Vernier template synthesis of complex molecular knots

分子结是现代合成化学发展出的最美丽、最迷人的结构之一。这种缠结分子的形成通常通过自组装进行，通常在结骨架可以系在周围的模板存在下进行。这些过程在很大程度上取决于构成结的构建块的设计。迄今为止制备的合成分子结的数量相对较少且复杂性较低，这反映了这项任务的难度。本项目的目的是使用所谓的游标模板制备前所未有的复杂性的分级“多级”分子结。这种方法允许通过设计具有不同数量的相互作用位点的两种元件来从相对小的结构单元和模板制备延伸结构，使得不有利于形成1：1加合物，而是形成更大的组装体。合成策略允许在手性和拓扑结构方面对各个交叉点进行定向设计。作为原理的第一个证明，具有总共12个交叉点的三叶结将从含有吡啶二甲酰胺的配体与镧系元素作为模板离子制备。这些结将通过光谱和晶体学手段以及纳米级表征技术来表征。研究结内镧系元素的特殊物理学和顺磁性质也允许有针对性地探测分子的溶液状态，这是结形成的相关状态。所描述的分子将是有史以来合成的最复杂的分子结，并且可以为缠结和交织材料的发展提供基础知识。

Molecular knots are among the most beautiful and fascinating structures modern synthetic chemistry has developed. The formation of such entangled molecules typically proceeds via self-assembly, often in the presence of a template that the knot backbone can be tied around. These processes are to a very high degree dependent on the design of the building blocks that make up the knot. The relatively low number and the low complexity of the synthetic molecular knots prepared until now reflects the difficulty of this task.The aim of this project is to prepare hierarchical, “multi-level” molecular knots of unprecedented complexity using so-called Vernier templating. This method allows for the preparation of extended structures from relatively small building blocks and templates by designing both elements with a different number of sites for mutual interaction, so that the formation of 1:1 adducts is not favoured and instead bigger assemblies are formed. The synthetic strategy allows for a directed design of the individual crossing-points in terms of handedness and topology. As a first proof of principle, a trefoil-of-trefoil knot with a total of twelve crossings will be prepared from ligands containing pyridinedicarboxylamides with lanthanoids as template ions. These knots will be characterised by both spectroscopic and crystallographic means, as well as through nanoscale characterisation techniques. Studies of the special photophysical and paramagnetic properties of the lanthanoids inside the knots also allow for a targeted probing of the solution state of the molecule, which is the relevant state for knot formation. The described molecules would be the most complex molecular knots ever synthesised, and could provide fundamental knowledge towards the development of entangled and interwoven materials.