Structural and electronic comparison of 1st row transition metal complexes of a tripodal iminopyridine ligand.
Structural and electronic comparison of 1st row transition metal complexes of a tripodal iminopyridine ligand.
复制标题
DOI：
10.1021/ic301909u
复制
发表时间：
2012-11
影响因子：
4.6
通讯作者：
Ashley M. McDaniel;A. Rappé;M. P. Shores
中科院分区：
文献类型：
--
作者：
Ashley M. McDaniel;A. Rappé;M. P. Shores
我们报道了一系列二价三维过渡金属配合物（Cr to Zn, 1-7）的制备和表征，这些配合物具有多齿，三足亚氨基吡啶希夫碱配体三甲基6,6',6″-((1E, 1E,1″E)-（（nitrilotris（乙烷-2,1-二基））三is（azanylylidene)）三is-(methanylylidene)）三nicotinate （L(5-OOMe)）。在1-5和7上进行的x射线结构研究揭示了复杂的几何结构，从局部八面体协调到向三角棱柱几何到七坐标环境的显著畸变。无论配位方式如何，磁性和光谱研究表明配体提供中等强度的配体场：在所有探测温度下，Fe配合物是低自旋的，而Co和Mn配合物是高自旋的。循环伏安图表现出多重可逆的基于配体的还原，这在整个系列中相对一致；然而，Cr配合物1的电化学行为与其他配合物有着根本的不同。对配体、阴离子和配合物1-7进行了时间依赖（TD）密度泛函理论（DFT）和自然跃迁轨道（NTO）计算分析：计算光谱再现了观测到的可见吸收光谱的主要差异特征，而NTO为观测到的特征提供了可行的解释。综合研究表明，所有配合物都含有与M（II）离子结合的中性配体，除了Cr配合物1，它最好被描述为与自由基阴离子配体结合的Cr（III）种。
We report the preparation and characterization of a series of divalent 3d transition metal complexes (Cr to Zn, 1-7), featuring the multidentate, tripodal iminopyridine Schiff-base ligand trimethyl 6,6',6″-((1E,1'E,1″E)-((nitrilotris(ethane-2,1-diyl))tris(azanylylidene))tris-(methanylylidene))trinicotinate (L(5-OOMe)). X-ray structural studies carried out on 1-5 and 7 reveal complex geometries ranging from local octahedral coordination to significant distortion toward trigonal prismatic geometry to heptacoordinate environments. Regardless of coordination mode, magnetic and spectroscopic studies show the ligand to provide moderately strong ligand fields: the Fe complex is low-spin, while the Co and Mn complexes are high-spin at all temperatures probed. Cyclic voltammograms exhibit multiple reversible ligand-based reductions, which are relatively consistent throughout the series; however, the electrochemical behavior of the Cr complex 1 is fundamentally different from those of the other complexes. Time-dependent (TD) density functional theory (DFT) and natural transition orbital (NTO) computational analyses are presented for the ligand, its anion, and complexes 1-7: the computed spectra reproduce the major differential features of the observed visible absorption spectra, and NTOs provide viable interpretations for the observed features. The combined studies indicate that all complexes contain neutral ligands bound to M(II) ions, except for the Cr complex 1, which is best described as a Cr(III) species bound to a radical anionic ligand.