A push-and-pull model for allosteric anion binding in cage complexes

A series of electronic structure calculations has been carried out on an artificial anion binding host. The compound with four Pd(II) cations and a total of eight bis-monodentate pyridyl ligands forms by self-assembly an interpenetrated double cage with three binding pockets. Through the use of a simple push-and-pull model connecting the potentials of the different sites, we are able to explain the allosteric effect observed in anion binding. Two factors seem to be particularly significant in the latter, namely the flatness of the potential in each binding pocket as well as the length of the ligand. Our results are found to be in excellent agreement with the experimentally observed structures.