Fused 1,2,5-thia- and 1,2,5-selenadiazoles: Synthesis and application in materials chemistry

• Recent advances in synthesis of fused 1,2,5-thia- and -selenadiazoles are summarized. • Chalcogen exchange in 1,2,5-chalcogenadiazoles is emphasized. • Functionalization of fused 1,2,5-chalcogenadiazoles by cross-coupling reactions. • Important applications of fused 1,2,5-chalcogenadiazoles for organic photovoltaics. The existing or potential applications of fused 1,2,5-thia- and -selenadiazoles in material science predetermined the quickly growing interest in these heterocyclic systems. This digest summarizes the recent progress in synthetic approaches, functionalization and employment of smart molecular materials based on these heterocycles. New starting materials as well as unknown and unexpected procedures, including direct chalcogen exchange in 1,2,5-chalcogenadiazole rings, are reviewed. The functionalization of fused 1,2,5-thia- and -selenadiazoles by cross-coupling reactions, nucleophilic substitution by the Buchwald-Hartwig strategy and co-polymerization are emphasized. Important applications, especially in the field of organic photovoltaics, are considered.