EVALUATIONS CONCERNING THE HALOGEN BOND AND HYDROGEN BOND RELATIONSHIP

The chemical advances of this century are likely to be driven by the ability to predict and control noncovalent interactions. While the hydrogen bond continues to captivate the interests of scientists, the development of non-traditional noncovalent interactions offers unique solutions to tackle chemical problems. Understanding the interplay between the ubiquitous hydrogen bond and other noncovalent forces will further fundamental knowledge thereby accelerating novel functional designs. This dissertation examines the nature of the hydrogen bond and halogen bond relationship. With a renaissance in the early 2000’s, the halogen bond has become a functional alternative to the hydrogen bond. The halogen bond, as defined by IUPAC, occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. Although comparable to the hydrogen bond regarding strength, halogen bonds are more hydrophobic and significantly more directional than HBs. This, along with the fact that halogens are more polarizable than hydrogens, offers possible improved selectivity in various molecular recognition events (e.g. ligand-protein interactions, anion receptors, organocatalysis). Despite their frequent comparison, evaluations of their action on each other is rare. This dissertation makes significant progress towards addressing these deficiencies. Chapter 1 provides a broad-spectrum introduction to the halogen bond for those unfamiliar with the interaction. The chapter is tailored to emphasize comparative aspects of the halogen bond and hydrogen bond. Chapter 2 considers simultaneous halogen bond and hydrogen bond interactions with carbonyl and thiocarbonyl groups through a Cambridge Structural Database study. The analysis led to an alternative explanation for a purported geometrical orthogonality between the halogen bond and hydrogen bond when interac