Co-host: The Chemical Society of Japan, The Society of Synthetic Organic Chemistry, Japan (Cooperation)
It has been known that photo-irradiation of substituted norbornadienes leads to the one-way isomerization to highly strained quadricyclanes which undergo the reverse isomerization by electron-transfer sensitizations. Therefore, the photochemical pathways can be switched depending on the presence or absence of photosensitizers, which may be controlled by the reaction media where the sensitizers are dissolved. Such situations may be achieved with COOH-substituted norbornadienes and quadricyclanes when one of two isomers has a higher acidity and is soluble in water at an appropriate pH. Thus, the properties of such carboxylic acids were examined, and quite large difference in acidity by about 1.5 pKa unit was found for some norbornadiene and quadricyclane derivatives. Using these substances, photocontrol of interfacial mass transfer between organic and aqueous layers has been achieved, which may lead to novel flip-flop type photochromic systems.
