The chemistry of the non-covalent bond has developed rapidly over the last few decades. In particular, the successful construction of nanoscale assemblies by non-covalent forces has been described more frequently in the recent literature. This significant progress is largely due to transferring of concepts found in the biological systems (e.g., the tobacco mosaic virus and the DNA double helix) to the area of synthetic chemistry. As an example, the architecture of the double helix, perhaps the most well-known biological self-assembling structure, remarkably demonstrates the ability of biological systems to construct large supramolecules by multiple aggregations of relatively simple building blocks by means of hydrogen bonding. Scientists have begun to employ such synthetic strategy adopted in Nature to construct nanoscale systems. The use of pseudorotaxane assemblies formed between the suitably sized crown ethers and dipyridinium salts (paraquats) or dibenzylammonium ions is a viable synthetic strategy to construct non-covalent systems because of their selectivity and strong hydrogen bonding ability. We describe the syntheses and characterization of non-covalent assemblies of different sizes and shapes via the pseudorotaxane approach. A series of dendritic pseudorotaxanes were efficiently prepared from self-assembling complimentary building blocks, namely a triply charged ammonium ion and the 1st, 2nd, and 3rd generations of benzyl ether dendrons bearing dibenzo-24-crown-8 moiety. The wholly complexed self-assembling dendrimers were evidenced by 1H NMR spectroscopy and mass spectrometry. Linear supramolecular pseudorotaxane polymers were formed with reversible chain extension in solution by self-assembly of two complimentary homoditopic molecules with secondary ammonium ion and dibenzo-24-crown-8 moieties. The fraction of the cyclic dimer and the size of the linear suprastructures were determined in solution by 1H NMR spectroscopy as a function of concentration. Viscosity measurements corroborated the presence of aggregates of large hydrodynamic volume at high concentrations. The solid state samples of the supramolecular polymers, prepared by freeze-drying, were analyzed by DSC and optical microscopy and shown to be distinct from the starting materials and the cyclic dimer. Fibers and films were formed from high concentration solutions, corroborating the polymeric nature of the aggregates. Similarly, polymolecular arrays were formed in solution from a heteroditopic self-complimentary molecule, comprising bis-m-phenylene-32-crown-10 and a paraquat unit. Side-chain polypseudorotaxanes were prepared from spontaneous association of polymethacrylates bearing dibenzo-24-crown-8 and secondary ammonium ions. The complexation behavior in solution was investigated using 1H NMR spectroscopy. The solid state samples of side-chain polypseudorotaxanes, prepared by freeze-drying, showed noticeable changes in thermal behavior and morphology from the individual components. / Ph. D.

Des supramolécules basées sur la reconnaissance de viologènes par des curcubit[n]urils (CB[n]) ont été étudiées. Les systèmes développées incluent des [3]-, [4]- et [7]pseudorotaxanes, composés de multimères à base de viologène et de CB[7] ou CB[8]. L’étude physicochimique a montré que ces supramolécules sont interconverties électrochimiquement entre un état complexé, défini par les pseudorotaxanes, et un état dissocié comprenant chacun des partenaires. Le désassemblage résulte d’une pimérisation intra/intermoléculaire entre radicaux viologènes.L’étude physicochimique de complexes pentacoordinés basés sur la reconnaissance d’azo-aryl-imidazoles par une porphyrine à anse phénanthroline a été menée; l’objectif étant d’utiliser les propriétés d’isomérisation photoinduite trans-cis d’azo-chromophores pour dissocier ces complexes. Les complexes initiaux sont alors régénérés par relaxation thermique. La stabilité et les propriétés cinétiques des complexes pentacoordinés ont été évaluées. / Supramolecules based on the recognition of redox-active bipyridiniums by cucurbit[n]uril (CB[n]) have been studied. The investigated systems include a [3]-, a [4]- and a [7]pseudorotaxane, each of them composed of a multimeric viologen-based thread molecule and CB[7] or CB[8]. The physicochemical approach emphasized that these systems can be electrochemically switched between a complexed state, defined by the pseudorotaxanes, and an uncomplexed state comprising their components. The disassembly results from intra/intermolecular pimerization of the viologen radicals.A physicochemical approach of pentacoordinated complexes of a phen-strapped porphyrin with azo-arylimidazoles has been undertaken with the aim to use the photoinduced trans-cis isomerization properties of azo-chromophores to dissociate the complexes. Thermal equilibration reinstates the thermodynamically favoured complexes. The strength and the kinetic properties of these pentacoordinated species have been evaluated.

Due in large part to the growth and development of reliable surface characterization techniques, as well as to advances in the physical and chemical techniques used to modify surfaces, the technology of surface modification has seen rapid expansion over the past two decades. A major thrust of this research is the growth of controlled/"living" polymeric brushes from the surface of various substrates, an advance that promises to be a facile and reproducible way of altering surface properties. A unique initiator bearing ATRP (atom transfer radical polymerization), cleavage, and condensation functionalities was prepared and attached to the hydrolyzed surface of silica gel. Preliminary results indicate that control of reversibly terminated grafts of varying degrees of polymerization with polydispersity indices approaching 1.5 can be readily achieved-significant findings in the quest to design desired surface characteristics. Important physical characteristics may also be altered by way of varying molecular topologies. In the second major research thrust, the use of self-assembly to construct such topologies in the form of pseudorotaxanes fashioned from diverse macrocycles with multifarious guest ions is discussed. While the underlying goal was to investigate and understand the mode of complexation based on such environmental factors as substituent affects and neighboring group influences, new insight was gained on the synthetic manipulation of cooperative events-events that freely occur in nature. The complexation behavior of several functionalized bis-(meta-phenylene)-32-crown-10 macrocycles with various paraquat guest moieties was. As expected, studies indicated that electron-donating substituents on the crown ether drive association, a likely result of increased p -p interactions among host and guest species. The association between a bicyclic macrocycle and dimethyl paraquat was also investigated. Not surprisingly, binding of paraquat by the bicyclic was much stronger than the binding found in analogous macrocycles. Lastly, the endgroup functionalization of poly(propyleneimine) dendrimers with two crown ether macrocycles was performed and the complexation with host-specific guests studied. Curiously, two extreme binding regimes were found: the larger 32-membered crown ether assembly displayed anti-cooperative behavior upon complexation with paraquat, while the smaller 24-membered macrocyclic system exhibited cooperative effects with 2o ammonium ions. These cooperative results are among the very first described for non-biological systems and hint at their potential use in developing highly efficient, synthetically designed supramolecular systems. / Master of Science