Structural and Spectroscopic Investigations of Two [Cu₄X₆]^2– (X = Cl^–, Br^–) Clusters: A Joint Theoretical and Experimental Work

Herein we report a joint experimental and theoretical investigation on two tetranuclear Cu­(I) clusters stabilized by halide ligands. These clusters are of high interest due to their spectroscopic and optical properties, more precisely both clusters exhibit thermochromism. The compounds synthesized by the hydrothermal method have been characterized by single-crystal X-ray diffraction, UV–visible spectroscopy and quantum calculations. Modeled structures have been investigated by means of DFT and TD-DFT methods. Anharmonic computations have been performed to better achieve the vibrational investigation. Computations of the triplet excited states permit us to get more insights into the structure and electronic structure of the excited states responsible for the luminescence properties. Calculations are in agreement with the observed phosphorescence wavelengths