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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- 作者：Hongyu Chen ; Marie-Noë ; lle Collomb ; Carole Duboc ; Geneviè ; ve Blondin ; Eric Riviè ; re ; J. W. Faller ; Robert H. Crabtree ; and Gary W. Brudvig
- 刊名：Inorganic Chemistry
- 出版年：2005
- 出版时间：December 12, 2005
- 年：2005
- 卷：44
- 期：25
- 页码：9567 - 9573
- 全文大小：116K
- 年卷期：v.44,no.25(December 12, 2005)
- ISSN：1520-510X
文摘
An unprecedented atom connectivity, MnIV(
-O)MnIV(-O)2MnIV(-O)MnIV, is found in the complex [MnIV4O4(EtO-terpy)4(OH)2(OH2)2](ClO4)6·8H2O (EtO-terpy = 4'-ethoxyl-2,2':6',2' '-terpyridine), which has been characterized byX-ray crystallography, X-ray powder diffraction, EPR spectroscopy, and magnetic studies. This complex is the firstexample of a compound where a MnIV 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 MnIV4 oxidation state assignment. Thedi--oxo- and mono--oxo-bridged Mn-Mn distances are 2.80 and 3.51 Å, respectively. The variable-temperaturemagnetic susceptibility data for this complex, in the range of 10-300 K, are consistent with an S = 0 ground stateand were fit using the spin Hamiltonian 
HDvV = -J1
21 - J211A - J11A2A (S1 = S1A = S2 = S2A = 3/2) withJ1 = -432 cm-1 and J2 = -164 cm-1 (where J1 and J2 are exchange constants through the mono--oxo and thedi--oxo bridges, respectively). The first excited spin state of this tetramer is a spin triplet state at 279 cm-1 abovethe diamagnetic ground state. The next spin states are the S = 1 and S = 2 levels at about 700 and 820 cm-1above the S = 0 ground state, respectively. These large energy gaps are consistent with the absence of an EPRsignal for this complex, even at high temperature.
-O)MnIV(-O)2MnIV(-O)MnIV, is found in the complex [MnIV4O4(EtO-terpy)4(OH)2(OH2)2](ClO4)6·8H2O (EtO-terpy = 4'-ethoxyl-2,2':6',2' '-terpyridine), which has been characterized byX-ray crystallography, X-ray powder diffraction, EPR spectroscopy, and magnetic studies. This complex is the firstexample of a compound where a MnIV 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 MnIV4 oxidation state assignment. Thedi--oxo- and mono--oxo-bridged Mn-Mn distances are 2.80 and 3.51 Å, respectively. The variable-temperaturemagnetic susceptibility data for this complex, in the range of 10-300 K, are consistent with an S = 0 ground stateand were fit using the spin Hamiltonian HDvV = -J121 - J211A - J11A2A (S1 = S1A = S2 = S2A = 3/2) withJ1 = -432 cm-1 and J2 = -164 cm-1 (where J1 and J2 are exchange constants through the mono--oxo and thedi--oxo bridges, respectively). The first excited spin state of this tetramer is a spin triplet state at 279 cm-1 abovethe diamagnetic ground state. The next spin states are the S = 1 and S = 2 levels at about 700 and 820 cm-1above the S = 0 ground state, respectively. These large energy gaps are consistent with the absence of an EPRsignal for this complex, even at high temperature.