Se⋯π Chalcogen Bonding in 1,2,4-Selenodiazolium Tetraphenylborate Complexes

The series of substituted 1,2,4-selenodiazolium tetraphenylborate complexes were synthesized via cyclization between 2-pyridylselenylchloride, followed by the anion metathesis, and fully characterized. The utilization of tetraphenylborate anion, a strong π-electron donor via its phenyl rings, promoted the formation of assemblies exhibiting selenium–π interactions. The chalcogen bonding (ChB) interactions involving the π-systems of the tetraphenylborate anion were studied using density functional theory (DFT) calculations, where “mutated” anions were used to estimate the strength of the Se···π chalcogen bonds. Moreover, molecular electrostatic potential (MEP) surfaces were used to investigate the electron-rich and poor regions of the ion pairs. The quantum theory of atoms-in-molecules (QTAIM) and the noncovalent interaction (NCI) plot methods based on the topology of the electron density were used and combined to characterize the ChBs. The investigation reported herein disclosed that the formation of symmetrical dimers can be broken by the introduction of a stronger π-acceptor and, consequently, forming stronger Se···π contacts with selenodiazolium cations.