ORGN 576 |
| Phenyl-1,2,4-thiadiazoles substituted at position 4' with either electron donating (2 & 5) or electron withdrawing (3 & 6) substituents are less photoreactive than 1 or 4 in acetonitrile (ACN) solvent. However, 2, 3, 5 and 6 are more photoreactive in cyclohexane (CH) solvent than in ACN. In ACN, the fluorescence spectra of 2, 3, 5 and 6 exhibit moderate to large Stokes' shifts which are decreased in magnitude in CH. This suggests that charge transfer is associated with the excited states of these thiadiazoles. Fluorescence in ACN is suggested to originate from non-reactive TICT excited states which exhibit large Stokes' shifts. In CH, TICT excited states would be less stabilized and the S1(p,p*) states are suggested to be of lower energy and lead to the observed photochemical reactions.
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Asymmetric Reactions, Heterocycles, Aromatics, Combinatorial, and Physical Organic Chemistry
8:00 PM-10:00 PM, Wednesday, 31 August 2005 Washington DC Convention Center -- Hall A, Poster
Division of Organic Chemistry |
