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 (Cs,2A’) and 2 (Cs,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.