Halogen bonding: a new territory for anion sensing

Abstract The field of anion sensing and recognition has grown significantly due to the need for selective identification, extraction, and transport of negatively charged species essential to chemical, biological, medical, and environmental processes. However, advancements in anion coordination chemistry have lagged behind cation chemistry due to the unique challenges posed by anions, including low charge-to-radius ratios, high solvation enthalpies, diverse geometries, and pH sensitivity. Traditional approaches employing hydrogen bonding and other non-covalent interactions have achieved some success, but designing effective synthetic receptors remains a challenge. Recently, halogen bonding (XB) has emerged as a powerful alternative, offering comparable directionality and binding strengths to hydrogen bonds. This review highlights significant advancements in the past decade, focusing on the development of solution-phase anion receptors utilizing XB. It explores their complementarity to hydrogen bonding, particularly in competitive solvent environments, and underscores XB’s growing role in advancing anion recognition and supramolecular chemistry.