Pd(μ-L)₄Pt <i>vs.</i> Pd(μ-L)₄RuCl₂: chlorido ancillary ligands as defining factors in the host–guest interactions of M(μ-L)₄M′ heterodimetallic supramolecular architectures

In supramolecular architectures, the interactions between host and guest molecules are governed by non-covalent forces such as hydrogen (H) bonding, hydrophobic and electrostatic interactions. We alter here the cavity microenvironment to control the interactions between guest and host molecules and study the effects of introducing axial chlorido ligands through the use of an octahedral building block in M(μ-L)₄M' architectures. We prepared the heterodimetallic Pd(μ-L)₄Pt C⁴ _Pt and Pd(μ-L)₄RuCl₂C⁴ _Ru architectures and demonstrated the role of 'classic' non-covalent forces in their host-guest chemistry with anionic and neutral molecules, while the cages also underwent disassembly and reassembly upon addition of external stimuli. This culminated in the isolation of a 1 : 1 host-guest complex between C⁴ _Pt and the dianionic 1,5-naphthalenedisulfonate which was characterized by single crystal X-ray diffraction studies. These showed the guest occupied the central cavity and was held in place by H bonding. The <i>endo</i>-chlorido ligand in C⁴ _Ru played an important role in the capture of neutral guest molecules. In particular, it allowed for finetuning of the cavity properties of the supramolecular architectures by limiting the formation of H bonds and restricting the cavity size while offering alternative interactions.