Spektroskopische Untersuchungen zum Jahn-Teller-Effekt des Cu2+-Ions in Verbindungen vom Typ A2 CuL6, I / Spectroscopic Ivestigations with Respect to the Jahn-Teller-Effect of Cu(II) in Compounds of the Type A2CuL6, I

Structural relations between perovskite-related lattices of the type A 2 CuL 6 and the perovskite compounds A 2 (12) [BCu] (6) L 6 (1: 1 order in the octahedral sites, elpasolite type) are demonstrated by two examples, the compounds A,Cu(OH) 6 [A = Ba, Sr] and Ba 2 CuF 6 . From the ESR spectra a coupling of Jahn-Teller-distorted Cu-ligand-octahedra in these compounds corresponding to a “disturbed” type of antiferrodistortive order can be deduced. This result is in agreement with recent X-ray structure determinations. The ligand field spectra of the hydroxocuprates(II) indicate tetragonally elongated CuO 6 -octahedra with very long axial distances. From the ESR investigations further conclusions can be drawn concerning structural differences between the Ba- and the Sr-compound [Sr 2 Cu(OH 6 )], the atomic parameters of which are still unknown.