Abstract
This work investigates the dependence of the Cl− → Cu2+ Charge Transfer (CT) bands with the local structure around Cu2+ in the Jahn-Teller CuCl4- 6 complexes formed in layer chloroperovskites with the K2NiF4-type structure. We present experimental results on the variation of the first CT band of CuCl4- 6 with hydrostatic pressure in the 0–80 kbar range. The study has been carried out in CuCl4- 6 formed either as impurity in Cu2+-doped crystals or in pure A2CuCl4 compounds in order to establish structural correlations. A noteworthy feature is the redshift undergone by the first CT band at about 26000 cm−1, upon pressure in all the investigated systems. This redshift is interpreted in terms of anisotropic distortions of the octahedral elongated CuCl4- 6 complex. MS-Xα and Extended Hückel calculations of the electronic structure around the D4h equilibrium geometry allow us to establish correlations between the energy shift and the structural distortions of the complex.