Va. Bren et al., BIPHOTOCHROMIC NORBORNADIENE SYSTEMS, Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystals, 297, 1997, pp. 247-253
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.