(1)H NMR spectroscopic elucidation in solution of the kinetics and thermodynamics of spin crossover for an exceptionally robust Fe(2+) complex.
(1)H NMR spectroscopic elucidation in solution of the kinetics and thermodynamics of spin crossover for an exceptionally robust Fe(2+) complex.
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(1)H NMR 光谱阐明了异常坚固的 Fe(2 ) 配合物的自旋交叉动力学和热力学
DOI：
10.1039/c6dt01895e
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发表时间：
2017
影响因子：
4
通讯作者：
D. Schaarschmidt
中科院分区：
文献类型：
--
作者：
H. Petzold;P. Djomgoue;G. Hörner;S. Heider;C. Lochenie;B. Weber;T. Rüffer;D. Schaarschmidt
合成了一系列以顺/反-1，2-二氨基环己烷（4）为中心单元的六齿配体（5/6）的铁离子自旋交叉（SCO）配合物[Fe（5/6）]2+。4与2，2 ′-联吡啶-6-甲醛或1，10-菲咯啉-2-甲醛3还原胺化得到配体。配体5/6的螯合作用和刚性结构导致异常稳健的Fe 2+和Zn 2+络合物，即使在高温下在配位溶剂如DMSO中也能保持其结构。使用变温（VT）1H NMR光谱和VT维斯光谱研究了它们的溶液行为。SCO行为被发现为所有的Fe 2+络合物在这个系列中集中在室温附近和远高于室温。我们首次证明了SCO的热力学和动力学可以通过VT ~ 1H NMR谱来推断。另一种方案使用线性校正项C1模型的Fe 2 + SCO配合物的化学位移。通过激光闪光光解（LFP）验证了由VT 1H NMR获得的[Fe（rac-trans 5）]2+的SCO的速率常数，具有良好的一致性（对于NMR/LFP，1/（kHL + kLH）= 33.7/35.8 ns）。配合物[Fe（rac-trans 5）]2+的转变温度T1/2和溶剂化色性的溶剂依赖性归因于仲胺与溶剂形成氢键。对映体纯的络合物可以从R，R-或S，S-1，2-二氨基环己烷（R，R-反式-4或S，S-反式-4）开始制备。配合物的高稳定性减少了可能的配体混乱，并允许制备由具有反手性的Zn和Fe配合物的1：1混合物组成的[Zn（R，R-5）][Fe（S，S-5）]（ClO 4）4·（CH 3CN）的准外消旋晶体。
A series of Fe2+ spin crossover (SCO) complexes [Fe(5/6)]2+ employing hexadentate ligands (5/6) with cis/trans-1,2-diamino cyclohexanes (4) as central building blocks were synthesised. The ligands were obtained by reductive amination of 4 with 2,2′-bipyridyl-6-carbaldehyde or 1,10-phenanthroline-2-carbaldehyde 3. The chelating effect and the rigid structure of the ligands 5/6 lead to exceptionally robust Fe2+ and Zn2+ complexes conserving their structure even in coordinating solvents like dmso at high temperatures. Their solution behavior was investigated using variable temperature (VT) 1H NMR spectroscopy and VT Vis spectroscopy. SCO behavior was found for all Fe2+ complexes in this series centred around and far above room temperature. For the first time we have demonstrated that the thermodynamics as well as kinetics for SCO can be deduced by using VT 1H NMR spectroscopy. An alternative scheme using a linear correction term C1 to model chemical shifts for Fe2+ SCO complexes is presented. The rate constant for the SCO of [Fe(rac-trans-5)]2+ obtained by VT 1H NMR was validated by Laser Flash Photolysis (LFP), with excellent agreement (1/(kHL + kLH) = 33.7/35.8 ns for NMR/LFP). The solvent dependence of the transition temperature T1/2 and the solvatochromism of complex [Fe(rac-trans-5)]2+ were ascribed to hydrogen bond formation of the secondary amine to the solvent. Enantiomerically pure complexes can be prepared starting with R,R- or S,S-1,2-diaminocyclohexane (R,R-trans-4 or S,S-trans-4). The high robustness of the complexes reduces a possible ligand scrambling and allows preparation of quasiracemic crystals of [Zn(R,R-5)][Fe(S,S-5)](ClO4)4·(CH3CN) composed of a 1 : 1 mixture of the Zn and Fe complexes with inverse chirality.
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影响因子：
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作者：
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发表时间：
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影响因子：
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作者：
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