Charge-transfer effects on the fluorescence spectra of 9-aminocamptothecin: Steady-state and time-resolved fluorescence studies

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The steady-state and time-resolved fluorescence of 9-amino-20 (S)-camptothecin (ACAM) were measured in a series of organic solvents. The molecule exhibits charge-transfer (CT) fluorescence in nonhydrogen-bonding polar solvents. The solvatochromic data have been utilized to estimate the dipole moment of the molecule in the lowest excited singlet state. The CT fluorescence of ACAM is quenched in polar and hydrogen-bonding solvents. The fluorescence quenching of ACAM by methanol, water, and 2,2,2-trifluoroethanol were studied in 1,4-dioxane. The quenching efficiency is linearly related to hydrogen bond-donating capacity of the quencher molecule. Semiempirical AM1 molecular orbital calculations have been performed to calculate excitation energies, oscillator strengths, and ground and excited-state dipole moments of ACAM as well of the parent drug, camptothecin. © 1998 Elsevier Science S.A. All rights reserved.

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Journal of Photochemistry and Photobiology A: Chemistry

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