Title page for ETD etd-01092004-112614


Type of Document Master's Thesis
Author Fletcher, Amy L.
Author's Email Address afletche@vt.edu
URN etd-01092004-112614
Title Thermodynamically Driven (Reversible) End-Capping of Pseudorotaxanes to Produce Rotaxanes
Degree Master of Science
Department Chemistry
Advisory Committee
Advisor Name Title
Gibson, Harry W. Committee Chair
McGrath, James E. Committee Member
Ward, Thomas C. Committee Member
Keywords
  • Supramolecular Chemistry
  • Self-Assembly
  • Pseudorotaxane
  • Rotaxane
Date of Defense 2003-08-29
Availability unrestricted
Abstract
Rotaxanes can be synthesized using a thermodynamically driven approach of self-assembly. The thermodynamically driven approach is an efficient method to provide a better controlled synthesis of specific structures. This synthetic approach takes advantage of a labile bond between the guest molecule and the end stopper group. The reversibility of this bond allows for threading by the host molecule via chemical equilibrium. Intramolecular interactions such as hydrogen bonding and π-π stacking facilitate threading to form the pseudorotaxane which is endcapped to form the thermodynamically stable rotaxane.

In this work, the synthesis and characterization of rotaxanes using a thermodynamically driven approach is reported. New OH-functionalized secondary dibenzyl ammonium hexafluorophosphate and tetrafluoroborate salts were synthesized and complexed with dibenzo-24-crown-8. The complexation between the salts and dibenzo-24-crown-8 was observed using 1D and 2D 1H NMR spectroscopy. An association constant of 110 M-1 was determined by integration for the pseudorotaxane from the ammonium hexafluorophospate salt and dibenzo-24-crown-8. The new guest species were endcapped in situ as trityl ethers to form new thermodynamically stable rotaxanes. Further work to pursue would include synthesis of rotaxanes using functionalized crown ethers for polymerization to make polyrotaxanes and synthesis of self-assembled polymers using this synthetic method.

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