Strength and Nature of Hydrogen Bonding Interactions in Mono- and Di-Hydrated Formamide Complexes

ANGELINA, EMILIO; PERUCHENA, N. M.

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Año: 2011 vol. 115 p. 4701 - 4710

1089-5639

ABSTRACT 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–hydrated and di–hydrated formamide complexes shows a mutual reinforcement of the interactions, and some of these complexes can be considered as “bi–functional 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–electron and p–electron delocalization were found. To explain the nature of such interactions, the atoms in molecules theory, in conjunction with reduced variational space self-consistent field (RVS) decomposition analysis, were carried out. Based in the local Virial theorem, the characteristics of the local electron energy density components, at the bond critical points (BCPs) (the ¼Ñ 2ρb 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.