Crowned spirooxazines

The formation of the merocyanine form 119 can be induced by addition of heavy metal cations (Pb, La, Eu, Tb ) to a solution of a spirooxazine 118 containing a crown ether group in the B-ring (Equation 1). The chelation occurs first to the crown ether and then to the negatively charged oxygen. In contrast, 118 does not react upon addition of alkaline earth metal cations (Mg, Ca, Ba ) <2005JP0504>. 

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 spirooxazine, 9-12, which can chelate metal ions were synthesized, and the effects of complexation on their photochromic behavior have been investigated [15-17]. 

Figure 50 (a) Structures of aza-crown ethers and thiacrown ethers containing spirop3rans, spirooxazines, and spirothiopyrans. 

Extension of this work to other aza-crown ethers and thiacrown ethers containing spiropyrans, spirooxazines, and spirothiopyrans (Figure 50a), based on similar design principles for the binding of different types of metal ions, has subsequently been reported. " " On the other hand, Inouye and coworkers also reported cryptand-containing... 

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