Fundamental Research on Chemi-and Bioluminescence for High-Efficiency Light Emission

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In the chemiluminescence and bioluminescence, the light emission is brought out from an excited state of carbonyl compounds formed by thermal decomposition of unstable intermediates, such as dioxetanes in the former and dioxetanones in the latter, respectively. The mechanism of the thermal decomposition to give an excited state of carbonyl compounds is still unclear, because the concerted way leads to a triplet state which gives only weak emission. Schuster reported CIEEL mechanism which contains intramolecular electron transfer, but recently the idea was found not to explain some experimental facts.In this research the oxygenation mechanism of chemi-and bio-luminescent compounds and thermal decomposition mechanism of dioxetanes were investigated. The results obtained are as follows : The oxygenation of imidazopyrazinone which is a main part of luciferins was carried out, and the structure of the dioxetanone was determined. Various derivatives of lophine (2,4,5-triphenylimidazol) were prepared and a structural condition which has very high quantum yield (0.8) was found, and involvement of the intramolecular electron transfer was suggested. Compounds which have electron rich olefinic structure, for example the reduced species of biisoquinolinium salts were found to react with molecular oxygen and/or superoxide. For newly prepared 3-aryl dioxetanes which decompose at room temperature to give emission, the conformation of the aryl group to the dioxetane ring was shown to have strong effect on the emission intensity and on the stability of the dioxetanes.