EPR spectroscopic study of a dinuclear copper(II) complex of tolfenamic acid

The copper(II) complex with tolfenamic acid [Cu(tolf)2(H2O)]2 was studied by X-band and K-band EPR spectroscopies in the temperature range from 90 to 300 K. The Cu2+ ions in dinuclear complex show a strong antiferromagnetic exchange interaction with |J| = 292 cm−1. The EPR spectra, which were observed for [Cu(tolf)2(H2O)]2, are typical powder spectra of the copper pairs. The spectra exhibit the hyperfine structure in low temperature range. The values of the spin-Hamiltonian parameters were determined on the basis of the best fit for the simulated spectra at both K-band (0.75 cm−1) at T = 298 K and X-band (0.3 cm−1) at T = 93 K as compared with the experimentally observed spectra. These values show that the local environment around the copper species is distorted tetragonal pyramid. This EPR evidence is consistent with the crystallographic data.