Studies on the spin-Hamiltonian parameters of CuN 6 clusters and their tetragonal distortions due to Jahn-Teller effect for Cu 2+ in trigonal M(1-propyltetrazole) 6(BF 4) 2 (M = Zn, Fe) crystals

This paper reports the theoretical calculations for the anisotropic and isotropic spin-Hamiltonian parameters ( g factors and the hyperfine structure constants) of tetragonal CuN ₆ octahedral clusters due, respectively, to the static and dynamic Jahn-Teller effects for Cu ²⁺ ion in the trigonal M(=Zn, Fe) sites of M(1-propyltetrazole) ₆(BF ₄) ₂ crystals. The calculations are carried out using the high-order perturbation formulas based on a two-mechanism model, in which besides the contributions to spin-Hamiltonian parameters due to the crystal-field mechanism concerning the crystal-field excited states in the extensively used crystal-field theory, the contributions due to charge-transfer mechanism concerning the charge-transfer excited states (which are neglected in the crystal-field theory) are included. The calculated results are in reasonable agreement with the experimental values. From the calculations the tetragonal elongations Δ R = R_// - R_⊥ (where R_// and R_⊥ denote the Cu-N distances parallel with and perpendicular to the C ₄ axis) of CuN ₆ octahedral clusters due to Jahn-Teller effect are obtained. The results are discussed.