New linear high-valent tetranuclear manganese-oxo cluster relevant to the oxygen-evolving complex of photosystem II with oxo, hydroxo, and aqua coordinated to a single Mn(IV)
New linear high-valent tetranuclear manganese-oxo cluster relevant to the oxygen-evolving complex of photosystem II with oxo, hydroxo, and aqua coordinated to a single Mn(IV)
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DOI：
10.1021/ic051462m
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发表时间：
2005-12-12
影响因子：
4.6
通讯作者：
Brudvig, GW
中科院分区：
文献类型：
--
作者：
Chen, HY;Collomb, MN;Brudvig, GW
在复杂的 [(MnO4)-O-IV(EtOterpy)(4)(OH)(2)(OH2)(2)](ClO4)(6)(.)8H(2)O (EtO-terpy = 4'-乙氧基-2,2':6',2"-三联吡啶），已通过 X 射线晶体学、X 射线粉末衍射、EPR 光谱和磁性研究对其进行了表征。该配合物是第一个 Mn-IV 离子与所有三种类型的水衍生配体（氧代、羟基和水基）配位的化合物的例子。该配合物的键距和键角与 Mn(IV)4 氧化态分配一致， di-mu-oxo-和 mono-y-oxo-桥接 Mn-Mn 距离分别为 2.80 和 3.51 埃 该配合物的变温磁化率数据在 10-300 K 范围内与 S = 0 基态一致，并使用自旋哈密顿量 (H) over cap HDvV = -J(1)(S) over cap (2)(S) over cap (1) - 进行拟合。 J(2)(S) 盖帽 (1)(S) 盖帽 (1A) - J(1)(S) 盖帽 (1A)(S) 盖帽 (2A) (S-1 = S-1A = S-2 = S-2A = 3/2) 其中 J(1) = -432 cm(-1) 和 J(2) = -164 cm(-1) （其中 J(1) 和 J(2) 是交换常数，通过该四聚体的第一个激发自旋态是位于抗磁性基态上方 279 cm(-1) 处的自旋三重态，下一个自旋态是分别位于 S = 0 基态上方约 700 cm(-1) 和 820 cm(-1) 处的 S = 1 和 S = 2 能级，即使在高温。
An unprecedented atom connectivity, Mn-IV(mu-O)Mn-IV(mu-O)MnIV(u-O)Mn-IV, is found in the complex [(MnO4)-O-IV(EtOterpy)(4)(OH)(2)(OH2)(2)](ClO4)(6)(.)8H(2)O (EtO-terpy = 4'-ethoxyl-2,2':6',2"-terpyridine), which has been characterized by X-ray crystallography, X-ray powder diffraction, EPR spectroscopy, and magnetic studies. This complex is the first example of a compound where a Mn-IV ion is coordinated by all three types of water-derived ligands: oxo, hydroxo, and aqua. Bond distances and angles for this complex are consistent with a Mn(IV)4 oxidation state assignment, The di-mu-oxo- and mono-y-oxo-bridged Mn-Mn distances are 2.80 and 3.51 angstrom, respectively. The variable-temperature magnetic susceptibility data for this complex, in the range of 10-300 K, are consistent with an S = 0 ground state and were fit using the spin Hamiltonian (H) over cap HDvV = -J(1)(S) over cap (2)(S) over cap (1) - J(2)(S) over cap (1)(S) over cap (1A) - J(1)(S) over cap (1A)(S) over cap (2A) (S-1 = S-1A = S-2 = S-2A = 3/2) with J(1) = -432 cm(-1) and J(2) = -164 cm(-1) (where J(1) and J(2) are exchange constants through the mono-mu-oxo and the di-mu-oxo bridges, respectively). The first excited spin state of this tetramer is a spin triplet state at 279 cm(-1) above the diamagnetic ground state. The next spin states are the S = 1 and S = 2 levels at about 700 and 820 cm(-1) above the S = 0 ground state, respectively. These large energy gaps are consistent with the absence of an EPR signal for this complex, even at high temperature.