Aqueous media are competitive environments in which to perform host-guest chemistry, particularly when the guest is highly charged. While hydrophobic binding is a recognized approach to this challenge in which apolar pockets can be designed to recognize apolar guests in water, complementary strategies are required for hydrophilic anions like chloride. This talk will present evidence of such an alternative mechanism, used everyday by proteins yet rare for artificial receptors, wherein hydrophobic interactions are shown to be responsible for organizing and stabilizing an aryl-triazole foldamer to help extract hydrophilic chloride ions from increasingly aqueous solutions. Therein, a double helical complex gains stability upon burial of ~80% of the pi surfaces that simultaneously create a potent solvent-excluding microenvironment for hydrogen bonding. The chloride's overall affinity to the duplex is substantial in 25% water v/v in acetonitrile (log �2 = 12.6) and it remains strong (log �2 = 13.0) as the water content is increased to 50%. With the rise in predictable designs of abiological foldamers, this water-assisted strategy can in principle be utilized for binding other hydrophilic guests. 

Hydrophobic collapse of foldamers to catch chloride in water

247th National Meeting (2014)

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