Novel metal template strategies for the construction of rotaxanes and catenanes

摘要

The template synthesis of rotaxanes and catenanes has allowed a detailed study ofudtheir intrinsically novel and interesting properties. A key strategy has been theuddeployment of transition metal ions with their well-defined coordination geometriesudallowing high-yielding and facile preparation of interlocked architectures.udKnowledge of how to exploit the coordination sphere of metal ions and the design ofudligands for the creation of intermediates that are pre-disposed to undergoud‘stoppering’ or ‘clipping’ has been a crucial requirement for this approach. ThisudThesis is in three parts describing the use of three dimensional, two dimensional andudone dimensional coordination geometries in the synthesis of interlockedudarchitectures.udFirstly, the octahedral coordination geometry of cobalt(III) was utilized to organizeuddianionic pyridine-2,6-dicarboxamido ligands in a mutually orthogonal arrangementudsuch that ring closing metathesis macrocyclizations gave access to interlocked orudentwined products. A ‘figure-of-eight’ complex was obtained from a doubleudmacrocyclizations, whereas a catenate was accessed through a singleudmacrocyclization. The topology of the isomers was proved by X-ray crystallography.udAn analogous [2]rotaxane was synthesized and the interlocked nature of theudrotaxane demonstrated by 1H NMR spectroscopy and mass spectrometry.udSecondly, an “active” metal template strategy, in which the metal ion plays a dualudrole – acting to both organize ligands and catalyze mechanical bond formation –udallowed rotaxanes be constructed using the square planar coordination geometryudand Lewis acidic nature of a palladium(II) complex. The interlocked nature of theudrotaxane was proved by X-ray crystallography, demonstrating that a nitrile groupudpresent in the thread acted as a “station” for the Pd(II)-macrocycle. Thisudobservation led to the construction of a two “station” degenerate molecular shuttleudin which the dynamics of translocation were controlled by reagent addition andudobserved by 1H NMR techniques.udLastly, the linear coordination geometry of gold(I) was successfully used as audtemplate for construction of rotaxanes and catenanes via a ‘clipping’ strategy. Theudlinear coordination geometry and the interlocked nature of the gold(I)-catenate was proved by X-ray crystallography, the rotaxane architecture was proved by 1H NMRudspectroscopy and mass spectrometry.udChapters Two, Three and Four are in the form of articles that have been published inudpeer-reviewed journals, and are reproduced, in their published format, in theudAppendix. No attempt has been made to rewrite the published work; as audconsequence the numbering of compounds, whilst consistent within each Chapter, isudnot consistent throughout this Thesis. Another consequence is that the many failedudsynthetic routes have been left out. I hope the reader will forgive these omissions asudwell as the slight repetition that occurs in the introduction and bibliography of eachudchapter. Additionally, preceding each Chapter is a brief synopsis that places theudwork in context and acknowledges the contributions of my fellow researchers.