Title

Selectivity and mechanism in cation-macrocycle interactions

Date of Award

1991

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Chemistry

First Committee Member

George W. Gokel, Committee Chair

Abstract

Studies of cation interactions with macrocycles have grown exponentially throughout the 1980s, culminating with the 1987 Nobel prize being awarded for significant contributions to macrocycle chemistry. The studies presented here explore the selectivity and mechanism of cation-macrocycle interactions, with a particular emphasis on lariat and bibracchial lariat ethers. Stereochemical and thermodynamic contributions to the overall binding are examined, and the free-energy change of cation-macrocycle complexation is further partitioned into its enthalpic and entropic components.The remarkably high binding of Ca$\sp{2+}$ by diaza dipeptide bibracchial lariat ethers in water is the highest reported to date, and their selectivity for Ca$\sp{2+}$ over Na$\sp{+}$ in water exceeds 10$\sp4$ and even 10$\sp5$ with certain derivatives. Enthalpic and entropic contributions to this unusual binding are examined, and a procedure for obtaining this data is described. A mechanism for this remarkable calcium ion binding and selectivity is proposed. Comprehensive tables of binding constants, with multiple references, are presented for a host of macrocycles.

Keywords

Chemistry, Analytical; Chemistry, Organic; Chemistry, Physical

Link to Full Text

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