Title:
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The palladium(II) directed synthesis of mechanically interlocked molecular architectures
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This thesis describes the use of Pd(II) as a template in the synthesis of mechanically interlocked molecular architectures and is in three parts. Firstly, the steric and electronic parameters governing the synthesis of a [2]rotaxane utilising the preferred square planar coordination geometry of Pd(II) were investigated. Using a tridentate pyridine 2,6-dicarboxamido macrocyclic precursor and a 2,6-dimethoxypyridine unit capped with bulky terminating groups the [2]rotaxane was accessed using ring closing olefin metathesis in the crucial cyclisation step. Based on these findings the assembly of a similar [2]catenane was achieved. In this case the desired product and two of its molecular isomers were prepared selectively depending on the order in which the precursor units were cyclised. Secondly, both catenanes and rotaxanes assembled in this way were shown to contain an unusual intercomponent pyridine-amide-pyridine hydrogen bond motif following abstraction of the Pd(II) template. As a result, a range of diverse noncovalent binding interactions were observed with the [2]rotaxane and [2]catenane that are not found with similar, but not mechanically interlocked, fragments including non-native transition metal coordination and encapsulation of a sulfonic acid guest. All the neutral, anionic and cationic complexes were characterised in solution using 1H NMR spectroscopy and in the solid state using X-ray crystallography. Thirdly, the control of large amplitude sub-molecular motion in two novel [2]catenanes was achieved. In both cases the co-conformation of the rings was confirmed in solution using 1H NMR spectroscopy and in the solid state using X-ray crystallography.
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