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 T-n <-- T-1 absorptions indicate that EADs isomerize adiabatically between the Z and E isomers in the lowest excited triplet state by overcoming an activation barrier (E(a) = 19-46 kJ mol(-1)) of the perpendicularly twisted geometry. The activation parameters of isomerization, Delta H double dagger (17-42 kJ mol(-1)) and Delta S double dagger (-40 to -113 J K-1 mol(-1)), decrease in the order of 2-, 1-, and 9-isomers; however, Delta G double dagger (50-54 kJ mol(-1)) is almost constant irrespective of the substitution position of the anthracene nucleus.
New reagents for the syntheses of fluorescent chemosensors. Anthrylogous ethylene dibromides
摘要:
Ethylene dibromide is an important building block used in the construction of crown ethers, aza macrocycles, and cryptands. We describe herein the syntheses of two new compounds that serve as anthrylogous derivatives of ethylene dibromide. Each compound can be utilized in the syntheses of fluorescent chemosensors retaining the essential binding properties of the parent ligands.