The photochromism of two spiro compounds, a spiropyran and a spirooxazine, dissolved in alcoholic solutions of metal alkoxides M(OR)(n) (M = Zr, Al) has been studied. In the case of the aluminium alkoxide Al(OsBu)(3), special photochromic behaviour is observed characteristic of complexation between the coloured form of the dyes and the aluminium, This chemical interaction induces a considerable shift in the absorption spectra and a significant retardation rate in the dark. Addition of ethyl acetoacetate, a bidentate chelate of aluminium, leads to the disappearance of this particular photochromic behaviour. (C) Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003.