A Unified Treatment of the Relationship Between Ligand Substituents and Spin State in a Family of Iron(II) Complexes.
A Unified Treatment of the Relationship Between Ligand Substituents and Spin State in a Family of Iron(II) Complexes.
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DOI：
10.1002/anie.201600165
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发表时间：
2016-03-18
期刊：
影响因子：
--
通讯作者：
Halcrow MA
中科院分区：
文献类型：
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作者：
Kershaw Cook LJ;Kulmaczewski R;Mohammed R;Dudley S;Barrett SA;Little MA;Deeth RJ;Halcrow MA
配体对金属离子自旋状态的影响对于生物无机化学和合成应用的贱金属催化剂的生产是至关重要的。从[Fe(Bpp)2]2+(bpp=2，6-二{吡唑-1-基)衍生的配合物可以是高自旋、低自旋或自旋交叉(SCO)的活性，这取决于配体的取代基。SCO溶液中点温度(T)与相关Hammett参数的关系图表明，络合物的低自旋态是由吸电子的吡啶(X)取代基稳定的，也是由给电子的吡唑(Y)取代基稳定的。此外，当考虑具有卤代X或Y取代基的络合物的子集时，这两组化合物反而表现出相同的趋势，即T小幅降低以增加取代基电负性。密度泛函理论计算再现了这些不同的趋势，这些趋势源于吡啶和吡唑取代基对Fe-Lσ和π 成键的相互影响。
The influence of ligands on the spin state of a metal ion is of central importance for bioinorganic chemistry, and the production of base‐metal catalysts for synthesis applications. Complexes derived from [Fe(bpp)2]2+ (bpp=2,6‐di{pyrazol‐1‐yl}pyridine) can be high‐spin, low‐spin, or spin‐crossover (SCO) active depending on the ligand substituents. Plots of the SCO midpoint temperature (T ) in solution vs. the relevant Hammett parameter show that the low‐spin state of the complex is stabilized by electron‐withdrawing pyridyl (“X”) substituents, but also by electron‐donating pyrazolyl (“Y”) substituents. Moreover, when a subset of complexes with halogeno X or Y substituents is considered, the two sets of compounds instead show identical trends of a small reduction in T for increasing substituent electronegativity. DFT calculations reproduce these disparate trends, which arise from competing influences of pyridyl and pyrazolyl ligand substituents on Fe‐L σ and π bonding.