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Recognition and sensing of ions is an important front in supramolecular organic chemistry. One remarkable extension of this kind of work is the application of selective switching processes to logic gate operations. In this study, we have designed selective metal ion chelators for zinc and cadmium ions based on dansylamide fluorophores and dipicolylamine chelators. The zinc complex of a previously reported difluoroboradiazaindacene-bipyridyl derivative was shown to respond anions by an increase in emission intensity. We also discovered a hitherto unknown reaction of difluoroboradiazaindacenes and showed that this reaction can be exploited in a very selective sensing of fluoride ions in acetone solutions. The remarkable chemistry of these boradiazaindacene dyes, especially the bipyridyl derivative, allowed us to propose the first example of a unimolecular &ldquo / molecular subtractor&rdquo / . A single molecule can carry out substraction of binary inputs, when these inputs are fluoride anion and zinc cation.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 359-363). Available also in a digital version from Dissertation Abstracts.

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The development of dimetallic metal complexes into functional and selective recognition agents for monophosphorylated peptides is described. The development of dimetallic metal complexes into functional and selective phosphopeptide recognition agents is described. Scaffold functionalization was conducted to assess whether binding affinity for phosphate monoesters could be modulated. A protocol for the facile synthesis of symmetric and asymmetric pyridine-functionalized bis-dipicolylamine (BDPA) scaffolds was thus first optimized. Zn(II) complexes were screened for the ability to bind to various phosphate monoesters of biological relevance using isothermal titration calorimetry (ITC). An expanded family of compounds was then screened using a variety of biophysicial and biological techniques for the ability to bind to disrupt Stat3 dimer both in biophysical assays and in whole cells. Several compounds displayed the ability to potently disrupt Stat3 dimer formation at low micromolar doses. Moreover, one compound emerged as having potent anti-cancer activity against MDA468, a solid breast cancer tumor line. Efforts were subsequently redirected towards the development of Zn(II)-BDPA receptors which mimicked the pY, pY+X recognition motif displayed by human SH2 domains. A family of ditopic biphenyl-based receptors, computationally predicted to adopt this binding mode, were synthesized and screened against a family of high-profile pY-containing phosphopeptides. The reported family of mimetics displayed a wide variance in cytotoxicity against common cancer cell lines, supporting our structure-activity hypothesis. Selectivity observed in our fluorescence intensity assay did not hold in a cellular context. We next pursued the development of selective receptors for phosphopeptides containing pS instead of pY. A diverse family of Zn(II)-BDPA receptors featuring a 2’ substituted benzothiazole core were synthesized, and their binding affinities toward model phosphopeptides assessed. A central conclusion of this project is that development of potent, selective receptors for anionic and hydrophobic peptides will likely be possible only by using receptors with cationic or hydrophobic pendants, and by maximizing phosphopeptide-specific interactions. Lastly, investigations into the use of bowl-type receptors as phosphopeptide recognition agents are presented. Synthesis of a prototype bowl receptor and early efforts to characterize the receptor’s binding preferences using ITC are reported. Progress-to-date in the development of a FRET system, which will be used to measure the receptor’s affinity for different dephosphorylation motifs, is also reported.