Return electron transfer within geminate radical ion pairs. Observation of the Marcus inverted region

1987 ◽  
Vol 109 (12) ◽  
pp. 3794-3796 ◽  
Author(s):  
Ian R. Gould ◽  
Deniz Ege ◽  
Susan L. Mattes ◽  
Samir Farid
Keyword(s):  
Electron Transfer ◽  
Ion Pairs ◽  
Inverted Region ◽  
Marcus Inverted Region

scholarly journals Concerted proton-electron transfer reactions in the Marcus inverted region

Science ◽  
2019 ◽  
Vol 364 (6439) ◽  
pp. 471-475 ◽  
Author(s):  
Giovanny A. Parada ◽  
Zachary K. Goldsmith ◽  
Scott Kolmar ◽  
Belinda Pettersson Rimgard ◽  
Brandon Q. Mercado ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Rate Constants ◽  
Charge Recombination ◽  
Transfer Reactions ◽  
Inverted Region ◽  
Electron Transfer Reactions ◽  
Proton Coupled Electron Transfer ◽  
Marcus Inverted Region ◽  
A Charge ◽  
Theory Yield

Electron transfer reactions slow down when they become very thermodynamically favorable, a counterintuitive interplay of kinetics and thermodynamics termed the inverted region in Marcus theory. Here we report inverted region behavior for proton-coupled electron transfer (PCET). Photochemical studies of anthracene-phenol-pyridine triads give rate constants for PCET charge recombination that are slower for the more thermodynamically favorable reactions. Photoexcitation forms an anthracene excited state that undergoes PCET to create a charge-separated state. The rate constants for return charge recombination show an inverted dependence on the driving force upon changing pyridine substituents and the solvent. Calculations using vibronically nonadiabatic PCET theory yield rate constants for simultaneous tunneling of the electron and proton that account for the results.

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