Thermodynamics and kinetics of proton-coupled electron transfer: stepwise vs. concerted pathways

被引:182
作者
Mayer, JM [1 ]
Rhile, IJ [1 ]
机构
[1] Univ Washington, Dept Chem, Seattle, WA 98195 USA
来源
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS | 2004年 / 1655卷 / 1-3期
关键词
proton-coupled electron transfer; hydrogen atom transfer; electron transfer; proton transfer; Marcus theory; iron;
D O I
10.1016/j.bbabio.2003.07.002
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Reactions that involve transfer of an electron and a proton can proceed by stepwise pathways involving initial electron transfer (ET) or initial proton transfer (PT), or by a concerted pathway without an intermediate. The concerted mechanism is termed proton-coupled electron transfer (PCET). Understanding such reactions requires knowledge of the thermodynamics of the possible ET, PT, and PCET steps. Many reactions have a large thermochemical bias favoring the PCET pathway. This bias is often sufficient to rule out stepwise mechanisms. The DeltaGdegrees for ET, PT or PCET has a strong influence on the rate of that step. Using the terminology of Marcus theory, PT and PCET reactions at C-H bonds have higher intrinsic barriers than such reactions at O-H or N-H bonds. The intrinsic barriers to ET and PCET are often similar when there is a small intrinsic barrier to PT. Reactions with a thermochemical bias toward PCET and with similar intrinsic barriers for all the pathways are most likely to occur by concerted PCET. (C) 2004 Elsevier B.V. All rights reserved.
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页码:51 / 58
页数:8
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