A theoretical study of boron tetrahalides: Structures and electron affinities

A series of superhalogens, the boron tetrahalides, BF n Cl m - , n + m = 4, were studied at the B3LYP/aug-cc-pVTZ level of theory. Their adiabatic detachment energies, vertical detachment energies and geometries were the focus of this study. All molecules have large adiabatic detachment energies of 6.83, 4.97, 5.07, 5.23 and 5.27 eV for n = 4–0 respectively. The neutral molecules have two low energy isomers, with the exception of BF3Cl, that have very different geometries. These isomers are classified as non-covalent complexes with a halogen atom solvated by a boron trihalide, or a covalent structure with shorter B–F and B–Cl bonds. The covalent structure has not been reported in earlier studies. Our study indicates that all neutrals are weakly bound with low barriers for isomerization. All neutral covalent structures appear to be metastable with respect to isomerization and/or dissociation.