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

The equilibrium geometries, total energies and harmonic vibrational frequencies of planar low-lying states for Si2BX (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 Si2BLi, Si2BK and Si2BS species, the C2v isomer is the most stable planar structure, and for Si2BO species, the Cs 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 Si2BX (X = Li, K, O, S) strengthens the structural stability and make these species show strongly aromatic character.