INFLUENCE OF THE COPPER IONS ON THE CUXZN1-X(HCOO)2.2H2O SOLID-SOLUTION FORMATION

It was established that the isostructural salts Cu(HCOO)2 · 2H2O and Zn(HCOO)2 · 2H2O form a discontinuous series of solid solutions. The deviation from the classical isomorphous theory rules is due to the properties of the Jahn-Teller copper ions, which cause a strong radial deformation of the comparatively regular zinc octahedra, replacing the zinc ions in the Zn(HCOO)2 · 2H2O crystal structure. The observed shift in the absorption maximum in the visible range is explained by the preferential occupation of the two available lattice sites by the copper ions when they replace the zinc ions. The shift in the absorption maximum toward higher energies is evidence in favor of the hypothesis that the copper ions prefer a mixed coordination environment. The crystal structure of the solid solution Cu0.5Zn0.5(HCOO)2 · 2H2O may be treated from a crystallochemical point of view as a double salt. © 1992.