Synthesis, characterization, electrochemical and solvatochromic investigations of novel monomeric and polymeric vanadyl Schiff-base complexes

This article describes the synthesis and characterization of oxovanadium(IV) complexes containing tetradentate Schiff-base ligands derived from condensation of ethylenediamine, meso-1,2-diphenyl-1,2-ethylenediamine, 1,2-orthophenylenediamine and 1,2-cyclohexanediamine with 5-bromo-3-nitro-2-hydroxybenzaldehyde. The novel VOL1:[VO(5-Br-3-NO(2)salen)], VOL2 :[VO(5-Br-3-NO(2)saloph)] and VOL3: [VO(5-Br-3- NO(2)salchxn)] complexes were obtained in orange polymeric form with (V=O) stretching bands at 878, 884 and 884cm(-1), respectively, but the VOL4 complex was obtained as a green monomer with (VO) stretching band at 978cm(-1). The redox process in acetonitrile was reversible for VOL4 and Eo was determined to be approximately 950mV but for VOL1-3 this process was irreversible or quasireversible. The VOL4 Complex is considerably soluble in a wide variety of solvents and shows solvatochromic behavior. The B-2(2) -> (2) E(I) transition wavenumber shows a linear correlation to the D.N. of the solvent.