Endohedrally functionalized heteroleptic coordination cages for phosphate ester binding

Abstract

Metallosupramolecular hosts of nanoscopic dimensions, which are able to serve as selective receptors and catalysts, are usually composed of only one type of organic ligand, restricting diversity in terms of cavity shape and functional group decoration. We report a series of heteroleptic [Pd2A2B2] coordination cages that self-assemble from a library of shape complementary bis-monodentate ligands in a non-statistical fashion. Ligands A feature an inward pointing NH function, able to engage in hydrogen bonding and amenable to being functionalized with amide and alkyl substituents. Ligands B comprise tricyclic aromatic backbones of different shape and electronic situation. The obtained heteroleptic coordination cages were investigated for their ability to bind phosphate diesters as guests. All-atom molecular dynamics (MD) simulations in explicit solvent were conducted to understand the mechanistic relationships behind the experimentally determined guest affinities.