Schiff Base Complexes - International Journal of Research in ...
Schiff Base Complexes - International Journal of Research in ...
Schiff Base Complexes - International Journal of Research in ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
_____________________________________________<strong>Research</strong> Article<br />
Synthesis and Characterization <strong>of</strong> Tetradentate Co(II) <strong>Schiff</strong><br />
<strong>Base</strong> <strong>Complexes</strong> : Antimicrobial & DNA Cleavage Studies<br />
A. Nagajothi, A. Kiruthika, S. Chitra * and K. Parameswari<br />
Department <strong>of</strong> Chemistry, P.S.G.R.Krishnammal College for Women, Peelamedu,<br />
Coimbatore, Tamil Nadu, India.<br />
ABSTRACT<br />
Tetradentate N 2 O 2 type complexes <strong>of</strong> Co(II) have been synthesized by the condensation <strong>of</strong> o-<br />
phenylenediam<strong>in</strong>e, salicylaldehyde and isat<strong>in</strong> / naphthaldehyde / acetyl acetone. The complexes were<br />
characterized by elemental analyses, molar conductance, magnetic susceptibility, IR, Uv-Vis spectral data and<br />
thermal analyses. The elemental analysis <strong>of</strong> the complexes conf<strong>in</strong>e to the stoichiometry <strong>of</strong> the type<br />
[ML(H 2 O)(OAc)]. The complexes were found to be non-electrolytic <strong>in</strong> nature on the basis <strong>of</strong> low value <strong>of</strong> molar<br />
conductance. From the spectral datas an octahedral geometry has been proposed for all the complexes. The<br />
possible geometries <strong>of</strong> metal complex were evaluated us<strong>in</strong>g 3D molecular modell<strong>in</strong>g picture. The metal<br />
complexes have been screened for their antibacterial and antifungal activity. DNA cleavage activities <strong>of</strong> <strong>Schiff</strong><br />
bases and their metal complexes were monitored by agarose gel electrophoresis method <strong>in</strong> the presence <strong>of</strong><br />
H 2 O 2 .<br />
Key Words: o-phenylenediam<strong>in</strong>e, Salicylaldehyde, 2-hydroxy Naphthaldehyde, Isat<strong>in</strong>.<br />
1. INTRODUCTION<br />
<strong>Schiff</strong> bases have been play<strong>in</strong>g an important part <strong>in</strong><br />
the development <strong>of</strong> Co-ord<strong>in</strong>ation chemistry. <strong>Schiff</strong><br />
base metal complexes have been studied<br />
extensively because <strong>of</strong> their attractive chemical and<br />
physical properties and their wide range <strong>of</strong><br />
applications <strong>in</strong> numerous scientific areas. They<br />
play an important role <strong>in</strong> both synthetic and<br />
structural research, because <strong>of</strong> their preparative<br />
accessibility and structural diversity 1 . <strong>Schiff</strong> bases<br />
<strong>of</strong> o-phenylenediam<strong>in</strong>e and its complexes have a<br />
variety <strong>of</strong> applications <strong>in</strong>clud<strong>in</strong>g biological, cl<strong>in</strong>ical<br />
and analytical 2 .<br />
In this paper we report the synthesis,<br />
characterization, antimicrobial & DNA cleavage<br />
studies <strong>of</strong> new type tetradentate <strong>Schiff</strong> base ligands<br />
derived from ortho phenylene diam<strong>in</strong>e,<br />
salicylaldehyde and isat<strong>in</strong> / acetyl acetone / 2-<br />
hydroxy naphthaldehyde. The ligand has both<br />
oxygen and nitrogen donor sites. It coord<strong>in</strong>ates<br />
with the metal ion <strong>in</strong> a tetradentate manner.<br />
2. EXPERIMENTAL<br />
MATERIALS, METHODS AND<br />
INSTRUMENTS<br />
Elemental analyses were performed by us<strong>in</strong>g<br />
Elementar Vario EL III at STIC, CUSAT, Coch<strong>in</strong>.<br />
The IR spectra were recorded <strong>in</strong> KBr pellets us<strong>in</strong>g<br />
Shimadzu FTIR spectrometer (4000 – 400 cm -1 ).<br />
The UV-Vis electronic spectra (200 – 800 nm)<br />
were recorded us<strong>in</strong>g Lab India 3000 + double beam<br />
spectrophotometer. The magnetic susceptibility <strong>of</strong><br />
the complexes was recorded at room temperature<br />
us<strong>in</strong>g Gouy balance. The thermal analysis were<br />
performed with a Perk<strong>in</strong> Elmer (TGS-2 model)<br />
thermal analyzer at a heat<strong>in</strong>g rate <strong>of</strong> 10°C / m<strong>in</strong> <strong>in</strong><br />
the temperature range 40 - 800°C. The AFM<br />
images were recorded us<strong>in</strong>g Nova s<strong>of</strong>tware by<br />
Multimode Scann<strong>in</strong>g probe microscope (NTMDT,<br />
NTEGRA prima, Russia) with cantilever length,<br />
width and thickness 135, 30 and 2µm respectively<br />
and 0.35 – 6.06N/m force constant. The geometries<br />
<strong>of</strong> metal complex were evaluated us<strong>in</strong>g the<br />
molecular calculations with Argus lab 4.0.1<br />
version.<br />
Synthesis <strong>of</strong> <strong>Schiff</strong> <strong>Base</strong> Ligand L 1 / L 2 / L 3<br />
A solution <strong>of</strong> o-phenylenediam<strong>in</strong>e (0.1 mol) <strong>in</strong><br />
alcohol was added to a mixture <strong>of</strong> isat<strong>in</strong>/Acetyl<br />
acetone/ 2-hydroxy naphthaldehyde (0.1 mol) and<br />
salicylaldehyde (0.1 mol) <strong>in</strong> 20 ml alcohol. The<br />
mixture was refluxed for about 30 m<strong>in</strong>utes. The<br />
mixture was cooled <strong>in</strong> ice. The result<strong>in</strong>g precipitate<br />
was then filtered, washed with ethanol and dried.<br />
Synthesis <strong>of</strong> metal complexes (ML 1 / M 1 L 2 /<br />
M 1 L 3 )<br />
To an ethanolic solution <strong>of</strong> the <strong>Schiff</strong> <strong>Base</strong> Ligand<br />
L 1 / L2/ L 3 an ethanolic solution <strong>of</strong> the metal acetate<br />
[Cobalt Acetate] was added <strong>in</strong> a molar ratio (1:1).<br />
The mixture was refluxed for about 30 m<strong>in</strong>utes.<br />
The mixture was cooled <strong>in</strong> ice. The result<strong>in</strong>g<br />
precipitate was collected by filtration, washed with<br />
ethanol and dried.<br />
Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonl<strong>in</strong>e.com 1768
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
Antimicrobial studies<br />
The <strong>in</strong> vitro biological screen<strong>in</strong>g effects <strong>of</strong> the<br />
<strong>in</strong>vestigated compounds were tested aga<strong>in</strong>st the<br />
bacteria Staphylococcus Aureus, Escherichia Coli<br />
and Fungi Candida Albicans. Stock solutions were<br />
prepared by dissolv<strong>in</strong>g the compounds <strong>in</strong> DMSO<br />
and serial dilutions <strong>of</strong> the compounds were<br />
prepared <strong>in</strong> sterile distilled water to determ<strong>in</strong>e the<br />
m<strong>in</strong>imum <strong>in</strong>hibition concentration (MIC). The<br />
nutrient agar medium was poured <strong>in</strong>to Petri plates.<br />
A suspension <strong>of</strong> the tested microorganism (0.5 ml)<br />
was spread over the solid nutrient agar plates with<br />
the help <strong>of</strong> a spreader. Different dilutions <strong>of</strong> the<br />
stock solutions were applied on the 10 mm<br />
diameter sterile disc. After evaporat<strong>in</strong>g the solvent,<br />
the discs were placed on the <strong>in</strong>oculated plates. The<br />
Petri plates were placed at low temperature for two<br />
hours to allow the diffusion <strong>of</strong> the chemical and<br />
then <strong>in</strong>cubated at a suitable optimum temperature<br />
for 30 – 36 hrs. The diameter <strong>of</strong> the <strong>in</strong>hibition<br />
zones was measured <strong>in</strong> millimeters 3<br />
DNA studies<br />
DNA cleavage activities <strong>of</strong> <strong>Schiff</strong> base L 1 and their<br />
complexes (Ia, IIa & IIIa) with calf thymus DNA<br />
(CT DNA) were monitored by agarose gel<br />
electrophoresis method. The experiments were<br />
performed under aerobic conditions with H 2 O 2 as<br />
an oxidant by <strong>in</strong>cubation at 35 C for 2 h as<br />
follows: CT DNA 50 M <strong>of</strong> each <strong>Schiff</strong> base<br />
ligand L 1 and its Co complexes, 50 M <strong>of</strong> H 2 O 2 <strong>in</strong><br />
0.05 M Tris–HCl buffer (pH = 7.2). After<br />
<strong>in</strong>cubation, 1 μL <strong>of</strong> load<strong>in</strong>g buffer (bromophenol<br />
blue <strong>in</strong> H 2 O) was added to each tube and the mixed<br />
samples were loaded on 1 % agarose gel. The<br />
samples were electrophoresed at a constant voltage<br />
(50 V) for 2 h <strong>in</strong> Tris–acetic acid–EDTA buffer<br />
(pH 8.3). After electrophoresis, the gel was sta<strong>in</strong>ed<br />
for 30 m<strong>in</strong> by immers<strong>in</strong>g it <strong>in</strong> 1 g / cm 3<br />
ethidiumbromide (EB) solution. The cleavage was<br />
visualized by view<strong>in</strong>g the gel under UV light and<br />
photographed 4 .<br />
Synthesis <strong>of</strong> Nano Metal oxides<br />
The transition metal complexes were placed <strong>in</strong> a<br />
silica crucible and ignited <strong>in</strong> a muffle furnace at<br />
800ºC. The dehydrated mixture undergoes a<br />
vigorous, exothermic oxidation reduction reaction.<br />
The heat created causes a flame for several<br />
m<strong>in</strong>utes, result<strong>in</strong>g <strong>in</strong> volum<strong>in</strong>ous and foamy<br />
powder product occupy<strong>in</strong>g the entire reaction<br />
conta<strong>in</strong>er. The exothermic combustion reaction<br />
releases a large amount <strong>of</strong> heat, which can quickly<br />
heat up the system to reach a temperature higher<br />
than 1600ºC. The combustion method results <strong>in</strong><br />
uniform and pure powders <strong>of</strong> high surface to<br />
volume ratio. The size <strong>of</strong> the metal oxide was<br />
determ<strong>in</strong>ed us<strong>in</strong>g Atomic force Microscope.<br />
3. RESULTS AND DISCUSSION<br />
<strong>Schiff</strong> bases <strong>of</strong> o-phenylenediam<strong>in</strong>e and its<br />
complexes have a variety <strong>of</strong> applications <strong>in</strong>clud<strong>in</strong>g<br />
biological, cl<strong>in</strong>ical and analytical. Earlier work has<br />
shown that some drugs showed <strong>in</strong>creased activity<br />
when adm<strong>in</strong>istered as metal chelates rather that as<br />
organic compounds. The Co-ord<strong>in</strong>at<strong>in</strong>g possibility<br />
<strong>of</strong> o-phenylenediam<strong>in</strong>e has been improved by<br />
condens<strong>in</strong>g with a variety <strong>of</strong> carbonyl compounds.<br />
An attempt has been made to synthesize<br />
asymmetric <strong>Schiff</strong> bases from o-phenylenediam<strong>in</strong>e<br />
and salicylaldehyde with Isat<strong>in</strong> / Acetyl acetone /<br />
2-hydroxy naphthaldehyde. The synthetic routes <strong>of</strong><br />
the ligands and complexes are presented <strong>in</strong> scheme<br />
1.<br />
<strong>Schiff</strong> bases<br />
1. Isat<strong>in</strong> + o-phenylenediam<strong>in</strong>e +<br />
salicylaldehyde L 1<br />
2. Acetyl acetone + o-phenylenediam<strong>in</strong>e +<br />
sallicylaldehyde L 2<br />
3. 2-hydroxynaphthaldehyde+ o-<br />
phenylenediam<strong>in</strong>e +<br />
sallicylaldehyde L 3<br />
Metal complexes<br />
Co(OAc) 2 + L 1/ L 2 /L 3 Co(L 1/ L 2 /L 3 ) 2 [Ib, IIb,<br />
IIIb]<br />
Ib - Isat<strong>in</strong> Co complex [Co(L 1 ) 2 ]<br />
IIb - Acetyl acetone Co complex [Co(L 2 ) 2 ]<br />
IIIb - 2-hydroxy naphthadehyde Co complex<br />
[Co(L 3 ) 2 ]<br />
Scheme 1<br />
Elemental Analysis and Molar Conductance<br />
The metal complexes are <strong>in</strong>soluble <strong>in</strong> water and<br />
soluble <strong>in</strong> DMSO, DMF, CHCl 3 and acetone and<br />
slightly soluble <strong>in</strong> methanol and ethanol. The<br />
analytical data and physical properties <strong>of</strong> the<br />
ligands and complexes are presented <strong>in</strong> Table 1.<br />
The data are consistent with the calculated results<br />
from the empirical formula <strong>of</strong> each compound. The<br />
analytical data <strong>of</strong> the complexes confirm the 1:1<br />
metal to ligand stoichiometry.Cobalt complexes<br />
have a very low molar conductance < 45 ohm -1 cm -<br />
1<br />
mol -1 . The above molar conductance value<br />
confirm that the cobalt complexes are nonelectrolytes<br />
5 .<br />
IR spectra<br />
The significant IR bands for the ligands as well as<br />
its Co complex and their tentative assignments are<br />
complied and presented <strong>in</strong> Table 2 [Figs. 1-2]. In<br />
the IR spectrum <strong>of</strong> the <strong>Schiff</strong> bases ligands L 1 , L 2 ,<br />
L 3 a sharp band observed at 1616 cm -1 is assigned<br />
to the ν(C=N) mode <strong>of</strong> the azometh<strong>in</strong>e group. This<br />
shifts to lower wave numbers, 1606-1609 cm -1 <strong>in</strong><br />
all the complexes suggest<strong>in</strong>g the co-ord<strong>in</strong>ation <strong>of</strong><br />
the azometh<strong>in</strong>e nitrogen to the metal centres. This<br />
is further substantiated by the presence <strong>of</strong> a new<br />
band around 420-463 cm -1 assignable to ν(M-N) 6 .<br />
Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonl<strong>in</strong>e.com 1769
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
The characteristic phenolic ν(O-H) mode due to<br />
presence <strong>of</strong> a hydroxyl group at ortho position <strong>in</strong><br />
the ligand was observed around 3200-3500 cm -1 . A<br />
band at –̃ 1279 cm -1 due to ν(C-O) phenolic group<br />
was also observed <strong>in</strong> the ligand. The disappearance<br />
<strong>of</strong> phenolic ν(OH) band <strong>in</strong> all the complexes<br />
suggests the co-ord<strong>in</strong>ation by the phenolic oxygen<br />
after deprotonation to the metal ion. This is further<br />
supported by the shift<strong>in</strong>g <strong>of</strong> ν(C-O) phenolic band<br />
to lowers wave numbers –̃1250 cm -1 <strong>in</strong> the metal<br />
complex. The appearance <strong>of</strong> a new non-ligand band<br />
around 500-543 cm -1 <strong>in</strong> all the complexes due to<br />
ν(M-O) substantiates it 7 .<br />
A strong sharp band observed at 1700 cm -1 is<br />
assigned to ν(C=O) <strong>of</strong> isat<strong>in</strong> and acetyl acetone <strong>in</strong><br />
ligands L1 and L2. the <strong>in</strong>tensity <strong>of</strong> this band has<br />
not only reduced but has shifted to lower wave<br />
numbers <strong>in</strong> the correspond<strong>in</strong>g metal complexes<br />
confirm<strong>in</strong>g the <strong>in</strong>volement <strong>of</strong> the carbonyl group <strong>in</strong><br />
complexation with metal ion.<br />
In the cobalt complexes the appearance <strong>of</strong> two<br />
additional bands <strong>in</strong> the range 1610- 1578 cm -1 and<br />
1360-1310 cm -1 due to ν as(COO) and ν s(COO)<br />
modes respectively <strong>of</strong> acetate group suggest its<br />
unidentate co-ord<strong>in</strong>ation (Δ = > 200 cm -1 ) to the<br />
metal.The presence <strong>of</strong> co-ord<strong>in</strong>ated water <strong>in</strong> the Co<br />
complex is confirmed by the presence <strong>of</strong> bands<br />
around 890 –928 cm -1 8 .<br />
Electronic spectra and magnetic measurements<br />
The electronic spectral data and magnetic moments<br />
<strong>of</strong> the complexes are presented <strong>in</strong> Table 3 [Figs 3-<br />
4]. The electronic spectrum <strong>of</strong> free <strong>Schiff</strong> base<br />
showed three bands around 240, 350 and 450 nm<br />
characteristic <strong>of</strong> - * and n- * transitions. In the<br />
metal complex, this band is shifted to a longer<br />
wave length with <strong>in</strong>creas<strong>in</strong>g <strong>in</strong>tensity. This shift<br />
may be attributed to the donation <strong>of</strong> lone pair <strong>of</strong><br />
electrons <strong>of</strong> nitrogen <strong>of</strong> <strong>Schiff</strong> base to metal ion 9 .<br />
The cobalt(II) complexes exhibit two bands at 482<br />
– 472 nm and 350 – 306 nm <strong>in</strong> the electronic<br />
spectra. The bands can be assigned to 4 T 1g (F) →<br />
4 A 2g and 4 T 1g (F) → 4 T 1g (P) transitions respectively<br />
which are <strong>in</strong> accordance with Co(II) high sp<strong>in</strong><br />
octahedral geometry 8 . The magnetic moments <strong>of</strong><br />
Co(II) complexes (4.68 – 4.56 BM) suggest a high<br />
sp<strong>in</strong> octahedral configuration. The <strong>Schiff</strong> base L 3<br />
complexes with cobalt to give a cobalt complex <strong>in</strong><br />
which cobalt is <strong>in</strong> the +3 state. S<strong>in</strong>ce it was found<br />
to be diamagnetic with very low magnetic moment.<br />
This may be due to the oxidation <strong>of</strong> Co(II) to<br />
Co(III) dur<strong>in</strong>g complexation 10 .<br />
Thermogravimetric Analysis<br />
The TGA curve <strong>of</strong> the cobalt complex Ia is stable<br />
upto 120°C. A weight loss <strong>of</strong> 3.9% is observed<br />
around 128-163°C [Fig 5] correspond<strong>in</strong>g to the<br />
elim<strong>in</strong>ation <strong>of</strong> one coord<strong>in</strong>ation water. In the<br />
complexes IIa / IIIa this loss <strong>of</strong> coord<strong>in</strong>ated water<br />
is observed at 750°C (observed IIa-7.1% and IIIa-<br />
5.9%). In all the three cobalt complexes a weight<br />
loss <strong>of</strong> 12-14% was observed at a temperature<br />
range <strong>of</strong> 244-249°C correspond<strong>in</strong>g to the removal<br />
<strong>of</strong> one acetate group. The complexes show a step<br />
weight loss <strong>of</strong> 27 – 29% (observed Ia- 28.9%, IIa-<br />
27.9%, IIIa-29.5%). In the temperature range 343-<br />
372°C correspond<strong>in</strong>g to the elim<strong>in</strong>ation <strong>of</strong> part <strong>of</strong><br />
the <strong>Schiff</strong> base ligand viz. isat<strong>in</strong>, acetyl acetone and<br />
naphthyl groups from the coord<strong>in</strong>ation sphere <strong>of</strong><br />
the complex. The f<strong>in</strong>al residue corresponds to CoO<br />
> 800°C. The TGA data are presented <strong>in</strong> table 4.<br />
Probable structure<br />
O<br />
CH 3 COO<br />
Co<br />
O<br />
H 3 C<br />
CH 3 COO<br />
O<br />
Co<br />
O<br />
N<br />
H<br />
N<br />
H 2 O<br />
N<br />
C H 3<br />
N N<br />
H 2 O<br />
Ia<br />
[Co (L 1 ) (H 2 O)(OAC)]<br />
IIa<br />
[Co (L 2 ) (H 2 O)(OAC)]<br />
O<br />
CH 3 COO<br />
Co<br />
O<br />
N<br />
H 2 O<br />
N<br />
IIIa<br />
[Co (L 3 ) (H 2 O)(OAC)]<br />
Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonl<strong>in</strong>e.com 1770
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
Molecular Modell<strong>in</strong>g<br />
Molecular model<strong>in</strong>g <strong>of</strong> the studied complexes<br />
reveals m<strong>in</strong>imum energy values associated with the<br />
octahedral and square plannar geometry. This is <strong>in</strong><br />
a good agreement with the experimental results and<br />
confirmed the expected structure. The possible<br />
geometries <strong>of</strong> metal complexes were evaluated<br />
us<strong>in</strong>g the molecular calculations with Argus lab<br />
4.0.1 version s<strong>of</strong>tware. The metal complexes were<br />
built and geometry optimization was done us<strong>in</strong>g<br />
this s<strong>of</strong>tware. The molecular modell<strong>in</strong>g pictures<br />
and the energies <strong>of</strong> the metal complexes are shown<br />
<strong>in</strong> [figs 6-7].<br />
The details <strong>of</strong> important bond lengths as per 3D<br />
structure <strong>of</strong> Co(II) complex (Ia) [fig 9] are given <strong>in</strong><br />
table 5. These values are obta<strong>in</strong>ed as a result <strong>of</strong><br />
energy m<strong>in</strong>imization <strong>of</strong> Co(II) complex <strong>in</strong> Argus<br />
lab 4.0.1 version s<strong>of</strong>tware.<br />
The obta<strong>in</strong>ed bond lengths <strong>of</strong> the ligand L 1 based<br />
on the s<strong>of</strong>tware are between C(7)-O(14) and C(24)-<br />
O(13) 1.4968, C(9)-N(10) and C(12)-N(11) 1.5687,<br />
C(18)-N(10) and C(15)-N(11) 1.5895. <strong>Base</strong>d on the<br />
values from the table 5, it is observed that when<br />
these ligand are coord<strong>in</strong>ated with Co metal ion<br />
there is an <strong>in</strong>crease <strong>in</strong> the bond length between the<br />
mentioned atoms, which confirms the coord<strong>in</strong>ation<br />
<strong>of</strong> azometh<strong>in</strong>e group through nitrogen [N(10) and<br />
N(11)] and through phenolic oxygen [O(13) and<br />
O(14)]. When the atoms are coord<strong>in</strong>ated with the<br />
metal ion by donat<strong>in</strong>g a lone pair <strong>of</strong> electron there<br />
is a decrease <strong>of</strong> electron density on the<br />
coord<strong>in</strong>at<strong>in</strong>g atoms, hence bond length <strong>in</strong>creases <strong>in</strong><br />
metal complexes. This supports the proposed<br />
octahedral geometry around the cobalt metal ion 11 .<br />
Anti Microbial studies<br />
The antimicrobial activity <strong>of</strong> the cobalt complex Ia<br />
was studied aga<strong>in</strong>st two pathogenic bacterial stra<strong>in</strong>s<br />
(ie) one gram positive (staphylococcus Aureus) and<br />
one gram negative (Escherichia Coli) bacteria and<br />
one fungal stra<strong>in</strong> (Candida Albicans). [Fig 8-10]<br />
Antibacterial and antifungal potential <strong>of</strong> metal<br />
complexes were assessed <strong>in</strong> terms <strong>of</strong> zone <strong>of</strong><br />
<strong>in</strong>hibition <strong>of</strong> bacterial and fungal growth. The<br />
results <strong>of</strong> the antifungal and antibacterial activities<br />
are presented <strong>in</strong> table 6. The m<strong>in</strong>imum <strong>in</strong>hibitory<br />
concentrations (MIC) were calculated as the<br />
highest dilution show<strong>in</strong>g complete <strong>in</strong>hibition <strong>of</strong> the<br />
tested stra<strong>in</strong>s and are reported <strong>in</strong> table 7.<br />
Growth <strong>of</strong> bacterial & fungal pathogens on each<br />
concentration was checked to determ<strong>in</strong>e the<br />
m<strong>in</strong>imum concentration that <strong>in</strong>hibits the growth <strong>of</strong><br />
the organism. It is evident from the table 7 that the<br />
MIC value for the cobalt complex Ia was 125<br />
g/ml for both S.Aureus and E.Coli. Likewise the<br />
MIC value for fungi pathogen shows 62.5 g/ml<br />
for cobalt complex [Fig 11].<br />
The metal complexes were effective aga<strong>in</strong>st both<br />
bacteria and fungi. The cobalt complex shows<br />
better activity aga<strong>in</strong>st fungai, than the bacteria<br />
when compared with the standard cipr<strong>of</strong>loxac<strong>in</strong>.<br />
DNA Cleavage Studies<br />
The <strong>in</strong>vestigation <strong>of</strong> <strong>in</strong>teractions between doublestranded<br />
DNA and DNA b<strong>in</strong>d<strong>in</strong>g agents is crucial<br />
for understand<strong>in</strong>g biochemical processes as<br />
replication, repair, recomb<strong>in</strong>ation and expression <strong>of</strong><br />
genes. In pr<strong>in</strong>ciple, the possible b<strong>in</strong>d<strong>in</strong>g<br />
mechanisms <strong>of</strong> ligands to double stranded dsDNA<br />
can be divided <strong>in</strong>to sequence specific b<strong>in</strong>d<strong>in</strong>g and<br />
b<strong>in</strong>d<strong>in</strong>g modes that lack sequence specificity.<br />
Specific b<strong>in</strong>d<strong>in</strong>g between ligand (prote<strong>in</strong>) and<br />
receptor (dsDNA) <strong>of</strong>ten termed as molecular<br />
recognition is the basis for the <strong>in</strong>teraction <strong>of</strong> many<br />
transcription factors with DNA. Small agents that<br />
b<strong>in</strong>d unspecifically or with lower sequence<br />
specificity to dsDNA are <strong>of</strong>ten capable <strong>of</strong><br />
<strong>in</strong>fluenc<strong>in</strong>g or <strong>in</strong>hibit<strong>in</strong>g these processes and<br />
<strong>in</strong>tr<strong>in</strong>sically exhibit magnetic properties.<br />
Consequently these molecules f<strong>in</strong>d applications as<br />
pharmaceuticals ma<strong>in</strong>ly <strong>in</strong> the treatment <strong>of</strong> cancer.<br />
Others are employed as sta<strong>in</strong><strong>in</strong>g agents 12 .<br />
In the present study, the CT-DNA gel<br />
electrophoresis experiment was conducted at 35°C<br />
us<strong>in</strong>g the ligand L 1 & complex (Ia) <strong>in</strong> the presence<br />
<strong>of</strong> H 2 O 2 as an oxidant. It was found that at very low<br />
concentration, the complexes exhibit nuclease<br />
activity <strong>in</strong> the presence <strong>of</strong> H 2 O 2 . Control<br />
experiment us<strong>in</strong>g DNA alone does not show any<br />
significant cleavage <strong>of</strong> CT DNA even on longer<br />
exposure time. Cobalt complex cleaves DNA to a<br />
larger extent as compared with control DNA, [Fig-<br />
12]. This is due to the formation <strong>of</strong> redox couple <strong>of</strong><br />
the metal ions. In oxidative mechanism, metal ions<br />
<strong>in</strong> the complexes react with H 2 O 2 to generate the<br />
OH • which attacks at the C3 positions <strong>of</strong> the sugar<br />
moiety and f<strong>in</strong>ally cleaves DNA. Cobalt complex<br />
reacts with H 2 O 2 to form OH • , OH - and Co(III)<br />
form.<br />
Determ<strong>in</strong>ation <strong>of</strong> size <strong>of</strong> nano metal oxide<br />
The size <strong>of</strong> the metal oxide was determ<strong>in</strong>ed by<br />
Atomic Force Microscope. AFM provides a 3D<br />
pr<strong>of</strong>ile <strong>of</strong> the surface on a nanoscale by measur<strong>in</strong>g<br />
forces between a sharp probe (
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
<strong>Schiff</strong> base ligands. The ligands and complex were<br />
characterized by spectral and analytical data. <strong>Base</strong>d<br />
on these data an octahedral geometry has been<br />
assigned to the Co(II) complex. Molecular<br />
modell<strong>in</strong>g has been performed for the complexes<br />
us<strong>in</strong>g Argus 4.0.1 s<strong>of</strong>tware. The metal complexes<br />
were converted to their correspond<strong>in</strong>g nano metal<br />
oxides, the 2D and 3D AFM pictures <strong>of</strong> the oxides<br />
confirm their size to be <strong>in</strong> the range 0-100 nm. The<br />
antimicrobial studies carried out with the<br />
complexes confirm that they are good antifungal<br />
agents. Their MIC values be<strong>in</strong>g 125µg/litre. The<br />
<strong>in</strong>teraction <strong>of</strong> these complexes with CT-DNA was<br />
<strong>in</strong>vestigated by gel electrophoresis. The Co<br />
complex (Ia) cleaved DNA as compared to control<br />
and the <strong>Schiff</strong> base ligand <strong>in</strong> the presence <strong>of</strong> H 2 O 2 .<br />
Table 1: Elemental Analysis,Yield, Molar conductivity and Melt<strong>in</strong>g po<strong>in</strong>t <strong>of</strong> ligands and their Metal<br />
complexes<br />
Elemental Analysis, Found Conductance<br />
Complex Emp.Formula M.Wt<br />
(Calculated) %<br />
(ohm -1 cm -1 Melt<strong>in</strong>g po<strong>in</strong>t<br />
mol -1 (°C)<br />
C H N<br />
)<br />
L 1 C 21H 15N 3O 2 341 - - - - 277<br />
[Co(L 1) 2] C 23H 19N 3O 5.Co<br />
56 3.5 8<br />
475.93<br />
< 45 > 360<br />
(57.9) (4) (8.8)<br />
L 2 C18H 18N 2O 2 294 - - - - 298<br />
[Co(L 2) 2]<br />
C 20H 21N 2O 5.Co 427.93<br />
55<br />
(56.08)<br />
4<br />
(4.9)<br />
6<br />
(6.5)<br />
< 45 > 360<br />
L 3 C 24H 17N 2O 2 351 - - - - 326<br />
[Co(L 3) 2]<br />
C 26H 21N 2O 5.Co<br />
485.93<br />
63<br />
(64.2)<br />
4.1<br />
(4.3)<br />
5.2<br />
(5.8)<br />
< 45 > 360<br />
Table 2: IR spectral data for ligands and their metal complexes<br />
Complex (C=O) (C=N) (OH) (M-N) (M-O) (NH) (C-O) (H 2O)<br />
L 1 1707.06 1616.40 3319.60 3059.20 1279.81<br />
[Co(L 1) 2]<br />
1700.31 1607.72 421.46 500.54 3026.41 1245.09 929.72<br />
L 2 1700.31 1614.47 3228.95 1275.95<br />
[Co(L 2) 2]<br />
1699.34 1609.65 453.29 519.98 1243.16 925.86<br />
L 3 1616.40 3531.76 1279.81<br />
[Co(L 3) 2]<br />
1607.7 421.46 501.51 1254.74 928.76<br />
Table 3: Electronic Spectral & Magnetic moment data for the ligands and their complexes<br />
Ligand/<br />
Complex<br />
Absorbance<br />
nm<br />
L 1<br />
425 23529 n - *<br />
350 28571 - *<br />
L 2<br />
445 22471 n - *<br />
338 29585 - *<br />
L 3<br />
355<br />
479<br />
365<br />
28169<br />
20876<br />
27397<br />
- *<br />
n - *<br />
MLCT<br />
498 20080<br />
5 T 2g (F) 5 Eg<br />
492 20325<br />
5 T 2g (F) 5 Eg<br />
306 32679<br />
4 T 1g (F) 4 T 1g (P)<br />
[Co(L 1) 2]<br />
472 21186<br />
4 T 1g (F) 4 A 2g<br />
[Co(L 2) 2]<br />
[Co(L 3) 2]<br />
350 28571<br />
482 20746<br />
340 29411<br />
480 20833<br />
/cm -1 Assignment Geometry Magnetic moment (BM)<br />
4 T 1g (F) 4 T 1g (P)<br />
4 T 1g (F) 4 A 2g<br />
4 T 1g (F) 4 T 1g (P)<br />
4 T 1g (F) 4 A 2g<br />
- -<br />
- -<br />
- -<br />
Octahedral 4.68<br />
Octahedral 4.56<br />
Octahedral 0.85<br />
Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonl<strong>in</strong>e.com 1772
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
Table 4: Thermal Analysis data for metal complexes<br />
Complex<br />
Decomposition<br />
Weight loss %<br />
Lost fragment<br />
Temp°C<br />
Experimental Theoretical<br />
128.72-163.80 H 2O 3.9 4.5<br />
200-270 CH 3COO 13 14<br />
[Co(L 1) 2]<br />
270-410 28.9 30<br />
[Co(L 2) 2]<br />
> 600 Residue CoO 38.5 35.8<br />
100-170 Lattice H 2O 4.2 4<br />
180-300 CH 3COO 14.4 12<br />
700-830 H 2O 7.1 7<br />
>830 Residue CoO 28.9 30<br />
200-310 CH 3COO 12..1 10<br />
[Co(L 3) 2]<br />
343-372<br />
29.5 27<br />
720-820 H 2O 5.9 5<br />
>830 Residue CoO 37.08 40<br />
Table 5: Data from Molecular<br />
modell<strong>in</strong>g <strong>of</strong> [Co(L 1 ) 2 ] complex<br />
S.No Bonded atoms Bond length<br />
1 2 (C) - 7(C) 1.3586<br />
2 9 (C) - 10 (N) 1.3689<br />
3 17(C) – 20(C) 1.4348<br />
4 10(N) - 18 (C) 1.3654<br />
5 21(C) - 22(C) 1.0625<br />
6 13(O) – 24(C) 1.0774<br />
7 7(C) - 14(O) 1.0798<br />
8 8(C) - 33(H) 1.2672<br />
9 14(O) – 27(Co) 2.0556<br />
10 10(N) - 27(Co) 2.0774<br />
11 27(Co) - 28(O) 2.0374<br />
12 28(O) - 34(H)<br />
1.5637<br />
13 30(C) - 31(O) 1.3476<br />
14 32(C) - 38(H) 1.2978<br />
Table 6: Antibacterial & Antifungal activity data<br />
<strong>of</strong> <strong>Schiff</strong> base metal complexes<br />
Microorganism [Co(L 1) 2(H 2O)(OAc)]<br />
STD<br />
Cipr<strong>of</strong>loxac<strong>in</strong> (50 µg/disc)<br />
(mm)<br />
Bacteria E.Coli 10 20<br />
S.Aureus 11 25<br />
Fungi C.albicans 31 18<br />
Table 7: Determ<strong>in</strong>ation <strong>of</strong> MIC for antibacterial & antifungal activity<br />
500 250 125 62.5 31.25 15.62 7.8<br />
Microorganism<br />
µg/ml µg/ml µg/ml µg/ml µg/ml µg/ml µg/ml<br />
S.Aureus - - - + + + +<br />
Bacteria<br />
E.coli - - - + + + +<br />
Fungi C.Albicans - - - - + + +<br />
Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonl<strong>in</strong>e.com 1773
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
Table 8: Antibacterial &<br />
Antifungal activity: MIC values<br />
Microorganism MIC value<br />
S.Aureus 125 µg/ml<br />
Bacteria<br />
E.coli 125 µg/ml<br />
Fungi C.Albicans 62.5 µg/ml<br />
IR SPECTRAL DATA<br />
Fig. 1: IR Spectrum <strong>of</strong> L 1 <strong>Schiff</strong> base<br />
Fig. 2: IR Spectrum <strong>of</strong> Co(L 1 ) 2 complex<br />
UV Spectra<br />
Fig. 3: Electronic spectrum <strong>of</strong> L 1 <strong>Schiff</strong> base Fig. 4: Electronic spectrum <strong>of</strong> Co(L 1 ) 2<br />
Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonl<strong>in</strong>e.com 1774
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
THERMOGRAVIMETRIC ANALYSIS<br />
Fig. 5: TGA <strong>of</strong> Co(L 1 ) 2 complex<br />
MOLECULAR MODELLING<br />
Fig. 6: schiff base L 1<br />
Energy 93.61 kcal/mol<br />
Fig. 7: Metal complex [Co. L 1 (H 2 O)(OAc)]<br />
Energy 289.51 kcal/mol<br />
Antimicrobial studies<br />
Fig. 8: Zone <strong>of</strong> <strong>in</strong>hibition – bacteria<br />
S.Aureus image <strong>of</strong> [Co.L 1 (H 2 O)(OAc)]<br />
Fig. 9: Zone <strong>of</strong> <strong>in</strong>hibition - bacteria<br />
E.Coli image <strong>of</strong> [Co.L 1 (H 2 O) (OAc)]<br />
Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonl<strong>in</strong>e.com 1775
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
Fig. 10: Zone <strong>of</strong> <strong>in</strong>hibition - fungi<br />
C.Albicans image <strong>of</strong> [Co.L 1 (H 2 O) (OAc)]<br />
35<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
E.Coli<br />
S.Aureus C.Albicans<br />
Standard<br />
Co complex<br />
Fig. 11: Antimicrobial activity <strong>of</strong> the <strong>Schiff</strong> base complexes<br />
aga<strong>in</strong>st bacterial & fungal pathogens<br />
DNA CLEAVAGE STUDIES<br />
Fig. 12: Gel Diagram <strong>of</strong> calf-thymus DNA <strong>in</strong>duced by<br />
the <strong>Schiff</strong> base L 1 and its complex Ia <strong>in</strong> presence <strong>of</strong> oxidant<br />
H 2 O 2 by agarose gel electrophoretic pattern<br />
Lane from Left to Right<br />
(C) CT DNA alone<br />
(1) <strong>Schiff</strong> <strong>Base</strong> I + DNA + H 2O 2<br />
(2) Co(L 1) 2 +DNA + H 2O 2<br />
Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonl<strong>in</strong>e.com 1776
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
AFM IMAGES<br />
Fig. 13: AFM topographic images <strong>of</strong> cobalt oxide <strong>of</strong> IIa<br />
-[Co(L2)2(H2O)(OAc)] show<strong>in</strong>g 2D configuration <strong>in</strong> the<br />
material. The scanned area<br />
is 0.5 m x 0.5 m. Size <strong>of</strong> the particle = 15nm-20-nm<br />
Fig. 14: AFM topographic images <strong>of</strong> cobalt oxide <strong>of</strong> IIa-<br />
[Co(L2)2(H2O)(OAc)] show<strong>in</strong>g 3D configuration <strong>in</strong> the material.<br />
The scanned area is 0.5 m x 0.5 m.<br />
Size <strong>of</strong> the particle = 15nm-20-nm<br />
REFERENCES<br />
1. Bimal kumar, Rai BK and Nisha<br />
Ambastha. Synthesis, characterization and<br />
Antimicrobial screen<strong>in</strong>g <strong>of</strong> cobalt (II),<br />
Nickel (II) & copper(II) complexes with<br />
<strong>Schiff</strong> base derived from 2-phenyl<br />
Qu<strong>in</strong>oxal<strong>in</strong>e Thiosemicarbazone. Oriental<br />
J Chem. 2011;27:1173-1178.<br />
2. Raman N, Pitchaikani Raja Y and<br />
Kulandaisamy A. Synthesis and<br />
characterization <strong>of</strong> Cu(II), Ni(II), Mn(II),<br />
Zn(II) and Vo(II) <strong>Schiff</strong> base complexes<br />
derived from o-phenylenediam<strong>in</strong>e and<br />
acetoacetanilide. Proc Ind Acad Sci.<br />
2001;113:183-189.<br />
3. Raman N, Dhaveethu Raja J and<br />
Sakthivel A. Synthesis, spectral<br />
characterization <strong>of</strong> <strong>Schiff</strong> base transition<br />
metal complexes: DNA cleavage and<br />
antimicrobial activity studies. J Chem Sci.<br />
2007;119:303-310.<br />
4. Neelakantan MA, Russal Raj F,<br />
Dharmaraja J, Johnsonraja S and<br />
Jeyakumar T.Synthesis, Characterization<br />
and Biocidal Activities <strong>of</strong> Some <strong>Schiff</strong><br />
<strong>Base</strong> Metal <strong>Complexes</strong>, Spectrochimica.<br />
Acta. 2008; 71A:1599- 1609.<br />
5. Shilpa Sharma, Monica Bedi, Monica<br />
Gupta, Varshney S and Varshney<br />
AK.Studies <strong>of</strong> some new coord<strong>in</strong>ation<br />
compounds <strong>of</strong> Al(III) with<br />
Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonl<strong>in</strong>e.com 1777
<strong>International</strong> <strong>Journal</strong> <strong>of</strong> <strong>Research</strong> <strong>in</strong> Pharmaceutical and Biomedical Sciences ISSN: 2229-3701<br />
semicarbazones<br />
and<br />
thiosemicarbazones. 2010;3:483-489.<br />
6. Bhagat TM, Swamy DK and Deshpande<br />
MN. Synthesis and characterization <strong>of</strong><br />
transition metal complexes with newly<br />
synthesized substituted benzothiazole. J<br />
Chem and Pharm <strong>Research</strong>. 2012;4:100-<br />
104.<br />
7. Kulkarni, Sangamesh Patil A and Prema<br />
Badami S.Electrochemical Properties <strong>of</strong><br />
some Transition Metal <strong>Complexes</strong>:<br />
Synthesis, Characterization and Invitroantimicrobial<br />
studies <strong>of</strong> Co(II), Ni(II),<br />
Cu(II), Mn(II) and Fe(III) <strong>Complexes</strong>, Int.<br />
J Electrochem Sci. 2009; 94:717–729.<br />
8. Figgis BN and Lewis J. Co (II) AND Fe<br />
(III) <strong>Complexes</strong> <strong>of</strong> <strong>Schiff</strong> bases derived<br />
from Isat<strong>in</strong> with some am<strong>in</strong>o acids. Prog<br />
Inorg chem.. 1964;157:37-67.<br />
9. Kalia SB, Lumba K, Kaushal G and<br />
Sharma M. Magnetic and spectral studies<br />
on Co(II) chelates <strong>of</strong> a dithiocarbazate<br />
derived from isoniazid. Ind J chem.<br />
2007;46A: 1233-1239.<br />
10. Fahmideh Shabani, Lotf Ali, Saghat<br />
foroush and Shahriar Ghammamy.<br />
Synthesis, characterization and antitumour<br />
activity <strong>of</strong> iron (iii) <strong>Schiff</strong> base<br />
complexes with unsymmetric tetradentate<br />
ligands, Bull Chem soc. ETHIOP.<br />
2010;24:193 – 199.<br />
11. Mendu Padmaja, Pragathi J and<br />
Gyanakumari C. Synthesis, spectral<br />
characterization, molecular model<strong>in</strong>g and<br />
biological activity <strong>of</strong> first row transition<br />
metal complexes with <strong>Schiff</strong> base ligand<br />
derived<br />
from chromone-3-<br />
carbaldehyde and o-am<strong>in</strong>o benzoic acid. J<br />
Chem & Pharm Res. 2011;3: 602-613.<br />
12. Raman N, Ravichandran S and<br />
Thangaraja C. Copper(II), Cobalt(II),<br />
Nickel(II) and Z<strong>in</strong>c(II) complexes <strong>of</strong><br />
<strong>Schiff</strong> base derived from benzil-2,4-<br />
d<strong>in</strong>itrophenylhydrazone with anil<strong>in</strong>e. J<br />
Chem Sci. 2004 ;116:215–219.<br />
Vol. 3 (4) Oct – Dec 2012 www.ijrpbsonl<strong>in</strong>e.com 1778