Cationic merocyanine dyes by photomodulation of [4-(naphthopyran-3-yl) phenyl ]methines

摘要

A series of mono-, bis- and tris-4-(naphthopyran-3-yl)phenyl substituted methanols were efficiently syrithesised using a 4-(naphthopyran-3-yl)phenyllithium intermediate. The resulting substituted methanols displayed good photochromism leading to the reversible generation of red—orange photo-merocyanines. Acidic dehydration of the methanols gave intensely coloured cations which, upon subsequent UV irradiation, reversibly generated cationic photomerocyanines with long wavelength absorption maxima at ca. 640 nm.