Double Chalcogen Bonds: Crystal Engineering Stratagems via Diffraction and Multinuclear Solid-State Magnetic Resonance Spectroscopy.

Group 16 chalcogens potentially provide Lewis acidic σ-holes, which are able to form attractive supramolecular interactions with electron rich partners via chalcogen bonds. Here, we report a multifaceted experimental and computational study of a large series of novel chalcogen bonded cocrystals prepared using the principles of crystal engineering. Single-crystal X-ray diffraction studies reveal that dicyanoselenodiazole and dicyanotelluradiazole derivatives work as promising supramolecular synthons with the ability to form double chalcogen bonds with a wide range of electron donors including halides and oxygen- and nitrogen-containing heterocycles. An extensive 77 Se and 125 Te solid-state nuclear magnetic resonance spectroscopic investigations of a cocrystals establishes correlations between the NMR parameters of selenium and tellurium and the local ChB geometry. The relationships between the electronic environment of the chalcogen bond and the 77 Se and 125 Te chemical shift tensors were elucidated through a natural localized molecular orbital density functional theory analysis. This systematic study of chalcogen bond based crystal engineering lays the foundations for the preparation of the various multicomponent systems and establishes solid-state NMR protocols to detect these interactions in powdered materials.