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首页> 外文期刊>Polyhedron: The International Journal for Inorganic and Organometallic Chemistry >A mixed-valence Mn-6 cluster capped by nitronyl nitroxide units
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A mixed-valence Mn-6 cluster capped by nitronyl nitroxide units

机译：氮价氮氧化物单元封端的混合价Mn-6簇

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摘要

A mixed-valence Mn-6 cluster, [Mn6O2(t-BuCO2)(10)(H2O)(NNPY)(2)] (2), has been synthesized by the assembly of [Mn6O2(t-BuCO2)(10)(THF)(4)] (.) THF (1) with a nitrony] nitroxide radical molecule, 2-(p-pyridyl)-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide (NNPy). Complex 2 consists of [Mn6O2](10+) core and two NNPy radical attachments, where the [Mn6O2](10+) core is composed of two Mn-III ions (i.e., the inner Mn ions) bridged by two mu(4)-O2- and four Mn-III ions (i.e., the outer Mn ions) surrounding the inner Mn-III ions via the two mu(4)-O2-, forming an edge-shared double-tetrahedral polygon (vertices: Mn ions, centers: mu(4)-O2-). Bridges by pivalate groups in mu(2)- and mu(3)-modes assist the coordination spheres around these Mn ions. Two of the outer Mn-II ions in trans position are, to the sixth coordination site, Occupied by NNPy molecule (pyridine-N coordination). One of the outer Mn-II ions is occupied by a water molecule to complete octahedral geometry, but the rest of them is vacancy taking a square-pyramidal geometry. The variable-temperature direct current (DC) magnetic susceptibility was collected in the temperature range of 1.81 to 300 K at a 1 kOe appled field. The molar magnetic susceptibility (chi(M)) steadily increases from 0.053 emu mol(-1) at 300 K to 0.29 emu mol(-1) at 20 K. showing a kink (peak), and then increases rapidly to 0.70 emu mol(-1) at 1.81 K. The profile of this magnetic behavior indicates that the intracluster spin cancellation takes place bellow 20 K to derive an S-Mn6 = 0 by strong anti Ferromagnetic interaction between Mn ions. This is consequently leading to paramagnetic isolation of only the two nitronyl nitroxide units as if remaining as exchange-uncorrelated spin carriers. The variable-temperature ESR spectra show a sharp signal below 30 K with g = 2.00, proving the presence of free nitronyl nitroxide radical, in which double integral of such signal obeys the Curie-Weiss law that follows the susceptibility result in the low-temperature region. (c) 2005 Published by Elsevier Ltd.
机译：[Mn6O2（t-BuCO2）（10）（H2O）（NNPY）（2）]（2）的混合价Mn-6团簇是通过[Mn6O2（t-BuCO2）（10）的组装而合成的（THF）（4）]（。）具有硝基]硝基氧化物自由基分子的THF（1），2-（对吡啶基）-4,4,5,5-四甲基咪唑啉-1-氧基1-3氧化物（NNPy） 。配合物2由[Mn6O2]（10+）核和两个NNPy自由基附件组成，其中[Mn6O2]（10+）核由两个Mn-III离子（即内部Mn离子）构成，它们通过两个mu（4）桥接）-O2-和通过两个mu（4）-O2-围绕内部Mn-III离子的四个Mn-III离子（即外部Mn离子），形成一个边缘共享的双四面体多边形（顶点：Mn离子，中心：mu（4）-O2-）。在mu（2）-和mu（3）-模式下由新戊酸酯基构成的桥协助围绕这些Mn离子的配位球。在第六配位点，两个外Mn-II离子处于反位，被NPNPy分子占据（吡啶-N配位）。外部Mn-II离子之一被水分子占据，以完成八面体几何形状，但是其余的离子为空，呈方形金字塔形几何形状。在1 kOe Appled场中，在1.81至300 K的温度范围内收集了可变温度直流（DC）磁化率。摩尔磁化率（chi（M））从300 K时的0.053 emu mol（-1）稳定增加到20 K时的0.29 emu mol（-1），显示扭结（峰值），然后迅速增加至0.70 emu mol （-1）在1.81K。此磁性行为的轮廓表明，团簇内自旋抵消发生在20 K以下，通过Mn离子之间的强反铁磁相互作用得出S-Mn6 = 0。因此，这导致仅两个磺酰硝基氮氧化物单元的顺磁分离，好像保留为与交换无关的自旋载体一样。可变温度ESR谱在g = 2.00时显示低于30 K的尖锐信号，证明存在游离的硝酰基硝基氧自由基，其中此类信号的双积分服从居里-魏斯定律，该定律遵循低温下的磁化率结果地区。 （c）2005年由Elsevier Ltd.发布。

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