Cooperative Effects between Hydrogen Bonds and C=O•••S Interactions in the Crystal Structures of Sulfoxides

We report herein a comprehensive structural and computational study of noncovalent interactions between a carbonyl group and the sulfur atom of a sulfoxide group. Two main interaction topologies, each of them following precise geometrical parameters, have been unveiled after the analysis of hundreds of crystal structures. The analysis of experimental crystal structures has been accompanied by DFT calculations on simple systems in order to understand the factors that affect the interaction strength. We have seen that both interaction geometries are attractive and present different contributions from electrostatics and charge transfer to the total interaction energy. In all cases, cooperative effects involving hydrogen bonds, with the sulfoxide acting as the hydrogen bond acceptor, play an important role in the energy stabilization. Moreover, natural bond orbital and energy decomposition analysis have been performed to shed light into the physical origin of these noncovalent interactions.