Halogen Bonds in Clathrate Cages: A Real Space Perspective

Area of Science:

• Supramolecular Chemistry
• Chemical Physics
• Materials Science

Background:

• Clathrate hydrates are inclusion compounds where guest molecules are trapped within cages of host molecules, typically water.
• Halogen bonding is a non-covalent interaction involving an electrophilic region on a halogen atom and a nucleophilic site.
• Understanding guest-host interactions in clathrates is crucial for applications in gas storage, separation, and drug delivery.

Purpose of the Study:

• To investigate the nature of dihalogen-water cage interactions in specific clathrate structures.
• To determine if halogen bonding occurs in these systems despite existing hydrogen bonds.
• To analyze the role of chlorine and bromine as guest molecules in water clathrates.

Main Methods:

• Real space analyses were employed to study the interactions.
• Quantum Theory of Atoms in Molecules (QTAIM) calculations were performed.
• Interacting Quantum Atoms (IQA) analyses were utilized.

Main Results:

• Evidence of halogen bonding was found in both 5¹² and 5¹² 6² clathrate cages containing chlorine and bromine.
• Halogen bonding persists even when water molecules' lone pairs are involved in hydrogen bonding.
• The analyses provide detailed insights into the electronic structure and bonding characteristics within the cages.

Conclusions:

• Dihalogen-water interactions in clathrate cages exhibit characteristics of halogen bonding.
• The presence of halogen bonding contributes to the stability and structure of these clathrate systems.
• This work deepens the understanding of non-covalent interactions in complex molecular assemblies.