The Role of Chalcogen Bonding in Organic Dichalcogenides of Biological Interest

Dichalcogenides are important intermediates in the catalytic cycle of the Glutathione peroxidase (GPx), the enzyme regulating the level of reactive oxygen species (ROS). Due to their redox sensitivity, dichalcogenides are also employed in anticancer systems. The biological activity of these compounds can be related to the electrophilic behaviour of the chalcogen atoms, namely their ability to form Chalcogen Bonds (ChBs) with nucleophilic species. Herein we report the synthesis and the characterization of selenocystine hydrobromide and tellurocystine hydrochloride. X-ray analysis confirm the ability of these dichalcogenides to act as ChB donors. A combination of surface molecular electrostatic potential (MEP) and Quantum Theory of Atom in Molecules (QTAIM) analysis proves the σ-hole nature of the short contacts involving selenium and tellurium. ChBs involving tellurium are stronger, consistent with its major polarizability. The crystal structure of pyritinol, a synthetic analog of vitamin B6, is also reported, proving the different interactional landscape of disulfides compared to heavier dichalcogenides.