Abstract
The aim of this work is to investigate the Charge Transfer (CT) spectra of CuCl2- 4 and CuBr2- 4 complexes formed in Cu2+-doped A2MX4 crystals and their dependence with chemical pressure when Cu2+ replaces the divlent cation at the MCl2- 4 tetrahedral site. A salient feature of this study is the weak sensitivity exhibited by the CT bands to structural changes of the complex. A similar phenomenon has also been observed for pure chlorocuprates. The analysis carried out on the available family of chlorocuprates indicates that the CT band-shift induced by structural distortions in CuCl2- 4 is smaller than that of the corresponding Crystal Field (CF) bands. We present a perturbative model for explaining the weak sensitivity of the CT bands. We present a perturbative model for explaining the weak sensitivity of the CT bands. in comparison to the CF ones. The estimates of the model accounts for the spectroscopic results observed along the A2MCl4: Cu2+ series.