Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemistry

Supervisor

James A. Wisner

Abstract

This thesis exploits the use of a photochromic system in a self-complementary hydrogen bond array; i.e. the azo group, -N=N. The novelty of the approach described in this thesis resides in the double function of the azo group within the array: as a hydrogen bond acceptor site and as an element that promotes a structural change capable of disrupting the complexation equilibrium when irradiated with light.

The photo-isomerizable self-complementary hydrogen bond arrays presented are obtained by a general and practical synthetic method from inexpensive starting materials. Their self-complementary recognition was corroborated by 1H NMR dilution experiments and single crystal X-ray structures. In the course of these studies, it was observed that the electron withdrawing character of the substituents employed, the presence of solvent-solute interactions and the disposition of the binding sites have a significant effect over the dimerization constants obtained.

Likewise, some photochemical properties of these systems were studied, such as their UV-Vis absorption spectra, the cis/trans ratio at their photostationary state after trans- to cis- photoisomerization, the stability of the complexes present in solution after UV- light irradiation, and the decay profile of their cis-isomeric forms. The distribution profiles (or speciation diagrams) of monomers and dimers in toluene-d8 solutions at different cis/trans ratios of four of our photoswitchable self-complementary hydrogen bond arrays were achieved. From these speciation diagrams we were able to confirm that the mathematical approach employed to describe the systems’ equilibria provided us a reliable approximation of all complexation constants in solution after photoisomerization.


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