Single crystal E.P.R. studies of some first-row transition ions in hexaimidazole zinc(II)dichloride tetrahydrate

Abstract

Single crystal E.P.R. spectra of Fe(III) doped in hexaimidazole zinc(II) dichloride tetrahydrate have been investigated. The spectra are characteristic of Fe(III) occupying a substitutional zinc site and where it is under the influence of a strong tetragonal crystal field from the six imidazole ring nitrogens: superposed on this is a low symmetry crystal field potential from the various possible charge-compensating vacancies. A careful analysis of the spectrum indicates that the zero field term, D, is large compared to the Zeeman energy and all the three Kramers doublets are populated at the temperature of measurement. The spatial and chemical inequivalences, as well as deviation from cylindrical symmetry of the zero-field tensor, have been correlated with the configuration of charge-compensating vacancies derived from X-ray data of the host-lattice. Resonances from all three Kramers doublets were observed indicating that strain-broadening is negligible in the crystal.