Preorganization in a Cleft-Type Anion Receptor Featuring Iodo-1,2,3-Triazoles As Halogen Bond Donors

Preorganization via intramolecular hydrogen bonds
was applied in a cleft-type receptor by exploiting the excellent halogen
bond donor ability as well as hydrogen bond acceptor function of iodo-1,2,3-triazoles.
As investigated by isothermal calorimetric titrations, the restriction
of conformational freedom causes an enhanced entropic contribution
resulting in a strongly increased binding affinity. This efficient
way to improve the binding strength of 5-halo-1,2,3-triazoles paves
the way for applications of new charge-neutral halogen bond donors
in solution.