On the electronic structure of mono-rhenium oxide clusters: ReOn- and ReOn (n = 3, 4)

► Determined the structures of ReO3- and ReO4- and their neutrals. ► ReO4 possess a unique Re-O radical unit, and a high electron affinity (5.58 eV). ► Localized 5d electrons in ReO3- and ReO3 give rise to Re5+ and Re6+ centers.