Abstract
4-(2,6-Di(2H-indazol-2-yl)pyridin-4-yl)benzoic acid (1) and 10-(2,6-di(1H-pyrazol-1-yl)pyridin-4-yl)anthracene-9-carboxylic acid (2) were required for adsorption studies on Ag(111), with a view to subsequent iron(II) complexation and formation of well-ordered spin-responsive self-assembled monolayers. While the generation of these compounds has remained elusive, several intermediates and by-products were obtained, potentially useful as dipyrazolylpyridine-related derivatives and for metal ion coordination. 3,5-Dichloro-2,6-diindazolylpyridine-4-amine, which forms as a mixture of regioisomers, was synthesised, the mixture separated, and the components characterised (3,5-dichloro-2,6-di(2H-indazol-2-yl)pyridin-4-amine; 3,5-dichloro-2-(1H-indazol-1-yl)-6-(2H-indazol-2-yl)pyridin-4-amine; 3,5-dichloro-2,6-di(1H-indazol-1-yl)pyridin-4-amine). Their iron(II) complexes have been prepared and fully characterised, including single crystal X-ray structure determination. The complexes are instructive examples of the influence of ligand design (“steric jamming”) on the spin-crossover (SCO) activity of FeII centres. Bulky substitution, which entails twisted ligand conformation, increases intramolecular crowding. This prevents contraction of the metal coordination sphere, which would be a prerequisite for thermally inducible SCO. Mössbauer spectroscopy has revealed that the complexes remain predominantly high-spin (HS) between 20 and 200 K, and that a mixture of conformational HS isomers is present in the microcrystalline solid.
摘要
4-(2,6-二(2H-
吲唑-2-基)
吡啶-4-基)
苯甲酸(1)和 10-(2,6-二(1H-
吡唑-1-基)
吡啶-4-基)
蒽-9-
羧酸(2)需要在 Ag(111) 上进行吸附研究,以便随后与
铁(II)络合并形成有序的自旋响应自组装单层。虽然这些化合物的生成仍然难以捉摸,但已经获得了几种中间体和副产品,它们有可能用作二
吡唑吡啶相关衍
生物和
金属离子配位。合成了 3,5-二
氯-2,6-二
吲唑基
吡啶-4-胺,并分离了该混合物,确定了其组分的特性(3,5-二
氯-2,6-二(2H-
吲唑-2-基)
吡啶-4-胺);3,5-dichloro-2-(1H-indazol-1-yl)-6-(2H-indazol-2-yl)pyridin-4-amine; 3,5-dichloro-2,6-di(1H-indazol-1-yl)pyridin-4-amine).它们的
铁(II)配合物已经制备完成,并进行了全面的表征,包括单晶 X 射线结构测定。这些配合物是
配体设计("立体干扰")对 FeII 中心自旋交叉(SCO)活性影响的具有启发性的例子。大块取代导致
配体构象扭曲,从而增加了分子内的拥挤。这阻止了
金属配位球的收缩,而收缩是热诱导 SCO 的先决条件。摩斯鲍尔光谱显示,在 20 至 200 K 之间,复合物主要保持高自旋(HS),而且在微晶固体中存在构象 HS 异构体的混合物。