Novel modified spirooxazines (SOs) with additional chelating groups were synthesised and the crystal
structure of one of these was determined. UV–vis spectroscopic characterization of the photoisomerization
of the SO derivatives shows that the photochromic behaviour is altered with Zn2+ coordination. In
particular, addition of a group as in carboxylic acid 5 to the indole section of the SO increases the lifetime
of the merocyanine Zn 2+ complex by 20-fold compared to the methylated indole 6.