Co-existence of halogen- and chalcogen-bonding in sulphur-rich systems: a case study of halogenated dithiocarbamate esters

Abstract

A comprehensive survey of the crystallographic literature and computational study of halogenated dithiocarbamate esters reveals the co-existence and competition of chalcogen- and halogen-bonding interactions in the solid-state. An analysis of a series of literature structures featuring F, Cl, Br and I substituents demonstrate directional non-covalent contacts involving sulphur atoms, contributing to the formation of diverse supramolecular assemblies. Complementary DFT calculations, including molecular electrostatic potential (MEP) mapping, quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis, were performed on representative dimers to characterise the nature and strength of S···X and X···S interactions. Theoretical results confirm the presence of both chalcogen- and halogen-bonding motifs, with bifurcated interactions commonly observed for heavier halogens. Notably, chalcogen bonds involving thioether-S atoms often exhibit comparable or even greater interaction energies than the corresponding halogen bonds. These findings provide deeper insight into the subtle interplay of σ-hole interactions in sulphur-rich molecular systems and establish design principles for exploiting such interactions in supramolecular and crystal engineering contexts.