Synthesis, characterization and X-ray crystal structures of cyclam derivatives. 7. Hydrogen-bond induced allosteric effects and protonation cooperativity in a macrotricyclic bisdioxocyclam receptor

The unprecedented cooperative protonation properties displayed by a barrel-shaped macrotricyclic tetraamine incorporating two 14-membered bisamide rings maintained in a face-to-face arrangement is rationalized in terms of allosteric effects upon binding of the first and third protons.