Synthesis and Applications of 5-Membered Chalcogen-Nitrogen π-Heterocycles with Three Heteroatoms

The recent progress in the synthesis of the title heterocycles exemplified by closed- and open-shell 1,2,5-chalcogenadiazoles, 1,2,3-dichalcogenazoles and their hybrids (chalcogens: S, Se, and Te), and in actual or potential applications of these compounds in materials science and biomedicine, is discussed. The synthetic importance of the chalcogen exchange, both direct and indirect, is emphasized, as well as the significance of the heavier chalcogen derivatives in the design and synthesis of smart molecular materials.