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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands
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Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands

机译：旋转状态和几何形状与卤化物轴向配体的三级桨式桨轮络合物的温度依赖性

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摘要

Trinuclear cobalt paddlewheel complexes, [Co-3(dpa)(4)X-2] (dpa = the anion of 2,2-dipyridylamine, X = Cl-, Br-, -NCS-, -CN-, (NC)(2)N-), are known to demonstrate a thermally-induced spin-crossover (SCO). Despite a wealth of structural and magnetic information about such complexes, the role of the axial ligand on the characteristic SCO temperature (T-1/2) remains ambiguous. The situation is complicated by the observation that the solid state geometry of the complexes, symmetric or unsymmetric, with respect to the central cobalt ion, also appears to influence the SCO behavior. In order to seek trends in the relationship between the nature of the axial ligand, geometry and magnetic properties, we have prepared the first examples of tricobalt paddlewheel complexes with axial fluorido and iodido ligands, as well as two new chlorido and bromido solvates. Their SCO properties are discussed in the context of an examination of previously reported chlorido and bromido adducts. The main conclusions are: (1) T-1/2 values follow the trend I- Br- approximate to Cl- F-; (2) while the molecular geometry is predominantly guided by crystal packing for the Cl-, Br- and I- derivatives, the presence of an axial fluoride may favor a more symmetric core; (3) the magnetic characterization of a second example of an unsymmetric complex supports the observation that they display dramatically lower T-1/2 values than their symmetric analogues; and (4) SCO in crystallographically symmetric compounds apparently occurs without loss of molecular or crystallographic symmetry, while a gradual geometric transformation linking the temperature dependence of quasi-symmetric to unsymmetric in crystallographically unconstrained compounds was found.
机译：三核钴水轮络合物，[CO-3（DPA）（4）X-2]（DPA = 2,2-吡啶胺的阴离子，X =氯离子，BR-，-NCS-，-C = N-，（NC） （2）N - ），是已知的表现出热致自旋交叉（SCO）。尽管大量关于这样的复合物的结构和磁信息，轴向配体上的特性SCO温度（T-1/2）中的作用仍然不明确。情况由观察复杂的是，复合物，对称或不对称，相对于所述中央钴离子的固态的几何形状，也出现影响SCO行为。为了寻求在轴向配体，几何形状和磁特性的性质之间的关系的趋势，我们已制备的第一实施例三钴水轮络合物具有轴向fluorido和iodido配体，以及两个新chlorido和bromido溶剂化物。他们的SCO属性在之前报道chlorido和bromido加合物的审查的范围内讨论。主要结论是：（1）T-1/2的值遵循趋势I-＆LT; BR-近似于氯离子＆LT; F-; （2），而分子的几何形状主要是由为氯离子，BR-和I-衍生物晶体堆积引导的轴向氟化物的存在可能有利于更对称的芯; （3）非对称复合支撑它们显示显着降低T-1/2个值比它们的对称类似物的观察的第二实施例的磁特性;和（4）在SCO晶体对称化合物显然没有发生分子或晶体对称性的损失，而逐渐几何变换联准对称不对称在结晶学上无约束的化合物的温度依赖性被发现。

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