Halogen Bonding in Hypervalent Halogen-Based Systems: Structural Determinants and Supramolecular Diversity

This review presents the first systematic analysis of supramolecular organization in halonium-based systems driven by halogen bonding (XB) interactions. Through comprehensive examination of approximately 600 crystal structures from the Cambridge Structural Database, we establish major principles governing XB-directed assembly patterns across diverse halonium species. Monocationic halonium salts paired with monoanionic counterions constitute over 50% of characterized structures, predominantly forming 0D (85%) and 1D (15%) assemblies. Heterotetrameric motifs—cyclic assemblies comprising two cations and two anions connected through four intermolecular XBs—emerge as the dominant organizational principle (58% of structures). Critically, anion geometry plays the decisive role in directing supramolecular architecture, while cation structure exerts minimal influence. Iodonium (91%) and bromonium derivatives follow consistent assembly trends favoring heterotetrameric motifs, whereas chloronium salts exhibit anomalous behavior. Polycharged systems generate more complex 1D and 2D networks through linking of basic heterotetrameric units. Zwitterionic halonium compounds utilize analogous dimeric motifs as building blocks for extended 1D, 2D, and 3D assemblies, demonstrating promise as building blocks for noncovalent organic frameworks. These findings establish halonium salts as reliable platforms for predictable XB-based crystal engineering.