Theoretical Study of the Structures of C2+nB10-n (n=0∼10) Cluster with Two Planar Pentacoordinate Carbons

Using B3LYP/6-311 + G** method, the initial geometrical structures of boron-carbon clusters C2+nB10-n (n = 0 similar to 10) containing double planar pentacoordinate carbon (ppC) were optimized and their vibrational frequencies were calculated. Present results showed that C2+nB10-n (n=0 similar to 2) clusters are stable, in which the Wiberg bond index (WBI) of ppC-B bonds are between 0.511 and 0.909 and the WBIs of ppC-C are 0.2254 (n=1) and 0.8586 (n=2), as well as the WBIs of ppC are 3.778 and 3.879, i.e. the three molecules include double ppCs and ppCs obey octal rule; the C2+nB10-n (n=3 similar to 6) clusters with the lowest energy contain one ppC, while the lowest energy C2+nB10-n (n>6) clusters have no ppC. In addition, only the C2+nB10-n (n=0 similar to 2) clusters do not include dangling bonds, and the numbers of 71 electron in the C2+nB10-n (n=0 similar to 2) clusters are 6, 7 and 8, respectively. Calculated NICS(O) values indicate that the strong aromaticity mainly locates at the centers of the three-membered rings. The vertical transition energies of C2+nB10-n (n=0 similar to 2) clusters are 1.91, 0.56 and 3.12 eV.