Vernier template synthesis of complex molecular knots

分子结是现代合成化学发展起来的最美丽、最迷人的结构之一。这种纠缠分子的形成通常是通过自组装进行的，通常在模板存在的情况下，结主链可以被捆绑在模板周围。这些过程在很大程度上取决于构成结的构件的设计。迄今为止制备的合成分子结的相对较少的数量和较低的复杂性反映了这项任务的难度。这个项目的目的是利用所谓的游标模板来制备分层的、“多层次”的、前所未有的复杂分子结。这种方法允许从相对较小的构建块和模板中制备扩展结构，通过设计具有不同数量的相互作用位点的元素，因此不赞成1:1加合物的形成，而是形成更大的组装体。综合策略允许在手性和拓扑方面对单个交叉点进行定向设计。作为第一个原理证明，将用含有吡啶二羧基酰胺的配体和类镧离子作为模板离子制备三叶结。这些结将通过光谱学和晶体学手段以及纳米级表征技术来表征。对结内类镧的特殊光物理和顺磁特性的研究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。所描述的分子将是迄今为止合成的最复杂的分子结，并且可以为纠缠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.