Summary.
Steady state quenching studies of curcumin, 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, fluorescence by hydrogen peroxide were conducted in acetonitrile solution. A quenching rate constant, k q, of 1.05 × 1010 M −1 · s−1 was obtained with a short fluorescence lifetime of 347 ps. The reaction rate constant, which is within the diffusion-limited regime, is activation-controlled. The rate constant of deactivation of the thermally excited curcumin was 1.2 orders of magnitude more nonradiative (2.67 × 109 s−1) than radiative (2.16 × 108 s−1). The reaction was exothermic with a ΔG° of −1.97 eV and solvent reorganization energy of 1.37 eV. These values indicate that the electron transfer reaction is solvent-mediated with electron transfer rate constant, k ET, of 2.16 × 1010 s−1.
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Iwunze, M. Fluorescence Quenching Studies of Curcumin by Hydrogen Peroxide in Acetonitrile Solution. Monatshefte für Chemie 135, 231–240 (2004). https://doi.org/10.1007/s00706-003-0112-3
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DOI: https://doi.org/10.1007/s00706-003-0112-3