Exploring the Role of Substitution on the Formation of Se⋯O/N Noncovalent Bonds

In this article, we have examined the effect of substitution on the formation of neutral XHSe⋯O/N (X = -H, -F, -CH₃, -CF₃, -Cl, -OH, -OCH₃, -NH₂, -NHCH₃, -CN) noncovalent bonds with the oxygen atom from H₂O molecule and the nitrogen atom from NH₃ being the electron donor atoms, respectively. In addition to this, analysis has also been performed on XMeSe⋯O/N complexes to study the effect of the role of hydrogen bonding with the hydrogen atoms of the methyl group on Se⋯O/N interactions. Binding energy calculations were performed to determine the strength of these contacts. The obtained results establish the fact that the presence of a methyl group influences the strength of the observed Se⋯O/N interactions. Also in some cases, the O-H⋯Se interaction was observed to be more preferable over the Se⋯O interaction. The major contribution for stabilization of such Se⋯O/N interactions is from an interplay among the electrostatics and the exchange energy. To obtain deeper insights and understanding of such Se⋯O/N contacts, a topological analysis, using the QTAIM approach were also performed. This analysis showed that although the presence of a Me group modifies the Se⋯O/N interaction, it does not necessitate the formation of hydrogen bonds. To obtain insights into the orbital contributions, a natural bond orbital (NBO) analysis were performed which depicts that the strength of such interactions were derived via charge transfer from the oxygen/nitrogen lone pair to the σ∗ orbital of the Se-X bond.