Theoretical studies on the EPR parameters and local structure of Cu2+ center in [Co(nicotinamide)2(H2O)4](saccharinate)2 crystal

Local structure and electron paramagnetic resonance (EPR) parameters for Cu2+ center in [Co(nicotinamide)(2)(H2O)(4)](saccharinate)(2) (CoNAS) crystal are theoretically investigated using high-order perturbation formulas for 3d(9) ions in rhombically elongated octahedra. In the calculated formulas, the related molecular orbital coefficients are acquired from the superposition model which enables to correlate the crystal field parameters and hence the EPR parameters with the studied Cu2+ center, the admixtures of d-orbitals in the ground state wave function as well as the ligand orbital and spin-orbit coupling contributions are taken into account. Based on the studies, the [CuO4N2](12-) cluster of the studied Cu2+ center are found to suffer the axial and perpendicular bond length variations Delta z (approximate to 0.0612 angstrom) along z-axis and delta r (approximate to 0.0360 angstrom) along x- and y-axes, respectively, due to the Jahn-Teller effect.