Competition of Hydrogen Bonds, Halogen Bonds, and π-π Interactions in Crystal Structures. Exploring the Effect of One Atom Substitution

Abstract

Understanding the variables that influence intermolecular interactions is crucial for the design and synthesis of crystal structures with functional properties, a primary goal in crystal engineering. This study investigates the competition among three types of interactions: hydrogen bonds (HBs), halogen bonds (XBs), and π···π interactions. We prepared simple molecules without steric hindrance and analyzed their crystal structures. The geometric analysis revealed the presence of various intermolecular interactions, including HBs, XBs, and π···π stacking interactions. Hirshfeld surfaces, NCI, and interaction energies were used to investigate these interactions further. The results demonstrate that the interactions between fluorinated aromatic rings and the pyridines are the most significant, followed by C-H···F hydrogen bonds. Furthermore, competition between XBs and π-interactions was observed in a brominated ligand. The findings highlight the complexity of intermolecular interactions in crystal structures and the influence of atom substitutions on the preference for specific interactions.