竞争还是协同:分子内两类磷键Sb…X(X=O、N、F)和Sb…π的关系

Competition or Cooperativity: Study on the Interplay of Both Intramolecular Pnictogen Bonds, Sb-X(X=O, N, F) and Sb-π Interactions

本文通过选取多个双官能团有机分子(甲氧基甲基苯(1)、苄基二甲胺(2)、氟甲基苯(3))和无机分子SbCl3,利用密度泛函理论详细考察了两类分子内磷键Sb…X(X=O、N、F)与Sb…π之间的作用关系。研究结果表明,分子内均存在两种作用,并且二者是竞争关系,不存在协同性。溶剂化效应对磷键有一定的影响,但并不改变二者的关系。分子1、2、3的结合能依次为-14.0、-17.0、-9.0 kcal·mol^(-1)。对于1,结合以Sb…O键为主,Sb…π为辅;对于2,结合基本均来自于Sb…N作用;而对于3,结合则以Sb…π作用为主。该结果体现了相互作用随原子序数的渐变性,为通过磷键调控体系的性质提供了理论依据。

The interplay of both types of pnictogen bonds, Sb…X(X=O, N, F) and Sb…π, occurring in the same molecules, have been thoroughly investigated using density functional theory by selecting several bifunctional organic molecules, including(methoxymethyl)benzene(1), benzyldimethylamine(2), and(fluoromethyl)benzene(3), and an inorganic molecule of SbCl3. The results show that both pnictogen bonds coexist in three complexes in a competition mode, not in synergistic one. Though the solvation exerts an influence on both types of pnictogen bonds to some degree, it does not change the relationship between them. For species 1, 2 and 3, the binding energies with SbCl3are-14.0,-17.0,-9.0 kcal·mol-1, respectively. For 1, Sb…O pnictogen bond is the major binding force linking the complex with Sb…π as the minor one. The binding force in 2 almost originates from the Sb…N pnictogen bond. As for 3, the binding is principally ascribed to Sb…π pnictogen bond, with Sb…F offering small contribution. The study demonstrates the gradual change of the pnictogen bonds as the atomic number of elements, and provides a theoretical basis in modulating the properties of the molecules by pnictogen bonds.