Hyperfine coupling to the bridging (17)O in the di-mu-oxo core of a Mn(III)-Mn(IV) model significant to the core electronic structure of the O(2)-evolving complex in photosystem II.
Hyperfine coupling to the bridging (17)O in the di-mu-oxo core of a Mn(III)-Mn(IV) model significant to the core electronic structure of the O(2)-evolving complex in photosystem II.
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与 Mn(III)-Mn(IV) 模型的 di-mu-oxo 核心中的桥接 (17)O 的超精细耦合对于光系统 II 中 O(2) 演化复合物的核心电子结构具有重要意义。
DOI：
10.1021/ja073179n
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发表时间：
2007
影响因子：
15
通讯作者：
Scholes,CharlesP
中科院分区：
文献类型：
--
作者：
Usov,OlegM;Grigoryants,VladimirM;Tagore,Ranitendranath;Brudvig,GaryW;Scholes,CharlesP
Di-μ-oxo MnIII−MnIV二聚体是绿色植物放氧中心耦合混价锰的模型。使用最近报道的将水氧交换到di-μ-oxo交叉桥中的方法(泰戈尔，R.；陈，H.；克拉布特里，R.H.；Brudvig，G.W.J.Am。化学。Soc.2006,128,9457−9465)，我们用电子顺磁共振和电子核双共振研究了氧电子-自旋超精细耦合。我们将17O引入到了MnIIIμ-−联吡啶二聚体的氧-氧交叉桥上。恩多尔证据是12.8±1.0兆赫兹的di-μ-oxo17O超精细耦合。当通过与H_217O(I=5/2)交换交联桥氧制备二聚体时，与H_216O(I=0)交换的二聚体的窄而高分辨的EPR特征被加宽。由17O引起的电子顺磁共振展宽由一个模型定量地再现，其中二聚体具有两个等价的二μ-氧代交叉桥联的17Ο，并且17O的超精细耦合与Endor的结果高度一致。这项工作明确地指出了共价自旋转移到交叉桥联的二μ-氧杂氧上的证据，这些氧提供了混合价锰中心之间的化学键和反铁磁耦合。
Di-μ-oxo MnIII−MnIVdimers are models for coupled, mixed-valence manganese in the oxygen-evolving centers of green plants. Using a recently reported method of exchanging water oxygen into the di-μ-oxo cross-bridges (Tagore, R.; Chen, H.; Crabtree, R. H.; Brudvig, G. W.J.Am. Chem. Soc.2006,128, 9457−9465), we have incorporated17O into the μ-oxo cross bridges of the MnIII−MnIVbipyridyl dimer for study of oxygen electron-spin hyperfine couplings by electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR). The ENDOR evidence was for a di-μ-oxo17O hyperfine coupling of 12.8 ± 1.0 MHz. Narrow and highly resolved EPR features from dimers exchanged with H216O (I= 0) became broadened when the dimer was prepared by exchanging the cross bridging oxygens with H217O (I=5/2). The EPR broadening due to17O was quantitatively reproduced by a model where the dimer has two equivalent di-μ-oxo cross-bridging17Ο, and the17O hyperfine coupling was highly consistent with that determined by ENDOR. This work explicitly points out evidence for covalent spin transfer to the cross-bridging di-μ-oxo oxygens which provide chemical bonds and antiferromagentic coupling between the mixed-valence manganese centers.