高等学校化学学报

高等学校化学学报 ›› 2001, Vol. 22 ›› Issue (1): 122.

• 研究论文 • 上一篇    下一篇

N-苄叉基-2-氨基噻唑及其类似物的构象和分子内的扭曲驱动力

虞忠衡, 宣正乾, 郭彦伸, 彭晓琪, 王桐信, 金祥林   

  1. 中国科学院化学研究所, 分子动态与稳态国家重点实验室, 北京 100080
  • 收稿日期:2000-06-09 出版日期:2001-01-24 发布日期:2001-01-24
  • 通讯作者: 虞忠衡(1944年出生),男,理学博士,研究员,博士生导师,从事物理有机化学的研究.
  • 基金资助:

    国家自然科学基金(批准号:29872042);国家重点基础研究发展规划项目(批准号:G1998010100)资助

The Conformation of N-Phenylmethylene-2-thiazoleamine Species and the Driving Forces for Twisting Molecule

YU Zhong-Heng, XUAN Zheng-Qian, GUO Yan-Shen, PENG Xiao-Qi, WANG Tong-Xin, JIN Xiang-Lin   

  1. State Key Laboratory of Stable and Unstable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China
  • Received:2000-06-09 Online:2001-01-24 Published:2001-01-24

PDF (PC)

被引次数

12

摘要： 确定了N-苄叉基-2-氨基噻唑(2a)和N-对硝基苄叉基-2-氨基噻唑(2b)的晶体结构.结合已报道的N-对硝基苄叉基-2-氨基嘧啶(1a),N-对硝基苄叉基-2-氨基吡啶(1b)和N-苄叉基-3-氨基吡啶(2c)的晶体结构,利用AM1,RHF,DFT方法和6-311G,6-311G**基组,优化每个分子的22个旋转构象(θ=0°～90°).由DFT法所得到的最优构象的扭角θ(1a,22°;1b,0°;1c,42°;2a、2b:0°)与实验值(1a,26°;1b,20°;1c,46°;2a,8.8°;2b,3.8°)最接近.尽管分子最优构象扭角的差异很大,但总电子能最稳定的构象都在θ=±42°附近.在任一分子、任何电子态中,离域的π体系总是失稳定的,全平面构象不是π体系最稳定的构象.无论是离域的还是定域的π体系,它们均倾向于扭曲的几何构象.π电子的离域是分子扭曲的驱动力之一.与经典观点相反,非键原子间的核排斥作用是分子扭曲的阻力,而不是动力.

关键词: 共轭效应, 扭角驱动力, 构象, N-苄叉基-2-氨基噻唑, N-对硝基苄叉基-2-氨基噻唑

Abstract: The crystal structures of N-phenylmethylene-2-thiazoleamine(2a) and N-[(4-nitrophenyl)methylene]-2-thiazoleamine (2b) were determined. Twenty-two rotational geometries(θ=0°90°) of each of two molecules were optimized using AM1, RHF/6-311G** B3LYP/6-311Gand B3LYP/6-311G** The twist angles of their preferential geometries obtained from DFTare both 0°, which are most close to the experimental values (2a, θ=8.9°; 2b, θ=3.9°) of all angles obtained from various optimized methods. Although there is a great difference in the twist angles of the five molecules, 2a, 2b, N-(4-nitrophrnyl)methylene-2-pyrimidineamine (1a), N-(4-nitrophenyl)methylene-2-pyridine-amine (1b) and N-phenyl)methylene-3-pyridineamine (1c ), their lowest total electronic energies occur in the optimized geometries with the similar twist angles which are in the region of θ from 37 to 42° and almost have nothing to do with the optimized methods (HFand DFT) and Gaussian basis sets. The π system in the geometry with θ=0° is destabilized no matter whether it is delocalized or not. It appears that the π system always prefers a twisted geometry. The driving force for out-of-plane twist of the molecules arises from the electronic interaction, and the nuclear repulsion is, practically, a resistance for distortion of molecule.

Key words: Resonance effect, Driving force for distorting stilbene-like species, Conformation, N-phenylmethylene-2-thiazoleameine, N-(4-Nitrophemyl)methylene-2-thiazoleameine

中图分类号: 

TrendMD: