A Strong Positive Allosteric Effect in the Molecular Recognition of Dicarboxylic Acids by a Cerium(IV) Bis[tetrakis(4-pyridyl)porphyrinate] Double Decker.

With increasing number of bound dicarboxylic acid molecules, the binding of further molecules by the title compound becomes more favorable (a 1:4 complex is depicted schematically on the right). The association constant for binding of the first guest molecule is small, since the increase in Gibbs free energy due to binding is outweighed by the energy loss asssociated with the suppression of rotation of the porphyrin rings. Once rotation has been suppressed, further guest molecules can be more effectively bound (positive allosteric effect). © 1998 WILEY-VCH Verlag GmbH, Weinheim, Fed. Rep. of Germany.