The host lattice influence on the Jahn-Teller effect of the Cu(H₂O)₆²⁺complex studied by EPR in K₂Zn(SO₄)₂.6H₂O and (NH₄)₂Zn(SO₄)₂.6H₂O Tutton salt crystals

Abstract

The EPR investigations of Cu2+ doped K2Zn(SO4)2.6(H2O) and (NH4)2Zn(SO4)2.6(H2O) Tutton salts in a temperature range of 4.2-300 K are reported. The analysis of the temperature dependences of the g-factors points to significant differences between Jahn-Teller Cu(H2O)62+ complexes in the ammonium and potassium compounds. In the ammonium salts the energy difference 12, between the ground and excited configurations, is found to be temperature dependent. This is explained by the lattice contribution to the adiabatic potential. Various mechanisms of such an influence are proposed. For the discussed case it is suggested that thermal librations of the ammonium groups will change the strength of the hydrogen bonds between the sulphate groups and water octahedra and in this way influence the Jahn-Teller complex.