Tsuzuki Seiji, Mikami Masuhiro, Yamada Shinji
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan.
J Am Chem Soc. 2007 Jul 11;129(27):8656-62. doi: 10.1021/ja071372b. Epub 2007 Jun 14.
Geometries and interaction energies of benzene complexes with pyridine, pyridinium, N-methylpyridinium were studied by ab initio molecular orbital calculations. Estimated CCSD(T) interaction energies of the complexes at the basis set limit were -3.04, -14.77, and -9.36 kcal/mol, respectively. The interactions in the pyridinium and N-methylpyridinium complexes should be categorized into a cation/pi interaction, because the electrostatic and induction interactions greatly contribute to the attraction. On the other hand, the interaction in the pyridine complex is a pi/pi interaction. The dispersion interaction is mainly responsible for the attraction in the benzene-pyridine complex. Short-range interactions including charge-transfer interactions are not important for the attraction in the three complexes. The most stable pyridinium complex has a T-shaped structure, in which the N-H bond points toward the benzene, while the N-methylpyridinium complex prefers a slipped-parallel structure. The benzene-pyridine complex has two nearly isoenergetic (Slipped-parallel and T-shaped) structures.
通过从头算分子轨道计算研究了苯与吡啶、吡啶鎓、N-甲基吡啶鎓配合物的几何结构和相互作用能。在基组极限下，配合物的估计CCSD(T)相互作用能分别为-3.04、-14.77和-9.36 kcal/mol。吡啶鎓和N-甲基吡啶鎓配合物中的相互作用应归类为阳离子/π相互作用，因为静电和诱导相互作用对吸引力有很大贡献。另一方面，吡啶配合物中的相互作用是π/π相互作用。色散相互作用是苯-吡啶配合物中吸引力的主要原因。包括电荷转移相互作用在内的短程相互作用对这三种配合物的吸引力并不重要。最稳定的吡啶鎓配合物具有T形结构，其中N-H键指向苯，而N-甲基吡啶鎓配合物更喜欢滑移平行结构。苯-吡啶配合物有两种能量几乎相等的（滑移平行和T形）结构。
