In this study, the spin-Hamiltonian parameters (g and A), molecular orbital coefficients, and other spectroscopic properties of vanadyl-doped sodium dihydrogen phosphate dihydrate (NaH2PO4 center dot 2H(2)O) powders have been investigated by experimental and theoretical methods, including electron paramagnetic resonance (EPR) and optical absorption spectroscopies. The results show axially symmetric crystalline field around VO2+ ion. The optical absorption spectra exhibit three characteristic bands of VO2+ ions in tetragonal symmetry. EPR and optical data were used in a complementary way to calculate spin-Hamiltonian parameters and molecular orbital coefficients. The octahedral and the tetragonal field parameters were theoretically calculated on the basis of crystal field theory. These parameters were used to determine various bonding parameters which characterize the nature of bonding in the complex. The theoretical results are supported by experimental results.