B3@Si12+: strong stabilizing effects of a triatomic cyclic boron unit on tubular silicon clusters†
Remarkably strong effects of the aromatic B3 cycle in stabilizing tubular silicon clusters were observed for the first time. The doped cluster B3@Si12+ presents a novel structural motif for silicon clusters in which a B3 cycle is encapsulated into a (6 × 2) Si12 prism giving rise to a high symmetry stable tubular structure (D3h). A large amount of electron density is transferred to the boron cycle, and the B3δ− unit not only retains a delocalized bonding pattern within the Si12 prism but also enables a two-fold aromaticity for the resulting silicon double ring. This double ring can be used as a building block to make longer nanotubes.