A 2-dimensional lattice which contained isolated Cu2+ ions was studied by using charge transfer and electron paramagnetic resonance techniques at temperatures ranging from 10 to 300K. It was found that both types of data were consistent with the existence of 2 different sites for Cu2+, although the same D2h CuCl64- center was formed. It was noted that the longest and intermediate Cu2+-Cl- bonds of the complex alternated in the ab-plane, while the shortest bond was aligned along the c-direction; perpendicular to the layer. The temperature dependence of the electron paramagnetic resonance spectra demonstrated the existence of dynamic features that were associated with 2 (but not 3) equivalent wells on a given site. All of the features were consistent with the existence of an additional strain term which reflected the 2-dimensional host lattice as well as the usual Jahn-Teller term for cubic symmetry. The electron paramagnetic resonance spectrum in the ab-plane was isotropic, due to exchange interactions between the two Cu2+ sites.

R.Valiente, L.M.Lezama, F.Rodríguez, M.Moreno: Materials Science Forum, 1997, 239-241, 729-32