论吡咯与双卤分子间的卤键

Theoretical studies on the halogen bond between pyrrole and dihalogen molecules

运用量子化学微扰理论MP2方法,采用6-311++G(d,p)基组,对吡咯与双卤分子XY(XY=ClF BrF,BrCl)形成的卤键复合物进行构型全优化,得到各分子的稳定几何构型和分子间相互作用能。利用电子密度拓扑分析方法分析卤键复合物的拓扑性质,探讨了该类分子间卤键的作用本质。证明吡咯与双卤分子间存在Y—X…N和Y—X…π2类相互作用,且后者比前者强。复合物中的卤键介于共价键与离子键之间,偏于静电作用成分为主。形成卤键后,2种类型卤键复合物中的电子受体X—Y键伸长,其振动频率发生红移。用电子密度拓扑分析程序GTA-2000,将π型卤键体系中π电子与σ电子分开处理,绘制出π电子密度等值线图和Laplacian量等值线图,更加形象地说明π型卤键的存在和作用本质。利用AIM程序计算了卤键复合物中各原子电子积分的性质,原子积分性质随着卤键形成发生了改变。

The full geometry optimizations for the halogen-bonded systems,pyrrole...XY（XY=ClF,BrF,BrCl）,were carried out using MP2 methods at 6-311＋＋G（d,p） levels.Geometries and interaction energies of the halogen-bonded complexes were calculated,indicating that two types of intermolecular interactions（n-halogen bonded andπ-halogen bonded） were observed and theπ-halogen bonded interaction was the more stable one The topological properties of halogen-bonded complexes were investigated by the topological analysis of electron density.The nature of halogen bond was investigated,indicating that this kind of halogen bond is between covalent and ionic bonds,with the electrostatic interaction being dominant The formation of halogen bonds resulted in an elongation of X—Y bonds and red-shift of vibrational frequencies.Program GTA2000 by ourselves was used to deal with theπ-electron separating fromπ-type halogen bond complexes,it could describe the contours ofπ-electronic density and Laplacian.Program AIM2000 was compiled to calculate the electron integral.And the results gave a clear description of changes of the integration over atomic basin.