Mononuclear pervanadyl (VO < inf > 2 < /inf > < sup > + < /sup > ) complexes with tridentate schiff bases: Self-assembling via C-H ⋯ oxo and π-π interactions

Abstract

Pervanadyl (VO2+) complexes with N-(aroyl)-N′-(picolinylidene)hydrazines (HL = Hpabh, Hpath and Hpadh; H stands for the dissociable amide hydrogen) are described. The Schiff bases were obtained by condensation of 2-pyridine-carboxaldehyde with benzhydrazide (Hpabh), 4-methylbenzhydrazide (Hpath) and 4-dimethylaminobenzhydrazide (Hpadh), respectively. The reaction of [VO(acac)2] and HL in acetonitrile in air affords the complexes of general formula [VO2L]. The diamagnetic nature and EPR silence confirm the +5 oxidation state of vanadium in these complexes. Infrared spectra of the complexes are consistent with the enolate form of the coordinated ligands. Electronic spectra show charge transfer bands in the range 486-233 nm. The complexes are redox active and display an irreversible reduction (-0.64 to -0.72 V vs. Ag/AgCl). The crystal structures of all the complexes have been determined. In each complex, the metal centre is in a distorted trigonal-bipyramidal N2O3 coordination sphere formed by the pyridine-N, the imine-N and the deprotonated amide-O donor L- and two oxo groups. The planar ligand satisfies one equatorial and two axial positions. The other two equatorial positions are occupied by the two oxo groups. In the solid state, the molecules of each of the three complexes form a chain-like arrangement via the azomethine-H ⋯ oxo interactions. Interchain weak π-π interactions lead to two dimensional networks for [VO2(pabh)] and [VO2(path)]. On the other hand, [VO2(padh)] forms a two-dimensional network through interchain N-methyl-H ⋯ oxo interactions. © WILEY-VCH Verlag GmbH, 2001.