### 抜粋

The geometrical and electronic structures of large cyclic polyenes, annulenes, with 18, 30, 42, 54, and 66 CH units, which belong to a subgroup of aromatic (4n + 2)π electron systems and can exhibit a delocalized D_{6h} geometry, are studied using the MNDOC (C for correlation) method coupled with a conventional perturbation treatment. The optimized D_{6h} structures have nearly equal C-C bond lengths of approximately 1.4 Å, in contrast to the D_{3h} ones which exhibit strong bond-length alternation. It is well-known that the Hartree-Fock-based self-consistent-field (SCF) methods generally prefer bond-alternation structures to bond-equalization ones. However, second-order energy (always minus) is larger in the D_{6h} structures, due to the small HOMO-LUMO gap in the D_{6h} structures with nearly equal C-C bond lengths. It is clarified that these two effects strongly compete in the structure of [18]- and [30]annulenes; in [18]annulehe the D_{6h} structure is 6.4 kcal/ mol more favorable, but in [30]annulene the D_{6h} structure is less stable by 4.6 kcal/mol. Moreover, in [42]-, [54]-, and [66]annulenes, the D_{3h} structures are clearly more stable than the corresponding D_{6h} ones.

元の言語 | 英語 |
---|---|

ページ（範囲） | 5697-5701 |

ページ数 | 5 |

ジャーナル | Journal of physical chemistry |

巻 | 100 |

発行部数 | 14 |

DOI | |

出版物ステータス | 出版済み - 4 4 1996 |

外部発表 | Yes |

### All Science Journal Classification (ASJC) codes

- Engineering(all)
- Physical and Theoretical Chemistry

## フィンガープリント Electron correlation effects and possible D<sub>6h</sub> structures in large cyclic polyenes' の研究トピックを掘り下げます。これらはともに一意のフィンガープリントを構成します。

## これを引用

_{6h}structures in large cyclic polyenes.

*Journal of physical chemistry*,

*100*(14), 5697-5701. https://doi.org/10.1021/jp953420x