| This dissertation documents the interactions between environmentally significant anions, principally nitrate and fluoride, with a family of known polyammonium macromonocycles and macrobicycles. Three analytical methods used for assessing these highly p[H] and solvent dependent receptor-substrate interactions were: potentiometry, crystallography, and 19F nuclear magnetic resonance (NMR) spectroscopy. This integrated study of the solution and solid-state binding of nitrate, chloride, and fluoride by acid salts of the Schiff base cryptands 1,4,12,15,18,26,31,39-octaaza-pentacyclo-[13.13.13.1.6,10 1.20,241.33,37] tetratetraconta-4,6,7,9,11,18,20(43),21,23,26,31,33(42),34,36,38-pentadecaene (MEACryp), 1,4,11,14,17,24,29,36-octaaza-pentacyclo-[12.12.2.2.6,9 2.19,222.31,34] tetratetraconta-4,6,7,9,10,16,19,20,22,23,29,31,32,34,35-pentadecaene (PEACryp), and 1,4,12,15,18,-26,31,39,42,43,44-undecaaza-pentacyclo-[13.13.13.1. 6,101.20,241.33,37] tetratetraconta-4,6,7,9,11,18,20(43),21,23,26,31,33(42),34,36,38-pentadecaene (PyEACryp) has yielded new insights into ligand conformation and modes of substrate binding under varying conditions of p[H].; Fluoride binding as well as the competitive binding of chloride by acid salts of MEACryp were explored and demonstrated using 19F NMR. Low temperature 19F NMR spectra in DMSO/water solutions were employed to differentiate modes of binding, by identifying the chemical shifts of internally and externally coordinated F- HF species with acid salts of MEACryp, PEACryp, and PyEACryp.; Crystallographic analysis of halide and nitrate complexes of these same receptors graphically illustrated connections between solid state modes of binding and those revealed by 19F NMR spectra. These solid state "snapshots" underscore the considerable structural flexibility of these cryptands. Apical N-N bridgehead distances vary between ∼5.5 A and 10.7 A depending on protonation state, substrate, and mode of binding. Also included in this work is the crystal structure of MeaCryp·6HNO 3, which showed unprecedented encapsulation of two discrete nitrate ions in an eclipsed conformation. A recurrent theme in these structures is the importance of water mediated hydrogen bonds between the protonated amines of the receptors and the anionic substrates, particularly nitrate. Solvent molecules play an integral role in formation of the crystal lattice of the octaaza free base, MEACryp.; Synthetic advances in this work include a new method for obtaining crystalline free base from the halide salts of octaazacryptophanes and a new anthracene-appended bibracchial Schiff base macromonocycle. Finally, a new tripodal polyamide/amine starting material, 2-amino-N-(2-{lcub}bis-[2-(-aminoacetylamino)ethyl]-amino{rcub}-ethyl)-acetamide, was designed and synthesized for future work on anion receptors possessing greater p[H] flexibility. |
