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首页> 外文期刊>Chemistry: A European journal >Electronic,Vibrational,and Structural Properties of a Spin-Crossover Catecholato-Iron System in the Solid State:Theoretical Study of the Electronic Nature of the Doublet and Sextet States
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Electronic,Vibrational,and Structural Properties of a Spin-Crossover Catecholato-Iron System in the Solid State:Theoretical Study of the Electronic Nature of the Doublet and Sextet States

机译：自旋交叉邻苯二酚-铁系统在固态中的电子，振动和结构性质：双态和六态电子性质的理论研究

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摘要

As a functional model of the catechol dioxygenases,[(TPA)Fe-(Cat)]BPh_4 (TPA = tris(2-pyridylme-thyl)amine and Cat = catecholate dia-nion) exhibits the purple-blue coloration indicative of some charge transfer within the ground state.In contrast to a number of high-spin bioinspired systems,it was previously shown that,in the solid state,[(TPA)Fe(Cat)]BPh_4 undergoes a two-step S = 1/2=S = 5/2 spin-crossover.Therefore,the electronic and vibrational characteristics of this compound were investigated in the solid state by UV/Vis absorption and resonance Raman spectroscopies over the temperature range of the transition.This allowed the charge-transfer transitions of the low-spin (LS) form to be identified.In addition,the vibrational progression observed in the NIR absorption of the LS form was assigned to a five-membered chelate ring mode.The X-ray crystal structure solved at two different temperatures,shows the presence of highly distorted pseudo-octahedral ferric complexes that occupy two nonequivalent crystalline sites.The variation of the molecular parameters as a function of temperature strongly suggests that the two-step transition proceeds by a successive transition of the species in the two nonequivalent sites.The thermal dependence of the high-spin fraction of metal ions determined by Mossbauer experiments is consistent with the magnetic data,except for slight deviations in the high temperature range.The optimized geometries,the electronic transitions,vibrational frequencies,and thermody-namic functions were calculated with the B3LYP density functional method for the doublet and the sextet states.The finding of a ground state that possesses a significant mixture of Fe~(III)-cat-echolate and Fe~(II)-semiquinonate configurations is discussed with regard to the set of experimental and theoretical data.
机译：作为邻苯二酚双加氧酶的功能模型，[（TPA）Fe-（Cat）] BPh_4（TPA =三（2-吡啶甲基-乙基）胺，Cat =儿茶酚酸二阴离子）呈现紫蓝色表示某些电荷与许多高旋转生物启发系统相反，先前显示，在固态下，[（TPA）Fe（Cat）] BPh_4经历两步S = 1/2 = S = 5/2自旋交越点。因此，在过渡温度范围内，通过紫外/可见吸收和共振拉曼光谱研究了该化合物在固态下的电子和振动特性。此外，将在LS形式的NIR吸收中观察到的振动进程指定为五元螯合环模式。X射线晶体结构在两个不同的温度下分解，显示存在高度扭曲的伪八面体三价铁配合物o非等价结晶位点。分子参数随温度的变化强烈表明两步转变是通过物质在两个非等价位点的连续转变而进行的。通过Mossbauer实验确定的数据与磁性数据一致，除了在高温范围内略有偏差外。采用B3LYP密度函数方法计算了双峰和双峰的最佳几何形状，电子跃迁，振动频率和热动力函数。结合实验和理论数据，讨论了一种基态的发现，该基态具有Fe〜（III）-cat-echolate和Fe〜（II）-半奎宁酸酯构型的显着混合物。

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