Photoionization efficiency spectroscopy and density functional theory investigations of RhHo2On (n=0-2) clusters

Abstract

The experimental and theoretical adiabatic ionization energies (IEs) of the rhodium-holmium bimetallic clusters RhHo2On (n=0–2) have been determined using photoionization efficiency spectroscopy and density functional theory (DFT) calculations. Both sets of data show the IE of RhHo2O to be significantly lower than the values for RhHo2 and RhHo2O2, which are found to be similar. This indicates that there are significant changes in electronic properties upon sequential addition of oxygen atoms to RhHo2. The DFT investigations show that the lowest energy neutral structures are a C2v triangle for RhHo2, a C2v planar structure for RhHo2O where the O atom is doubly bridged to the Ho–Ho bond, and a C2v nonplanar structure for RhHo2O2, where the O2 is dissociative and each O atom is doubly bridged to the Ho–Ho bond in the cluster above and below the RhHo2 trimer plane. Good correlation between the experimental and computational IE data imply that the lowest energy neutral structures calculated are the most likely isomers ionized in the molecular beam. In particular, the theoretical adiabatic IE for the dissociative RhHo2O2 structure is found to compare better with the experimentally determined value than the corresponding lowest energy O2 associative structure.