Studies of polyphotochromic behaviour of supermolecules by NMR spectroscopy. Part 1. A bis-spirooxazine with a (Z)-ethenic bridge between each moiety

Abstract

The photoproducts resulting from the irradiation of a closed colourless biphotochromic molecule formed by two spironaphthoxazine entities linked through an ethenic bridge and its model compound, a singular spironaphthoxazine joined by a double bond to a 2-methoxynaphthalene nucleus in the Z configuration have been studied by high resolution ¹H NMR spectroscopy. At low temperature, a clean conversion between closed and open structures has been observed with the demonstration of mono and bi opening of the biphotochromic molecule. In contrast, studies at ambient temperature have implied an irreversible loss of the photochromic properties, with the formation of diastereoisomers, resulting from the cyclisation–oxidation reaction of the systems. But, by carrying out experiments on degassed samples, a significant reversion to closed initial structures was observed.