Catenation and Aggregation of Multi-Cavity Coordination Cages.
A series of metal-mediated cages, having multiple cavities, was synthesized from PdII cations and tris- or tetrakis-monodentate bridging ligands and characterized by NMR spectroscopy, mass spectrometry, and X-ray methods. The peanut-shaped [Pd3 L1 4 ] cage deriving from the tris-monodentate ligand L1 could be quantitatively converted into its interpenetrated [5Cl@Pd6 L1 8 ] dimer featuring a linear {[Pd-Cl-]5 Pd} stack as an unprecedented structural motif upon addition of chloride anions. Small-angle neutron scattering (SANS) experiments showed that the cigar-shaped assembly with a length of 3.7 nm aggregates into mono-layered discs of 14 nm diameter via solvophobic interactions between the hexyl sidechains. The hepta-cationic [5Cl@Pd6 L1 8 ] cage was found to interact with polyanionic oligonucleotide double-strands under dissolution of the aggregates in water, rendering the compound class interesting for applications based on non-covalent DNA binding.