Positive homotropic allosteric binding of benzenediols in a hydrindacene-based exoditopic receptor: cooperativity in amide hydrogen bonding.

The preparation and complexation properties of a hydrindacene-based exoditopic receptor, that exhibits a positive homotropic allosteric binding process toward benzenediols, are described. The exoditopic receptors form 1:2 complexes with resorcinols, catechol, and 3-hydroxybenzyl alcohol with K2/K1 = 3-33. Both the entropy and the enthalpy terms are important in this allosteric system; the crystallographic studies provide the first clear evidence that the cooperativity in amide hydrogen bonding by polarization contributes to the positive homotropic allosteric binding property.