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首页> 外文期刊>Chemistry: A European journal >Complexes of click-derived bistriazolylpyridines: Remarkable electronic influence of remote substituents on thermodynamic stability as well as electronic and magnetic properties
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Complexes of click-derived bistriazolylpyridines: Remarkable electronic influence of remote substituents on thermodynamic stability as well as electronic and magnetic properties

机译：点击衍生的双三唑基吡啶的配合物：远程取代基对热力学稳定性以及电子和磁性的显着电子影响

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摘要

2,6-Bis(1,2,3-triazol-4-yl)pyridine (btp) ligands with substitution patterns ranging from strongly electrondonating to strongly electron-accepting groups, readily prepared by means of Cu-catalyzed 1,3-dipolar cycloaddition (the "click" reaction), were investigated with regard to their complexation behavior, and the properties of the resulting transition-metal compounds were compared. Metal-btp complexes of 1:1 stoichiometry, that is, [Ru-(btp)Cl_2(dmso)] and [Zn(btp)Br_2], could be isolated and were crystallographically characterized: they display octahedral and trigonal-bipyramidal coordination geometries, respectively, and exhibit high aggregation tendencies due to efficient π-π stacking leading to low solubilities. Metal-btp complexes of 1:2 stoichiometry, that is, [Fe-(btp) _2]~(2+) and [Ru(btp)_2]~(2+), could also be synthesized and their metal centers show the expected octahedral coordination spheres. The iron compounds exhibit quite a complex magnetic behavior in the solid state including spin crossover near room temperature, and hysteresis and locking into high-spin states on tempering at 400 K, depending on the substituents on the btp ligands. Cyclic voltammetry studies of [Ru(btp) _2]~(2+) reveal strong modulation of the oxidation potentials by more than 0.6 V and a clear linear correlation to the Hammett constant (σ_(para)) of the substituent at the pyridine core. Isothermal titration calorimetry was used to measure the thermodynamics of the Fe ~(II)-btp complexation process and enabled accurate determination of the complexation enthalpies, which display a linear relationship with the σ_(para) values for the terminal phenyl substituents. Detailed NMR spectroscopic studies finally revealed that in the case of Fe~(II) complexation, dynamics are rapid for all investigated btp derivatives in acetonitrile, while replacing Fe~(II) by Ru~(II) or changing the solvent to dichloromethane effectively slows down ligand exchange. The results nicely demonstrate the utility of substituent parameters, originally developed for linear free-energy relationships to explain reactivity in organic reactions, in coordination chemistry, and to illustrate the potential to customdesign btp ligands and complexes thereof with predictable properties. The fast equilibration of the [Fe-(btp)_2]~(2+) complexes together with their tunable stability and interesting magnetic properties should enable the design of dynamic metallosupramolecular materials with advantageous properties.
机译：2,6-双（1,2,3-三唑-4-基）吡啶（btp）配体，具有从强电子给体到强电子接受基团的取代模式，易于通过铜催化的1,3-双极性制备研究了环加成反应（“喀哒”反应）的络合行为，并比较了所得过渡金属化合物的性质。可以分离出化学计量比为1：1的金属-btp络合物，即[Ru-（btp）Cl_2（dmso）]和[Zn（btp）Br_2]，并进行晶体学表征：它们显示八面体和三角-双锥体配位几何分别由于有效的π-π堆积导致较低的溶解度而表现出高聚集趋势。也可以合成化学计量比为1：2的金属-btp络合物，即[Fe-（btp）_2]〜（2+）和[Ru（btp）_2]〜（2+），并且它们的金属中心显示预期的八面体协调范围。铁化合物在固态下表现出非常复杂的磁性能，包括在室温附近发生自旋交叉，并且在btp配体上的取代基上，磁滞和在400 K回火时锁定为高自旋态。 [Ru（btp）_2]〜（2+）的循环伏安研究表明，氧化电位有超过0.6 V的强调节作用，并且与吡啶核上取代基的Hammett常数（σ_（para））具有明显的线性相关性。等温滴定量热法用于测量Fe〜（II）-btp络合过程的热力学，并能够精确测定络合焓，该焓与末端苯基取代基的σ_para值呈线性关系。最终的详细NMR光谱研究表明，在Fe〜（II）络合的情况下，所有研究过的btp衍生物在乙腈中的动力学都是快速的，而用Ru〜（II）代替Fe〜（II）或将溶剂更改为二氯甲烷则有效地减缓了动力学。下配体交换。结果很好地证明了取代基参数的实用性，该参数最初是为线性自由能关系开发的，用于解释配位化学中有机反应的反应性，并说明定制设计btp配体及其配合物具有可预测特性的潜力。 [Fe-（btp）_2]〜（2+）配合物的快速平衡及其可调谐的稳定性和令人感兴趣的磁性能，应该能够设计出具有有利性能的动态金属超分子材料。

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