期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 128, 期 29, 页码 9457-9465出版社
AMER CHEMICAL SOC
DOI: 10.1021/ja061348i
关键词
-
资金
- NIGMS NIH HHS [GM32715] Funding Source: Medline
A time-resolved mass spectrometric technique has been used for the determination of rates of exchange of mu-O atoms with water for the complexes [(mes-terpy)(2)Mn-2(III/IV)(mu-O)(2)(H2O)(2)](NO3)(3) (1, mes-terpy = 4'-mesityl-2,2': 6', 2-terpyridine), [(bpy)(4)Mn-2(III/IV)(mu-O)(2)](ClO4)(3)(2, bpy = 2,2'-bipyridine), [(phen)(4)Mn-2(III/IV)(mu-O)(2)](ClO4)(3)(3, phen = 1,10-phenanthroline), [(bpea)(2)Mn-2(III/IV)(mu-O)(2)(mu-OAc)](ClO4)(2) (4, bpea) bis(2-pyridyl) ethylamine), [(bpea)(2)Mn-2(IV/IV)(mu-O)(2)(mu-OAc)](ClO4)(3) (4(ox)), [(terpy)(4)Mn-4(IV/IV/IV/IV)(mu-O)(5)(H2O)(2)]( ClO4)(6) (5, terpy = 2,2': 6', 2-terpyridine), and [(tacn)(4)Mn-4(IV/ IV/ IV/ IV)(mu-O)(6)]Br-3.5(OH)(0.5)center dot 6H(2)O (6, tacn = 1,4,7-triazacyclononane). The rate of exchange of mu-OAc bridges with free acetate in solution has been measured for complexes 4 and 4ox. These are the first measurements of rates of ligand exchange on biologically relevant high-valent Mn complexes. The data analysis method developed here is of general utility in the quantitation of isotope exchange processes by mass spectrometry. We find that the presence of labile coordination sites on Mn increases mu-O exchange rates, and that all-MnIV states are more inert toward exchange than mixed Mn-III-Mn-IV states. The rates of mu-O exchange obtained in this work for a di-mu-oxo Mn-2(III/IV) dimer with labile coordination sites are compared with the oxygen isotope incorporation rates from substrate water to evolved dioxygen measured in different S states of the oxygen evolving complex (OEC) of photosystem II (PSII). On the basis of this comparison, we propose that both substrate waters are not bound as mu-O bridges between Mn atoms in the S-2 and S-3 states of the OEC.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据