Dual Cation/Anion Binding in Crown Ether-Based Coordination Cages
J. Am. Chem. Soc.: RESOLV member Prof. Guido H. Clever and his team report the synthesis of a series of flexible bidentate pyridyl ligands featuring crown ether-based backbones with ring sizes ranging from 15 to 30 atoms.
Depending on ligand size, geometry, and flexibility, palladium-mediated self-assembly resulted in either mononuclear PdL2 chelate complexes or lantern-shaped Pd2L4 coordination cages capable of guest binding within their macrocyclic and self-assembled cavities.
In particular, the Pd₂L₄ cage based on a dibenzo-24-crown-8 ligand backbone shows pseudorotaxane formation with the cationic dibenzylammonium (DBA) guest, which was found to influence both cage assembly and anion binding. Guest displacement and cage-to-cage transfer experiments demonstrate an allosteric enhancement of the cage’s binding affinity toward naphthalene-1,5-disulfonate upon DBA binding, further supported by theoretical calculations, thus opening up potential applications for the development of stimuli responsive catalysts, selective multitopic receptors and more.
