Adsorption Forms of Water Molecules on Gas-Phase Platinum Clusters Pt3 + Studied by Vibrational Photodissociation Spectroscopy

Abstract

Abstract The vibrational spectra of Pt3(H2O) m + (m = 1–4) cluster were measured in the 3000–3800 cm−1 range via infrared photodissociation (IRPD) spectroscopy. The IRPD spectra were recorded through the photodissociation of Pt3(H2O) m +-Ar (m = 1–3) complexes and Pt3(H2O)4 + cations upon vibrational excitation. The spectra were compared to the vibrational spectra of several stable isomers obtained by density functional theory (DFT) calculations and the adsorption forms of the water molecules were subsequently discussed. The IRPD spectra of all the studied Pt3(H2O) m + cations exhibited intense peaks at ∼3600 and 3700 cm−1. This suggested that the water molecules mainly adsorb onto the Pt clusters in molecular form and that each molecule binds directly to a Pt atom via its O atom side. For the water-rich Pt3(H2O)4 + cations, all four water molecules were directly bound to the Pt atoms; however, according to the DFT calculations, the fourth H2O molecule could bind to a first-layer water molecule through hydrogen bonding.