Towards the Development and Coordination Chemistry of Rotaxane- and Catenane-based Ligands

Abstract

Rotaxanes and Catenanes are among the most studied platforms of mechanically interlocked molecules. The synthesis of these molecules has become easier with the development of the active template Cu-mediated alkyne-azide cycloaddition (AT-CuAAC) approach which allows the efficient synthesis of smaller rotaxanes and catenanes from accessible and versatile starting materials. The potential applications of these classes of molecules have been demonstrated in catalysis, sensing and the synthesis of mechanically chiral molecules. In this thesis, 2 aspects of the synthesis and application of rotaxanes and catenanes are addressed. Firstly, although bipyridine macrocycles are useful in the synthesis of small rotaxanes and catenanes, we set out to study if this efficient method could also be extended to mono-pyridine macrocycles. The other aspect is about their coordination chemistry. Despite the AT-CuAAC approach naturally producing interlocked ligands, the study of their coordination chemistry is relatively limited. Given that interlocked architectures have previously been reported to offer a binding pocket that leads to highly kinetically stablised complexes, we set out to design ligands to create complexes with high stability, ultimately for applications in medical imaging. In this thesis, the first chapter will introduce previously reported approaches to rotaxanes and catenanes from the statistical approach to the AT-CuAAC reaction, which will be employed in this work. The application in sensing, catalysis and chirality of rotaxanes and catenanes which were synthesized using the AT-CuAAC reaction is reviewed. The development of rotaxane- and catenane-based ligands for various types of transition metals is then discussed. In chapter 2, the development of rotaxane- and catenane-based ligands to towards highly kinetically stable CuII complexes is discussed. The third chapter focusses on the potential of pyridine functionalized macrocycles as an alternative to the bipyridine macrocycle for the synthesis of small rotaxane. The effect of binding site modification is also evaluated. Lastly, the possibility of using the catenane based ligand to tackle 2 fundamental issues for lanthanide coordination is testified.

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ORCID for Stephen Goldup: orcid.org/0000-0003-3781-0464

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