Photokinetic behaviour of biphotochromic supramolecular systems Part 1.: A bis-spirooxazine with a (Z)ethenic bridge between each moiety

The photochromic behaviour of a bichromophoric molecule formed by two naphthospirooxazine moieties linked through an ethenic double bond has been studied. The photochemical and thermal evolution of this molecule and its model compound, a naphthospirooxazine linked by a double bond to a 2-methoxy-naphthalene group, was followed spectrophotometrically and by HPL chromatography. Photocoloration occurred with fairly high quantum yield (phi similar to 0.2) for both molecules. Identification of the photoproducts was helped by information from a parallel NMR study and by comparison with the results previously obtained on related monochromophoric compounds. The photoreaction was thermally irreversible at room temperature while a slow photobleaching (phi similar to 10(-3)) accompanied by degradation was observed. A photoreaction mechanism is proposed implying the photocyclisation at the ethenic double bond level. (C) 2001 Elsevier Science B.V. All rights reserved.