Pyridyldiimine macrocyclic ligands: Influences of template ion, linker length and imine substitution on ligand synthesis, structure and redox properties
Pyridyldiimine macrocyclic ligands: Influences of template ion, linker length and imine substitution on ligand synthesis, structure and redox properties
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吡啶二亚胺大环配体：模板离子、连接基长度和亚胺取代对配体合成、结构和氧化还原性质的影响
DOI：
10.1016/j.poly.2021.115044
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发表时间：
2021
期刊：
影响因子：
2.6
通讯作者：
Tomson, Neil C.
中科院分区：
文献类型：
--
作者：
Thierer, Laura M.;Wang, Qiuran;Brooks, Sam H.;Cui, Peng;Qi, Jia;Gau, Michael R.;Manor, Brian C.;Carroll, Patrick J.;Tomson, Neil C.
通过围绕碱土金属三氟甲磺酸盐进行 [2 + 2] 缩合，合成了一系列 2,6-二亚氨基吡啶衍生的大环配体。在大环合成子的吡啶环的4位上包含叔丁基，形成可溶于常见有机溶剂的大环配合物，从而可以通过核磁共振波谱、质谱、溶液相紫外-可见光谱、循环伏安法和单晶X射线晶体学对配合物的物理性质进行系统比较。晶体学测定的固态结构表明配体扭曲增加，同时离子尺寸减小或大环尺寸（18、20 或 22 元环）增加。大环内的折叠和扭曲程度可以使用源自 Npyr-M-Npyrbond 角度的参数以及吡啶二亚胺 (PDI) 和吡啶二亚胺 (PDAI) 片段在固态结构内彼此的相对方向来量化。使用循环伏安法和紫外-可见光谱来比较大环中氧化还原活性PDI和PDAI组分与氧化还原非活性金属配位时亚胺π*轨道的相对能量。两种方法都表明亚胺碳上从甲基取代到氢取代的变化降低了配体π*系统的能量。
A series of 2,6-diiminopyridine-derived macrocyclic ligands have been synthesized via [2 + 2] condensation around alkaline earth metal triflate salts. The inclusion of atert-butyl group at the 4-position of the pyridine ring of the macrocyclic synthons results in macrocyclic complexes that are soluble in common organic solvents, thereby enabling a systematic comparison of the physical properties of the complexes by NMR spectroscopy, mass spectrometry, solution-phase UV–Vis spectroscopy, cyclic voltammetry and single-crystal X-ray crystallography. Solid-state structures determined crystallographically demonstrate increased twisting in the ligand, concurrent with either a decrease in ion size or an increase in macrocycle ring size (18, 20, or 22 membered rings). The degree of folding and twisting within the macrocycle can be quantified using parameters derived from the Npyr-M-Npyrbond angle and the relative orientation of the pyridinediimine (PDI) and pyridinedialdimine (PDAI) fragments to each other within the solid state structures. Cyclic voltammetry and UV–Vis spectroscopy were used to compare the relative energies of the imine π* orbital of the redox active PDI and PDAI components in the macrocycle when coordinated to redox inactive metals. Both methods indicate the change from a methyl to hydrogen substitution on the imine carbon lowers the energy of the ligand π* system.