Abstract: EPR spectra of VO-Met and VO-Met Phen systems in glycol and water (1:1) solution at various acidities have been observed at low temperature. It was found that in different pH ranges different structural complexes were formed. According to Johnson's rule and IR, their possible structures were suggested. The bonding parameters of complexes were calculated by EPR parameters. It can be seen that the δ² of complexes decrease as the number of ligands bound to vanadium increase. This means that the covalent bonding between vanadium and ligands increase as amino acid ligands replace water ligands. Using electronic spectral data, the crystal field parameters were calculated. The coordination law was discussed. It was obtained that the coordination capacity of phen is much stronger than one of Met.

Key words: Methionine, Phenanthroline, VO(Ⅱ) complex, EPR, Crystal field parameter