Year of Award

2019

Document Type

Dissertation - Campus Access Only

Degree Type

Doctor of Philosophy (PhD)

Degree Name

Chemistry (Organic Option)

Other Degree Name/Area of Focus

Organic and Supramolecular Chemistry

Department or School/College

Department of Chemistry and Biochemistry

Committee Chair

Michael D. DeGrandpre

Commitee Members

Chris P. Palmer, Nigel D. Priestley, Donald Stierle, Edward Rosenberg

Keywords

Organic chemistry

Publisher

University of Montana

Abstract

Natural and synthetic molecules employ noncovalent interactions to engender molecular form and function. The halogen bond is a recently rediscovered noncovalent interaction that has proven advantageous in the solution, solid and gas phases. Analogous to the hydrogen bond in strength, the halogen bond elicits unique tunability and strict directionality. When this project began halogen bond solution studies and organocatalysis were limited, providing motivation for this work. This research focuses on elucidating fundamental features of the halogen bond and its interplay with the hydrogen bond for anion recognition and organocatalysis. Crystal structures and solution phase titrations validate the versatility of the halogen bond as a tactical noncovalent interaction for molecule recognition. Additional studies evaluated the impact of a hydrogen bond on a halogen bond donor, resulting in a novel molecule preorganization tactic and innovative method of augmenting halogen bond strength. This concept, pioneered in this work, called the hydrogen bond enhanced halogen bond. The hydrogen bond enhanced halogen bond functionality was demonstrated through organocatalytic studies. Collectively this work will inspire new generations of halogen bond-based anion receptors and organocatalysts that will provide powerful alternatives to the classic halogen or hydrogen bond in supramolecular chemistry.

Chapter 1 provides a succinct historical perspective introducing the hydrogen bond, the halogen bond, the halogen bond in anion recognition and organocatalysts that motivated our studies. Chapter 2 elucidates the preliminary fundamental characteristics of halogen and hydrogen bond receptors with the medically relevant perrhenate anion, highlighting the potential soft substrate selectivity. Chapter 3 further examines and compares the halogen and hydrogen bond receptors with soft neutral and anionic guests, offering early quantification of halogen bond hard–soft acid–base complementarity. Chapter 4 introduces the hydrogen bond-enhanced halogen bond through a receptor redesign, establishing a novel method of halogen bond augmentation and receptor preorganization. Chapter 5 compares the hydrogen bond-enhanced halogen bond to the halogen bond in organocatalysis in a benchmark halide reaction, further proving the hydrogen bond-enhanced halogen bond as a rational design tool to enhance the halogen bond in supramolecular chemistry. Chapter 6 is a summary and future perspective of the project.

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© Copyright 2019 Asia Marie Stephanie Riel