Structures and aromaticity of the planar Si2BX (X=Li, K, O, S) clusters

The equilibrium geometries, total energies and harmonic vibrational frequencies of planar low-lying states for Si 2 BX (X = Li, K, O, S) species are investigated at B3LYP/6-311+G ∗ and B3PW91/6-311+G ∗ levels. The research results show that for Si 2 BLi, Si 2 BK and Si 2 BS species, the C 2 v isomer is the most stable planar structure, and for Si 2 BO species, the C s isomer is the most stable planar structure. Negative nucleus independent chemical shift (NICS) values indicate the existence of aromaticity in planar structures for these species. A detailed molecular orbital (MO) analysis further reveals that a delocalized π MO for two isomers of Si 2 BX (X = Li, K, O, S) strengthens the structural stability and make these species show strongly aromatic character.