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Free‐energy correlation for catalysis of outer sphere electron‐transfer reactions by noncoordinated pyridine derivatives
Author(s) -
Fanchiang YuehTai
Publication year - 1982
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550141203
Subject(s) - chemistry , pyridine , electron transfer , marcus theory , reaction rate constant , diquat , outer sphere electron transfer , paraquat , photochemistry , atomic orbital , molecule , computational chemistry , molecular orbital , electron , ion , medicinal chemistry , organic chemistry , kinetics , quantum mechanics , physics
Recent experimental data concerning the rate constants and their free energy of the outer sphere electron‐transfer reactions, as catalyzed by noncoordinated pyridine derivatives in aqueous solution, are examined for possible correlation. For the electron transfer reactions between V aq 2+or Eu aq 2+and the bipyridyl derivatives, such as N , N '‐dimethyl‐4,4′‐bipyridyl (paraquat) or diquat, the data are correlated quite well by the Marcus equation. The electron exchange rate constant, 5 × 10 7 M −1 ·s −1 , for an organic radical ion and its parent molecule obtained from semiquinones or their related compounds can be applied to these pyridine derivatives. However, in some cases such as electron transfer from paraquat or diquat cation radical to Co(en) 3 3+ , positive departures from the Marcus model are observed. These positive departures are interpreted in terms of interaction between the molecular orbitals of electron donors and electron acceptors in the transition state.