氢键的量子化学研究(一)

Abstract

本文通过耦合簇CCSD等量子化学方法，对各种类型氢键选择有代表性分子进行了计算，还包括锂键、钠键和卤键，观察了形成氢键前后的MO和Δρ，认为它们有着共同的机制、本质，需要建立新的氢键概念。氢键新概念总的可表述为：氢键是分子内、分子间处于能级较高部位的电子(HOMO)，在轨道对称性相符时，向能级较低部位(LUMO)偏移部分电子，形成了双方共享电子能量降低的较稳定静电作用体系。量子化学计算描述了这种现象和事实。用计算实例介绍了这种电子偏移的基本情况和氢键新概念具体细节。 In this paper, the coupled cluster CCSD and other quantum chemistry methods are employed to study various kinds of representative hydrogen bond systems, as well as lithium bond, sodium bond and halogen bond systems; the MO and Δρ are observed before and after the formation of hydrogen bonds. We believe that these bonds have the common underlying mechanism, and a new concept about H-bond is needed to be established. The new concept of H-bond can be described as follows: When orbital symmetries are properly matched, the intramolecular or intermolecular electrons at high-energy level (HOMO) will partially transfer to lower energy regions (LUMO) and forms electron-shared, energy-reduced, relatively stable electrostatically interacting system. Quan- tum chemistry calculations faithfully described this phenomenon and fact. With practical calculation examples, the basic character of the electron transfer and the specific details of the new concept of H-bond are introduced.