152020-17-2Relevant articles and documents
Photochemical "Across-a-Ridge" Z-E Isomerization of (Ethenyl-2-d)anthracenes in the Triplet State
Karatsu, Takashi,Misawa, Hiroaki,Nojiri, Mikiko,Nakahigashi, Naoko,Watanabe, Seiichi,et al.
, p. 508 - 512 (1994)
Deuterated ethenylanthracenes, 1-, 2-, and 9-(ethenyl-(Z)-2-d)anthracene, and 2-(ethenyl-(E)-2-d)anthracene ((Z)-1-, 2-, and 9-EAD, and (E)-2-EAD, respectively) undergo photochemical Z-E isomerization under thermal activation.The temperature dependence of their isomerization quantum yields and the temperature independence of lifetimes of their Tn 1 absorptions indicate that EADs isomerize adiabatically between the Z and E isomers in the lowest excited triplet state by overcoming an activation barrier (Ea = 19-46 kJ mol-1) of the perpendicularly twisted geometry.The activation parameters of isomerization, ΔH (17-42 kJ mol-1) and ΔS (-40 to -113 J K-1 mol-1), decrease in the order of 2-, 1-, and 9-isomers; however, ΔG (50-54 kJ mol-1) is almost constant irrespective of the substitution position of the anthracene nucleus.
