Anti‐Hofmeister Anion Selectivity via a Mechanical Bond Effect in Neutral Halogen‐Bonding [2]Rotaxanes

Exceptionally strong halogen bonding (XB) donor-chloride interactions are exploited for the chloride anion template synthesis of neutral XB [2]rotaxane host systems which contain perfluoroaryl-functionalised axle components, including a remarkably potent novel 4,6-dinitro-1,3-bis-iodotriazole motif. Halide recognition properties in aqueous-organic media, determined via extensive 1H NMR halide titration experiments, reveal rotaxane exhibit dramatically enhanced affinities hydrophilic Cl− and Br−, but conversely diminished hydrophobic I−, relative to their non-interlocked counterparts. Crucially, this mechanical bond effect induces binding selectivity directly opposes Hofmeister bias. Free-energy analysis enhancement demonstrates by interlocked as rare general strategy engineer anti-Hofmeister bias synthetic receptor design.