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.