Oxovanadium (IV) complexes of bidentate [N,O] donor Schiff-base ligands: synthesis and mesomorphism

A series of new oxovanadium(IV) Schiff-base complexes of the type VO(L)₂], L?=?N-(4-n-alkoxysalicylaldimine)-4′-dodecyloxyaniline, n?=?6, 8, 16, and 18] have been synthesized. The compounds were characterized by FT-IR, ¹H-NMR, ¹³C-NMR, UV-Vis, FAB-mass, and magnetic susceptibility measurements. The mesomorphic behavior of the compounds was studied by polarized optical microscopy and differential scanning calorimetry. The compounds are all highly thermally stable exhibiting smectic mesomorphism. Non-electrolytic nature of the complexes was ascertained by solution electrical conductance measurements. Cyclic voltammetry revealed a quasireversible single-electron response for VO(V)/VO(IV) couple. A ν_V=O stretching mode at ～970?cm^?1 indicates absence of any intermolecular V=O?···?V=O interactions. Density functional theory study was carried out using DMol3 at BLYP/DNP level to determine energy optimized structure revealed a distorted square pyramidal geometry for the vanadyl complexes.