Perrhenate and pertechnetate complexes of dicationic pyridinium-fused 1,2,4-selenodiazoles featuring Se⋯O chalcogen bonding and anion⋯anion interactions

Abstract

Coupling between 2-pyridylselenyl chloride and various cyanopyridinium salts resulted in the formation of dicationic pyridinium-fused 1,2,4-selenodiazoles. Novel bicyclic heterocycles are highly soluble in water and readily precipitate pertechnetate and perrhenate anions from aqueous media. All the novel compounds were comprehensively characterized using 1H and 13CNMR techniques, ESI-MS, and X-ray diffraction analysis (for eight compounds). Theoretical calculations have shown the intricate nature of chalcogen bonding (ChBs) and anion-π interactions across a series of compounds, each exhibiting unique bonding patterns and interaction energies. Compounds [1]H(ReO4)2, [2]H(ReO4)2, [3](ReO4), [2]H(TcO4)2 and [3](TcO4) displayed complex assemblies, highlighting the role of ion-pair interactions, bifurcated ChBs, and directional mater bonds.