Covalency effects on the E.S.R. spectra of VO2 in hexaaquo magnesium dihydrogen ethylenediaminetetraacetic acid

The E.S.R. spectra of VO2+ doped in hexa-aquo magnesium dihydrogen ethylenediaminetetra-acetic acid and two magnesium Tutton's salts are studied. VO2+ is found to enter the lattice substitutionally into the Mg sites. Only one set of eight lines is observed and transitions due to other orientations of the V-O bond were not observed. The V-O bond is found to coincide with the Mg-Ow1 bond direction. The electric field symmetry at the Mg site is found to be rhombic. The Fermi contact term and the bonding coefficient are evaluated from the spin-Hamiltonian parameters and these values, together with the low value of Az, indicate a high degree of covalency in the Mg(H2O)6 octahedron, brought about by the participation of the water molecules in large scale hydrogen bonding.