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首页> 外文期刊>Chemistry: A European journal >Nucleation process in the cavity of a 48-tungstophosphate wheel resulting in a 16-metal-centre iron oxide nanocluster
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Nucleation process in the cavity of a 48-tungstophosphate wheel resulting in a 16-metal-centre iron oxide nanocluster

机译：48钨磷酸盐轮腔中的成核过程，形成了16个金属中心的氧化铁纳米簇

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摘要

The 16-Fe-III-containing 48-tungsto-8-phosphate [P8W48O184Fe16(OH)(28)(H2O)(4)](20-) (1) has been synthesised and characterised by IR and ESR spectroscopy, TGA, elemental analyses, electrochemistry and susceptibility measurements. Single-crystal X-ray analyses were carried out on Li4K16[P8W48O184Fe16(OH)(28)(H2O)(4)]center dot 66H(2)O center dot 2KCl (LiK-1, orthorhombic space group Pnnm, a=36.3777(9)angstrom, b = 13.9708(3) angstrom, c = 26.9140(7) angstrom, and Z=2) and on the corresponding mixed sodium-potassium salt Na9K11-[P8W48O184Fe16(OH)(28)(H2O)4]center dot 100H(2)O (NaK-1, monoclinic space group C2/c, a = 46.552(4) angstrom, b = 20.8239(18) angstrom, c = 27.826(2) angstrom, = 97.141(2)degrees and Z = 4). Polyanion 1 contains-in the form of a cyclic arrangement-the unprecedented {Fe-16(OH)(28)(H2O)}(20+) nanocluster, with 16 edge- and corner-sharing FeO6 octahedra, grafted on the inner surface of the crown-shaped [H7P8W48O184](33-) (P8W8) precursor. The synthesis of I was accomplished by reaction of different iron species containing Fell (in presence of O-2) or Fe-III ions with the P8W, anion in aqueous, acidic medium (pH approximate to 4), which can be regarded as an assembly process under confined geometries. One fascinating aspect is the possibility to model the uptake and release of iron in ferritin. The electrochemical study of 1, which is stable from pH I through 7, offers an interesting example of a highly iron-rich cluster. The reduction wave associated with the Fe-III. centres could not be split in distinct steps independent of the potential scan rate from 2 to 1000 mVs(-1); this is in full agreement with the structure showing that all 16 iron centres are equivalent. Polyanion 1 proved to be efficient for the electrocatalytic reduction of NO., including nitrate. Magnetic and variable frequency EPR measurements on I suggest that the Fe-III ions are strongly antiferromagnetically coupled and that the ground state is tentatively spin S=2.
机译：含有16-Fe-III的48-钨8-磷酸盐[P8W48O184Fe16（OH）（28）（H2O）（4）]（20-）（1）的合成和表征已通过IR和ESR光谱，TGA，元素分析，电化学和磁化率测量。在Li4K16 [P8W48O184Fe16（OH）（28）（H2O）（4）]中心点66H（2）O中心点2KCl（LiK-1，正交晶系空间群Pnnm，a = 36.3777）上进行单晶X射线分析（9）埃，b = 13.9708（3）埃，c = 26.9140（7）埃，Z = 2）以及相应的钠钾盐混合盐Na9K11- [P8W48O184Fe16（OH）（28）（H2O）4]中心点100H（2）O（NaK-1，单斜空间群C2 / c，a = 46.552（4）埃，b = 20.8239（18）埃，c = 27.826（2）埃，= 97.141（2）度和Z = 4）。聚阴离子1以循环排列的形式包含前所未有的{Fe-16（OH）（28）（H2O）}（20+）纳米簇，其内表面接枝了16个边缘和角落共享的FeO6八面体冠状[H7P8W48O184]（33-）（P8W8）的前体。通过在含水酸性介质（pH值约为4）中，使含有Fell（在O-2存在）或Fe-III离子的不同铁物种与P8W阴离子反应，可以完成I的合成。受限几何条件下的组装过程。一个令人着迷的方面是可以模拟铁蛋白中铁的吸收和释放的可能性。从1到7的pH值稳定的电化学研究1提供了一个有趣的高铁簇的例子。还原波与Fe-III有关。中心不能按照与2到1000 mVs（-1）的潜在扫描速率无关的不同步骤进行拆分;这与显示所有16个铁心都相等的结构完全吻合。事实证明，聚阴离子1对于电催化还原NO（包括硝酸盐）非常有效。对I进行的磁和变频EPR测量表明，Fe-III离子强烈反铁磁耦合，并且基态暂定自旋S = 2。

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