Exploration of structure, potential energy surface, and stability of planar C3B3

The geometrical structures, potential energy surface, stability, and bonding character of low-energy isomers of planar C₃B₃ were systematically explored and investigated at the B3LYP/6-311+G(d)// CCSD(T)/6-311+G(d) level for the first time. A large number of planar structures for low-energy isomers of C₃B₃ are located and reported. In particular, isomers 1 (C_s,²A’) and 2 (C_s,²A’), with a belt-like structure corresponding to the lowest-energy structures of planar C₃B₃, are revealed. Based on molecular orbital (MO) and natural bond orbital (NBO) analyses, delocalized σ MOs, multi-centered σ MOs, and delocalized π MOs play an important role in stabilizing the structures of low-energy isomers of C₃B₃. It is interesting to note from isomerization analysis that the interconversion of isomers 2 and 7 can be realized through two isomerization channels. The results demonstrate that isomers 1, 2, 3, 4, 7, 9, 12, 17, 19, and 20 of C₃B₃ are stable both thermodynamically and kinetically at the B3LYP/ 6-311+G(d)//CCSD(T)/ 6-311+G(d) level, and that they are observable in the laboratory, which is helpful for future experimental studies of C₃B₃.