Perrhenate and Pertechnetate Complexes of Dicationic Pyridinium-fused 1,2,4-Selenodiazoles Featuring Se⋯O Chalcogen Bonding and Anion⋯Anion Interactions

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 1 H and 13 C NMR 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 matere bonds.