnL
5.61 x 104
1.4 x 105
3.6.3. CD spectral studies
The CD spectral analysis is very useful when it
comes to the investigation of morphological changes in
DNA double strands due to the interaction with small
molecules. The band at 286 nm, due to base stacking, and
at 238 nm, due to right handed helicity of the DNA [25],
are very sensitive towards the interaction with such small
molecules. Any change in the base stacking pattern or the
helicity of the strands is manifested by a change in the band
position, the intensity, or both. The intensity of the bands at
286 nm and 238 nm undergoes small changes for the
synthesized NiL, CuL and ZnL complexes as shown in
Figure 11. This indicates that the complexes interact with
the DNA double strands by the intercalative mode between
the base pairs of DNA strands without any significant
change in the right-handed helicity of the DNA.
Fig. 11. CD spectra recorded over the wavelength range
220-320 nm for solutions containing 2:1 ratio of CT-DNA
(200 μM) and mononuclear NiL, CuL & ZnL complexes
(100 μM)
3.6.4. Viscosity measurements
To further clarify the nature of the binding
interaction between NiL, CuL and ZnL complexes and
DNA, viscosity measurements were carried out on CT-
DNA by varying the concentration of the complexes.
Spectroscopic data are necessary, but not sufficient to
support a binding mode. Classical intercalative mode
causes a significant increase in viscosity of DNA solution
due to separation of base pairs at intercalation sites and
increase in overall DNA length [26]. In contrast, complexes
those bind exclusively in the DNA grooves typically cause

20
International Journal of Research in Inorganic Chemistry 2015; 5(3): 14-20
less positive or negative or no change in DNA viscosity.
The relative specific viscosity of DNA increases with
increase in the concentration of the complexes revealing
strong evidence for the interaction of the complex with CT-
DNA by intercalation mode as represented in Figure 12.
Fig. 12. Viscosity measurements of the complexes NiL,
CuL & ZnL
4. Conclusion
A novel macroacyclic Schiff base ligand was
synthesized and characterized. Reactions of the ligand with
cobalt(II), nickel(II), copper(II) and zinc(II) ions yielded
mononuclear complexes that were characterized by
elemental analyses, spectroscopic methods (IR, electronic,
NMR and mass spectra), and molar conductivity
measurements. The DNA-binding properties of the all the
complexes have been investigated by electronic absorption,
fluorescence, CD spectra and viscosity measurements. The
results obtained indicate that these complexes bind to DNA
via an intercalation binding mode.
References
1. Mani Alagesan, Nattamai S.P. Bhuvanesh and
Nallasamy Dharmaraj, Dalton Trans., 42 (2013) 7210-
7223.
2. B. Armitage, Chem. Rev. 98 (1998) 1171-1200.
3. H. T. Chifotides, K. R. Dunbar, Acc. Chem. Res. 38
(2005) 146-156.
4. W. K. Pogozelski, T. D. Tullius, Chem. Rev. 98 (1998)
1089-1107.
5. T. Storr, K. H. Thompson, C. Orvig, Chem. Soc. Rev.
35 (2006) 534-544.
6. G. Giaccone, R. S. Herbst, C. Manegold, G. Scagliotti,
R. Rosell, V. Miller, R. B. Natale, J. H.Schiller, J. von
Pawel, A. Pluzanska, M. Gatzemeier, J. Grous, J. S.
Ochs, S. D. Averbuch, M.K. Wolf, P. Rennie, A.
Fandi, D. H. Johnson, J. Clin. Oncol. 22 (2004) 777-
784.
7. J. Reedijk, Chem. Commun. (1996) 801-806.
8. A. Barve, A. Kumbhar, M. Bhat, B. Joshi, R. Butcher,
U. Sonawane, R. Joshi, Inorg. Chem. 48 (2009) 9120-
9132.
9. E. Wong, C. M. Giandomenico, Chem. Rev. 99 (1999)
2451-2466.
10. M. A. Fuertes, C. Alonso, J. M. Perez, Chem. Rev. 103
(2003) 645-662.
11. A. I. Matesanz, C. Hernandez, A. Rodriguez, P. Souza,
Dalton Trans. 40 (2011) 5738-5745.
12. A. Vijayaraj, R. Prabu, R. Suresh, C. Sivaraj, N.
Raaman, V. Narayanan, J. Coord. Chem., 64 (2011)
637-650.
13. Mriganka Das, Rajendar Nasani, Manideepa Saha,
Shaikh M Mobin, Suman Mukhopadhyay, Dalton
Trans., 44 (2015) 2299-2310.
14. C. Joel, S. Theodore David, R. Biju Bennie, S. Daniel
Abraham and S. Iyyam Pillai, J. Chem. Pharm. Res.,
7(5) (2015) 1159-1176.
15. C. Joel, S. Theodore David, R. Biju Bennie, S. Daniel
Abraham and S. Iyyam Pillai, Der Pharma chem., 6 (4)
(2014) 244-254.
16. N. DeVries, J. Reedijk, Inorg. Chem., 30 (1991) 3700–
3703.
17. G. Das, R. Shukala, S. Mandal, R. Singh, P.K.
Bharadwaj, J.V.Singh, K.H. Whitmire, Inorg. Chem.,
36 (1997) 323.
18. F.M. Ashmawy, R.M. Issa, S.A. Amer, C.A. Mc
Auliffe, R.V.Parish, J. Chem. Soc., Dalton Trans.,
(1987) 2009.
19. M. Shakir,N. Begum, S. Parveen, P. Chingsubam, S.
Tabassum, Synth. React. Inorg. Met. Org. Chem., 34
(2004) 1135.
20. Natarajan Raman and Chinnathangavel Thangaraja,
Transit. Metal Chem., 30 (2005) 317–322.
21. N. Raman, J. Dhaveethu Raja and A. Sakthivel, J.
Chem. Sci., 119 (2007) 303–310.
22. Tarek M.A. Ismail, J. Coord. Chem., 58 (2005) 141–
151.
23. C. Joel, S. Theodore David, R. Biju Bennie, S. Daniel
Abraham, M. Seethalakshmi, S. Iyyam Pillai, Int.
J. Inorg. Bioinorg. Chem., 4(4) (2014) 52-60.
24. Y. Zhang, Y. Huang, J. Zhang, D.W. Zhang, J.L. Liu,
Q. Liu, H.H. Lin, X.Q. Yu, Sci. China Chem., 54
(2011) 129–136.
25. Vijay Kumar Chityala, K. Sathish Kumar, Ramesh
Macha, Parthasarathy Tigulla, and Shivaraj, Bioinorg
Chem Appl., 2014 (2014) 691260.
26. V. I. Ivanov, L. E. Minchenkova, A. K. Schyolkina and
A. I. Poletayev, Biopolymers,12 (1973) 89–110.
Source of support: Nil; Conflict of interest: None declared