CH Donor-Based Anion Recognition

CH H-bonding has been established as a relatively weak H-bonding [149-155]. Flood and co-workers synthesized a series of shape-persistent macrocycles 85a-d [156]. Receptor 85a was found to bind chloride anion in 1 1 stoichiometry and the 

The Flood group further prepared macrocycle 86 for complexing bifluoride anion [158]. Anion binding was abetted by CH H-bonding provided by both the 

3- triazole and phenylene subunits. This more flexible receptor allowed bifluoride anion to be bound in a non-tilted binding mode, which is different from that of the parent triazolophane. 

Craig and co-workers demonstrated that oligomer 87 could fold to provide a cavity that stabilized intermolecular interactions between the electropositive CH 

3- triazole sites and electron-rich guests, including anions [159]. Chloride-induced folding was confirmed via 2D NOESY experiments in acetone, as well as through molecular modeling studies. 

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