Characterization of proton coupled electron transfer in a biomimetic oxomanganese complex: Evaluation of the DFT B3LYP level of theory.
Characterization of proton coupled electron transfer in a biomimetic oxomanganese complex: Evaluation of the DFT B3LYP level of theory.
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DOI：
10.1021/ct900615b
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发表时间：
2010-01-29
影响因子：
5.5
通讯作者：
Batista, Victor S.
中科院分区：
文献类型：
--
作者：
Wang, Ting;Brudvig, Gary;Batista, Victor S.
分析了B3 LYP密度泛函理论（DFT）模拟混合价氧锰配合物1 [（bpy）2 MnIII（μ-O）2 MnIV（bpy）2]3+（bpy = 2，2 '-bipyridine）质子耦合电子转移（PCET）的能力和局限性.复合物1作为一个原型的合成模型的氧化还原过程的研究类似于那些负责在光系统II（PSII）的放氧复合物（OEC）的水氧化。DFT B3 LYP自由能计算的氧化还原电位和pKa的根据热力学循环形式主义与连续溶剂化模型相结合。我们发现，氧代配体的pKa强烈依赖于复合物的氧化态，改变约10个pH单位（即，从pH~2到pH~12）。这些计算结果与通过溶液磁化率和近红外光谱测定的实验pKa以及通过循环伏安测量报告的氧化还原电位的pH依赖性一致，表明络合物1的III，IV→III，III还原与二-μ-氧代桥的质子化耦合如下：[（bpy）2MnIII（μ-O）2 MnIV（bpy）2]3++H++e−→[（bpy）2MnIII（μ-O）（μ-OH）MnIII（bpy）2]3+.因此，很自然地期望类似的氧化还原过程可能强烈地调节PSII的OEC中的氧代和羟基/水配体的pKa，导致OEC在氧化态转变时的去质子化。
The capabilities and limitations of the Becke-3–Lee–Yang–Parr (B3LYP) density functional theory (DFT) for modeling proton coupled electron transfer (PCET) in the mixed-valence oxomanganese complex 1 [(bpy)2MnIII(μ-O)2MnIV(bpy)2]3+ (bpy = 2,2'-bipyridyl) are analyzed. Complex 1 serves as a prototypical synthetic model for studies of redox processes analogous to those responsible for water oxidation in the oxygen-evolving complex (OEC) of photosystem II (PSII). DFT B3LYP free energy calculations of redox potentials and pKa's are obtained according to the thermodynamic cycle formalism applied in conjunction with a continuum solvation model. We find that the pKa's of the oxo-ligands depend strongly on the oxidation states of the complex, changing by approximately 10 pH units (i.e., from pH~2 to pH~12) upon III,IV→III,III reduction of complex 1. These computational results are consistent with the experimental pKa's determined by solution magnetic susceptibility and near-IR spectroscopy as well as with the pH dependence of the redox potential reported by cyclic voltammogram measurements, suggesting that the III,IV→III,III reduction of complex 1 is coupled to protonation of the di-μ-oxo bridge as follows: [(bpy)2MnIII(μ-O)2 MnIV(bpy)2]3++H++e−→[(bpy)2MnIII(μ-O)(μ-OH)MnIII(bpy)2]3+. It is thus natural to expect that analogous redox processes might strongly modulate the pKa's of oxo and hydroxo/water ligands in the OEC of PSII, leading to deprotonation of the OEC upon oxidation state transitions.
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影响因子：
--
作者：
Marten, B;Kim, K;Honig, B
通讯作者：
Honig, B
影响因子：
4.4
作者：
BECKE, AD
通讯作者：
BECKE, AD
影响因子：
15
作者：
COOPER, SR;CALVIN, M
通讯作者：
CALVIN, M
影响因子：
15
作者：
McNamara, William R.;Snoeberger, Robert C.;Batista, Victor S.
通讯作者：
Batista, Victor S.
影响因子：
32.5
作者：
Li, Gonghu;Sproviero, Eduardo M.;Batista, Victor S.
通讯作者：
Batista, Victor S.