CATION COMPLEXATION, PHOTOCHROMISM, AND REVERSIBLE ION-CONDUCTING CONTROL OF CROWNED SPIRONAPHTHOXAZINE

A spironaphthoxazine derivative incorporating a monaza-12-crown-4 moie ty at the 5'-position has been designed as a light-resistant, cation-c omplexable photochromic compound. Complexation of alkali metal ions by the crown moiety in the crowned spironaphthoxazine allows the spirona phthoxazine skeleton to isomerize to its corresponding open colored fo rm, even under dark conditions. Specifically, Li+ complexation greatly stabilizes the open colored form due to the intramolecular interactio n between its oxo group and crown-complexed cation, as well as the sel ective Li+ complexation of its 12-crown-4 moiety. Taking advantage of the high Li+ selectivity in the cation-induced isomerization of crowne d spironaphthoxazine, the thermal stability of the open colored form c an be modulated continuously by added Li+ concentrations. Even in the presence of the metal ion, UV- and visible-light irradiation led to fu rther isomerization to the open form and back-isomerization to the ini tial closed form, respectively. Photoisomerization of crowned spironap hthoxazine to its open form promoted Li+ binding due to the additional axial interaction with the crown-complexed Li+, while that back to th e closed form attenuated the cation binding. The photoinduced change i n the cation-binding ability of crowned spironaphthoxazine, which poss esses high light-fatigue resistance, has led to a highly reversible, p hotochemical switching system of ionic conduction.