Proton-coupled electron transfer reactions: Evaluation of rate constants
Proton-coupled electron transfer reactions: Evaluation of rate constants
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DOI：
10.1021/jp961025g
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发表时间：
1996-09-19
影响因子：
--
通讯作者：
Cukier, RI
中科院分区：
文献类型：
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作者：
Cukier, RI
最近的一个理论[Cukier， r.i.j.物理学]。化学，1995,99,16101]，预测质子耦合电子转移（PCET）反应的速率得到进一步发展。在PCET中，电子和质子可以连续转移，电子转移（ET）之后是质子转移（PT），称为ET/PT，或者它们可以在一个隧道事件中同时转移，称为ETPT。由于质子电荷以类似于电子-溶剂耦合的方式耦合到溶剂偶极子上，为了评估PCET速率常数，必须知道溶剂化对质子势能表面形状的影响。我们展示了如何使用介电连续统理论来获得质子溶剂化表面，这取决于电子是处于初始状态还是最终状态。质子将通过质子表面初始和最终电子态之间的frank - condon因子影响PCET速率。质子能级也会影响PCET工艺的活化能。在模拟电子供体-氢键界面-电子受体系统的几种模型反应配合物中，对ETPT和ET/PT通道对应的速率进行了评估。该方法首先以吡啶-吡啶氢键阳离子中的PCET为例进行了说明，其中反应络合物的对称性限制了系统参数的数量。然后，研究了脒-羧酸盐给受体配合物中的PCET，并与已有的实验数据进行了比较。最后，我们在光系统II的一部分中研究了PCET，涉及酪氨酸残基的氧化，酪氨酸残基的酚质子与组氨酸残基的氮形成氢键。
A recent theory [Cukier, R. I. J. Phys. Chem. 1995, 99, 16101] that predicts the rate of a proton-coupled electron transfer (PCET) reaction is developed further. In PCET, the electron and proton may transfer consecutively, electron transfer (ET) followed by proton transfer (PT), designated as ET/PT, or they may transfer concertedly, in one tunnel event, designated as ETPT. Since the proton charge is coupled to the solvent dipoles in a fashion similar to the electron-solvent coupling, the effect of solvation on the shape of the proton potential energy surface must be known in order to evaluate the PCET rate constant. We show how dielectric continuum theory can be used to obtain the proton-solvated surfaces that are dependent on whether the electron is in its initial or final state. The proton will affect the PCET rate via Franck-Condon factors between the proton surfaces for the initial and final electron states. The proton energy levels will also influence the activation energy for the PCET process. The rates corresponding to the ETPT and ET/PT channels are evaluated for several model reaction complexes that mimic electron donor-hydrogen-bonded interface-electron acceptor systems. The methodology is first illustrated with PCET in pyridinium-pyridine hydrogen-bonded cations, where the reaction complex symmetry restricts the number of system parameters. Then, PCET in amidinium-carboxylate donor-acceptor complexes is studied and compared with the available experimental data. Finally, we study PCET in a part of the photosystem II oxygen-evolving complex involving the oxidation of a tyrosine residue whose phenolic proton is hydrogen bonded to a nitrogen of a histidine residue.