Electron paramagnetic resonance studies on VO(IV)-D-aspartic acid and VO(IV)-D-aspartic acid α-benzylester complexes

Abstract

A detailed electron paramagnetic study has been done on oxovanadium(IV)-D-aspartic acid and oxovanadium(IV)-D-aspartic acid α-benzylester complexes, molar ratio 1:1 and 1:2 in the physiological pH range. Their isotropic and anisotropic spin Hamiltonian parameters have been calculated to second order and the superimposed mixed species spectral patterns have been simulated. The complexes display an approximate C 4v geometry whose relative hyperfine coupling constant values are connected with the ligand field strength on the equatorial plane. Furthermore it seems that aspartic acid, in some circumstances, binds oxovanadium(IV) acting as tridentate ligand, and aspartic acid α-benzylester can coordinate the metal-ion giving complexes with six-membered chelate rings (α-NH 2/β-COO − donor groups). Our EPR results are in agreement with those of UV-visible and CD spectral measurements.