Synthesis, Characterization, and Application of Water-Soluble Chiral Calix[4]arene Derivatives in Spectroscopy and Capillary Electrokinetic Chromatography

• Main Author: Hamilton, Kim
• Other Authors: Andrew W. Maverick
• Format: Others
• Language: en
• Published: LSU 2003
• Subjects: Chemistry
• Online Access: http://etd.lsu.edu/docs/available/etd-0710103-222546/

This dissertation is an account of the synthesis, characterization, and application of novel water-soluble chiral calixarenes in spectroscopy and capillary electrophoresis. It is divided into four sections. The first part describes the synthesis and nuclear magnetic resonance (NMR) characterization of four p-t-butylcalix[4]arenes bearing L-amino acid moieties on their lower rims (CX4-AA). The structure and conformation of the derivatives have been determined using one- and two-dimensional NMR techniques. Proton and carbon-13 spectra show that the derivatives are tetra-substituted and adopt a cone conformation. The preparation and characterization of silica-bonded calixarene stationary phases for capillary electrochromatography is also reported in Chapter 2. A novel synthesis has been attempted, in which one monomer unit of the calixarene is covalently attached to aminopropyl silica (APS) via the formation of a peptide bond between the carboxylate terminus of the calixarene-amino acid moiety and the primary amine of APS. Elemental analyses of the calixarene stationary phases show increases in the percentages of carbon, hydrogen, and nitrogen compared to unmodified APS. Carbon-13 cross polarization-magic angle spinning NMR (CP-MAS NMR) is used to confirm successful attachment of the calixarenes to APS. The third part focuses on the use of these derivatives as pseudostationary phases in electrokinetic capillary chromatography (EKC). Comparisons have been made pointing out the structural influence of each derivative on its selectivity toward enantiomeric and atropisomeric pairs. Electrokinetic parameters such as buffer pH, chiral selector concentration, and organic modifier concentration are varied to yield the best compromise between analyte resolution and elution times. Spectroscopic studies of calixarene inclusion complexes generally focus on the properties of molecules whose absorption and emission bands do not overlap those of calixarenes. In order to investigate the complexation behavior of CX4-AA derivatives with binaphthyl atropisomers, special considerations had to be taken because CX4-AA emission signals overlap those of binaphthyls. In Chapter 4, a steady-state fluorescence method is proposed which investigates and corrects for inner-filter effects of calixarenes during complexation studies of guests with overlapping absorption and emission. Association constants and complex stoichiometries are then determined from steady state fluorescence measurements and general correlations between EKC and fluorescence data are established.