'Ship-in-a-bottle' synthesis and photochromism of spiropyrans encapsulatedwithin zeolite Y supercages

The ship-in-a-bottle synthesis of three spiropyrans inside the NaY supercag es was carried out by the condensation of 2-methylene-1,3,3-trimethylindoli ne with the appropriate substituted benzaldehyde. After the reaction, spiro pyrans were detected in the supernatant and the zeolites became coloured. C ombustion chemical and thermogravimetric analyses confirmed the presence of organic material within the solid. UV-Vis and Raman spectroscopies are com patible with the formation of the merocyanine form of the spiropyran photoc hromic system. Upon visible irradiation the solids bleach, and in some case s the coloration is regained upon standing in the dark for long periods. Th is abnormal photochromic behaviour is the reverse of that observed for the spiropyran/merocyanine system in ethanol and illustrates the possibility of zeolites as media to alter the molecular properties of incorporated guests . (C) 2000 Elsevier Science Ltd. All rights reserved.