Schiff Base Complexes - International Journal of Research in ...

International Journal of Research in Pharmaceutical and Biomedical Sciences ISSN: 2229-3701 

_____________________________________________Research Article 

Synthesis and Characterization of Tetradentate Co(II) Schiff 

Base Complexes : Antimicrobial & DNA Cleavage Studies 

A. Nagajothi, A. Kiruthika, S. Chitra * and K. Parameswari 

Department of Chemistry, P.S.G.R.Krishnammal College for Women, Peelamedu, 

Coimbatore, Tamil Nadu, India. 

ABSTRACT 

Tetradentate N 2 O 2 type complexes of Co(II) have been synthesized by the condensation of o- 

phenylenediamine, salicylaldehyde and isatin / naphthaldehyde / acetyl acetone. The complexes were 

characterized by elemental analyses, molar conductance, magnetic susceptibility, IR, Uv-Vis spectral data and 

thermal analyses. The elemental analysis of the complexes confine to the stoichiometry of the type 

[ML(H 2 O)(OAc)]. The complexes were found to be non-electrolytic in nature on the basis of low value of molar 

conductance. From the spectral datas an octahedral geometry has been proposed for all the complexes. The 

possible geometries of metal complex were evaluated using 3D molecular modelling picture. The metal 

complexes have been screened for their antibacterial and antifungal activity. DNA cleavage activities of Schiff 

bases and their metal complexes were monitored by agarose gel electrophoresis method in the presence of 

H 2 O 2 . 

Key Words: o-phenylenediamine, Salicylaldehyde, 2-hydroxy Naphthaldehyde, Isatin. 

1. INTRODUCTION 

Schiff bases have been playing an important part in 

the development of Co-ordination chemistry. Schiff 

base metal complexes have been studied 

extensively because of their attractive chemical and 

physical properties and their wide range of 

applications in numerous scientific areas. They 

play an important role in both synthetic and 

structural research, because of their preparative 

accessibility and structural diversity 1 . Schiff bases 

of o-phenylenediamine and its complexes have a 

variety of applications including biological, clinical 

and analytical 2 . 

In this paper we report the synthesis, 

characterization, antimicrobial & DNA cleavage 

studies of new type tetradentate Schiff base ligands 

derived from ortho phenylene diamine, 

salicylaldehyde and isatin / acetyl acetone / 2- 

hydroxy naphthaldehyde. The ligand has both 

oxygen and nitrogen donor sites. It coordinates 

with the metal ion in a tetradentate manner. 

2. EXPERIMENTAL 

MATERIALS, METHODS AND 

INSTRUMENTS 

Elemental analyses were performed by using 

Elementar Vario EL III at STIC, CUSAT, Cochin. 

The IR spectra were recorded in KBr pellets using 

Shimadzu FTIR spectrometer (4000 – 400 cm -1 ). 

The UV-Vis electronic spectra (200 – 800 nm) 

were recorded using Lab India 3000 + double beam 

spectrophotometer. The magnetic susceptibility of 

the complexes was recorded at room temperature 

using Gouy balance. The thermal analysis were 

performed with a Perkin Elmer (TGS-2 model) 

thermal analyzer at a heating rate of 10°C / min in 

the temperature range 40 - 800°C. The AFM 

images were recorded using Nova software by 

Multimode Scanning probe microscope (NTMDT, 

NTEGRA prima, Russia) with cantilever length, 

width and thickness 135, 30 and 2µm respectively 

and 0.35 – 6.06N/m force constant. The geometries 

of metal complex were evaluated using the 

molecular calculations with Argus lab 4.0.1 

version. 

Synthesis of Schiff Base Ligand L 1 / L 2 / L 3 

A solution of o-phenylenediamine (0.1 mol) in 

alcohol was added to a mixture of isatin/Acetyl 

acetone/ 2-hydroxy naphthaldehyde (0.1 mol) and 

salicylaldehyde (0.1 mol) in 20 ml alcohol. The 

mixture was refluxed for about 30 minutes. The 

mixture was cooled in ice. The resulting precipitate 

was then filtered, washed with ethanol and dried. 

Synthesis of metal complexes (ML 1 / M 1 L 2 / 

M 1 L 3 ) 

To an ethanolic solution of the Schiff Base Ligand 

L 1 / L2/ L 3 an ethanolic solution of the metal acetate 

[Cobalt Acetate] was added in a molar ratio (1:1). 

The mixture was refluxed for about 30 minutes. 

The mixture was cooled in ice. The resulting 

precipitate was collected by filtration, washed with 

ethanol and dried. 

Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonline.com 1768


Antimicrobial studies 

The in vitro biological screening effects of the 

investigated compounds were tested against the 

bacteria Staphylococcus Aureus, Escherichia Coli 

and Fungi Candida Albicans. Stock solutions were 

prepared by dissolving the compounds in DMSO 

and serial dilutions of the compounds were 

prepared in sterile distilled water to determine the 

minimum inhibition concentration (MIC). The 

nutrient agar medium was poured into Petri plates. 

A suspension of the tested microorganism (0.5 ml) 

was spread over the solid nutrient agar plates with 

the help of a spreader. Different dilutions of the 

stock solutions were applied on the 10 mm 

diameter sterile disc. After evaporating the solvent, 

the discs were placed on the inoculated plates. The 

Petri plates were placed at low temperature for two 

hours to allow the diffusion of the chemical and 

then incubated at a suitable optimum temperature 

for 30 – 36 hrs. The diameter of the inhibition 

zones was measured in millimeters 3 

DNA studies 

DNA cleavage activities of Schiff base L 1 and their 

complexes (Ia, IIa & IIIa) with calf thymus DNA 

(CT DNA) were monitored by agarose gel 

electrophoresis method. The experiments were 

performed under aerobic conditions with H 2 O 2 as 

an oxidant by incubation at 35 C for 2 h as 

follows: CT DNA 50 M of each Schiff base 

ligand L 1 and its Co complexes, 50 M of H 2 O 2 in 

0.05 M Tris–HCl buffer (pH = 7.2). After 

incubation, 1 μL of loading buffer (bromophenol 

blue in H 2 O) was added to each tube and the mixed 

samples were loaded on 1 % agarose gel. The 

samples were electrophoresed at a constant voltage 

(50 V) for 2 h in Tris–acetic acid–EDTA buffer 

(pH 8.3). After electrophoresis, the gel was stained 

for 30 min by immersing it in 1 g / cm 3 

ethidiumbromide (EB) solution. The cleavage was 

visualized by viewing the gel under UV light and 

photographed 4 . 

Synthesis of Nano Metal oxides 

The transition metal complexes were placed in a 

silica crucible and ignited in a muffle furnace at 

800ºC. The dehydrated mixture undergoes a 

vigorous, exothermic oxidation reduction reaction. 

The heat created causes a flame for several 

minutes, resulting in voluminous and foamy 

powder product occupying the entire reaction 

container. The exothermic combustion reaction 

releases a large amount of heat, which can quickly 

heat up the system to reach a temperature higher 

than 1600ºC. The combustion method results in 

uniform and pure powders of high surface to 

volume ratio. The size of the metal oxide was 

determined using Atomic force Microscope. 

3. RESULTS AND DISCUSSION 

Schiff bases of o-phenylenediamine and its 

complexes have a variety of applications including 

biological, clinical and analytical. Earlier work has 

shown that some drugs showed increased activity 

when administered as metal chelates rather that as 

organic compounds. The Co-ordinating possibility 

of o-phenylenediamine has been improved by 

condensing with a variety of carbonyl compounds. 

An attempt has been made to synthesize 

asymmetric Schiff bases from o-phenylenediamine 

and salicylaldehyde with Isatin / Acetyl acetone / 

2-hydroxy naphthaldehyde. The synthetic routes of 

the ligands and complexes are presented in scheme 

1. 

Schiff bases 

1. Isatin + o-phenylenediamine + 

salicylaldehyde L 1 

2. Acetyl acetone + o-phenylenediamine + 

sallicylaldehyde L 2 

3. 2-hydroxynaphthaldehyde+ o- 

phenylenediamine + 

sallicylaldehyde L 3 

Metal complexes 

Co(OAc) 2 + L 1/ L 2 /L 3 Co(L 1/ L 2 /L 3 ) 2 [Ib, IIb, 

IIIb] 

Ib - Isatin Co complex [Co(L 1 ) 2 ] 

IIb - Acetyl acetone Co complex [Co(L 2 ) 2 ] 

IIIb - 2-hydroxy naphthadehyde Co complex 

[Co(L 3 ) 2 ] 

Scheme 1 

Elemental Analysis and Molar Conductance 

The metal complexes are insoluble in water and 

soluble in DMSO, DMF, CHCl 3 and acetone and 

slightly soluble in methanol and ethanol. The 

analytical data and physical properties of the 

ligands and complexes are presented in Table 1. 

The data are consistent with the calculated results 

from the empirical formula of each compound. The 

analytical data of the complexes confirm the 1:1 

metal to ligand stoichiometry.Cobalt complexes 

have a very low molar conductance < 45 ohm -1 cm - 

1 

mol -1 . The above molar conductance value 

confirm that the cobalt complexes are nonelectrolytes 

5 . 

IR spectra 

The significant IR bands for the ligands as well as 

its Co complex and their tentative assignments are 

complied and presented in Table 2 [Figs. 1-2]. In 

the IR spectrum of the Schiff bases ligands L 1 , L 2 , 

L 3 a sharp band observed at 1616 cm -1 is assigned 

to the ν(C=N) mode of the azomethine group. This 

shifts to lower wave numbers, 1606-1609 cm -1 in 

all the complexes suggesting the co-ordination of 

the azomethine nitrogen to the metal centres. This 

is further substantiated by the presence of a new 

band around 420-463 cm -1 assignable to ν(M-N) 6 . 



The characteristic phenolic ν(O-H) mode due to 

presence of a hydroxyl group at ortho position in 

the ligand was observed around 3200-3500 cm -1 . A 

band at –̃ 1279 cm -1 due to ν(C-O) phenolic group 

was also observed in the ligand. The disappearance 

of phenolic ν(OH) band in all the complexes 

suggests the co-ordination by the phenolic oxygen 

after deprotonation to the metal ion. This is further 

supported by the shifting of ν(C-O) phenolic band 

to lowers wave numbers –̃1250 cm -1 in the metal 

complex. The appearance of a new non-ligand band 

around 500-543 cm -1 in all the complexes due to 

ν(M-O) substantiates it 7 . 

A strong sharp band observed at 1700 cm -1 is 

assigned to ν(C=O) of isatin and acetyl acetone in 

ligands L1 and L2. the intensity of this band has 

not only reduced but has shifted to lower wave 

numbers in the corresponding metal complexes 

confirming the involement of the carbonyl group in 

complexation with metal ion. 

In the cobalt complexes the appearance of two 

additional bands in the range 1610- 1578 cm -1 and 

1360-1310 cm -1 due to ν as(COO) and ν s(COO) 

modes respectively of acetate group suggest its 

unidentate co-ordination (Δ = > 200 cm -1 ) to the 

metal.The presence of co-ordinated water in the Co 

complex is confirmed by the presence of bands 

around 890 –928 cm -1 8 . 

Electronic spectra and magnetic measurements 

The electronic spectral data and magnetic moments 

of the complexes are presented in Table 3 [Figs 3- 

4]. The electronic spectrum of free Schiff base 

showed three bands around 240, 350 and 450 nm 

characteristic of - * and n- * transitions. In the 

metal complex, this band is shifted to a longer 

wave length with increasing intensity. This shift 

may be attributed to the donation of lone pair of 

electrons of nitrogen of Schiff base to metal ion 9 . 

The cobalt(II) complexes exhibit two bands at 482 

– 472 nm and 350 – 306 nm in the electronic 

spectra. The bands can be assigned to 4 T 1g (F) → 

4 A 2g and 4 T 1g (F) → 4 T 1g (P) transitions respectively 

which are in accordance with Co(II) high spin 

octahedral geometry 8 . The magnetic moments of 

Co(II) complexes (4.68 – 4.56 BM) suggest a high 

spin octahedral configuration. The Schiff base L 3 

complexes with cobalt to give a cobalt complex in 

which cobalt is in the +3 state. Since it was found 

to be diamagnetic with very low magnetic moment. 

This may be due to the oxidation of Co(II) to 

Co(III) during complexation 10 . 

Thermogravimetric Analysis 

The TGA curve of the cobalt complex Ia is stable 

upto 120°C. A weight loss of 3.9% is observed 

around 128-163°C [Fig 5] corresponding to the 

elimination of one coordination water. In the 

complexes IIa / IIIa this loss of coordinated water 

is observed at 750°C (observed IIa-7.1% and IIIa- 

5.9%). In all the three cobalt complexes a weight 

loss of 12-14% was observed at a temperature 

range of 244-249°C corresponding to the removal 

of one acetate group. The complexes show a step 

weight loss of 27 – 29% (observed Ia- 28.9%, IIa- 

27.9%, IIIa-29.5%). In the temperature range 343- 

372°C corresponding to the elimination of part of 

the Schiff base ligand viz. isatin, acetyl acetone and 

naphthyl groups from the coordination sphere of 

the complex. The final residue corresponds to CoO 

> 800°C. The TGA data are presented in table 4. 

Probable structure 

O 

CH 3 COO 

Co 

O 

H 3 C 

CH 3 COO 

O 

Co 

O 

N 

H 

N 

H 2 O 

N 

C H 3 

N N 

H 2 O 

Ia 

[Co (L 1 ) (H 2 O)(OAC)] 

IIa 

[Co (L 2 ) (H 2 O)(OAC)] 

O 

CH 3 COO 

Co 

O 

N 

H 2 O 

N 

IIIa 

[Co (L 3 ) (H 2 O)(OAC)] 



Molecular Modelling 

Molecular modeling of the studied complexes 

reveals minimum energy values associated with the 

octahedral and square plannar geometry. This is in 

a good agreement with the experimental results and 

confirmed the expected structure. The possible 

geometries of metal complexes were evaluated 

using the molecular calculations with Argus lab 

4.0.1 version software. The metal complexes were 

built and geometry optimization was done using 

this software. The molecular modelling pictures 

and the energies of the metal complexes are shown 

in [figs 6-7]. 

The details of important bond lengths as per 3D 

structure of Co(II) complex (Ia) [fig 9] are given in 

table 5. These values are obtained as a result of 

energy minimization of Co(II) complex in Argus 

lab 4.0.1 version software. 

The obtained bond lengths of the ligand L 1 based 

on the software are between C(7)-O(14) and C(24)- 

O(13) 1.4968, C(9)-N(10) and C(12)-N(11) 1.5687, 

C(18)-N(10) and C(15)-N(11) 1.5895. Based on the 

values from the table 5, it is observed that when 

these ligand are coordinated with Co metal ion 

there is an increase in the bond length between the 

mentioned atoms, which confirms the coordination 

of azomethine group through nitrogen [N(10) and 

N(11)] and through phenolic oxygen [O(13) and 

O(14)]. When the atoms are coordinated with the 

metal ion by donating a lone pair of electron there 

is a decrease of electron density on the 

coordinating atoms, hence bond length increases in 

metal complexes. This supports the proposed 

octahedral geometry around the cobalt metal ion 11 . 

Anti Microbial studies 

The antimicrobial activity of the cobalt complex Ia 

was studied against two pathogenic bacterial strains 

(ie) one gram positive (staphylococcus Aureus) and 

one gram negative (Escherichia Coli) bacteria and 

one fungal strain (Candida Albicans). [Fig 8-10] 

Antibacterial and antifungal potential of metal 

complexes were assessed in terms of zone of 

inhibition of bacterial and fungal growth. The 

results of the antifungal and antibacterial activities 

are presented in table 6. The minimum inhibitory 

concentrations (MIC) were calculated as the 

highest dilution showing complete inhibition of the 

tested strains and are reported in table 7. 

Growth of bacterial & fungal pathogens on each 

concentration was checked to determine the 

minimum concentration that inhibits the growth of 

the organism. It is evident from the table 7 that the 

MIC value for the cobalt complex Ia was 125 

g/ml for both S.Aureus and E.Coli. Likewise the 

MIC value for fungi pathogen shows 62.5 g/ml 

for cobalt complex [Fig 11]. 

The metal complexes were effective against both 

bacteria and fungi. The cobalt complex shows 

better activity against fungai, than the bacteria 

when compared with the standard ciprofloxacin. 

DNA Cleavage Studies 

The investigation of interactions between doublestranded 

DNA and DNA binding agents is crucial 

for understanding biochemical processes as 

replication, repair, recombination and expression of 

genes. In principle, the possible binding 

mechanisms of ligands to double stranded dsDNA 

can be divided into sequence specific binding and 

binding modes that lack sequence specificity. 

Specific binding between ligand (protein) and 

receptor (dsDNA) often termed as molecular 

recognition is the basis for the interaction of many 

transcription factors with DNA. Small agents that 

bind unspecifically or with lower sequence 

specificity to dsDNA are often capable of 

influencing or inhibiting these processes and 

intrinsically exhibit magnetic properties. 

Consequently these molecules find applications as 

pharmaceuticals mainly in the treatment of cancer. 

Others are employed as staining agents 12 . 

In the present study, the CT-DNA gel 

electrophoresis experiment was conducted at 35°C 

using the ligand L 1 & complex (Ia) in the presence 

of H 2 O 2 as an oxidant. It was found that at very low 

concentration, the complexes exhibit nuclease 

activity in the presence of H 2 O 2 . Control 

experiment using DNA alone does not show any 

significant cleavage of CT DNA even on longer 

exposure time. Cobalt complex cleaves DNA to a 

larger extent as compared with control DNA, [Fig- 

12]. This is due to the formation of redox couple of 

the metal ions. In oxidative mechanism, metal ions 

in the complexes react with H 2 O 2 to generate the 

OH • which attacks at the C3 positions of the sugar 

moiety and finally cleaves DNA. Cobalt complex 

reacts with H 2 O 2 to form OH • , OH - and Co(III) 

form. 

Determination of size of nano metal oxide 

The size of the metal oxide was determined by 

Atomic Force Microscope. AFM provides a 3D 

profile of the surface on a nanoscale by measuring 

forces between a sharp probe (


Schiff base ligands. The ligands and complex were 

characterized by spectral and analytical data. Based 

on these data an octahedral geometry has been 

assigned to the Co(II) complex. Molecular 

modelling has been performed for the complexes 

using Argus 4.0.1 software. The metal complexes 

were converted to their corresponding nano metal 

oxides, the 2D and 3D AFM pictures of the oxides 

confirm their size to be in the range 0-100 nm. The 

antimicrobial studies carried out with the 

complexes confirm that they are good antifungal 

agents. Their MIC values being 125µg/litre. The 

interaction of these complexes with CT-DNA was 

investigated by gel electrophoresis. The Co 

complex (Ia) cleaved DNA as compared to control 

and the Schiff base ligand in the presence of H 2 O 2 . 

Table 1: Elemental Analysis,Yield, Molar conductivity and Melting point of ligands and their Metal 

complexes 

Elemental Analysis, Found Conductance 

Complex Emp.Formula M.Wt 

(Calculated) % 

(ohm -1 cm -1 Melting point 

mol -1 (°C) 

C H N 

) 

L 1 C 21H 15N 3O 2 341 - - - - 277 

[Co(L 1) 2] C 23H 19N 3O 5.Co 

56 3.5 8 

475.93 

< 45 > 360 

(57.9) (4) (8.8) 

L 2 C18H 18N 2O 2 294 - - - - 298 

[Co(L 2) 2] 

C 20H 21N 2O 5.Co 427.93 

55 

(56.08) 

4 

(4.9) 

6 

(6.5) 

< 45 > 360 

L 3 C 24H 17N 2O 2 351 - - - - 326 

[Co(L 3) 2] 

C 26H 21N 2O 5.Co 

485.93 

63 

(64.2) 

4.1 

(4.3) 

5.2 

(5.8) 

< 45 > 360 

Table 2: IR spectral data for ligands and their metal complexes 

Complex (C=O) (C=N) (OH) (M-N) (M-O) (NH) (C-O) (H 2O) 

L 1 1707.06 1616.40 3319.60 3059.20 1279.81 

[Co(L 1) 2] 

1700.31 1607.72 421.46 500.54 3026.41 1245.09 929.72 

L 2 1700.31 1614.47 3228.95 1275.95 

[Co(L 2) 2] 

1699.34 1609.65 453.29 519.98 1243.16 925.86 

L 3 1616.40 3531.76 1279.81 

[Co(L 3) 2] 

1607.7 421.46 501.51 1254.74 928.76 

Table 3: Electronic Spectral & Magnetic moment data for the ligands and their complexes 

Ligand/ 

Complex 

Absorbance 

nm 

L 1 

425 23529 n - * 

350 28571 - * 

L 2 

445 22471 n - * 

338 29585 - * 

L 3 

355 

479 

365 

28169 

20876 

27397 

- * 

n - * 

MLCT 

498 20080 

5 T 2g (F) 5 Eg 

492 20325 

5 T 2g (F) 5 Eg 

306 32679 

4 T 1g (F) 4 T 1g (P) 

[Co(L 1) 2] 

472 21186 

4 T 1g (F) 4 A 2g 

[Co(L 2) 2] 

[Co(L 3) 2] 

350 28571 

482 20746 

340 29411 

480 20833 

/cm -1 Assignment Geometry Magnetic moment (BM) 

4 T 1g (F) 4 T 1g (P) 

4 T 1g (F) 4 A 2g 

4 T 1g (F) 4 T 1g (P) 

4 T 1g (F) 4 A 2g 

- - 

- - 

- - 

Octahedral 4.68 





Table 4: Thermal Analysis data for metal complexes 

Complex 

Decomposition 

Weight loss % 

Lost fragment 

Temp°C 

Experimental Theoretical 

128.72-163.80 H 2O 3.9 4.5 

200-270 CH 3COO 13 14 

[Co(L 1) 2] 

270-410 28.9 30 

[Co(L 2) 2] 

> 600 Residue CoO 38.5 35.8 

100-170 Lattice H 2O 4.2 4 

180-300 CH 3COO 14.4 12 

700-830 H 2O 7.1 7 

>830 Residue CoO 28.9 30 

200-310 CH 3COO 12..1 10 

[Co(L 3) 2] 

343-372 

29.5 27 

720-820 H 2O 5.9 5 

>830 Residue CoO 37.08 40 

Table 5: Data from Molecular 

modelling of [Co(L 1 ) 2 ] complex 

S.No Bonded atoms Bond length 

1 2 (C) - 7(C) 1.3586 

2 9 (C) - 10 (N) 1.3689 

3 17(C) – 20(C) 1.4348 

4 10(N) - 18 (C) 1.3654 

5 21(C) - 22(C) 1.0625 

6 13(O) – 24(C) 1.0774 

7 7(C) - 14(O) 1.0798 

8 8(C) - 33(H) 1.2672 

9 14(O) – 27(Co) 2.0556 

10 10(N) - 27(Co) 2.0774 

11 27(Co) - 28(O) 2.0374 

12 28(O) - 34(H) 

1.5637 

13 30(C) - 31(O) 1.3476 

14 32(C) - 38(H) 1.2978 

Table 6: Antibacterial & Antifungal activity data 

of Schiff base metal complexes 

Microorganism [Co(L 1) 2(H 2O)(OAc)] 

STD 

Ciprofloxacin (50 µg/disc) 

(mm) 

Bacteria E.Coli 10 20 

S.Aureus 11 25 

Fungi C.albicans 31 18 

Table 7: Determination of MIC for antibacterial & antifungal activity 

500 250 125 62.5 31.25 15.62 7.8 

Microorganism 

µg/ml µg/ml µg/ml µg/ml µg/ml µg/ml µg/ml 

S.Aureus - - - + + + + 

Bacteria 

E.coli - - - + + + + 

Fungi C.Albicans - - - - + + + 



Table 8: Antibacterial & 

Antifungal activity: MIC values 

Microorganism MIC value 

S.Aureus 125 µg/ml 

Bacteria 

E.coli 125 µg/ml 

Fungi C.Albicans 62.5 µg/ml 

IR SPECTRAL DATA 

Fig. 1: IR Spectrum of L 1 Schiff base 

Fig. 2: IR Spectrum of Co(L 1 ) 2 complex 

UV Spectra 

Fig. 3: Electronic spectrum of L 1 Schiff base Fig. 4: Electronic spectrum of Co(L 1 ) 2 



THERMOGRAVIMETRIC ANALYSIS 

Fig. 5: TGA of Co(L 1 ) 2 complex 

MOLECULAR MODELLING 

Fig. 6: schiff base L 1 

Energy 93.61 kcal/mol 

Fig. 7: Metal complex [Co. L 1 (H 2 O)(OAc)] 

Energy 289.51 kcal/mol 

Antimicrobial studies 

Fig. 8: Zone of inhibition – bacteria 

S.Aureus image of [Co.L 1 (H 2 O)(OAc)] 

Fig. 9: Zone of inhibition - bacteria 

E.Coli image of [Co.L 1 (H 2 O) (OAc)] 



Fig. 10: Zone of inhibition - fungi 

C.Albicans image of [Co.L 1 (H 2 O) (OAc)] 

35 

30 

25 

20 

15 

10 

5 

0 

E.Coli 

S.Aureus C.Albicans 

Standard 

Co complex 

Fig. 11: Antimicrobial activity of the Schiff base complexes 

against bacterial & fungal pathogens 

DNA CLEAVAGE STUDIES 

Fig. 12: Gel Diagram of calf-thymus DNA induced by 

the Schiff base L 1 and its complex Ia in presence of oxidant 

H 2 O 2 by agarose gel electrophoretic pattern 

Lane from Left to Right 

(C) CT DNA alone 

(1) Schiff Base I + DNA + H 2O 2 

(2) Co(L 1) 2 +DNA + H 2O 2 



AFM IMAGES 

Fig. 13: AFM topographic images of cobalt oxide of IIa 

-[Co(L2)2(H2O)(OAc)] showing 2D configuration in the 

material. The scanned area 

is 0.5 m x 0.5 m. Size of the particle = 15nm-20-nm 

Fig. 14: AFM topographic images of cobalt oxide of IIa- 

[Co(L2)2(H2O)(OAc)] showing 3D configuration in the material. 

The scanned area is 0.5 m x 0.5 m. 

Size of the particle = 15nm-20-nm 

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