Solvent reorganization energy in excited-state electron-transfer reactions. Quenching and geminate-pair back electron transfer
Journal Article
·
· Journal of Physical Chemistry
- Boston Univ., MA (United States)
The temperature dependencies of the quenching rate constants (k{sub q}) and cage escape yields of the redox products ({eta}{sub ce}) from the electron-transfer reaction of {sup *}Ru(bpy){sub 3}{sup 2+} (bpy = 2,2`-bipyridine) with nine aromatic amines in deaerated 1:1 (v/v) CH{sub 3}CN/H{sub 2}O solutions have been determined. Values of {lambda}, the solvent reorganization energy for electron-transfer quenching and back electron transfer within the solvent cage, have been extracted from plots of log(k{sub q}T{sup 1/2}) vs 1/T and log(({eta}{sub ce}{sup -1}-1)T{sup 1/2}) vs 1/T, respectively. For the quenching process, {lambda} is not a constant value for the series of quenchers; in general, higher values of {lambda} are exhibited by primary amines and lower values by tertiary amines. The structure and size of the quenchers and the nature of the ring substituents contribute to the value of {lambda}. For the back-electron-transfer reaction within the geminate redox pair formed in the quenching process, the more sterically hindered two-ring amines exhibit a higher value of {lambda} (1.1{+-}0.08 eV) than do the majority of the one-ring amines (0.82{+-}0.04 eV). A Marcus plot of log({eta}{sub ce}{sup -1} -1) vs {Delta}G{degree}{sub bt} shows a correlation within only the inverted region for systems with the same {lambda}. 46 refs., 5 figs., 1 tab.
- OSTI ID:
- 380771
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 35 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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