Publication Date

2014-07-29

Availability

Open access

Embargo Period

2014-07-29

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Chemistry (Arts and Sciences)

Date of Defense

2014-06-20

First Committee Member

Angel E. Kaifer

Second Committee Member

James N. Wilson

Third Committee Member

Francisco M. Raymo

Fourth Committee Member

Konstantinos Kavallieratos

Abstract

This dissertation investigates the inclusion complexation behavior of various guest molecules with host molecules cucurbit[8]uril (CB8) and cucurbit[7]uril (CB7). Additionally, new supramolecular systems mediated by cucurbituril host molecules are described. The investigation of these systems have been carried out by a wide range of techniques including NMR Spectroscopy, UV-Visible Spectroscopy, Electrospray Ionization Mass Spectrometry (ESI-MS) and electrochemical methods such as cyclic voltammetry and square-wave voltammetry. Chapter 1 briefly describes supramolecular chemistry and host-guest chemistry. Besides, the cucurbit[n]uril family, which are the host molecules that has been studied in this thesis, is presented and the synthesis of cucurbiturils, their structural properties and binding behaviors of each host molecule are summarized. In Chapter 2, three new guest molecules to form 1:2 host:guest complexes within the cavity of CB8 have been designed and synthesized. Monocationic phenyl-pyridinium derivatives have been studied to form ternary complexes in CB8 cavity. The binding behavior, stoichiometry of complexation and the binding affinities of guest molecules in the presence of one half equiv of host molecule CB8 have been investigated by 1H-NMR spectroscopy, UV-Visible spectroscopy, ESI-MS and PGSE-NMR techniques. In Chapter 3, dimeric forms of two guest molecules, which have been confirmed to form ternary complexes with CB8 in chapter 1, have been introduced and their interactions with CB8 to form supramolecular polymers were investigated. However, instead of forming supramolecular polymers, molecular loops, in which both binding sites of one guest molecule bind to the same CB8 molecule, are formed. The photochemistry experiments, which were performed in the presence of CB8, produced covalently bonded but small species mediated by CB8. In Chapter 4, the formation and kinetics of cucurbituril complexes in non- aqueous solvents have been investigated. Although it has been proposed that the hydrophobic forces are the predominant forces for the formation cucurbituril inclusion complexes, favored ion-dipole interactions solely form inclusion complexes with binding constants that reach 103 M-1 in an organic solvent. Additionally, kinetics of inclusion complexation of two guest molecules at two different temperatures have been studied. In Chapter 5, the effect of presence of a water-structure breaker, urea, on the binding constants and on the electrochemistry of various guest molecules has been investigated. In addition to the impacts of encapsulation on the electrochemistry of the encapsulated guests, the electrochemical response of residues that are adjacent to the cucurbituril portals has also been studied in the absence and in the presence of urea.

Keywords

cucurbiturils; encapsulation; electrochemistry; urea; non-covalent interactions

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