Physical Organic Studies in the Design and Application of Supramolecular Anion Hosts
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Date
2021-11-23
Authors
Fargher, Hazel
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Publisher
University of Oregon
Abstract
Hosts for supramolecular anion binding are used for a range of applications, including real-time detection, anion transport, catalysis, extraction, and molecular machines. These applications are the result of thousands of research articles with commonly studied anions such as the halides and oxoanions. Fundamental work has allowed researchers to understand how host binding pocket geometry, non-covalent motifs, and solvophobic effects work in concert to achieve properties required in each application. Often overlooked in anion binding research are the hydrochalcogenide anions, hydrosulfide (HS–) and hydroselenide (HSe–). Both anions play important roles in biological systems. At physiological pH, HS– is favored over hydrogen sulfide (H2S), an endogenous gasotransmitter. HSe– is the intermediate in the metabolic pathway of selenium. The reactivity of these anions, however, has made studying their supramolecular chemistry challenging. As a result, there are only three families of hosts for HS–, and before 2019, no reported receptors for HSe–.
In this thesis we focus on fundamental research into anion binding of the hydrochalcogenide anions. In Chapter II we show the first receptors for HSe–. In Chapter III we investigate the effect of changing the polarity of a C–H bond on binding with the hydrochalcogenide and halide anions. This study revealed a preference of an aryl C–H hydrogen bond donor for HS–. To investigate this finding further, in Chapter IV we study the equilibrium isotope effect of deuteration of the C–H hydrogen bond donor on anion binding and in Chapter V we use over 423,000 C–H…S contacts found in the Cambridge Structural Database to create a guide for identifying C–H…S contacts in the solid state. In the final chapters of this thesis, we expand upon the scope of applications of our hosts. In Chapter VI we show that our hosts can modulate the reactivity of HS– and in Chapter VII we use anion receptors to disrupt the Hofmeister bias in liquid-liquid extraction. Finally, in Chapter VIII we conclude with a summary of host motifs compatible with hydrochalcogenide anion binding and outline future work.
This dissertation includes published and unpublished co-authored material.
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Keywords
anion binding, hydrochalcogenide, hydroselenide, hydrosulfide, receptor, supramolecular