Mononuclear Co(III), Ni(II) and Cu(II) complexes of 2-(2,4-dichlorobenzamido)-N'-(3,5-di-tert-butyl-2-hydroxybenzylidene)benzohydrazide: Structural insight and biological assay

A series of mononuclear metal complexes of Co(III), Ni(II) and Cu(II) with 2-(2,4-dichlorobenzamido)-N '-(3,5-di-tert-butyl-2-hydroxybenzylidene)benzohydrazide (LH3) have been synthesized and characterized using various physico-chemical, spectroscopic and single crystal X-ray diffraction techniques. Structural studies of [Co(LH)(LH2)]center dot H2O (4) revealed the presence of both amido and imidol tautomeric forms of LH3, resulting in a distorted octahedral geometry around the Co(III) ion. [Ni(LH)(H2O)]center dot H2O (5) and [Cu(LH)(H2O)]center dot H2O (6) are isomorphous structures and crystallize in the monoclinic P2(1)/c space group. The crystal structures of 4, 5 and 6 are stabilized by hydrogen bonds formed by the enclathrated water molecules, C-H center dot center dot center dot pi and pi center dot center dot center dot pi interactions. Complexes along with the ligand (LH3) were screened for their in vivo anti-inflammatory activity (carrageenan-induced rat paw edema method) and in vitro antioxidant activity (DPPH free radical scavenging assay). Metal complexes have shown significant anti-inflammatory and antioxidant potential.