Electronic Structure of Superoxidized Radical Cationic Dodecaborate-Based Clusters.

The expanding field of boron clusters has attracted continuous theoretical efforts to understand their diverse structures and unique bonding. We recently discovered a new reversible redox event of B12(O-3-methylbutyl)12 in which the superoxidized radical cationic form [B12(O-3-methylbutyl)12]•+ was identified and isolated for the first time. Herein, comprehensive (TD-)DFT studies in tandem with electrochemical experiments were employed to demonstrate the generality of the reported behavior across perfunctionalized B12(OR)12 clusters (R = aryl or alkyl). While the spin density of radical cationic clusters is delocalized in the core region, the oxidation brings about notable gains of positive partial charges on the supporting groups whose electronics can readily tune the redox potential of the 0/•+ couple. The underlying changes of frontier orbitals were elucidated, and the resulting [B12(OR)12]•+ species manifest a general diagnostic absorption as a consequence of mixed local/charge-transfer excitations.