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

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Not available / text

Molecular recognition is a major branch of modern organic chemistry, and it resides at the forefront of supramolecular chemistry. Supramolecular chemistry refers to the study of the noncovalent intermolecular interaction that are crucial for biological processes, catalytic systems, the organization of crystalline or solution phase superstructures, and molecular recognition to name a few examples. The following dissertation reports research efforts from the Anslyn group into three topics of fundamental interest to the molecular recognition community: cooperativity, array sensing, and the development of highly selective sensors for minimally functionalized analytes. Chapter 1 is a review of the most fundamental points of molecular recognition as it applies to the experimental work that follows. Intermolecular association phenomena are driven by multiple discrete, noncovalent interactions, and cooperativity is a measure of the efficiency with which these interactions are employed in a given system. Cooperativity is poorly understood despite its ubiquity in biological and molecular recognition contexts. The first synthetic hostguest system exhibiting positive cooperativity in water is reported in Chapter 2. The utility of sensitive but unselective sensors when applied in an array format has recently come to light. Chapter 3 details an array of polyaromatic fluorophores dissolved in an aqueous surfactant solution that was used to sense nitrated explosives. This exceptionally unselective quenching process was able to detect and discriminate nitrated explosives such as RDX and TNT at concentrations as low as 19 [mu]M. Finally, Chapters 4 and 5 report different approaches to the sensing of enantiomeric excess in [alpha]-chiral alcohols using an indicator displacement paradigm. Chapter 4 explores unprecedented efforts to convert the Sharpless catalytic epoxidation system to the first Ti[superscript IV]-based molecular recognition system. Chapter 5 focuses upon a two-stage approach of derivatization of the [alpha]-chiral alcohol to a metal chelating ligand followed by employment of the derivative in an indicator displacement assay. / text

The dissertation focuses on the recent discovery in supramolecular chemistry of novel macrocyclic compounds with NH and CH donor groups. Chapter 1 provides a brief overview of the anions under study, supramolecular chemistry, the relevant other anion receptors, as well as previous findings involving the use of CH donor groups as functional building blocks. Chapter 2, as the major focus of this dissertation, describes a pyrrolyl-based triazolophane, incorporating CH and NH donor groups, which acts as a receptor for the pyrophosphate anion in chloroform solution. It shows selectivity for this trianion, followed by HSO₄− > H₂PO₄− > Cl− > Br− (all as the corresponding tetrabutylammonium salts), with NH−anion interactions being more important than CH−anion interactions. In the solid state, the receptor binds the pyrophosphate anion in a clip-like slot via NH and CH hydrogen bonds. Chapter 3 describes a pyrrole–based triazolium–phane which has been prepared through “click” chemistry in moderate yield. It displays a high selectivity for tetrahedral oxyanions relative to various test monoanions and trigonal planar anions in mixed polar organic–aqueous solvent media. It was also found that the binding affinity and selectivity of the macrocycle to the anions are solvent dependent. Several crystal structures were solved. They confirm that the cationic macrocycle ring binds pyrophosphate and phosphate anions in the solid state. Finally, chapter 4 describes a novel 1,3,4-substituted 1,2,3-triazolium salt found to function as an effective precursor for the synthesis of structurally characterized cationic silver(I) and ruthenium(II) carbene complexes of overall 1:2 ligand-to-metal stoichiometry. The Ag(I) complex crystallized in the form of an eight silver atom containing cluster, whereas the Ru(II) complex proved to be a discrete species and was found to be capable of initiating the ring-opening metathesis polymerization of norbornene upon activation with (trimethylsilyl)diazomethane. / text

The focus of the research presented in this thesis is the design, synthesis, and anion recognition properties of a structurally novel class of poly(amides) that incorporates the diaminocyclobutenedione (squaramide) group into the polymer backbone. In Chapter 1, a brief overview of different anion-responsive synthetic macromolecules is presented. Emphasis is placed on the wide structural diversity of the polymers, the mechanisms of their anion-induced responses, and features such as signal amplification, multivalency, and cooperative behavior that can be exploited productively in the context of anion recognition and sensing. Chapter 2 describes a new method for the regioselective preparation of squaramides, using Lewis acid-catalyzed condensations of diethyl squarate and different anilines. Zinc trifluoromethanesulfonate promotes efficient condensations of anilines with squarate esters, providing access to symmetrical and unsymmetrical squaramides in high yields from readily available starting materials. Colorimetric anion-sensing behavior and computational studies illustrating the enhanced hydrogen bond donor ability and acidity of squaramides in comparison to ureas are presented. In Chapter 3, the application of the synthetic method described above to the selective preparation of polysquaramides composed of 1,2-isomeric repeat units is described. The optical, thermal and aggregation properties of these materials are also discussed. Finally, Chapter 4 describes self-assembly properties as well as applications of these materials in the area of anion recognition and sensing. Incorporating an anion-binding squaramide group into a polymeric architecture results in drastic alterations in the selectivity and magnitude of its anion-induced response, resulting in a sensitive and discriminating turn-on fluorescence sensor for dihydrogenphosphate ions. This unusual behavior is the result of a cooperative, anion-triggered aggregation process that was further probed by dynamic light scattering (DLS), transmission electron microscopy (TEM) and laser confocal microscopy.