Synthesis, characterization and anticancer activity of mono- and dinuclear Ni(II) and Co(II) complexes of a Schiff base derived from o-vanillin

• Published in: Polyhedron
• Main Author: Bahron H.; Khaidir S.S.; Tajuddin A.M.; Ramasamy K.; Yamin B.M.
• Format: Article
• Language: English
• Published: Elsevier Ltd 2019
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85060229906&doi=10.1016%2fj.poly.2018.12.055&partnerID=40&md5=f934a8202617f7f192acf1406ab36817

A Schiff base ligand, 6,6′-dimethoxy-2,2′-[o-phenylenebis(nitrilomethylidyne)]diphenolato (LA), and its mononuclear and dinuclear Ni(II) and Co(II) complexes were synthesized. Structural elucidation was carried out via elemental analysis, molar conductivity, IR, NMR, UV–Vis spectroscopy, TGA and magnetic susceptibility. Single crystal X-ray diffraction of the Ni(LA) complex revealed a square planar geometry of the Ni(II) centre, with the ligand acting as a tetradentate ONNO chelate. Upon coordination to the metal centers, the ν(C[dbnd]N) and ν(C–O) peaks shifted to lower frequencies, with appearance of new peaks assignable to ν(M–N) and ν(M–O) in the ranges 535–560 and 421–460 cm−1, respectively. Ni(LA) and Ni2(LA) complexes are diamagnetic, whereas the Co(LA) and Co2(LA) complexes are paramagnetic with 3 unpaired electrons each. All the complexes displayed low molar conductivities in acetonitrile indicating non-electrolytic behavior. Anticancer screening against human colorectal cancer HCT116 cell lines revealed that both dinuclear complexes were more active than their mononuclear counterparts. Ni2(LA) showed the highest potency with an IC50 value of 0.81 μM. © 2019