A hollow tetrahedral cage of hexadecagold dianion provides a robust backbone for a tuneable sub-nanometer oxidation and reduction agent via endohedral doping

Abstract

We show, via density functional theory calculations, that dianionic Au₁₆²⁻ cluster has a stable, hollow, T_d symmetric cage structure, stabilized by 18 delocalized valence electrons. The cage maintains its robust geometry, with a minor Jahn–Teller deformation, over several charge states (q = −1,0,+1), forming spin doublet, triplet and quadruplet states according to the Hund’s rules. Endohedral doping of the Au₁₆ cage by Al or Si yields a geometrically robust, tuneable oxidation and reduction agent. Si@Au₁₆ is a magic species with 20 delocalized electrons. We calculate a significant binding energy for the anionic Si@Au₁₆/O₂⁻ complex and show that the adsorbed O₂ is activated to a superoxo-species, a result which is at variance with the experimentally well-documented inertness of Au₁₆⁻ anion towards oxygen uptake.