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 napht hospirooxazine moieties linked through an ethenic double bond has been stud ied. The photochemical and thermal evolution of this molecule and its model compound, a naphthospirooxazine linked by a double bond to a 2-methoxy-nap hthalene group, was followed spectrophotometrically and by HPL chromatograp hy. 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 p reviously 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 photore action mechanism is proposed implying the photocyclisation at the ethenic d ouble bond level. (C) 2001 Elsevier Science B.V. All rights reserved.