Synthesis, Characterization, and In-Vitro Anti-Microbial and Anti-Oxidant Activities of Co+2, Ni+2, Cu+2 and Zn+2 Complexes of 5-chloro-2-hydroxybenzaldehyde-N-(2-oxo1,2-dihydro-3H-indol-3-ylidene) hydrazone

New transition metal complexes of a Schiff base (5-chloro-2-hydroxybenzaldehyde-N-(2-oxo-1,2-dihydro-3H-indol-3- ylidene)hydrazone) have been synthesized, characterized and evaluated in-vitro for their anti-microbial and anti-oxidant activities. Modern characterization techniques including CHN, IR, UV-Vis, AAS and SEM have been employed for characterization. The bis Schiff base found to be a tridentate ligand and coordinated to the metal centers through its phenolic oxygen, azomethine nitrogen and carbonyl group. On the basis of spectral evidences and magnetic susceptibility data of complexes, square planner geometry is proposed for C^u+2 complex, distorted tetrahedral geometry is proposed for Zn⁺² while octahedral geometries are proposed for Co⁺² and Ni⁺² complexes. Results of antimicrobial studies revealed that the metal complexes are more potent bactericide and fungicide agents. This boost in activity can be explained on the basis of chelation theory suggesting that chelation reduces the polarity of metal ions which increase the lipophilic nature of the complex and hence is able to cross the lipid barrier layer of cell membrane to interfere normal cell functions leading to cell death. On the other hand however, Schiff base ligand showed more DPPH radical scavenging activity compared to the complexes which is attributed to the presence of OH group in the Schiff base.