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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Structure,magnetism and photomagnetism of mixed-ligand tris(pyrazolyl)methane iron(II)spin crossover compounds
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Structure,magnetism and photomagnetism of mixed-ligand tris(pyrazolyl)methane iron(II)spin crossover compounds

机译：混合配体三（吡唑基）甲烷铁（II）自旋交联化合物的结构，磁性和光磁性

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A range of bis-facial tridentate chelate complexes of type [Fe((R-pz)3CHX(3,5-Me2pz)3CH)](BF4)2 has been characterised that contain two different tris-pyrazolylmethane ligands,with variations in R being H(complex 1 crystallised as polymorphs la and lb)and 4-Me(2),as well as R = H with a CH2OH arm off the methane carbon(3).A tris(pyridyl)methane analogue is also described(4).The tris(3,5-dimethylpyrazolyl)methane co-ligand(3,5-Me2pz),and the BF_4~-counterion,are constant throughout.The spin-crossover properties of these Fe(II)d6 compounds have been probed in detail by variable temperature magnetic,Mossbauer spectral and crystallographic methods.The effects of distortions from octahedral symmetry around the Fe(II)centres,of crystal solvate molecules(1.5 MeCN in 2 and 2 MeCN in 3)and of supramolecular/crystal packing,are discussed.In the case of 1,subtle twisting of pyrazole rings occurs,as a function of temperature,that has a greater effect upon the relative positions of the Fe(II)chelate molecules in polymorph lb than in polymorph la;this is thought to drive the cooperativity differences observed in the magnetism of the polymorphs.Comparisons are also made between 1 to 4 and their homoleptic,parent [Fe(L)2]~(2+)materials.The complexes were screened for the LIESST(light induced excited spin state trapping)effect by measurements of diffuse absorption spectra on the surface of powder samples,at different temperatures.One example,2,showed a 2-step thermal spin crossover transition and it was probed in detail for its photomagnetic features.The T(LIESST)and T_(l/2)values for 2 did not obey an empirical relationship,T(LIESST)= 150 - 0.3T_(1/2)followed by many Fe(II)(N-donor)_6 crossover compounds of the bis-tridentate(meridional)type,and possible reasons for this are discussed.
机译：[Fe（（R-pz）3CHX（3,5-Me2pz）3CH）]（BF4）2类型的一系列双齿三齿螯合物的特征是含有两个不同的tris-吡唑基甲烷配体，R是H（复合物1结晶为多晶型物La和lb）和4-Me（2），以及R = H，CH2OH臂远离甲烷碳（3）。还描述了三（吡啶基）甲烷类似物（4 ）。三（3,5-二甲基吡唑基）甲烷共配体（3,5-Me2pz）和BF_4〜-抗衡常数在整个过程中都是恒定的。已经探究了这些Fe（II）d6化合物的自旋交叉特性通过变温磁性，Mossbauer光谱和晶体学方法详细研究。在Fe（II）中心周围的八面体对称，晶体溶剂化物分子（1.5 MeCN在2和2 MeCN在3）和超分子/晶体堆积对八面体对称的畸变的影响，在1的情况下，吡唑环发生细微的扭曲，随温度的变化，这对Fe（II）螯合物的相对位置具有更大的影响多晶型物lb中的e分子比多晶型物la中的e分子;这被认为是驱动多晶型物的磁性中观察到的协同性差异。还比较了1至4与它们的同质母体[Fe（L）2]〜（2+通过在不同温度下测量粉末样品表面的扩散吸收光谱来筛选配合物的LIESST（光诱导激发自旋态俘获）效应。一个例子2显示了两步热自旋交叉转变2的T（LIESST）和T_（l / 2）值不符合经验关系，T（LIESST）= 150-0.3T_（1/2）讨论了双三齿（子午线）型Fe（II）（N-给体）_6交换化合物及其可能的原因。

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