Identification of static JT in copper(II) doped hexaimidazole M(II) lattices: M=Co and Ni: an EPR study

Single crystal EPR studies on Cu(II) doped paramagnetic host lattices, hexaimidazole M(II) dichloride tetrahydrate (M=Co and Ni), isomorphous with M=Zn, have been carried out from room temperature to 77K to understand the nature of Jahn-Teller (JT) distortion in these paramagnetic host systems. The paramagnetic impurity, doped in the present two paramagnetic host lattices, shows anisotropic EPR spectra with superhyperfine from ligands, even at room temperature. An interesting observation noticed in the EPR spectra at room temperature is that there are more resonances corresponding to the second site in the paramagnetic hosts than in the diamagnetic host at 4.2K. This difference in behavior between the diamagnetic and paramagnetic host lattices indicates a change in the depth of the JT valleys. The spin Hamiltonian parameters are evaluated for Cu(II) ion in both the host lattices and the relaxation times have been calculated for the ion in cobalt host lattice only.