A systematic structural study of halogen bonding versus hydrogen bonding within competitive supramolecular systems

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Crystallography

Background:

• Halogen bonds are increasingly important in supramolecular synthesis and materials chemistry.
• Understanding the interplay between hydrogen and halogen bonds is crucial due to their similar properties and comparable strength.
• Predicting the dominant interaction in systems with both bond types presents a significant challenge.

Purpose of the Study:

• To investigate the competitive and complementary roles of hydrogen and halogen bonds in co-crystallization.
• To develop predictive guidelines for determining the primary interaction in supramolecular systems.
• To rationalize synthon preferences based on molecular properties.

Main Methods:

• Co-crystallization of molecules with competing hydrogen- and halogen-bond donors and various acceptor molecules.
• Characterization of co-crystals using Infrared (IR) spectroscopy.
• Determination of crystal structures using single-crystal X-ray diffraction (24 structures obtained).
• Analysis of synthon preferences correlated with calculated molecular electrostatic potential (MEP) values.

Main Results:

• Successfully obtained 24 co-crystal structures, revealing outcomes of competing hydrogen and halogen bonding.
• Identified specific synthon preferences for hydrogen- and halogen-bond donors in the studied co-crystals.
• Demonstrated a correlation between MEP values and the observed primary interactions.

Conclusions:

• Molecular electrostatic potentials provide practical guidelines for predicting primary synthons in co-crystal formation.
• Appropriate weighting of potential differences is essential for accurate predictions.
• This work advances the understanding of non-covalent interactions in designing supramolecular materials.