Theoretical investigation of substituent effects on the relative stabilities and electronic structure of [BX] clusters.

In this study, we provide a theoretical evaluation of relative stabilities and electronic structure for [BX] clusters (n = 10, 12, 13, 14, 15, 16). Structural and electronic characteristics of [BX] clusters are examined by comparison with the [BX] counterparts with a focus on the substituent effects (X = H, F, Cl, Br, CN, BO, OH, NH) on the electronic structure, electron detachment energies, formation enthalpies, and charge distributions. For the electronic structure and electron detachment energies, substituent effects on boron clusters are shown to follow a very similar trend to the mesomeric and inductive effects (± M and ± I) of π-conjugated systems, and the most stable derivatives in terms of HOMO/LUMO and electron detachment energies are calculated for CN and BO substituents due to strong -M effects. In the case of formation enthalpies for larger boron clusters (n ≥ 13), the icosahedral barrier is shown to increase with the halogen and CN substitution, whereas it is possible to reduce the icosahedral barrier for the cases of X = OH and NH. It is shown that this reduction results from destabilizing the [BX] cluster with electronic (+ M) and symmetry effects induced by OH and NH ligands.