Synthesis, characterization, electrochemistry and antimicrobial activities of bis(hydroxamato)oxidovanadium (IV) complexes

摘要

The bis (hydroxamato)oxidovanadium(IV) complexes of composition [VO(HL1,2)2] { [HL1 = 4-NO2C6H4 CONHO]-, 4-nitrobenzohydroxamate; HL2 = [2-Cl-4-NO2C6H3CONHO]- 2-chloro-4-nitrobenzohydroxamate} have been synthesized by the reactions of VOSO4.5H2O with two equivalents of potassium salts of respective hydroxamic acids in aqueous methanol. The characterization of complexes has been accomplished by elemental analyses, molar conductivity, magnetic moment measurements, electronic and spectral (IR, ESR and mass) studies. The magnetic moment and ESR spectra indicated +4 oxidation state of vanadium. The IR spectra suggested bonding through hydroxylamine and carbonyl oxygen (O,O coordination). Inferred from spectral studies a square-pyramidal geometry around vanadium has tentatively been proposed for complexes. The thermal behavior of complexes has been studied by TGA technique. The antimicrobial activities of the newly synthesized complexes, ligands and precursor have been evaluated against some pathogenic bacteria E.coli, S.aureus, S.typhi, S.paratyphi, S.epidermidis and K.pneumoniae and fungi A. niger, B. fulva and M. circinelloides by minimum inhibitory concentration method. The complexes exhibited promising antimicrobial activity relative to free ligands and standard drug compounds. The coordination compounds of complexes with 2-cyanopyridine and 4- aminobenzonitrile have also been synthesized and characterized by physicochemical and IR spectral technique.