Synthesis, spectroscopy, electrochemistry, crystal structures and in vitro cytotoxicity of mononuclear molybdenum(VI) complexes incorporating tridentate ONO donor aroylhydrazone with auxiliary coordination site

Abstract

Four new mononuclear cis-dioxidomolybdenum(VI) complexes with the general formula [MoO2LD], where H2L = tridentate aroylhydrazone and D = MeOH, pyridine (py), imidazole (im) and 3-picoline (β-pic) have been synthesized by the reaction of bis(acetylacetonato)dioxomolybdenum(VI) with hydrazone derived from 2-hydroxy-3-methoxybenzaldehyde and 3-methoxybenzhydrazide in presence of nitrogen containing bases. The synthesized aroylhydrazone and the complexes were analysed by CHN analysis, electronic and FT-IR spectral studies, molar conductivity measurements, 1H NMR spectroscopy and cyclic voltammetry. The molecular and crystal structures of all the four complexes were elucidated by single crystal X-ray diffraction analysis. All the complexes adopt a distorted octahedral environment around the molybdenum centre with a cis oxo configuration coordinated by the enolized dianionic form of the hydrazone ligand, L2− in a tridentate manner through two deprotonated hydroxyl groups and one azomethine nitrogen atom. The structural analysis also revealed that the molybdenum coordination preferences in conjunction with the ligand donor capabilities offers a supplementary sixth coordination site for all the complexes which could be easily coordinated by competitive ligands such as solvents or N-bases by simply modifying the reaction conditions such as solvent, reaction time etc. Furthermore the in vitro cytotoxicity of the synthesized aroylhydrazone and all the complexes were assayed against lymphoma ascites cell line.