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.

Dephasing Relaxation of the Electron Spin Echo of the Vibronic Cu(H2O)6 Complexes in Tutton Salt Crystals at Low Temperatures

“…The wavy lines show the phonon-controlled tunneling process leading to the ESE dephasing. NH 4 groups linked by hydrogen bonds to the SO 4 groups (38). The effect of the third coordination sphere formed by ammonium groups is so strong that the Jahn-Teller deformation of Cu(H 2 O) 6 appears along Cu-O(7) in the ammonium compound, instead of Cu-O(8) as in other Tutton salts (see Fig.…”

“…10) is EPR spectroscopy, supported by X-ray diffraction data and theoretical calculations (8). The energy differences between the wells can be determined from vibronic averaging of the g factors in EPR spectra (8,(37)(38)(39), and energy can be experimentally found from ESE dephasing studies. These parameters are summarized in Table 4.…”

Electron Spin Relaxation in Pseudo-Jahn–Teller Low-Symmetry Cu(II) Complexes in Diaqua(L-Aspartate)Zn(II)·H2O Crystals

“…This state is practically unpopulated below room temperature. A two-well model has been used to describe the vibronic dynamics of octahedral Cu(H 2 O) 2+ 6 complexes in Tutton salt crystals (25)(26)(27). In Zn(L-aspartate) · 3H 2 O:Cu 2+ this model is valid above 100 K, when the two lowest energy distorted configurations are thermally populated.…”

Electronic structure and dynamics of low symmetry Cu2+ complexes in kainite-type crystal KZnClSO4·3H2O: EPR and ESE studies

“…12. Application of the Silver-Getz model to Cu 2+ complexes in Tutton salts [25,26] and in Cd(HCOO) 2 Á2H 2 O [27] confirms that the d 12 varies with temperature suggesting restricted validity of the model.…”