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Asian Journal of Biochemical and Pharmaceutical Research Issue 2 (Vol. 1) 2011 ISSN: 2231-2560 

Asian Journal of Biochemical and Pharmaceutical Research 

Research Article 

Synthesis, Spectroscopic Characterization, DNA Cleavage And Antimicrobial Activity 

Of Binuclear Copper(II), Nickel(II) And Oxovanadium(Iv) Schiff Base Complexes 

N. Mahalakshmi and R.Rajavel* 

Department of Chemistry, Periyar University, Salem, Tamilnadu, India. 

Received: 3 May 2011; Revised: 23May 2011; Accepted: 28May. 2011 

Abstract: A new series of transition metal complexes of Cu(II), Ni(II) and VO(II) have been synthesized from 

the Schiff base (L) derived from 2-carboxybenzaldehyde and 3,3’,4,4’-tetraminobiphenyl. Structural features 

were obtained from their elemental analyses, IR, magnetic susceptibility, molar conductance, UV–Vis and ESR 

spectral studies. The data show that these complexes have composition of [M2(L)]X type. (Where M = (Cu(II), 

Ni(II), and VO(II) X=ClO4 - , SO4 2- L = binucleating tetradendate ligand). The UV–Vis, ESR, magnetic 

susceptibility and spectral data of the complexes suggest a square–planar geometry around the central metal ion 

except VO(II) complex which has square–pyramidal geometry. The redox behavior of copper, Nickel and 

vanadyl complexes was studied by cyclic voltammetry. The interaction study of the copper complex with CT- 

DNA was carried out using cyclic voltammetry. The pUC18 DNA cleavage study was monitored by gel 

electrophoresis method. The results suggest that binuclear Cu(II), Ni(II) and VO(II) complexes cleaves pUC18 

DNA in presence of the oxidant H2O2. The invitro antimicrobial activities of the synthesized compounds have 

been tested against the gram negative and gram positive bacteria’s. The binuclear Schiff base complexes were 

found to be higher antibacterial activity than the free ligand. 

Keywords: Schiff base, binuclear, pUC18 DNA cleavage, Antimicrobial, CT-DNA, 2-carboxybenzaldehyde. 

INTRODUCTION: 

Schiff bases and their metal complexes play an important role in the development of coordination 

chemistry, resulting in an enormous number of publications, ranging from pure synthetic work to 

physicochemical [1] and biochemical relevant studies of metal complexes and found wide range of 

applications [2-6]. Mokhles M. Abd-Elzaher has been studied by spectroscopic characterization of 

some tetradentate Schiff Bases and their complexes with Nickel, Copper and Zinc [7]. Schiff bases 

derived from an amine and any aldehyde are a class of compounds which co-ordinate to metal ions via 

the azomethine nitrogen [8]. Metal complexes of Schiff bases derived from substituted 

salicylaldehydes and various amines have been widely investigated because of their wide applicability 

[9-12].Chelating ligands containing O and N donor atoms show broad biological activity and are of 

special interest because of the variety of ways in which they are bonded to metal ions [13]. It is well 

known that several Schiff base complexes have anti-inflammatory, antipyretic, analgesic, anti-diabetic, 

anti-bacterial, anti-cancer and anti-HIV activity [14, 15]. The interaction of transition metal complexes 

with DNA has been extensively studied in the development of new tools for nanotechnology [16, 17]. 

In the present investigation we report here the synthesis, spectroscopic, redox, DNA cleavage studies, 

antimicrobial and DNA cleavage studies and analytical characterizations of new tetradentate N2O2 

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Asian Journal of Biochemical and Pharmaceutical Research Issue 2 (Vol. 1) 2011 

donor type Schiff base and their metal complexes. Our general strategy for preparing the desired 

ligand was based on the condensation of a suitable aldehyde precursor with aminobiphenyl. In this 

paper the synthesis of new tetradentate N2O2 donor type Schiff base and its metal complexes (Cu(II), 

Ni(II) and VO(II)) derived by the condensation of 3,3’,4,4’-tetraminobiphenyl and 2carboxybenzaldehyde 

is described. 

EXPERIMENTAL: 

All the chemicals used were chemically pure and AR grade. Solvents were purified and dried 

according to standard procedures [18]. Metals were purchased from Merck. 3,3’,4,4’tetraminobiphenyl 

and 2- carboxybenzaldehyde were obtained from Aldrich. Other chemicals were 

also purchased from Merck and Aldrich. 

Synthesis: Caution! Perchlorate salts are potentially explosive and were handled only in small 

quantities with care. 

Physical measurements 

The elemental analysis were carried out with a Carlo-Erba 1106-model 240 Perkin Elmer 

analyzer. The solution conductivity measurements were performed to establish the charge type of the 

complexes. The complexes were dissolved in MeCN/DMF/DMSO and molar conductivities of 10 -3 M 

of their solutions at 29 0 C were measured. Infrared spectra were recorded on the Perkin Elmer FT-IR- 

8300 model spectrometer using KBr disc and Nujol mull techniques in the range of 4000-400 cm -1 . 

Electronic absorption spectra in the UV-Visible range were recorded on Perkin Elmer Lambda -25 

between 200-800 nm by using DMF as the solvent Magnetic susceptibility data were collected on 

powdered sample of the compounds at room temperature with PAR155 vibrating sample 

magnetometer. EPR spectra were recorded on a Varian JEOL-JES-TE100 ESR spectrophotometer at 

X-band microwave frequencies for powdered samples at room temperature. Cyclic voltammetry 

studies were performed on a CHI760C electrochemical analyzer in single compartmental cells at 29 0 C 

with H2O/DMSO (95:5) solution using tetrabutylammonium perchlorate (TBAP) as a supporting 

electrolyte. 

Preparation of binucleating tetradentate Schiff base ligand 

The binucleating tetradentate Schiff base was prepared by condensation of tetramine with 

appropriate aldehydes (Scheme 1). 3,3’,4,4’-tetraminobiphenyl (0.214 g; 1 mmol) in 20 ml of 

methanol was stirred with 2 carboxybenzaldehyde (0.600 g; 4 mmol) in 20 ml of methanol for 4 h.The 

resulting yellow solid was separated and dried in vacuum. Yield: 80%. 

Synthesis of binuclear Schiff base complexes 

[Cu2(L)]4ClO4 (1) 

[Ni2(L)]4ClO4 (2) 

[VO2(L)]2SO4 (3) 

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Metal(II) perchlorates of [Cu(II), Ni(II)] and [VO(II)] sulphate (0.2 mmol) and the potential 

binucleating Schiff base ligand (0.1 mmol) were dissolved in DMF (20 ml) and the mixture was heated 

to reflux for 3 h and the reactions were monitored by TLC. After partial evaporation of the solvent, 

solid (65–75%) metal(II) Schiff base complexes (Scheme 2) were separated and dried in vacuum. The 

analysis results are in good consistency with proposed formulas in Table 1. 

Cyclic voltammetry 

All voltammetric experiments were performed with a CHI760C electrochemical analyzer, in 

single compartmental cells using Tetrabutylammonium perchlorate as a supporting electrolyte. The 

redox behavior of the complexes have been examined in absence and in presence of CT-DNA at a 

scan rate 0.2 Vs −1 in the potential range +1.2 to -2.0 V. A three-electrode configuration was used, 

comprised of a glassy carbon electrode as the working electrode, a Pt-wire as the auxiliary electrode, 

and an Ag/AgCl electrode as the reference electrode. The electrochemical data such as cathodic peak 

potential (Epc) and anodic peak potential (Epa) were measured. 

Gel Electrophoresis 

The cleavage of pUC18 DNA was determined by agarose gel electrophoresis [19]. The gel 

electrophoresis experiments were performed by incubation of the samples containing 40 μM pUC18 

DNA, 50 μM metal complexes and 50 μM H2O2 in Tris-HCl buffer (pH 7.2) at 37 o C for 2 h. After 

incubation, the samples were electrophoresed for 2 h at 50 V on 1% agarose gel using Tris-acetic acid- 

EDTA buffer (pH 7.2). The gel was then stained using 1 μg cm -3 ethidium bromide (EB) and 

photographed under ultraviolet light at 360nm. All the experiments were performed at room 

temperature.performed at room temperature unless otherwise mentioned. 

Antimicrobial activity 

The in vitro antibacterial activity of the ligand and the complexes were tested against the 

bacteria’s Bacillus subtilis, Klebsiella pneumoniae, Escherichia coli and Staphylococcus aureus by 

well diffusion method using nutrient agar as the medium. Streptomycin was used as standard for 

bacteria. The stock solution (10 -2 mol L -1 ) was prepared by dissolving the compound in DMF and the 

solution was serially diluted in order to find minimum inhibitory concentration (MIC) values. In a 

typical procedure, a well was made on the agar medium inoculated with microorganisms in a Petri 

plate. The well was filled with the test solution and the plate was incubated for 24 h for bacteria at 35 

o C. During the period, the test solution diffused and the growth of the inoculated microorganisms was 

affected. The inhibition zone was developed, at which the concentration was noted. 

RESULTS AND DISCUSSION 

The binuclear Schiff base ligand prepared and reacts with transition metals Cu(II), Ni(II), and 

VO(II) . The Schiff base ligand has been synthesized from 2- carboxybenzaldehyde and 3,3’,4,4’tetraminobiphenyl 

(scheme 1) ( C44H30N4O8) in 2:1 mole ratio. The results of elemental analyses were 

in good agreement with those required by the proposed formulae given in Table 1. The data in 

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consistent with the earlier reports support the proposed formulation of the binuclear complexes 

(scheme 2). The higher conductance values (Table 2) of chelates support the electrolytic (1:2) nature 

of metal complexes. The new binuclear complexes are stable, hygroscopic with higher melting points, 

insoluble in water, soluble in acetonitrile, chloroform, DMF and DMSO. 

IR spectra 

The important IR absorption frequencies of the synthesized complexes are shown in Table 3. 

The azomethine nitrogen υC=N stretching frequency of the free ligand appears around 1626 cm -1 , which 

is shifted to lower frequencies in the spectra of all the complexes (1600-1610 cm -1 ). These bands are 

shifted to lower wave numbers indicating the involvement of azomethine nitrogen in coordination to 

the metal ion [20]. The above i.r. data clearly indicate that the carbonyl groups of 2carboxybenzaldehyde 

have reacted with the amine groups of 3,3’,4,4’-tetraminobiphenyl through the 

condensation of the metal atoms. The ligand displays υC-O absorptions at 1310 cm -1 . On complexation 

this band is shifted to higher frequency in the range of 1350-1375 cm -1 for all the Schiff base 

complexes which suggest that the carbonyl group is involved in coordination in the enol form through 

deprotonation [21, 22]. This is further supported by the disappearance of the υOH in the range of 3400- 

3440 cm -1 in all the complexes. Accordingly, the ligand acts as a tetradendate chelating agent bonded 

to the metal ion via two –C-O groups & two –C=N azomethine nitrogen atoms of the Schiff base 

(scheme 2).Assignment of the proposed coordination sites is further supported by the appearance of 

medium bands at 480-510cm -1 and 430-470 cm -1 which could be attributed to M-O, M-N respectively 

[23]. In addition, the Oxovanadium complexes shows a band at 981 cm -1 attributed to V=O stretching 

frequency [24]. A further examination of Infrared spectra of complexes shows the presence of a band 

in the 1060-1110 cm -1 region. The strong band is ascribable to ClO4 - & SO4 2- ions [25]. 

Electronic Epectra 

The UV-visible spectra are often very useful in the evaluation of results furnished by other 

methods of structural investigation. The electronic spectral measurements were used for assigning the 

stereochemistries of metal ions in the complexes based on the positions and number of d-d transition 

peaks. The electronic absorption spectra of the Schiff base ligand and its complexes were recorded in 

DMF solution in the range of 200 to 800 nm regions and the data are presented in Table 4. The 

absorption spectrum of free ligand consist of an intense bands centered at 330 nm attributed to n- π* 

transitions of the azomethine group. Another intense band in higher energy region of the spectra of the 

free ligand was related to π→π * transitions of benzene rings. These transitions are also found in the 

spectra of the complexes, but they shifted towards lower frequencies, confirming the coordination of 

the ligand to the metal ions. Further, the d-d transition of the complex showed a broad band centered at 

530 nm for Cu(II) complex Fig. 1. This is due to 2 B1g → 2 A1g transition [26]. The spectra of Ni(II) 

complex in the visible region at about 475 and 490 nm is assigned to 1 A1g → 1 A2g, 1 A1g → 1 B1g, 

transitions, suggesting an approximate square planar geometry of the ligand around the metal ions 

[27]. The intense charge transfer band at 460-470 nm in Oxovanadium(IV) complex assigned to 2 B2 → 

2 A1, 2 B2 → 2 E transitions. This is due to electron delocalization over whole molecule on complexation. 

Based on these data, a square planar geometry has been assigned to the complexes except VO(II) 

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complex which has square pyramidal geometry. These values are comparable with other reported 

complexes [28]. 

Magnetic Properties 

The magnetic moments of the solid state complexes were measured at room temperature. The 

measured magnetic moments of mononuclear copper(II) complex 1.68B.M. Magnetic susceptibility 

measurements shows that these complexes are paramagnetic, which corresponds to the +2 oxidation 

state of copper(II) complexes. The magnetic moment of binuclear Cu(II) complex 1.59 B.M. It can be 

observed that the magnetic moment values of binuclear copper(II) complexes are slightly lower than 

the mononuclear copper(II) complexes. The strong antiferromagnetic coupling that was found for 

binuclear copper(II) complexes were explained as the good super exchange properties [29]. Similarly, 

the magnetic moment of binuclear Ni(II) complex has 2.54 B.M. indicating a geometry [30], and the 

magnetic moment of binuclear VO(II) complex 4.40 B.M. indicating a square–pyramidal geometry 

[31]. 

ESR spectra 

The ESR spectra of transition metal(II) complexes provide information of importance in 

studying the metal ion environment. The X-band ESR spectrum of the copper complex was recorded 

on a powder solid at room temperature Fig. 2. It exhibits an axial signal which can be interpreted in 

terms of tetrahedral species with a strong signal in the low field region, corresponding to g = 2.06, 

and a weak signal in the high field region due to g || = 2.12. Splitting of the signal in the high field 

region may be due to a difference in surroundings between the two copper(II) centers suggesting a 

binuclear structure for this complex [32]. As seen in Table 5, the presence of g || > g is evidence for 

square planar geometry around copper(II) atom [33]. The axial symmetry parameter (G) value of 

Cu(II) complex (less than 4) show that the exchange interaction is negligible. The Cu(II) complex is 

dimer with the unpaired electron lies in the dx 2 - y 2 orbital. Its interesting to note that the g || > g > 

2.0023, indicating that the ground state of Cu(II) is predominantly dx 2 - y 2 . The observed values of 

Vanadyl complex g || = 2.04 > g = 1.98 indicates that the unpaired electron is present in the dxy 

orbital with square pyramidal geometry around the VO(II) chelates [34]. 

Cyclic Voltammetry Studies 

Electroanalytical techniques are the most effective and versatile methods available for the 

mechanistic study of redox systems. The important parameters of a cyclic voltammogram are the 

magnitudes of the anodic peak potential (Epa) and cathodic peak potential (Epc). Cyclic voltammetry 

has been employed to study the interaction of complex with CT-DNA. The cyclic voltammogram of 

complex 1 in the absence of CT-DNA shows in Fig. 3(a) reveals non-Nernstain but fairly 

reversible/quasi-reversible one electron redox process involving Cu(II)/Cu(I) couple. The cyclic 

voltammograms of complexes were obtained in H2O/DMSO (95:5) solution, at scan rate 0.2 Vs 

529 

−1 over 

a potential range from +1.2 to -2.0 V. In the absence of CT-DNA, complex 1 and other complexes data 

are listed in Table 6. the anodic peak potential (Epa) of complex 1 appeared at – 0.410 V and the 

cathodic (Epc) at –1.320 V. The cyclic voltammograms of complex 1 reveals a one electron


quasireversible wave attributed to the redox couple Cu(II)/Cu(I) with the formal electrode potential, 

E O = -0.865 V, and ΔEp= - 0.910 V which is larger than the Nernstian value observed for the one 

electron transfer couple. On addition of CT-DNA, the complex 1 Fig. (3b) shows a shift in Epc= (- 

1.100 V), Epa= (+0.212 V) and ΔEp= (0.888 V) values indicating strong binding of binuclear complex 

with CT-DNA. The decrease in ratio of anodic to cathodic peak signify that adsorption of Cu(I) is 

enhanced in the presence of CT-DNA. Further, the shift in E 0 value and increase in peak heights 

potentials suggest that both Cu(II) and Cu(I) form of complex 1 bind to CT-DNA [35]. 

Cleavage of Plasmid pUC18 DNA 

DNA cleavage is controlled by relaxation of supercoiled circular conformation of pUC18 DNA 

to nicked circular conformation and linear conformation. When circular plasmid DNA is conducted by 

electrophoresis, the fastest migration will be observed for the supercoiled form (Form I). If one strand 

is cleaved, the supercoils will relax to produce 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. Figure 4 

illustrates the gel electrophoresis experiments showing the cleavage of plasmid pUC18 DNA induced 

by the three binuclear complexes. The control experiments did not show any apparent cleavage of 

DNA (lane 1 & 2). Copper binuclear complex in the presence of H2O2 (lane 1) at higher concentration 

(50μM) shows more cleavage activity compared to binuclear Nickel and Oxovanadium(IV) 

complexes. The supercoiled plasmid DNA was completely degraded. This shows that a slight increase 

in the concentration over the optimal value led to extensive degradations, resulting in the 

disappearance of bands on agarose gel [36]. Nickel binuclear complex in the presence of H2O2 

resulting the conversion of supercoiled form (Form-I) into linear form (Form-III) (lane 4). 

Oxovanadium binuclear complex in the presence of H2O2 (lane 5) at higher concentration (50μM) 

shows cleavage activity in which supercoiled DNA (Form-I) cleaved and supercoiled form converted 

to open circular form (Form-II). The results revealed that the Cu(II), Ni(II) complexes have more 

cleavage than VO(II) complex . Probably this may be due to the formation of redox couple of the 

metal ions and its behaviour. Further the presence of a smear in the gel diagram indicates the presence 

of radical cleavage [37]. 

Antimicrobial activity 

The ligand and their complexes have been tested for invitro growth inhibitory activity against 

gram-positive microbes Bacillus subtilis, staphylococcus aureus and gram-negative microbes 

Klebsiella pneumonia, Escherichia coli by using well-diffusion method. As the test solution 

concentration increases, the biological activity also increases. It is found that the activity increases 

upon co-ordination. The increased activity of the metal chelates can be explained on the basis of 

chelation theory [38]. The orbital of each metal ion is made so as to overlap with the ligand orbital. 

Increased activity enhances the lipophilicity of complexes due to delocalization of pi-electrons in the 

chelate ring [39]. In some cases increased lipophilicity leads to breakdown of the permeability barrier 

of the cell [40, 41]. The results revealed that the metal complexes Cu(II), Ni(II) and VO(II) have 

higher antimicrobial activity than the ligand are shown in Figs. 7(a), 7(b) and 7(c) and Table 8. 

530

CONCLUSION: 


The N2O2 type Schiff base ligand is synthesized from 2-carboxybenzaldehyde and 3,3’,4,4’tetraminobiphenyl. 

It acts as a tetradentate ligand and forms stable complexes with transition metal 

ions such as Copper(II), Nickel(II), and Oxovanadium(IV). The ligand and its complexes are 

characterized using spectral and analytical data. The interaction of these complexes with CT-DNA was 

investigated by gel electrophoresis. All the transition metal complexes have higher activity than the 

control CT-DNA. The Cu(II), Ni(II) complexes have more activity than VO(II) complex and the 

control CT-DNA. . The metal complexes have higher antimicrobial activity than the free ligand. 

Scheme 1 Structure of binucleating tetradendate Schiff base ligand 

531


Where, M = Cu(II), Ni(II), X = 4ClO4 - 

Scheme 2 Structure of binuclear Cu(II), Ni(II), VO(II) Schiff base complexes 

532


Table 1 Physical characterization, analytical data of the ligand and binuclear Schiff basecomplexes 

Complexes 

( C44H30N4O8) 

(Ligand ) 

[Cu2(L)]4ClO4 

M. 

point 

Color 

Yield 

( % ) 

240 Yellow 90 - 

260 

[Ni2(L)]4ClO4 248 

Pale 

green 

Dark 

green 

80 

75 

[VO2 (L)]2SO4 279 Green 70 

533 

Found (Calculated) (%) 

M C N H 

10.14 

(10.45) 

9.43 

(9.47) 

12.54 

(12.59) 

71.15 

(71.56) 

41.83 

(41.90) 

42.17 

(42.24) 

49.62 

(49.66) 

7.54 

(7.68) 

4.43 

(4.46) 

4.47 

(4.52) 

5.26 

(5.29) 

4.04 

(4.06) 

2.06 

(2.25) 

2.08 

(2.10) 

2.44 

(2.47)


Table 2 Molar conductance data of the binuclear Schiff base the complexes 

Complexes 

[Cu2(L)]4ClO4 

[Ni2(L)]4ClO4 

[VO2 (L)]2SO4 

Solvent Molar conductance 

MeCN 

DMF 

MeCN 

DMSO 

MeCN 

DMSO 

Λm (ohm -1 cm 2 mol -1 ) 

534 

250 

210 

100 

135 

154 

142 

Types of 

electrolyte 

1:2 

1:2 

1:2 

1:2 

1:2 

1:2


Table 3 Infrared spectral data for the ligand and binuclear Schiff base complexes 

Complexes υ(-C-O) 

( C44H30N4O8) 

(Ligand) 

(cm -1 ) 

υ(-C=N) 

(cm -1 ) 

υ(-OH) 

(cm -1 ) 

535 

υ(V=O) 

(cm -1 ) 

υ(M-O) 

(cm -1 ) 

υ(M-N) 

(cm -1 ) 

1310 1626 3420 - - - - 

ClO4 - 

/SO4 2- 

(cm -1 ) 

[Cu2(L)]4ClO4 1350 1600 3390 - 510 460 1080 

[Ni2(L)]4ClO4 

[VO2(L)]2SO4 

1362 1610 3430 - 495 470 1110 

1375 1602 3385 981 480 430 1060 

Table 4 Absorption spectral data of the ligand and binuclear Schiff base complexes 

Complexes 

( C44H30N4O8) 

Ligand 

[Cu2(L)]4ClO4 

d-d 

Absorption (�max)(nm) 

π�� * 

Benzene/ imino 

n�� * 

Azomethine 

L�MCT 

- 273,254 330 - 

550 279,245 334 430 

[Ni2(L)]4ClO4 490 270,250 332 375 

[VO2 (L)]2SO4 470 275,242 333 420


Table 5 ESR spectral data of the binuclear Schiff base complexes 

Complexes g || g g iso G 

[Cu2(L)]4ClO4 2.12 2.06 2.07 2.03 

[VO2 (L)]2SO4 

2.04 1.98 2.02 -1.44 

Table 6 Cyclic voltammetric data of the binuclear Schiff base Complexes in DMSO solution. 

Complexes Couple Epc (V) Epa (V) ∆Ep(mv) 

[Cu2(L)]4ClO4 Cu(II)/ Cu(I) -0.563 -0.454 0.109 

[Ni2(L)]4ClO4 Ni(II)/Ni(I) 1.60 1.85 0.25 

[VO2 (L)]2SO4 

VO(IV)/ VO(III) 

VO(IV)/VO(V) 

536 

0.61 

-1.63 

0.75 

-0.52 

0.14 

1.11


Table 7 Antibacterial activity of the ligand and binuclear Schiff base complexes 

Klebsiella pneumoniae 

(mm) 

Escherichia coli 

(mm) 

537 

Staphylococcus aureus 

(mm) 

Bacillus subtilis 

Complexes 25 50 75 100 25 50 75 100 25 50 75 100 25 50 75 100 

(mm) 

(μl) (μl) (μl) (μl) 

( C44H30N4O8) 10 12 12 14 11 12 14 14 11 13 14 16 11 13 15 18 

[Cu2(L)]4ClO4 11 13 14 17 12 13 15 16 12 14 15 16 10 14 17 19 

[Ni2(L)]4ClO4 12 15 17 18 13 14 15 18 13 15 16 19 12 15 17 20 

[VO2(L)]2SO4 13 14 16 19 14 15 17 19 14 15 17 19 11 13 16 18


Fig. 1 Absorption spectra of the binuclear Cu(II) Schiff base complex [Cu2(L)]ClO4. 

Fig. 2 X-band ESR spectra of binuclear Cu(II) Schiff base complex [Cu2(L)]ClO4 at room temperature. 

Fig. 3 Cyclic voltammogram (scan rate 0.2 Vs−1, DMSO, 29 ◦ C) of 

Fig. 3a Complex 1 alone 

Fig. 3b Complex 1 in presence of CT-DNA [Complex 1] 1 × 10 −3 M, [DNA] 6 × 10 −3 M. 

538


Fig 4. Changes in the agarose gel electrophoretic pattern of pUC18DNA induced by H2O2 and metal 

complexes: Lane 1, DNA alone; Lane 2, DNA alone + H2O2; Lane 3, DNA + Cu binuclear complex + 

H2O2; Lane 4, DNA + Ni binuclear complex + H2O2; Lane5, DNA + VO binuclear complex + H2O2. 

Fig. 5 Difference between the antimicrobial activity of binuclear ligand & metal complexes 

Fig. 5a (1) ligand ( C44H30N4O8), (2) [Cu2(L)]4ClO4 , (3) [Ni2(L)]4ClO4, (4) [VO2(L)]2SO4 

539


Zone of inhibition (mm) 

20 

15 

10 

5 

0 

Staphylococcus aureus 

1 2 3 4 5 6 7 8 

Complexes 

Fig. 5b Difference between the antimicrobial activity of binuclear ligand & metal complexes (1) ligand ( 

C44H30N4O8), (2) [Cu2(L)]4ClO4 , (3) [Ni2(L)]4ClO4, (4) [VO2 (L)]2SO4. [X axis –Zone of Inhibition (mm)] 

Fig. 5c Difference between the antimicrobial activity of binuclear ligand & metal complexes (1) ligand 

(C44H30N4O8), (2) [Cu2(L)]4ClO4 , (3) [Ni2(L)]4ClO4, (4) [VO2 (L)]2SO4. [X axis –Zone of Inhibition (mm)] 

540 

25 (μl) 

50 (μl) 

75 (μl) 

100 (μl)


Fig. 5d Difference between the antimicrobial activity of binuclear ligand & metal complexes (1) ligand 

(C44H30N4O8), (2) [Cu2(L)]4ClO4 , (3) [Ni2(L)]4ClO4, (4) [VO2 (L)]2SO4. [X axis –Zone of Inhibition 

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*Correspondence Author: R.Rajavel, Department of Chemistry, Periyar University, Salem, 

Tamilnadu, India. 

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