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Passage from Stepwise to Concerted Dissociative Electron Transfer through Modulation of Electronic States Coupling
Author(s) -
Costentin Cyrille,
Donati Ludovic,
Robert Marc
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200801240
Subject(s) - electron transfer , chemistry , diabatic , photochemistry , fragmentation (computing) , ion , chloride , bond cleavage , electrochemistry , electron capture , dissociation (chemistry) , concerted reaction , catalysis , electrode , organic chemistry , thermodynamics , physics , computer science , adiabatic process , operating system
Reductive cleavage of the three cyanobenzyl chloride isomers in N , N ‐dimethylformamide gives new insights into the factors that control the mechanism during dissociative electron transfer. Within the family of investigated compounds, electrochemical reduction leads to expulsion of the chloride ion. While electron transfer is concerted with breaking of the CCl bond and acts as the rate‐determining step in the case of both the ortho and para isomers, an intermediate anion radical is formed before rapid fragmentation in the case of the meta isomer. Such an unexpected mechanistic shift (all key thermodynamic parameters are very similar for the three chlorides) is interpreted in the framework of a modified version of the dissociative electron‐transfer model that includes electronic coupling effects between the diabatic states of the products. These effects appear to control the very existence of a transient species along the reaction pathway.