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Time Resolved Resonance Raman Study of the Rate of Separation of a Geminate Ion Pair into Free Ions in a Medium Polarity Solvent

Published inJournal of the American Chemical Society, vol. 116, no. 20, p. 9182-9186
Publication date1994
Abstract

The rate of separation into free ions of a geminate ion pair generated by photoinduced electron transfer between 9,lO-anthraquinone excited to the lowest triplet state and 1,2,4-trimethoxybenzenein 1,1,2,2-tetrachloroethane has been measured at different temperatures by nanosecond time-resolved resonance Raman spectroscopy (TR3). The intrinsic activation energy for the separation amounts to 0.04 eV, suggesting that the center-to-center interionic distance in the geminate ion pair is about 7.5 A. The activation barrier is due to a loss of electrostatic stabilization upon separation to a distance of about 9.5 A, where a solvent molecule or part of it can interpenetrate to increase the solvation energy. This suggests that the geminate ion pair is a loose ion pair but is not truly solvent separated.

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VAUTHEY, Eric et al. Time Resolved Resonance Raman Study of the Rate of Separation of a Geminate Ion Pair into Free Ions in a Medium Polarity Solvent. In: Journal of the American Chemical Society, 1994, vol. 116, n° 20, p. 9182–9186. doi: 10.1021/ja00099a037
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ISSN of the journal0002-7863
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