Title

Syntheses of ion-carrier lariat ethers: Their cation binding ability and cation transport properties, and, Syntheses of steroidal lariat ethers: Their amphiphilic behavior and self-assembly properties

Date of Award

1991

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Chemistry

First Committee Member

George W. Gokel, Committee Chair

Abstract

Supramolecular chemistry terminology and principles were included in a brief introductory chapter aimed to familiarize the reader with this chemistry field.A series of novel nitrogen-pivot lariat ethers were synthesized to determine the influence of amide and ester moieties on their cation binding ability. The synthetic procedure used was straightforward although purification proved challenging. Equilibrium stability (binding) constants studies and conformational studies (performed by $\sp1$H NMR spectroscopy) gave evidence of significant sidearm contribution to cation complexation.The above series of compounds also showed interesting cation-carrier behavior when submitted to transport experiments in both liquid membranes and synthetic vesicles. These lariat ethers displayed better transport efficiency than monensin and nonactin (naturally occurring carriers) under our transport conditions. In addition, it was demonstrated for the first time that, even though, both homogeneous binding constants and picrate extraction constants are useful predictors of transport efficiency, the former is better than the latter within the series of compounds studied. Furthermore a direct correlation was found between binding constants and transport rates in both liquid membranes and synthetic vesicles.Finally, amphiphiles containing an azacrown ether binding site were prepared to study the structural features which influence molecular aggregation. The first example of niosomes (nonionic liposomes) was obtained by dispersion of 15-membered ring analogues in water. Unusual aggregation behavior was obtained for an 18-membered ring analogue. Experimental results suggest that upon addition of potassium chloride, cholesteryl-N-(aza-18-crown-6)acetate has the ability to undergo variations in its aggregation state from micelles when no salt is added to vesicles in the presence of salt.

Keywords

Chemistry, Organic

Link to Full Text

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