Biphotochromic and ionochromic benzoxazolyl-substituted spirobipyrans

Abstract Novel photochromic spirobipyrans bearing benzoxazole group in the 3H-naphthopyran fragment have been synthesized. Spiro-conjugated benzopyran and naphthopyran fragments cause the observed dual photochromism of the molecules. In the presence of Cd2+, Mn2+, Co2+, Ni2+, Zn2+, Cu2+ metal ions thermal isomerization of the spirobipyrans is observed, followed by the formation of the intensely coloured complexes of the merocyanine form. The long-wavelength absorption band of the complexes is located at λ>600 nm.