EPR and optical absorption studies on VO(2+) ions in sodium citrate single crystals

X-band electron paramagnetic resonance (EPR) studies of VO(2+) ions in sodium citrate single crystals have been done at room temperature. Detailed EPR analysis indicates the presence of two magnetically inequivalent VO(2+) sites. Both the vanadyl complexes are found to take up substitutional position. The angular variation of the EPR spectra in three planes ba*, bc and ca* are used to determine principal g and A tensors. For the two sites the spin Hamiltonian parameters are, Site I: g(x)=1.9680, g(y)=2.0053, g(z)=1.9124, A(x)=79, A(y)=76, A(z)=185; Site II: g(x)=1.9650, g(y)=2.0067, g(z)=1.9418, A(x)=78, A(y)=70, A(z)=186 x 10(-4)cm(-1). The optical absorption study is also carried out at room temperature and absorption bands are assigned to various transitions. The theoretical band positions are obtained using energy expressions and a good agreement is found with the experimental values. By correlating EPR and optical data different molecular orbital coefficients are evaluated and the nature of bonding in the crystal is discussed.