Density functional theory and topological analysis on the hydrogen bonding interactions in N-protonated adrenaline–DMSO complexes

Abstract

In this study, complexes formed via hydrogen bond interactions between N-protonated adrenaline (AdH⁺) and DMSO have been studied by density functional theory (DFT). The relevant geometries, energies, and IR characteristics of the hydrogen bonds (H-bonds) have been systematically investigated. The natural bond orbital (NBO) and the quantum theory of atoms in molecule (QTAIM) analysis have also been applied to understand the nature of the hydrogen bonding interactions in complexes. The H-bonds involving amino or hydroxyls as H-donor are dominant H-bonds in complexes and are attributed to strong H-bonds. The weak H-bonds, such as π H-bonds and H-bonds involving methyl (DMSO) or methenyls (C2H6 and C5H7 of AdH⁺) as H-acceptors, were found in complexes as well. The complexes in which the dominant H-bond involves amino of AdH⁺ as H-donor are more stable than those with the dominant H-bond involving hydroxyls as H-donor. Some relationships between various properties of QTAIM, NBO, geometry as well as frequency were also investigated.