Boron oxide B5O6 and B5O6-clusters with a hexagonal B3O3 ring: Overturn of potential energy landscapes by one electron

Boron oxide clusters feature novel structures and nonclassical chemical bonding, owing to the electron deficiency of boron. We report on a quantum chemical study on structural, electronic, and bonding properties of B5O6 and B 5 O 6- clusters through global-minimum (GM) searches and electronic structure calculations. The neutral B5O6 cluster is shown to assume a GM structure composed of a boroxol core, a terminal boronyl, and a terminal BO2 group, which differs distinctly from anion GM B 5 O 6- cluster. The latter has a boroxol core and three terminal ligands: two boronyls and one O- unit. One electron completely overturns the potential energy surfaces of the present system, which is governed by the nature of frontier molecular orbitals in two types of structures. As a consequence, one electron can make a difference by as much as 2- 3 eV. The structural transformation is also elucidated using a proposed possible mechanism of boronyl ligand migration.