Crowned spironaphthoxazine

Complexation of alkali metal ions by the crowned spironaphthoxazine allowed the spironaphthoxazine skeleton to isomerize to its corresponding open colored form, even under dark conditions. Specifically, lithium cation complexation stabilized the open form owing to the intramolecular interaction between its oxo group and the crown-complexed cation (Scheme 1). 

K. Kimura, T. Yamashita, M. Kaneshige, and M. Yokoyama, Crowned spironaphthoxazine lithium ion-selective coloration and ion-regulated thermal stability of its colored form, J. Chem. Soc., Commun., 1992, 969-971. 

K. Kimura, M. Kaneshige, T. Yamashita, and M. Yokoyama, Cation complexation, photochromism, and reversible ion-conducting control of crowned spironaphthoxazine, 7. Org. Chem. 59, 1251— 1256 (1994). 

For the spironaphthoxazines conjugated with aza-15(18)-crown-5(6)-ether moieties at 6 -position of naphthalene fragment (13a,b) it was found that the addition of Li+ and alkaline earth (Mg2+, Ca2+, Sr2 and Ba2+) metal cations to 13a,b solutions results in a hypsochromic shift of the UV absorption band of the spiro form and a bathochromic shift of the absorption band of the merocyanine form in the visible region [36], In addition, the equilibrium shifts to the merocyanine form, and the lifetime of the photoinduced merocyanine form increases (Scheme 15). The isomerization of crown-containing compound 13a,b to the colored merocyanine form was promoted most strongly by the presence of metal ions, which are expected to be the best recognized by the crown ether ring (Scheme 15). 

Fedorova, O.A., Gromov, S.P., Strokach, Yu.P., Pershina, Yu.V., Sergeev, S.A., Barachevsky, V.A., Pepe, G., Samat, A., Guglielmetti, R., Alfimov, M.V. (1999) Crown-containing spironaphthoxazines and spiropyrans. 1. Synthesis and anion- capped complexes of photochromic aza-15-crown-5 ethers with flexible... 

Spironaphthoxazine with a crown ether, 8, also shows photochromic behavior that is sensitive to the type of alkali and alkaline earth metal ions [14]. Other derivatives of spiropyran and spiro oxazine, 9-12, which can chelate metal ions were synthesized, and the effects of complexation on their photochromic behavior have been investigated [15-17]. 

A spironaphthoxazine derivative incorporating a monoaza-12-crown-4 entity at the 5 -position has been prepared by Kimura el al.19 It is a light-resistant, cation-complexable photochromic compound. 

M. Inouye, M. Ueno, K. Tuschiya, N. Nakayama, T. Konishi, and T. Kitao, Alkali-metal cation recognition induced isomerization of spirobenzopyrans and spironaphthoxazines possessing a crown ring as a recognition site Multifunctional artificial receptors, 7. Org. Chem. 57, 5377— 5383 (1992). 

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