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Degree

Doctor of Philosophy, Ohio State University, Chemistry, 2006.

Abstract

The role of cooperativity, correlated motions, and dynamic equilibria in chiral amplification is investigated using pyridine-2,6-dicarboxamide dendritic structures. Synthetic first-, second-, and third-generation dendritic structures with chiral, non-racemic anthranilate substituted amides adopt well-defined secondary conformations in the solid state as well as aqueous and organic solutions. Through cooperative, correlated motions local chirality can be transferred throughout the folded dendritic structure biasing one of the two enantiomeric helical conformations, M or P. Further analysis of the ethylene glycol terminal groups associated with these dendritic structures displayed a correlation of the helical state and the helical bias to the conformation of the OCCO glycol terminal bonds. The correlation of the OC-CO bond from gauche+ in the M helical state to gauche- in the P helical state is a solvent-responsive change that is amplified throughout the helically folded structure resulting in the change in helical bias. However, the gauche/antirelationship associated with the CO-CC bond is directly correlated to the M and P helical states. The synthetic pyridine-2,6-dicarboxamide dendritic structures endure these global conformational changes through cooperative, correlated motions in the dynamic secondary states. At increased generations there is an increase in terminal groups within close proximity and enhanced synchronized motions. With enhanced cooperative, correlated motions less chiral composition is necessary to affect the same helical bias as the corresponding chirally saturated derivative. Unsymmetrical pyridine-2,6-dicarboxamide dendrons consisting of chiral and achiral anthranilate terminal groups give rise to an dis-proportional chiral amplification compared to the amount of chiral composition and a clear example of the “sergeants-and-soldiers” principle. Pyridine-2,6-dicarboxamide-based dendrons adopt dynamic helical secondary conformations through cooperative, correlated motions and endure global structural changes as well as enhanced chiral amplification.

Subject Headings

Chemistry, Organic

Keywords

cooperative, correlated motions; dendrimer; chirality amplification; chirality switching; dynamic secondary conformations

Advisor

Jon R Parquette

Pages

372p.

Document number: osu1155049363
Permalink: http://rave.ohiolink.edu/etdc/view?acc_num=osu1155049363

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