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首页> 外文期刊>Chemistry: A European journal >A New Generation of Metal String Complexes:Structure,Magnetism,Spectroscopy,Theoretical Analysis,and Single Molecular Conductance of an Unusual Mixed-Valence Linear [Ni5]~(8+)Complex
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A New Generation of Metal String Complexes:Structure,Magnetism,Spectroscopy,Theoretical Analysis,and Single Molecular Conductance of an Unusual Mixed-Valence Linear [Ni5]~(8+)Complex

机译：新一代金属弦络合物的结构，磁性，光谱学，理论分析和不寻常的混合价线性[Ni5]〜（8+）络合物的单分子电导

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Two new linear pentanickel complexes [Ni5(bna)4(Cl)2][PF6]2(1)and [Ni5(bna)4(Cl)2][PF6]4(2;bna=bi-naphthyridylamide),were synthesized and structurally characterized.A derivative of 1,[Ni5(bna)4(NCS)2][NCS]2(3),was also isolated for the purpose of the conductance experiments carried out in comparison with [Ni5(tpda)4-(NCS)2](4;tpda = tripyridyldiamide).The metal framework of complex 2 is a standard [Ni5]~(10+)core,isoelectronic with that of [Ni5(tpda)4Cl2](5).Also as in 5,complex 2 has an antiferromag-netic ground state(J=-15.86 cm~(-1))resulting from a coupling between the terminal nickel atoms,both in high-spin sate(5 = 1).Complex 1 displays the first characterized linear nickel framework in which the usual sequence of Ni~(II)atoms has been reduced by two electrons.Each dinickel unit attached to the naphthyridyl moieties is assumed to undergo a one-electron reduction,whereas the central nickel formally remains Ni~(II).DFT calculations suggest that the metal framework of the mixed-valence complex 1 should be described as intermediate between a localized picture corresponding to Ni~(II)-Ni~I-Ni~(II)-Ni~I-Ni~(II)and a fully delocalized model represented as(Ni2)~(3+)-Ni~(II)- (Ni2)~(3+).Assuming the latter model,the ground state of 1 results from an anti- ferromagnetic coupling (J= -34.03 cm~(-1))between the two(Ni2)~(3+) fragments,considered each as a single magnetic centre(5 = 3/2).An interva- lence charge-transfer band is observed in the NIR spectrum of 1 at 1186 nm, suggesting,in accordance with DFT calculations,that 1 should be assigned to Robin-Day class II of mixed-valent complexes.Scanning tunnelling micro scopy(STM)methodology was used to assess the conductance of single mole cules of 3 and 4.Compound 3 was found ≈ 40% more conductive than 4, a result that could be assigned to the electron mobility induced by mixed-va lency in the naphthyridyl fragments.
机译：制备了两个新的线性五氧化镍配合物[Ni5（bna）4（Cl）2] [PF6] 2（1）和[Ni5（bna）4（Cl）2] [PF6] 4（2; bna =双萘甲酰胺）还合成了1，[Ni5（bna）4（NCS）2] [NCS] 2（3）的衍生物，用于与[Ni5（tpda）4]进行电导实验-（NCS）2]（4; tpda =三吡啶基二酰胺）。配合物2的金属骨架是标准的[Ni5]〜（10+）核，与[Ni5（tpda）4Cl2]（5）等电子。在图5中，复合物2具有反铁磁性基态（J = -15.86 cm〜（-1）），这是由于末端镍原子之间的耦合导致的，两者均为高旋态（5 = 1）。首先表征的线性镍骨架，其中Ni〜（II）原子的通常序列已被两个电子还原。假设连接到萘啶基部分的每个二镍单元都经历了一个电子还原，而中心镍正式保留为Ni〜 （II）.DFT计算表明混合态的金属骨架由于应将复合物1描述为对应于Ni〜（II）-Ni〜I-Ni〜（II）-Ni〜I-Ni〜（II）的局部图片与表示为（Ni2）〜的完​​全离域模型之间的中间对象（3 +）-Ni〜（II）-（Ni2）〜（3+）。假设是后者模型，则1的基态是由它们之间的反铁磁耦合（J = -34.03 cm〜（-1））产生的两个（Ni2）〜（3+）片段，每个都视为一个单一的磁性中心（5 = 3/2）。在1186 nm的NIR光谱中观察到了一个相互作用的电荷转移带，表明在根据DFT计算，应将1指定为Robin-Day II类混合价络合物。使用扫描隧道显微镜（STM）方法评估3和4的单分子的电导。导电性比4高40％，这可以归因于萘啶片段中混合能引起的电子迁移率。

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