Theoretical Density Functional Theory insights into the nature of chalcogen bonding between CX2 (X = S,Se, Te) and diazine from monomer to supramolecular complexes

Chalcogen bonding is a noncovalent interaction, highly similar to halogen and hydrogen bonding, occurring between a chalcogen atom and a nucleophilic region. Two density functional theory (DFT) approaches B3LY-D3 and B97-D3 were performed on a series of complexes formed between CX₂ (X = S, Se, Te) and diazine (pyridazine, pyrimidine and pyrazine). Chalcogen atoms prefer interacting with the lone pair of a nitrogen atom rather than with the π-cloud of an aromatic ring. CTe₂ and CSe₂ form a stronger chalcogen bond than CS₂. The electrostatic potential of CX₂ (X = S, Se and Te) reveals the presence of two equivalent σ-holes, one on each chalcogen atom. These CX₂ molecules interact with diazine giving rise to supramolecular interactions. Wiberg bond index and second-order perturbation theory analysis in NBO were performed to better understand the nature of the chalcogen bond interaction.