Chemical reactions of 8-quinolinol derivatives and their applications to biochemical tools and enzyme inhibitors

8-Quinolinol (8-hydroxyquioline, 8HQ) attracts much attention in material sciences and biorelated sciences, because of their simple structures, strong metal coordination properties, fluorescence properties, and extensive possibility of functionalization. In this review, five applications of 8HQ are described. The first application is 8HQ-linked macrocyclic tetraamines as fluorescent probes of zinc ions in living cell. The second and third sections provide the applications of 8HQ to inhibitors against dinuclear zinc hydrolase and to radioprotectors that can inhibit apoptosis of radiosensitive normal cells during radiotherapy. In the third section, finding of photochemical S-O bond cleavage reaction of 8HQ sulfonates (8HQS) under aqueous conditions, its mechanistic analysis and applications to photocleavable chemical linkers are described. Finally, the photophysical properties of iridium (III) complexes having 8HQ or its analogs will be presented. This knowledge will be useful in design and synthesis of useful molecules containing 8HQ units, in bioorganic chemistry, chemical biology, pharmaceutical science, material science, and other related scientific fields.