This Thesis explores the topic of large amplitude motion within molecular machines and the different mechanisms and molecular architectures that are exploited in order to achieve control over the relative positions of submolecular components with respect to one another. Chapter One provides a thorough survey of a vast range of molecular switches and machines that have been developed during the last two decades. The focus is on interlocked and non-interlocked systems that display highly controlled large amplitude motion and the principles that govern their operation. Initially, simple molecular switches and shuttles are described with the chapter finally arriving at complex molecular machines such as motors, ratchets and walking molecules. The importance of understanding the different mechanisms that dictate the operation of switchable molecular machines and their fundamental differences are highlighted throughout the chapter. Chapters Two to Four are devoted to reporting the author’s contributions to novel switchable molecular systems. Chapter Two describes the serendipitous discovery of an ion-pair template which has been exploited in rotaxane formation and the operation of an orthogonal interaction anion-switchable molecular shuttle. The macrocycle moves back and forth along the thread between a cationic pyridinium station and a metal coordinating triazole motif when chloride anions are bound and removed respectively from a palladium centre which is located inside the cavity of the macrocycle. Excellent positional integrity (>98%) of the ring at both stations is achieved due to the orthogonal binding modes in the two states of the shuttle. Chapter Three presents a non-interlocked molecular switch that operates through the manipulation of dynamic covalent chemistry. The switch is comprised of a “two legged”, small organic molecule (a “walking unit”), anchored to a three foothold track via one disulfide and one hydrazone bond. The acid promoted hydrazone exchange allows a specific ratio of the two positional isomers to be achieved at equilibrium. However, the system is also arranged in such a manner that the ratio can be biased towards one positional isomer when the hydrazone exchange is carried out alongside the photoisomerisation (Z  E) of a stilbene motif which is incorporated in the track. The isomerisation alters the relative free energies of the products by increasing the ring strain of one positional isomer with respect to the other, hence introducing bias into the system. The final chapter reports the logical progression of the work presented in Chapter Three and describes the pursuit of a four-station dynamic covalent energy ratchet, of which the net position of the walker unit can be driven away from a steady state, minimum energy distribution by orthogonal disulfide and hydrazone exchange and concomitant stilbene isomerisation. The endeavour towards the successful synthesis of this rather complex molecule is described alongside the principles for its proposed operation. Chapter Two is presented in the form of an article that has already been published in a peer-reviewed journal. No attempt has been made to rewrite this work other than a slight alteration in the order of figures in the text to allow for easier reading and re-formatting to ensure consistency of presentation throughout this thesis. The original paper is reproduced, in its published format in the Appendix. Chapters Two, Three and Four begin with a synopsis to provide a general overview of the work that is presented in addition to a grateful acknowledgement of the contribution of my fellow researchers.

This thesis describes the synthesis of polyyne rotaxanes and an investigation of their excited state photophysical properties. The threading of dumbbell-shaped carbon chains with macrocyclic components is a way to mechanically insulate and control the environment around the carbon chains. The resulting polyyne rotaxanes can serve as model compounds for insulated carbyne. Different strategies have been tested for the synthesis of polyyne rotaxanes with different topologies and structures. Study of rotaxanes in the excited states reveals strong electronic communication between an acetylenic thread and a macrocycle. Chapter 1 summarizes the field of acetylene scaffolding, introducing some recent achievements in acetylene chemistry. General synthetic methods for polyynes are discussed, and an introduction to active metal template synthesis of rotaxanes is given. Chapter 2 describes the synthesis of a family of polyyne rotaxanes with different axle lengths and macrocycles, prepared by homocoupling of terminal alkynes. Synthesis of hexayne rotaxane with functional pyridine end-group is presented and a number of crystal structures of polyyne rotaxanes are analyzed. Chapter 3 demonstrates the use of acetylene cross-coupling in the synthesis of rotaxanes. Synthesis of rotaxanes with different topological structure is provided. Chapter 4 details the excited state properties of polyynes studied by time -resolved spectroscopy. The complexes of rhenium(I) carbonyls with rotaxanes is presented and the excited state energy transfer in rotaxanes is studied. Chapter 5 explores new synthetic strategies for polyyne rotaxanes, using "masked" precursors. It also highlights the potential of carbenoid rearrangement of alkyliden es for the construction of linear and cyclic architectures. Chapter 6 is the summary of the project and general discussion of future directions. There are two appendices in the end of thesis: Appendix A covers the photophysics of rhenium tricarbonyl complex of the hexayne rotaxane with a small macrocycle and Appendix B reports work towards the synthesis of rotaxanes with platinum(II)-alkyne complexes.

Wong, Wing Yan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 76-79). / Abstracts in English and Chinese. / Contents --- p.i / Acknowledgments --- p.iii / Abstract --- p.iv / Abbreviations and Acronyms --- p.vii / Publications Originated from the Work of this Thesis --- p.ix / Chapter Part I: --- "Self-Assemblyy Stability Quantification, Controlled Molecular Switching, and Sensing Properties of an Anthracene-Containing Dynamic [2]Rotaxane" / Chapter Chapter 1 - --- Introduction / Chapter 1.1 --- Definition of Rotaxane --- p.2 / Chapter 1.2 --- Dynamic Covalent Chemistry in Rotaxane Synthesis --- p.5 / Chapter 1.3 --- Thermodynamic Template --- p.6 / Chapter 1.4 --- Molecular Sensing Properties in Rotaxane --- p.10 / Chapter 1.5 --- Examples --- p.13 / Chapter Chapter 2 - --- Anthracene-Containing Dynamic [2]Rotaxane / Chapter 2.1 --- Background --- p.17 / Chapter 2.2 --- Modification and Design of Dynamic [2]Rotaxane --- p.18 / Chapter 2.3 --- Self-Assembly of Rotaxane and Synthesis of Components --- p.19 / Chapter 2.4 --- Characterization / Chapter 2.4.1 --- 1H NMR Spectroscopy --- p.21 / Chapter 2.4.2 --- 13C NMR Spectroscopy --- p.23 / Chapter 2.4.3 --- Mass Spectrometry --- p.24 / Chapter 2.4.4 --- X-Ray Crystallography --- p.25 / Chapter 2.4.5 --- UV/Visible Absorption and Fluorescence Spectroscopies --- p.26 / Chapter 2.5 --- Effect of External Stimuli / Chapter 2.5.1 --- Addition of Water --- p.29 / Chapter 2.5.2 --- Addition of Acid --- p.33 / Chapter 2.5.3 --- Addition of Salts --- p.38 / Chapter 2.5.4 --- Addition of Amines --- p.40 / Chapter 2.6 --- Conclusions --- p.43 / Chapter Part II: --- Substituent Effect in Imine-Containing Molecular Tweezers / Chapter Chapter 3 - --- Molecular Tweezers / Chapter 3.1 --- Introduction --- p.46 / Chapter 3.2 --- Synthesis --- p.48 / Chapter 3.3 --- Characterization of Molecular Tweezers / Chapter 3.3.1 --- 1H NMR Spectroscopy --- p.49 / Chapter 3.3.2 --- Mass Spectrometry --- p.51 / Chapter 3.4 --- Characterization of Molecular Tweezers / Chapter 3.4.1 --- 1H NMR Spectroscopy --- p.51 / Chapter 3.4.2 --- X-Ray Crystallography --- p.59 / Chapter 3.4.3 --- Mass Spectrometry --- p.60 / Chapter 3.4.4 --- UV/Visible Absorption Spectroscopy --- p.61 / Chapter 3.5 --- Conclusions --- p.63 / Chapter Chapter 4 - --- Experimental Procedures / Chapter 4.1 --- General Information --- p.64 / Chapter 4.2 --- General Synthetic Procedures for Molecular Tweezers (34-40) --- p.65 / Chapter 4.3 --- Experimental Procedures --- p.65 / Chapter 4.4 --- Determination of Binding Constant K --- p.73 / References --- p.76 / Appendix / List of Spectra --- p.A-l / List of Crystal Data --- p.A-2

La synthèse de caténanes et rotaxanes remonte aux années 60. Aujourd'hui la plupart de ces molécules enchevêtrées, synthétisées comportent jusqu'à 4 éléments et ce nombre continu de croître. Toutefois, ces molécules restent relativement petites, comparées `a celles trouvées dans la nature tels que les caténanes présents dans l'ADN. Les caténanes et rotaxanes sont des molécules mécaniquement assemblées, composées de pièces mobiles, liées, ou non (ou plus d'elles), pouvant se mouvoir et/ou se déplacer par rapport aux autres. Cette architecture unique les rend très intéressants et fait d'eux des candidats potentiels pour les machines moléculaires, ainsi que pour des applications dans le domaine de l'optique non linéaire, en particulier dans la photonique, l'optoélectronique et le stockage de données optique. Dans ce travail, nous exposons les résultats de nos recherches portant sur les propriétés optiques non-linéaires de quelques caténanes et rotaxanes. Ces propriétés non-linéaires ont été abordées par différentes techniques. Les résultats montrent une importante contribution électronique dans la susceptibilité non-linéaire de troisième ordre confirmée par des calculs théoriques au niveau moléculaire. Nous exposons également les résultats des propriétés optiques non linéaires de l'ADN fonctionnalisé. Ces résultats montrent une recrudescence des non linéarités quand l'ADN modifiée est utilisé. Par ailleurs, on a observé les meilleurs résultats dans des expériences d'holographie quand l'ADN-CTMA est utilisé comme matrice pour le dopage du disperse red 1.

Thèse doctorat : Chimie Organo-Minérale : Strasbourg 1 : 2007. / Titre provenant de l'écran-titre. Bibliogr. 5 p.

Thesis (Ph. D.)--School of Textile and Fiber Engineering, Georgia Institute of Technology, 2004. Directed Haskell W. Beckham. / Includes bibliographical references.

No description available.

The focus of the following research was to use the self-assembly process to create rotaxanes between several large bisphenylene crown ethers (> 22 atoms) with secondary ammonium salts. Also of great interest was to understand the complexation behavior of the crown ethers with the salts, with emphasis on determining the stoichiometries and association constants of the complexations in solution using NMR spectroscopy. The stoichiometry of the complexes was determined by the mole ratio method and the association constants were calculated graphically. Bis-(m-phenylene)-26-crown-8 did not form a complex in solution with several secondary ammonium salts even though the cavity size is large enough to allow the formation of pseudorotaxanes. However, the larger crown ether, bis-(m-phenylene)-32-crown-10 (BMP32C10), did form a complex. The complex stoichiometry varied between 1:1 (crown:salt) in solution and 1:2 in the solid state as evidenced by NMR and X-ray crystallography, respectively. The solid state complexes were pseudorotaxanes. Also, an interesting "exo" complex was formed in the solid state between BMP32C10 and a secondary diammonium salt. The major binding force for the complexes in the X-ray structures was hydrogen bonding. Weaker secondary stabilization was achieved via aryl-aryl aromatic interactions. The difference between the stoichiometries in the two phases and the observance of an "exo" complex demonstrates that one must be careful in describing the complexes in each phase. Also investigated was the complexation formed between dibenzo-24-crown-8 (DB24C8) and secondary diammonium salts. The association constants for the complexes were found to be relatively higher. Due to the weaker association constants and the different stoichiometries of complexation the meta-susbtituted bisphenylene crown ethers were not recommended for the formation of larger complexes, i.e. polyrotaxanes. However, it is suggested that the DB24C8 moiety be used in components of supramolecular assemblies. The functionalization of poly(propylene imine) dendrimers with two different crown ethers as peripheral moieties was attempted. The 1st, 3rd, and 5th generation poly(propylene imine) dendrimers were functionalized with 1,3-phenylene-16-crown-5 moieties by reacting the surface primary amines with the corresponding succinimide ester of the crown ether. The larger DB24C8 succinimide ester was not as reactive and full functionalization was not achieved. / Ph. D.

In the last twenty years, chemists have devised numerous synthetic chemical systems in which self-replication operates, demonstrating that molecules can replicate themselves without the aid of enzymes and that self-replication is not a prerogative of nucleic acids only. However, the coupling of replication to other recognition-mediated events and its exploitation in the amplification of large supramolecular assemblies, such as mechanically interlocked molecules, have remained unexplored areas. Among mechanically interlocked molecules, rotaxanes represent particularly attractive targets because of their application as molecular switches. This thesis describes how the recognition-mediated synthesis of a rotaxane can be combined to the amplification of its structure by replication. Kinetic models for the integration of self-replication with the formation of a rotaxane are presented. The logical steps required to convert these models into molecular structures through consideration of the design criteria highlighted by the models are discussed and executed. The macrocyclic component is an essential part of a rotaxane. The synthesis of several novel macrocycles is presented. Their ability to bind guests in their cavities through hydrogen bonds was probed. The best macrocycle/guest pairs were integrated in the formation of rotaxanes. Further investigations on the stoppering reaction and on the various recognition processes involved in the system lead ultimately to the construction of self-replicating rotaxanes.

No description available.