✍ Scribed by David A. Shultz; Marye Anne Fox
No coin nor oath required. For personal study only.
The syntheses and fluorescence emission spectra of a series of bis-[n.l]-metacyclophanenylidenes u: n=4; 2: n=5; 2 n=6) are discussed. The photophysical properties of 1-2 am compared to a model compound, tetrakis-btolyl)-ethylene, 4. excited singlet. Varying the degree of phenyl ring torsional freedom drastically alters the fate of the arylethylene Compound 1 exhibits strong fluorescence at room temperature (0f = 0.43), while 2 and 2, though over ten times less fluorescent (Cat-Q) = O.O3,0f a)= O.Ol), are still at least ten times more fluorescent than 4 (0f < 0.001). These results are suggestive of the importance of phenyl ring torsional motion in the nonradiative decay of the excited singlet state. The light-induced ring closure, typical of arylethylenes, is attenuated in 1-9.
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