FLUORESCENCE CHARACTERISTICS OF INDOLES IN NON-POLAR SOLVENTS: LIFETIMES, QUANTUM YIELDS AND POLARIZATION SPECTRA

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Abstract

Abstract— Fluorescence lifetimes, quantum yields and polarization spectra were measured for indole, 3-methylindole and 2,3-dimethylindole in non-polar solvents. The results indicate simultaneous emission from thermally equilibrated 1La and 1Lb levels, with 1La1A dominating the 2,3-dimethylindole emission, and 1Lb1A dominating the indole emission. These results are consistent with previous assignments of the 0-0 transitions in absorption for these compounds. Radiative rates are: 1La1A, 2·0 × 108 S-1 and 1Lb1A. 0·62 → 108 S-1. In addition, the temperature dependence of the excitation and emission spectra are presented, which show that aggregation occurs with these indoles in hydrocarbons below approximately - 110°C. Possible applications to tryptophyl emission in the hydrophobic interiors of proteins are briefly discussed.

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