Departamento de Química, Facultad de Ciencias Exactas y Naturales y Agrimensura, Universidad Nacional del Nordeste, Corrientes, Argentina.
J Phys Chem A. 2011 May 12;115(18):4701-10. doi: 10.1021/jp1105168. Epub 2011 Apr 20.
In this work, mono- and di-hydrated complexes of the formamide were studied. The calculations were performed at the MP2/6-311++G(d,p) level of approximation. The atoms in molecules theory (AIM), based on the topological properties of the electronic density distribution, was used to characterize the different types of bonds. The analysis of the hydrogen bonds (H-bonds) in the most stable mono- and di-hydrated formamide complexes shows a mutual reinforcement of the interactions, and some of these complexes can be considered as "bifunctional hydrogen bonding hydration complexes". In addition, we analyzed how the strength and the nature of the interactions, in mono-hydrated complexes, are modified by the presence of a second water molecule in di-hydrated formamide complexes. Structural changes, cooperativity, and electron density redistributions demonstrate that the H-bonds are stronger in the di-hydrated complexes than in the corresponding mono-hydrated complexes, wherein the σ- and π-electron delocalization were found. To explain the nature of such interactions, we carried out the atoms in molecules theory in conjunction with reduced variational space self-consistent field (RVS) decomposition analysis. On the basis of the local Virial theorem, the characteristics of the local electron energy density components at the bond critical points (BCPs) (the 1/4∇ (2)ρ(b) component of electron energy density and the kinetic energy density) were analyzed. These parameters were used in conjunction with the electron density and the Laplacian of the electron density to analyze the characteristics of the interactions. The analysis of the interaction energy components for the systems considered indicates that the strengthening of the hydrogen bonds is manifested by an increased contribution of the electrostatic energy component represented by the kinetic energy density at the BCP.
在这项工作中，研究了甲酰胺的单水和二水复合物。计算是在 MP2/6-311++G(d,p) 水平近似下进行的。基于电子密度分布拓扑性质的原子在分子理论（AIM）被用于表征不同类型的键。对最稳定的单水和二水甲酰胺复合物中氢键（H 键）的分析表明，相互作用相互加强，其中一些复合物可以被认为是“双功能氢键水合复合物”。此外，我们分析了在二水甲酰胺复合物中存在第二个水分子时，单水复合物中相互作用的强度和性质如何发生变化。结构变化、协同作用和电子密度重新分布表明，二水复合物中的 H 键比相应的单水复合物中的 H 键更强，其中发现了σ-和π-电子离域。为了解释这种相互作用的性质，我们结合了简化变分空间自洽场（RVS）分解分析进行了原子在分子理论分析。基于局部维里定理，分析了键临界点（BCP）处局部电子能量密度分量（电子能量密度的 1/4∇(2)ρ(b)分量和动能密度）的特征。这些参数与电子密度和电子密度的拉普拉斯一起用于分析相互作用的特征。对所考虑的系统的相互作用能分量的分析表明，氢键的增强表现为 BCP 处动能密度表示的静电能分量的贡献增加。
