Relative anion binding affinity in a series of interpenetrated coordination cages.

Previously, we have reported on the quantitative self-assembly of a series of interpenetrated double-cages [Pd4Ligand8] with ligands based on various organic backbones. For dibenzosuberone-based cages it was shown that anion binding in the outer two pockets follows an allosteric mechanism. Herein we wish to report the anion binding capabilities of three related phenothiazine cages.

Template control over dimerization and guest selectivity of interpenetrated coordination cages.

We have previously shown that the self-assembly of dibenzosuberone-based bis-monodentate pyridyl ligands L(1) with Pd(II) cations leads to the quantitative formation of interpenetrated coordination cages [BF4@Pd4L(1)8]. The BF4(-) anion inside the central cavity serves as a template, causing the outer two pockets to show a tremendous affinity for allosteric binding of two small chloride anions. Here we show that derivatization of the ligand backbone with a bulky aryl substituent allows us to control the dimerization and hence the guest-binding ability of the cage by the choice of the templating anion.

Counterion dynamics in an interpenetrated coordination cage capable of dissolving AgCl.

In solution, the eight BF(4)(-) counterions of a positively charged D(4)-symmetric interpenetrated [Pd(4)ligand(8)](8+) double cage (1) are localized in distinct positions. At low temperatures, one BF(4)(-) ion is encapsulated inside the central pocket of the supramolecular structure, two BF(4)(-) ions are bound inside the equivalent outer pockets, and the remaining five BF(4)(-) ions are located outside the cage structure (expressed by the formula [3 BF(4)@1][BF(4)](5)). On warming, the two BF(4)(-) ions in the outer pockets are found to exchange with the exterior ions in solution whereas the central BF(4)(-) ion stays locked inside the central cavity (here written as [BF(4)@1][BF(4)](7)).