Metal-based biologically active compounds: synthesis, spectral and antioxidant studies of transition metal complexes with hydrazone derivatives

New series of Co+2, Ni+2, Cu+2 and Zn+2 complexes have been synthesized using a bio-active hydrazone compound 4-hydroxybenzaldehyde-N-[5-chloro-2-oxo-1,2-dihydro-3H-indol-3-ylidene], abbreviated as [HL]. Complexes were characterized using elemental analysis, FT-IR, UV-visible spectroscopy conductivity and magnetic susceptibility measurements. Results showed that the bi-dentate [HL] coordinated in a square planner manner with Cu+2 while for the rest of the M+2 ions, it coordinated in a octahedral fashion. Free ligand and its metal complexes were also studied for their antioxidant potential by employing two methods i.e. DPPH radical scavenging and reducing power assay. It was observed that the metal complexes were considerably more potent free radical scavenger and had better reducing abilities compared to the free ligand, furthermore, for both in vitro assays, metal complexes turned out to be better DPPH scavengers and had better reducing abilities than the standards used during biological assays