Understanding Non-Covalent Interactions in Diphenyldiselenide and Diphenylselenide Cocrystals Using a Combined 77Se Magic-Angle Spinning Solid-State NMR and Quantum Chemical Analysis Approach.

Chalcogen bonds are σ-hole interactions that arise from the net attractive forces between an electron-deficient chalcogen atom (such as selenium) and a Lewis base. In recent years, chalcogen bonds have become important noncovalent interactions, playing a key role in building supramolecular structures and functional materials. Given their significance, there is a continuous interest in gaining a deeper understanding of chalcogen interactions. In this study, we examined systems involving Se-I interactions, where diphenyldiselenide and diphenylselenide serve as selenium sources, while molecular iodine and 1,4-diiodotetrafluorobenzene act as iodine donors. We explore the intricate interplay between selenium's chemical environment and its role in noncovalent interactions, with a focus on Se···I chalcogen bonds and halogen bonds. An interdisciplinary approach combining solid-state NMR, single-crystal X-ray diffraction, and advanced quantum chemical analyses, such as the Quantum Theory of Atoms in Molecules (QTAIM), Non-Covalent Interactions analysis (NCI), the Extended Transition-State Method with Natural Orbitals for Chemical Valence (ETS-NOCV), and Interactive Quantum Atoms (IQA), were used to investigate the electronic and structural factors influencing selenium's behavior. By analyzing the chemical shift tensors, we demonstrate how they are influenced by both halogen and chalcogen bonding roles, in addition to the effects of crystal packing and weak interactions.