Quantum yields of the photochromic reactions of heterocyclic fulgides and fulgimides

Quantum yields of photocyclization of a fulgide 1a and its corresponding fulgimide 1b upon irradiation with ultraviolet light, and of the back decoloration reaction of the cyclic product 3 on irradiation with visible light, were determined in different solvents and in polymer matrices. The isomerization of the (Z)-isomers to the (E)-isomers is very sensitive to the glass transition temperature Tg of the matrix, especially in the case of copolymers of N-styrylfulgimides 1c with styrene where the photochrome is linked to the polymer chain.