FUNDAMENTAL INVESTIGATION ON ANION BINDING EMPLOYING THE HYDROGEN BOND ENHANCED HALOGEN BOND

Abstract

Noncovalent interactions play a critical role in chemistry and biochemistry. Understanding how to modulate closely situated noncovalent interactions is of utmost importance in the design of functional materials, supramolecular assemblies, pharmaceuticals, and catalysts. Over the past two decades, there has been a significant surge in research and applications on halogen bonds, driven by their exceptional properties such as high directionality and unique tunability when compared to hydrogen bonds. Taking inspiration from nature and other synthetic anion-binding receptors that effectively employ multiple noncovalent interactions in a concerted manner, we have developed an innovative preorganization strategy termed the Hydrogen Bond Enhanced Halogen Bond. This unique combination of hydrogen and halogen bond interactions yields an anion-binding performance over an order of magnitude greater than that achieved with either hydrogen bonds or halogen bonds alone. In-depth investigations, including examinations of solvent effects and substituent impacts, have been undertaken to gain insights into this interaction. We have also pushed the boundaries of this interaction by incorporating non-traditional C-H hydrogen bond donors. This dissertation provides significant insights of this interaction fueling the development of new generations of halogen bond-based anion receptors with exciting applications in anion recognition, organocatalysis, anion transport, and anion sensing. The ensuing chapters provide a comprehensive overview of this study. Chapter 1 introduces halogen bonding, tracing its evolution from hydrogen bonds, elucidating unique traits, and exploring preorganization strategies within the Hydrogen Bond Enhanced Halogen Bond (HBeXB). It also uncovers the captivating realm of anion binding through halogen bonds, highlighting their significance in applications. In Chapter 2, the investigation delves into intriguing solvatochromism and fluorescence responses to anions in halogen bonding anion receptors. Chapter 3 delves into the intricate interplay between hydrogen and halogen bonds, with a focus on quantification of the substituent effects in the hydrogen bond enhanced halogen bond. In Chapter 4, we delve into unconventional approaches to enhance halogen bonds using non-traditional hydrogen bonds, shedding light on anion binding in solution and offering innovative insights into this facet of XB···anion interaction. Finally, Chapter 5 summarizes our findings and offers a glimpse into the future