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Recognition and communication in supramolecular chemistry
Supramolecular chemistry, and in particular molecular recognition through non-covalent interactions is responsible for a vast number of vital biochemical functions. One class of these functions allows enzymes to tune the redox properties of cofactors derived from vitamin-B2 to engage in tasks specific to that protein. In our preliminary investigations, we studied a functional analog of these cofactors in the context of artificial receptors, designed to interact with the guest substance through a specific pattern of hydrogen bonding. We showed experimentally that even in systems that exhibit equivalent hydrogen bonding patterns, marked differences could be observed regarding modulation of molecular properties such as the redox potential of the guest. It was demonstrated computationally that these differences could be attributed to subtle changes in the natures of the hydrogen bonds themselves with the use of strongly polarizable hydrogen bond donors giving the greatest modulation of the physical characteristic of the guest. We then employed π-stacking units in conjunction with the same hydrogen bonding contacts to further explore the use of non-covalent interactions to tailor the physical properties of a guest substance. Experimental work showed that using two sets of non-covalent interactions in combination, marked differences could be observed in the binding of one guest oxidation state relative to another. These differences in binding manifested themselves directly as changes in the redox properties of the guest substance. The knowledge gained from this work allowed us to design and construct dual input electro- and photochemically controlled devices. In order to integrate molecular recognition with current technology, we endeavored to explore how substrate-receptor interactions would operate in the context of a macromolecular environment. Studies on the binding of an electron deficient guest molecule using a polymer appended with electron rich recognition units showed that substantial changes in polymer volume and thermal characteristics accompanied guest binding. Using specific interactions in the form of a hydrogen-bonding pattern it was demonstrated that efficient guest binding is strongly dependent on the exposure of the recognition units to the surrounding medium. Furthermore, we demonstrated that using specific interactions between recognition grafted polymers and complementary nanoparticles, extended well ordered aggregates could be produced. The efficient propagation of order was found to be promoted by compact polymers that were best able to fill the interstitial voids between the spherical particles. Finally, we studied the aggregates formed between complementary functionalized polymers. It was demonstrated that the self-assembly of complementary polymer strands lead to the formation of giant vesicles through specific interchain hydrogen bonding.
Gray, Mark, "Recognition and communication in supramolecular chemistry" (2003). Doctoral Dissertations Available from Proquest. AAI3078688.