Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (05): 1113-1119.doi: 10.3866/PKU.WHXB201203071


Structure and Stability of Compounds with Planar Pentacoordinate Carbons and Planar Tetracoordinate Carbons

WU Lin-Feng, LI Fei-Fei, ZHANG Cong-Jie   

  1. Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shannxi Normal University, Xi'an 710062, P. R. China
  • Received:2011-12-21 Revised:2012-02-21 Published:2012-04-26
  • Contact: ZHANG Cong-Jie
  • Supported by:

    The project was supported by the Fundamental Research Funds for the Central Universities, China (GK201002013) and State Key Laboratory for Physical Chemistry of Solid Surface (Xiamen University), China (2010).

Abstract: We have investigated the structures, gaps, IR spectra, electronic spectra, Wiberg bond indices (WBIs), and aromaticity of CB5C2H2(C3B2)nC2H2CB5 (n=1-5) with planar pentacoordinate carbons (ppC) and planar tetracoordinate carbons (ptC) at the B3LYP/6-311 + G** level. Calculations indicate that the five compounds with the lowest energies are located at the minima of the potential energy surfaces. The energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) vary between 0.5 and 1.2 eV; the first electronic transition wavelengths are between 1780 and 2910 nm and depend non-monotonically on the size of the compounds. WBIs of the five compounds show that they contain both ppC and ptC. The nucleus-independent chemical shift (NICS(0)) values of the centers of the three-membered rings of the CB5 sections on the right side of these compounds, as well as the C3B2 sections, are negative, while the NICS(0) values of only two centers of the three-membered rings of the CB5 sections on the left side are negative. In addition, since the NICS(0) of the centers of the three-membered rings are consistent with those of NICS(1), then local delocalization of the π electrons must play an important role in stabilizing these compounds.

Key words: Density functional theory, Planar pentacoordinate carbon atom, Planar tetracoordinate carbon atom, Aromaticity


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