Synthesis and characterization of host-guest complexes : metal-organic nanocapsules using aryl-substituted pyrogallol[4]arenes
Abstract
The desire to synthesize and control self-assembly of molecular nanocapsules has long been a focus within the supramolecular community due to the nanocapsules' potential applications as tools for encapsulation and delivery of host molecules, catalytic media sites, and gas sorption agents. Resorcin[4]arenes (RsC) and pyrogallol[4]arenes (PgC) have received considerable attention due to their preference to form the all-cis cone-shaped (rccc) structure, thus allowing dimeric and hexameric nanocapsule formation through complementary and structurally distinct intermolecular hydrogen bonding interactions or metal coordination. By changing the lower rim R group, one drastically alters the chemical environment. C-arylresorcin[4]arenes, for example, adopt a more kinetically stable 1,2-chair rctt stereostructure but show interconversion to the thermodynamic product, the all-cis rccc cone. In contrast, our studies of the C-arylpyrogallol[4]arenes unexpectedly suggest that the 1,2-chair rctt stereostructure is the thermodynamic product. Herein, we show that complexation of zinc and C-phenylpyrogallol[4]arene, as well as other benzyl derivatives, induces a conformational flip in these macrocycles from chair to cone. This formation of the zinc-seamed metal-organic nanocapsules has been tracked via NMR, X-ray Diffraction and Mass Spectroscopy studies. The results yield several important trends that can be applied towards both the study of supramolecular self-assembly and the utilization of these host-guest capsular entities for other purposes.
Degree
Ph. D.
Thesis Department
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OpenAccess.
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