Non-Covalent Interactions in Aqueous Media: Molecular Recognition Studies Through Circular Dichroism and Self-Assembly of Discrete Aggregates

Citation

Forman, Jonathan Eric (1996) Non-Covalent Interactions in Aqueous Media: Molecular Recognition Studies Through Circular Dichroism and Self-Assembly of Discrete Aggregates. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/ce8j-qk19. https://resolver.caltech.edu/CaltechTHESIS:12222020-175451626

Abstract

The application of circular dichroism (CD) spectroscopy to the study of molecular recognition phenomena in chiral water-soluble cyclophane hosts is described. The CD method produces results that complement and expand upon previous NMR studies. This includes allowing the measurement of larger binding constants by allowing studies to be carried out at lower concentrations.

Using the excitonic chirality method, these studies have provided a means of assigning the absolute stereochemistry of the ethenoanthracene building blocks used in preparation of the hosts. This information, along with an x-ray structure of one of the cyclophane molecules, has provided important information concerning host structure. The x-ray structure and CD spectral changes observed on guest binding have also served to provide direct experimental evidence for binding conformations of the hosts.

The chiral hosts have been shown to induce CD in achiral chromophoric guests. Analysis of this induced CD using INDO/S and coupled-oscillator calculations has provided valuable information concerning the conformations of the bound guest. These data complement information obtained in NMR studies (D values) and provide additional insights into the important factors that govern the binding event.

Finally, preliminary studies of self-assembling systems in aqueous media are reported. These studies employ etheno- and ethanoanthracene based structures designed to form aggregates with well defined order and discrete stoichiometries. These molecules are designed to aggregate through hydrophobic forces. The aggregate is kept from becoming a micelle using polar groups strategically placed to complement one another within the assembling structure.

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