- New Reagents for the Syntheses of Fluorescent Chemosensors. Anthrylogous Ethylene Dibromides
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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.
- Chae, Mi-Young,Cherian, Xavier M.,Czarnik, Anthony W.
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- Photochemical "Across-a-Ridge" Z-E Isomerization of (Ethenyl-2-d)anthracenes in the Triplet State
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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.
- Karatsu, Takashi,Misawa, Hiroaki,Nojiri, Mikiko,Nakahigashi, Naoko,Watanabe, Seiichi,et al.
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p. 508 - 512
(2007/10/02)
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