Development of Photofunctions of Open-shell Molecules Based on Coordination Chemistry

Abstract

　Stable radicals possessing open-shell electronic states exhibit vivid physical properties such as electric conductivity and magnetism attributed to unpaired electrons. Their luminescent properties, however, have been poorly investigated due to the rarity and low chemical stability in their photoexcited states. I have developed highly-photostable luminescent organic radicals as promising candidates for establishing novel photofunctions based on the doublet (or multiplet) state. I have shown that the coordination to metal ions can increase the emission quantum yield and photostability of the radicals. The absence of heavy atom effect has been suggested as a unique character of doublet-based fluorescence. These findings show that coordination chemistry is an efficient strategy to enhance, vary, or elucidate the photofunctions of radicals, and enables to extend the scope of this class of radicals toward molecular photonics.