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

Rh 2 O n + ( 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 Rh 2 O 7 + . A total of 29 geometries were obtained including cyclic Rh 2 O 3 , cyclic Rh 2 O 2 , 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 Rh 2 O 7 + 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 Rh 2 O 7 + , which contained one or more than one O 2 groups. It is concluded that the cyclic structure comprises a lower energy than that observed in pseudo-linear structures. In addition, Rh 2 O 7 + tends to be unstable when the coordination groups change from O 2 to O 2 - unit. Finally, the localized orbital bonding analysis indicates that Rh has oxidation states of 1 or 2 in cyclic Rh 2 O 7 + structures; this is true even in the presence of O 2- , O 2 - , and O 2 2- groups.