9-Aryl-phenalenones: Bioinspired thermally reversible photochromic compounds for photoswitching applications in the pico-to milliseconds range

Ultrafast photochromic molecules are being actively investigated to meet the demand for fast optical switching systems. Inspired on irreversible cyclization of 9-phenylphenalenone plant metabolites yield highly-coloured naphthoxanthenes purpose defense against pathogens, aryl-substituted phenalenones have been developed that undergo a similar but reversible reaction. The lifetime naphthoxanthene photoisomer spans nine orders magnitude, ranging from tens picoseconds milliseconds depending electronic properties 9-aryl group.