Charge Redistribution Effects on the UV-Vis Spectra of Small Ligated Gold Clusters: a Computational Study

We analyze and compare the UV-visible absorption profiles, computed at the TD-DFT level, of several thiolate, chloride, and phosphine ligand protected gold clusters with Au-13, Au-25, and Au-28 metallic cores. We show by investigating several model clusters and experimentally reported ones that the charge redistribution between the gold core and the ligand shell can be controlled by the electron acceptor or electron donor character of the ligands and their spatial distribution around the metallic core. A correlation between the increase of electronic charge in the gold core and a shift of the optical absorption band toward lower transition energies is highlighted The identified correlation between the partial charge on the metallic gold core and the position of the lowest electronic transition is robust and remains valid even for small dusters with little structural or electronic similarity.