Helical Pitch, Hydrophobic Binding, Chiral Templation, and Supramolecular Chelation of M-Phenylene Ethynylene Foldamers

"Several different m-phenylene ethynylene (m PE) folding oligomers or foldamers were designed, synthesized, and studied. These chain molecules have been shown to adopt a helical conformation under appropriate conditions in solution. A series of double TEMPO spin labeled oligomers were studied by electron spin resonance (ESR) spectroscopy to determine the helical pitch of folded mPE oligomers. Based on the relative degree of broadening observed in the ESR spectra it was determined that there are approximately six repeat units in a single helical turn of a folded mPE oligomer. A water-soluble oligomer with longer hexaethylene glycol sidechains was designed and synthesized to understand the binding properties of the hydrophobic helical cavity in aqueous solutions of acetonitrile. It was found to have an association constant with (-)-alpha-pinene of 1.4 +/- 0.09 x 106 M-1 in 90% water in acetonitrile, which was much higher than predicted from linear extrapolation in previous studies of less soluble oligomers. A mPE oligomer with a helicene moiety in the backbone was designed and synthesized to template the helical handedness of the folded conformation. The conformation of this oligomer was examined by circular dichroism spectroscopy and observed to be highly dependent on solvent composition. A series of pyridine terminated mPE oligomers that varied in chain length were synthesized and determined to form 2:1 complexes with palladium dichloride that were effectively twice the length of the individual strands. Examination by UV absorption and 1H NMR spectroscopy demonstrated that palladium-oligomer complexes of sufficient length had the ability to fold. Pyridine-terminated mPE oligomers of sufficient length showed positive cooperativity based on experimental determination of their association constants with palladium dichloride by isothermal calorimetry. The additional free energy of complexation for the folded oligomers is analogous to chelation by multidentate ligands, but here the ""multidentate ligand"" is held together by supramolecular rather than covalent bonds."

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Stone, Matthew Thomas

Contributors dc:contributor

• Moore, Jeffrey S.

• Chemistry, Organic

Language dc:language

eng

Identifier

(MiAaPQ)AAI3199150

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/87885