Vernier template synthesis of complex molecular knots

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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.