Selective Recognition of Chloride by a 24-Membered Macrocyclic Host with a Hydrophobic Methylenepyrene Substituent

A structure-guided design, synthesis, and characterization of neutral unclosed cryptand functionalized with a bulky and hydrophobic 1-methylene-pyrene substituent is described. The host selectively binds spherical chloride (Cl-) over bigger and more basic carboxylates (MeCO2-, PhCO2-) and dihydrogenphosphate (H2PO4-) in a competitive [D-6]DMSO + 0.5 % H2O solvent mixture. The capture of chloride is accompanied by formation of sandwich-type complex stabilized by pi-pi and CH-pi interactions. Step-wise addition of MeOH triggers release of the cargo in a controllable manner.