Spektroskopische Untersuchungen zum Jahn-Teller-Effekt des Cu2+-Ions in Verbindungen vom Typ A2CuL6, II / Spectroscopic Investigations with Respect to the Jahn-Teller Effect of Cu(II) in Compounds of the Type A2CuL6, II

Abstract

By means of EPR and ligand field spectroscopy a refinement of the Ba2CuF6 structure within the [CuF4/2F2]2--layers consisting of axially elongated CuF6-octahedra, 2-dimensionally connected by corners in an antiferrodistortive order, is given. In qualitative agreement with a recent structure determination by X-ray analysis the spectroscopic data prove, that the equatorial planes of the coupled CuF6-polyhedra form an angle of 2 γ > 90° (corresponding to a disturbed type of antiferrodistortive order). In contrast to 2 γ= 101° found by the X-ray investigation, the spectroscopic results suggest 2 γ = 119 (± 1)°, the consequence of which is an elongation of the Cu—F bond lengths and a remarkable orthorhombic distortion of the CuF6-octahedra.