Halogen Bonding in Solution

Stefan Huber

• Publisher: Wiley-VCH
• Year: 2021
• ISBN:
  9783527825745
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Long-awaited on the importance of halogen bonding in solution, demonstrating the specific advantages in various fields - from synthesis and catalysis to biochemistry and electrochemistry!

Halogen bonding (XB) describes the interaction between an electron donor and the electrophilic region of a halogen atom. Its applicability for molecular recognition processes long remained unappreciated and has mostly been studied in solid state until recently. As most physiological processes and chemical reactions take place in solution, investigations in solutions are of highest relevance for its use in organic synthesis and catalysis, pharmaceutical chemistry and drug design, electrochemistry, as well as material synthesis.

Halogen Bonding in Solution gives a concise overview of halogen bond interactions in solution. It discusses the history and electronic origin of halogen bonding and summarizes all relevant examples of its application in organocatalysis. It describes the use of molecular iodine in catalysis and industrial applications, as well as recent developments in anion transport and binding.

• Hot topic: Halogen bonding is an important interaction between molecules or within a molecule. The field has developed considerably in recent years, with numerous different approaches and applications having been published.
• Unique: There are several books on halogen bonding in solid state available, but this will be the first one focused on halogen bonding in solution.
• Multi-disciplinary: Summarizes the history and nature of halogen bonding in solution as well as applications in catalysis, anion recognition, biochemistry, and electrochemistry.

Aimed at facilitating exciting future developments in the field, Halogen Bonding in Solution is a valuable source of information for researchers and professionals working in the field of supramolecular chemistry, catalysis, biochemistry, drug design, and electrochemistry.

1
Halogen Bonding: An Introduction

Daniel A. Decato, Eric A. John, and Orion B. Berryman

University of Montana, Department of Chemistry and Biochemistry, 32 Campus Drive, Missoula, MT, 59812 USA

1.1 Introduction

The group 17 elements, known as halogens, are diatomic species in their elemental form with the chemical formula X₂ (where X = F, Cl, Br, I)1. In nature, they are seldom found in this manner due to their reactivity and thus are often presented as covalent or ionic species. However, the physical state of diatomic halogens provides initial insight into their capacity for noncovalent interactions. Moving down group 17, the elemental species exist in different phases from gas (F₂ and Cl₂) to liquid (Br₂) to solid (I₂). For simplicity, this observation is attributed to greater intermolecular dispersion forces afforded by the larger, more polarizable halogens and is quantifiable by physical properties such as boiling and melting point. This is the explanation that young chemists generally receive when being introduced to halogenated species and their physical properties. Later, in many organic curricula, these elements are presented as covalently bound components of molecules and are discussed within the context of molecular and bond dipoles, often in conjunction with concepts of electronegativity. Once again, the enhanced dispersion capacity of the halogens is often highlighted, explaining the higher boiling points of haloalkanes over hydrocarbons of comparable size and shape (e.g. ethane bp = −89 °C and bromomethane bp = 4 °C). Ultimately, the role of halogens in noncovalent interactions is neglected, giving way to their participation in classic reactions such as radical, substitution, and elimination pathways, which predictably leads to the misconception that halogens are simply electronegative leaving groups. This oversight is often reinforced in upper‐level courses, where halogens are shown to be the reactive site in many cross‐coupling reactions. Additionally, in classical inorganic chemistry, halides are depicted as weak field ligands and as prototypical examples in hard–soft acid–base theory. Even discussions of covalently bound halogens participating as hydrogen bond acceptors are atypical in university curricula.

In summary, halogens have traditionally been perceived as electronegative reactive species that participate in weak nondirectional noncovalent interactions (dispersion and as weak hydrogen bond acceptors). So how did scientists discover the ability of halogens to participate in a very directional and potent (comparable with hydrogen bond strength) noncovalent interaction, where the halogen is an electropositive species that is attracted to Lewis bases? To answer this, one should start with the definition of the halogen bond provided by the IUPAC in 2013 [2]. Then, early contributions from scientists who acknowledged an attractive interaction (more significant and directional than dispersion) can be acknowledged. Following the historical contributions, this introduction recounts the rediscovery of the halogen bond near the turn of the twenty‐first century. Finally, the chapter concludes by highlighting impactful nonsolution‐based examples that have helped construct the current understanding of the halogen bond, thereby providing context for the ensuing chapters on solution phase chemistry.

1.1.1 The Halogen Bond: Definition, Characteristics, Representations, and Parallels to the Hydrogen Bond

“A halogen bond 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”

IUPAC definition 2013 [2]

The depiction of a covalently bound halogen atom in traditional textbooks is that of an electron‐rich sphere (Figure 1.1a). This simplified description is applicable in many cases and helps account for the behavior of covalently bound halogens as hydrogen bond acceptors [3] and their “side‐on” interactions with metal cations [4]. However, the electron density around halogens is not uniform; the distribution of e...

Table of contents

• Cover
• Table of Contents
• Title Page
• Copyright
• Preface
• 1 Halogen Bonding: An Introduction
• 2 Thermodynamics of Halogen Bonding in Solution
• 3 Recognition with Macrocycles and Interlocked Systems
• 4 The Three‐Center Halogen Bond
• 5 Spectroscopy of Halogen Bonding in Solution
• 6 Anion Transport in Lipid Bilayer Membranes Using Halogen Bonds
• 7 Catalysis by Molecular Iodine
• 8 Halogen Bonding in Organocatalysis
• 9 Halogen Bonding in Electrochemistry
• 10 Halogen Bonds in Biomolecular Engineering
• 11 The Chalcogen Bond in Solution: Synthesis, Catalysis and Molecular Recognition
• Index
• End User License Agreement