Stable N- and N/S-Rich Heterocyclic Radicals

Over the last few decades the number of stable heterocyclic neutral radicals has dramatically increased. There have been significant efforts to use these unusual open-shell compounds in a broad array of applications that include use as reagents in synthesis, spin active probes in analysis, polymerization initiators, redox active ligands, and in the material sciences for their potential use in electronic devices. In this brief review, which covers the period since 2000, we survey advances in heterocyclic neutral organic radicals that contain either an endocyclic hydrazyl or thiazyl unit. Emphasis is on new synthetic methods, physical properties, and applications.