Substituent Effects in Carbazole Macrocycles: Synergistic C–H···I ⁻ Interactions for Selective Anion Recognition

Abstract Substituent effects play a key role in modulating the interactions between host macrocyclic receptors and guest anions. However, due to the inherent structural complexity and synthesis challenges of macrocyclic compounds, introducing substituents onto macrocyclic receptors poses substantial difficulties compared to noncyclic receptors. Given this backdrop, researchers are encouraged to develop new strategies to overcome these hurdles. The unique characteristics of the carbazole moiety make it an ideal building block for designing efficient anion receptors. These features provide important design strategies for the development of novel supramolecular recognition systems. Building on this foundation, this study investigates the substituent effects on iodine ion recognition using these macrocyclic receptors. Two tert‐butoxycarbonyl (Boc)‐substituted carbazole‐based macrocyclic derivatives, DBOCPBG and SBOCPBG , were successfully designed and synthesized, and their interactions with iodide were investigated. The interactions between the macrocycles and anions were systematically confirmed through UV–vis spectroscopy, fluorescence emission spectroscopy, and 1 H NMR titration experiments. Furthermore, the binding affinity of these macrocycles toward I − was quantitatively evaluated using UV–vis absorption studies. The binding constants determined subsequently showed that both DBOCPBG and SBOCPBG had a certain binding affinity for I − . These findings provide valuable insights for the design of improved anion receptors with enhanced selectivity and recognition capabilities.