In situ oxidation triggered heteroleptically deprotonated cobalt(III) and homoleptic nickel(II) complexes of diacetyl monoxime derived tri-nitrogen chelators; Synthesis, molecular structures and biological assay

Abstract

Two tri-nitrogen chelating unsymmetrical Schiff base ligands, 3-(hydroxyimino)-2-butanone-2-(1H-benzothiazol-2-yl)hydrazone and 3-(hydroxyimino)-2-butanone-2-(1H-benzimidazol-2-yl)hydrazone are synthesized by the condensation reaction of diacetyl monoxime with 2-hydrazino-benzothiazole/benzimidazole. Ligands have shown ML2 type octahedral coordination towards Ni(II) and in situ generated Co(III) ions. Ligands and complexes are characterized by various spectro-analytical techniques. Both the ligands have shown a similar mode of ligation, but a different mode of deprotonation towards the cobalt and nickel ions. Ligands are left neutral in the case of nickel complexes while anionic in the case of cobalt complexes. Further, in situ oxidation of Co(II) to Co(III) has triggered a different mode of deprotonation between the two ligands of the same cobalt complex. Out of the four complexes synthesized, three complexes are characterized by single crystal X-ray diffraction technique, to evidence the structural facts. A comparative account of bond lengths of two complexes of the benzothiazole based ligand is presented. Structures of all the four complexes have been checked preliminarily for their NCI-60 Human Cancer Cell Line anticancer screening. Further, one among the four, the nickel complex of benzothiazole core is used for one dose growth inhibition screening against 60 different human cancer cell lines. The tested complex has shown highest growth inhibition over a Non-Small Cell Lung Cancer cell line EKVX. In addition, compounds are screened for their antibacterial and antifungal potencies against few microorganisms. The complexes have shown promising antimicrobial potencies.