Synthesis and unexpected photochemical behaviour of biphotochromic systemsinvolving spirooxazines and naphthopyrans linked by an ethylenic bridge

Using the Wittig reaction, six new biphotochromic compounds have been prepa red by the coupling of conveniently functionalised spiro[indoline-naphthoxa zines] and naphthopyrans. Compared to molecules taken individually, unusual photochromic behaviour has been detected with compounds for which a double bond of Z-configuration links both entities by the 5 or 5 ' positions of t he naphthalenic parts. Indeed, in this case the thermally stable uncoloured and coloured forms (bistable system) can be photochemically converted acti ng as photochemical switches. (C) 2001 Elsevier Science Ltd. All rights res erved.