Originating from its exploitation in solid state crystal engineering and in materials design, halogen bonding (XB), the highly directional, attractive intermolecular non-covalent interaction between an electrophilic halogen atom and a neutral or charged Lewis base, has begun to emerge as a powerful complement to the ubiquitous hydrogen bonding (HB) interactions for solution phase applications in catalysis, medicinal chemistry, anion transport, and anion recognition. Regarding the latter, we and others have demonstrated that XB hosts often display superior anion affinities and contrasting selectivities in comparison to HB host analogues. However, examples of XB host systems that function in competitive aqueous media remain extremely rare due in part to the challenging syntheses of such systems. This is especially the case with elaborate XB mechanically interlocked molecules (MIMs), which due to their unique topological three-dimensional and highly preorganized cavities are capable of aqueous anion recognition. Herein we report a novel, remarkably potent electron deficient perfluoroaryl substituted bis-iodotriazole pyridinium XB donor motif, which is demonstrated to dramatically increase the strength of XB-anion interactions for recognition in aqueous media and the efficacy for an unprecedented near quantitative high yielding XB MIM synthesis of a rotaxane 1⋅PF₆ using anion templation.

Reference:

T. Bunchuay, A. Docker, A. J. Martinez-Martinez, P. D. Beer, Angew. Chem. Int. Ed. 2019, 58, 13823.

(https://onlinelibrary.wiley.com/doi/10.1002/anie.201907625)