Spectroscopic and theoretical studies on Cr (III), Mn (II) and Cu (II) complexes of hydrazone derived from picolinic hydrazide and O‐vanillin and evaluation of biological potency

Trivalent Cr (III) and divalent of both Mn (II) and Cu (II) complexes containing hydrazone ligands derived from the condensation of picolinohydrazide with O‐vanillin were synthesised and characterized by elemental analysis, spectral and magnetic measurements. The suggested octahedral structures were confirmed by applying DFT optimization and conformational studies. The thermal decomposition behaviour of Mn (II) complex is discussed. The evaluation of kinetic parameters (Ea, A, ∆H, ∆S and ∆G) of all thermal degradation stages have been evaluated using Coats‐Redfern and Horowitz‐Metzger approaches. The band gap results suggested that these complexes are semi‐conductors and lie in same range of highly efficient photovoltaic materials. Antibacterial studies showed that higher activity of complexes than of ligands. Assay on the antioxidant activity (DPPH and SOD) of the above complexes revealed the high SOD‐activity of Mn (II) complex and high DPPH‐activity for ligand.