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化学学报
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化学学报 ›› 2006, Vol. 64 ›› Issue (23): 2322-2326. 上一篇    下一篇

研究论文

C30卡宾三叶结分子结构与稳定性的理论研究

邓文叶, 邱文元*   

  1. (兰州大学化学化工学院 功能有机分子化学国家重点实验室 兰州 730000)
  • 投稿日期:2006-08-04 修回日期:2006-09-04 发布日期:2006-12-14
  • 通讯作者: 邱文元

Theoretical Studies on the Structure and Stability of C30 Carbyne Trefoil Knot

DENG Wen-Ye; QIU Wen-Yuan*   

  1. (Department of Chemistry, State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000)
  • Received:2006-08-04 Revised:2006-09-04 Published:2006-12-14
  • Contact: Qiu Wen-Yuan

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三叶结分子是最简单的非平凡纽结分子, C30卡宾三叶结分子是由一条闭合的(C≡C—)15 sp杂化碳链组成的, 是具有D3对称性的拓扑手性分子. 本文用密度泛函方法[DFT/RB3LYP/6-31G(D)]对分子结构和光谱性质进行了研究, 在优化构型的基础上通过自然键轨道(NBO)方法和轨道能级研究了它的共轭性、成键情况和稳定性, 并与平面型C30卡宾环分子进行了比较. 计算结果表明三叶结分子的三叶弧上形成了非平面的C≡C共轭和扭曲的内螺旋结构, 交叉处具有弱成键作用, 且分子轨道也发生了扭曲; 三叶结分子比卡宾环的共轭性和赝Jahn-Teller效应都明显小, 而总能量高. 因此, 分子打结是一个能量升高的过程.

关键词: C30卡宾三叶结, C30卡宾环, 振动光谱, 自然键轨道(NBO), 轨道能级

The trefoil is known as the simplest nontrivial molecular knot. The C30 carbyne trefoil knot studied is intertwined by the sp hybridized (C≡C—)15 chain, which is topologically chiral and belongs to D3 point-group of symmetry. Density functional theory (DFT) calculations have been carried on the molecular knot at the RB3LYP/6-31G(D) levels. Based on the optimized geometry, the vibrational spectra, natural bond orbital (NBO) and orbital energy level analysis for C30 carbyne trefoil knot have been calculated at the same level, and compared with the cyclo-C30 carbyne molecule. The results show that the electronic structure possesses three primary attributes: C≡C nonplanar conjugated structure, inherently helical structure and highly strained crossing bonds, and the molecular orbitals are also twisted. Furthermore, the tied trefoil knot has less conjugation property and Jahn-Teller effect but higher total energy than the cyclo-C30 carbyne, that is, the process of “tied” could increase the energy of molecules.

Key words: C30 carbyne trefoil knot, cyclo-C30 carbyne, vibrational spectrum, natural bond orbital (NBO), orbital energy level