Departamento de Química Física, Facultade de Ciencias, Universidade de Santiago de Compostela, Campus de Lugo, Avda. Alfonso X El Sabio, s/n 27002 Lugo, Galicia, Spain.
J Chem Phys. 2011 Oct 7;135(13):134310. doi: 10.1063/1.3643840.
The characteristics of the interaction between water and hydrogen sulfide with indole and a series of analogs obtained by substituting the NH group of indole by different heteroatoms have been studied by means of ab initio calculations. In all cases, minima were found corresponding to structures where water and hydrogen sulfide interact by means of X-H···π contacts. The interaction energies for all these π complexes are quite similar, spanning from -13.5 to -18.8 kJ/mol, and exhibiting the stability sequence NH > CH(2) ≈ PH > Se ≈ S > O, for both water and hydrogen sulfide. Though interaction energies are similar, hydrogen sulfide complexes are slightly favored over their water counterparts when interacting with the π cloud. σ-Type complexes were also considered for the systems studied, but only in the case of water complexes this kind of complexes is relevant. Only for complexes formed by water and indole, a significantly more stable σ-type complex was found with an interaction energy amounting to -23.6 kJ/mol. Oxygen and phosphorous derivatives also form σ-type complexes of similar stability as that observed for π ones. Despite the similar interaction energies exhibited by complexes with water and hydrogen sulfide, the nature of the interaction is very different. For π complexes with water the main contributions to the interaction energy are electrostatic and dispersive contributing with similar amounts, though slightly more from electrostatics. On the contrary, in hydrogen sulfide complexes dispersion is by far the main stabilizing contribution. For the σ-type complexes, the interaction is clearly dominated by the electrostatic contribution, especially in the indole-water complex.
采用从头计算方法研究了水和硫化氢与吲哚及通过取代吲哚中的 NH 基团获得的一系列杂原子类似物相互作用的特点。在所有情况下，都发现了对应于水和硫化氢通过 X-H···π 接触相互作用的结构的最小值。所有这些π配合物的相互作用能都非常相似，范围在-13.5 到-18.8 kJ/mol 之间，并且表现出 NH > CH(2) ≈ PH > Se ≈ S > O 的稳定性顺序，无论是对于水还是硫化氢。尽管相互作用能相似，但当与π云相互作用时，硫化氢配合物略优于其水对应物。还考虑了这些体系的σ型配合物，但只有在水配合物的情况下，这种类型的配合物才是相关的。只有在水和吲哚形成的配合物中，才发现了一个具有相当稳定的 σ 型配合物，其相互作用能高达-23.6 kJ/mol。氧和磷衍生物也形成与观察到的π型类似稳定性的σ型配合物。尽管水和硫化氢配合物表现出相似的相互作用能，但相互作用的性质却大不相同。对于与水的π配合物，相互作用能的主要贡献来自静电和色散，两者贡献相当，尽管静电贡献略多。相反，在硫化氢配合物中，色散是迄今为止主要的稳定贡献。对于σ 型配合物，相互作用明显由静电贡献主导，特别是在吲哚-水配合物中。
