Density Functional Theoretical Study on the Electronic Structure of Rh2O7 + with Low Oxidation States.

Abstract

Rh2On+ (n = 2–10) species are prepared by the reaction of the laser-ablated rhodium atoms with oxygen; furthermore, they are characterized by employing time-of-flight mass spectroscopy. To reveal the stable electronic structure, in this study, we performed the density functional theory calculations for the possible isomers of Rh2O7+. A total of 29 geometries were obtained including cyclic Rh2O3, cyclic Rh2O2, and ring-opening structures with doublet, quartet, sextet, and octet states. It is noteworthy that no Rh–Rh bond was observed for all the optimized Rh2O7+ isomers including oxides, peroxides, superoxides, and oxygen groups. The optimized geometries were also confirmed to exhibit minimum structural energies by employing harmonic frequency analysis at the same energy level. Generally, two types of oxygen-bridged geometries were discovered with cyclic and pseudo-linear Rh2O7+, which contained one or more than one O2 groups. It is concluded that the cyclic structure comprises a lower energy than that observed in pseudo-linear structures. In addition, Rh2O7+ tends to be unstable when the coordination groups change from O2 to O2– unit. Finally, the localized orbital bonding analysis indicates that Rh has oxidation states of 1 or 2 in cyclic Rh2O7+ structures; this is true even in the presence of O2–, O2–, and O22– groups.