BIPHOTOCHROMIC NORBORNADIENE SYSTEMS

Novel biphotochromic systems containing two norbornadiene moieties in one molecule or one norbornadienyl group in adiene-2-carbonyl)]-N-aryl aminomethylene-(2H)benzo have been prepared. Under UV/VIS irradiation the latter compounds undergo Z/E-isomerization acompanied by N --> O a cyl rearrangement and valence isomerization in the norbornadiene fragm ent. Bis-norbornadienyl derivatives upon irradiation convert through s tepwise isomerization into corresponding quadricyclanes. The back reac tions are catalyzed with trifluoroacetic acid at room temperature.