Helical Pitch, Hydrophobic Binding, Chiral Templation, and Supramolecular Chelation of M-Phenylene Ethynylene Foldamers
Stone, Matthew Thomas
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/87885
Description
Title
Helical Pitch, Hydrophobic Binding, Chiral Templation, and Supramolecular Chelation of M-Phenylene Ethynylene Foldamers
Author(s)
Stone, Matthew Thomas
Issue Date
2005
Doctoral Committee Chair(s)
Moore, Jeffrey S.
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Language
eng
Abstract
"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."
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
