The Nature of chemical bonds of the CaMn4O5cluster in oxygen evolving complex of photosystem II. Jahn-Teller distortion and its suppression by Ca doping in cubane structures
The Nature of chemical bonds of the CaMn4O5cluster in oxygen evolving complex of photosystem II. Jahn-Teller distortion and its suppression by Ca doping in cubane structures
复制标题
光系统 II 的放氧复合物中 CaMn4O5 簇化学键的性质。
DOI：
10.1002/qua.24280
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
M. Shoji and Y. Yoshioka
中科院分区：
文献类型：
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作者：
K. Yamaguchi;S. Yamanaka;H. Isobe;T. Saito;K. Kanda;Y. Umena;K. Kawakami;J. -R. Shen;N. Kamiya;M. Okumura;H. Nakamura;M. Shoji and Y. Yoshioka
采用UB 3LYP方法对立方烷Mn（III）4-ωMn（IV）ω O 4团簇（ω = 0-4）进行了全几何优化，研究了Mn（III）离子的Jahn-Teller（JT）效应.优化后的几何构型确定了Mn（III）2 Mn（X）（X = III，IV）在立方烷中的锐角三角形结构，表明了JT效应。对于Mn（IV）2 Mn（III）核，JT效应不明显，呈钝角三角形;对于Mn（IV）3核，JT效应减弱，呈等边三角形。还研究了立方烷结构中Mn离子与Ca（或Sr）离子之一的置换，以阐明Ca（II）离子的多种作用。即使对于Mn（III）2 Mn（X）（X = III，IV）核，Ca掺杂也抑制了JT效应，因为新形成了具有比Mn-Mn距离更长的Ca-Mn距离的锐角CaMnMn三角形。Ca掺杂对Mn（IV）2 Mn（III）晶体的JT效应也有抑制作用。光系统II（PSII）的放氧复合物（OEC）的CaMn 4 O 5簇（1）中的Ca掺杂的立方烷表现出两个锐角的CaMnMn三角形和一个几乎等边的CaMnMn三角形，这是因为额外的Mn 4（a）离子与立方烷配位使Mn 1（d）-Mn 3（B）距离延长。由于JT效应的抑制，Mn 1（d）Mn 2（c）Mn 3（B）三角形变为钝角，表明Mn 1（d）（III）Mn 2（c）（IV）Mn 3（B）（IV）价态在1的S1态。通过Ca（或Sr）掺杂改性的Mn（III）离子的JT畸变与通过双交换机制的团簇内电子转移的不稳定结构变形相耦合。新的XRD实验所揭示的1的结构异常对于PSII OEC水裂解反应的理论建模的几个指导原则的推导也是至关重要的。1的混合DFT计算结果也支持这些指导原则，提供可能的轨道和自旋相关图的水裂解反应。Huckel-Hubbard-Hund（HHH）模型用于定性理解这些图。目前的计算结果的影响进行了讨论，在有关的电子和自旋态的氧化还原活性钙掺杂的莫特绝缘体与磁性过渡金属，如锰，铁，钴，镍等强相关电子系统（SCES）的掺杂改性的钙，锶，锌等已被阐明为可能的候选人的生物启发的人工催化剂的水氧化。© 2012 Wiley Periodicals，Inc.
Full geometry optimizations of mixed‐valence (MV) cubane Mn(III)4‐ωMn(IV)ωO4cluster (ω = 0–4) by UB3LYP have been performed to elucidate Jahn‐Teller (JT) effects for the Mn(III) ions. The optimized geometries have elucidated acute triangle for Mn(III)2Mn(X) (X = III,IV) core in the cubane, indicating the JT effect. The JT effect is not remakable for Mn(IV)2Mn(III) cores, showing obtuse triangle and it diminishes in Mn(IV)3core with equilateral triangle. The replacement of one of Mn ions with Ca (or Sr) ion in the cubane structure has also been examined to elucidate multiple roles of Ca(II) ion. The Ca‐doping suppresses the JT effect even for Mn(III)2Mn(X) (X = III,IV) core because acute CaMnMn triangles with longer Ca‐Mn distances than the Mn‐Mn distance are newly formed. The suppression of the JT effect for Mn(IV)2Mn(III) by Ca doping is also found because of the same reason. The Ca‐doped cubane in the CaMn4O5cluster (1) of oxygen evolving complex (OEC) of photosystem II (PSII) exhibits two acute CaMnMn triangles and one almost equilateral CaMnMn triangle because of the elongation of the Mn1(d)‐Mn3(b)distance with the coordination of the extra Mn4(a)ion to the cubane. The Mn1(d)Mn2(c)Mn3(b)triangle becomes obtuse because of the suppression of the JT effect, indicating the Mn1(d)(III)Mn2(c)(IV)Mn3(b)(IV) valence state in the S1state of 1. The JT distortion for Mn(III) ions modified by the Ca(or Sr) doping is coupled with the labile structural deformation for intracluster electron transfers via double exchange mechanism in 1. The structural anomalies of 1 revealed by the new XRD experiment are also crucial for derivation of several guiding principles for theoretical modeling of water splitting reaction at OEC of PSII. The hybrid DFT computational results for 1 have also supported these guiding principles that provide possible orbital and spin correlation diagrams for water splitting reactions. The Huckel‐Hubbard‐Hund (HHH) model has been used for qualitative understanding of these diagrams. Implications of the present computational results are discussed in relation to electronic and spin states of redox active Ca‐doped Mott insulators constructed with magnetic transition metals such as Mn, Fe, Co, Ni, etc. Strongly correlated electron systems (SCES) modified by doping of Ca, Sr, Zn, etc. have been elucidated as possible candidates of bio‐inspired artificial catalysts for water oxidation. © 2012 Wiley Periodicals, Inc.