UV-Visible Absorption Spectra of Small Platinum Carbonyl Complexes and Particles: A Density Functional Theory Study

We investigate the influence of a carbonyl coating on the UV-visible absorption of platinum complexes and particles with the TDDFT method. We first investigate the Chini clusters [Pt-3(CO)(6)](n)(2-), n = 1-4, for which the absorption spectra are known. We show that PBE is realistic but displays convergence issues and that B3LYP overestimates intertriangle distances and absorption intensities. We discuss the structure of the spectra and the parallel vs perpendicular character of the transition dipole with respect to the stacking axis. We then investigate the spectra of model carbonylated platinum particles: [Pt-13(CO)(12)](2-) (with only terminal carbonyls) and [Pt-13(CO)(24)](2-) (with only bridging carbonyls). B3LYP proves much more realistic than in the case of Chini clusters. The influence of the morphology of the platinum particle and of the carbonyl coating on the absorption spectra is discussed. The results suggest an interpretation of a spectrum, recorded in a recent synthesis.