Abstract

The fluorescence quenching of 6-hydroxy-1,4-dimethylcarbazole (HDC) and α-tocopherol or vitamin E (α-toc) by methylene bromide (CH 2Br 2) in n-butanol was investigated by both stationary and time-dependence measurements. Nonlinear Stern-Volmer behavior was observed in both cases at higher quencher concentrations for these highly exothermic electron transfer (ET) intermolecular reactions. Both static and dynamic quenching models can fit the experimental data, but only the finite sink approximation model was able to recover both the mutual diffusion coefficient and the distance-averaged ‘activation energy controlled’ rate constant ( K a). The two ET reactions investigated are diffusion-controlled (α-toc) ( K a ⪢ K d) and diffusion-influenced (HDC) ( k a $ ̄ k d ) respectively.

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