Chatterjee Ruchira, Milikisiyants Sergey, Lakshmi K V
Department of Chemistry and Chemical Biology and The Baruch '60 Center for Biochemical Solar Energy Research, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Phys Chem Chem Phys. 2012 May 21;14(19):7090-7. doi: 10.1039/c2cp40416h. Epub 2012 Apr 10.
We use two-dimensional hyperfine sublevel correlation (HYSCORE) spectroscopy to investigate the coordination geometry of the nitrogen ligands of biomimetic models of the oxygen-evolving complex of photosystem II. In the 2D HYSCORE spectroscopy study, (bpy)2Mn(III)(μ-O)2Mn(IV)(bpy)23 (bpy, 2,2'-bipyridine) (1) and H2O(terpy)Mn(III)(μ-O)2Mn(IV)(terpy)OH23 (terpy = 2,2':6',2″-terpyridine) (2) exhibit electron-nuclear hyperfine interactions that depend on both the oxidation state of the manganese ion and the geometry of the nitrogen ligand. We observe four types of (14)N hyperfine interactions corresponding to the Mn(iii) and Mn(iv) ion of each mixed-valence complex and the equatorial and axial geometry of the ligand, respectively. The strongest and the weakest hyperfine interactions arise from the axial and equatorial ligands of the Mn(iii) ion, respectively. The hyperfine interactions of intermediate strength are due to the axial and equatorial ligands of the Mn(iv) ion. Based on the results of this study, we assign the location and ligand geometry of the Mn(iii) ion of the tetranuclear manganese-calcium-oxo cluster in the S2 state of photosystem II.
我们使用二维超精细能级相关（HYSCORE）光谱来研究光系统II析氧复合物的仿生模型中氮配体的配位几何结构。在二维HYSCORE光谱研究中，(bpy)2Mn(III)(μ-O)2Mn(IV)(bpy)23（bpy，2,2'-联吡啶）（1）和H2O(terpy)Mn(III)(μ-O)2Mn(IV)(terpy)OH23（terpy = 2,2':6',2″-三联吡啶）（2）表现出电子-核超精细相互作用，其依赖于锰离子的氧化态和氮配体的几何结构。我们观察到四种类型的（14）N超精细相互作用，分别对应于每个混合价配合物的Mn(iii)和Mn(iv)离子以及配体的赤道和轴向几何结构。最强和最弱的超精细相互作用分别来自Mn(iii)离子的轴向和赤道配体。中等强度的超精细相互作用归因于Mn(iv)离子的轴向和赤道配体。基于这项研究的结果，我们确定了光系统II的S2态中四核锰-钙-氧簇的Mn(iii)离子的位置和配体几何结构。
