Structurally Innovative Benzimidazole‐fused Ionic Organoselenium Compounds: Prevalence of Se···N/Se Chalcogen Bonds with the Selenocyanate Receptor

Abstract

The non‐covalent interactions in molecules play important roles towards their applications in various aspects such as molecular recognition, catalysis, supramolecular chemistry, structural biology, pharmacology etc. Interestingly, among various non‐bonding interactions, chalcogen bonding (ChB) has been extensively studied in different facets of crystal engineering over the last several years. The present study demonstrates the presence of Se···N or Se···Se ChB in the benzimidazole‐fused cyclic selenazonium selenocyanates (6‐8), cyclic selenazinium selenocyanates (9‐10) and the acyclic benzimidazolium analogs having two different types of selenocyanate units (11‐12). The final organoselenium compounds were synthesized from benzimidazole in several steps in reasonably good yields. The single crystal X‐ray structures of the compounds revealed that both the N atom and Se atom of the negatively charged SeCN unit act as ChB acceptors in building the Se···N or Se···Se ChB interactions along with the additional hydrogen bonding (HB) interactions. Moreover, the structural optimization and natural bond orbital (NBO) analyses were carried out using density functional theory (DFT) to calculate the natural charges on different Se centers and the strength of second‐order perturbation energy (E2) for the ChB interactions. Finally, electrostatic potential surface (SEP) of the compounds was developed to visualize the formation of σ‐holes.