EPR/ENDOR and Computational Study of Outer Sphere Interactions in Copper Complexes of Phenolic Oximes.
EPR/ENDOR and Computational Study of Outer Sphere Interactions in Copper Complexes of Phenolic Oximes.
复制标题
酚肟铜配合物中外层相互作用的 EPR/ENDOR 和计算研究。
DOI：
10.1021/acs.inorgchem.5b01180
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发表时间：
2015
影响因子：
4.6
通讯作者：
Healy MR
中科院分区：
文献类型：
--
作者：
Healy MR
铜配合物的酚肟族配体（3- x -水杨醛肟）被广泛用作金属溶剂萃取剂。在邻酚基团的3位上加入电负性取代基，可以用来支持配体间的氢键，从而增强萃取剂的强度。然而，研究这些配合物中相关的氢键是非常困难的。在这里，我们结合了EPR， ENDOR， DFT和x射线晶体学来研究这种效应。1h ENDOR数据分析显示，未取代配合物[Cu(L2)2]的Cu···H16（肟质子）距离从2.92 Å变化到X = CH2N(C6H13)2取代配合物[Cu(L3)2]的3.65 Å。DFT计算表明，这种变化是由氧基氢和酚基氧之间的氢键长度和强度的变化引起的。通过theNAandNQENDOR数据，还观察到两种配合物中Cu··H15（亚甲基质子）距离和Cu··N键参数的明显变化。用DFT和X射线晶体学证实了取代基(X)引起的配合物结构畸变和氧-酚氧氢键强度的变化。DFT直接证明了支撑配合物中h16与CH2N(C6H13)2的胺态氮相互作用的重要性，并表明这种高强度的相互作用不一定会导致铜萃取的增强，因为它会在配合物的内配位球中施加不利的几何形状。因此，ENDOR、DFT和X射线结构数据都表明，与酚氧原子邻位的氨基甲基取代基(X)在这些铜配合物中提供了特别强的配体间氢键支撑，这些外球相互作用可以显著影响结构和稳定性。
Copper complexes of the phenolic oxime family of ligands (3-X-salicylaldoximes) are used extensively as metal solvent extractants. Incorporation of electronegative substituents in the 3-position, ortho to the phenol group, can be used to buttress the interligand H-bonding, leading to an enhancement in extractant strength. However, investigation of the relevant H-bonding in these complexes can be exceedingly difficult. Here, we have combined EPR, ENDOR, DFT, and X-ray crystallography to study this effect. Analysis of the1H ENDOR data revealed a variation in the Cu···H16(oxime proton) distance from 2.92 Å for the unsubstituted complex [Cu(L2)2] to 3.65 Å for the X = CH2N(C6H13)2substituted complex [Cu(L3)2]. DFT calculations showed that this variation is caused by changes to the length and strength of the H-bond between the oximic hydrogen and the phenolate oxygen. Noticeable changes to the Cu···H15(azomethine proton) distances and the Cu···N bonding parameters were also observed in the two complexes, as revealed through theNAandNQENDOR data. Distortions in the structure of the complex and variations in the oximic proton to phenolate oxygen H-bond strength caused by the substituent (X) were confirmed by DFT and X-ray crystallography. DFT directly evidenced the importance of the interaction between H16and the amine nitrogen of CH2N(C6H13)2in the buttressed complex and indicated that the high strength of this interaction may not necessarily lead to an enhancement of copper extraction, as it can impose an unfavorable geometry in the inner coordination sphere of the complex. Therefore, ENDOR, DFT, and X-ray structural data all indicate that the aminomethyl substituent (X) ortho to the phenolic oxygen atom provides a particularly strong buttressing of interligand H-bonding in these copper complexes and that these outer sphere interactions can significantly influence structure and stability.
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