A strategy is presented that enables the quantitative assembly of a heterobimetallic [PdPtL4]4+ cage. The presence of two different metal ions (PdII and PtII) with differing labilities enables the cage to be opened and closed selectively at one end upon treatment with suitable stimuli. Combining an inert PtII tetrapyridylaldehyde complex with a suitably substituted pyridylamine and PdII ions led to the assembly of the cage. 1H and DOSY NMR spectroscopy and ESI mass spectrometry data were consistent with the quantitative formation of the cage, and the heterobimetallic structure was confirmed using single‐crystal X‐ray crystallography. The structure of the host–guest adduct with a 2,6‐diaminoanthraquinone guest molecule was determined. Addition of N,N′‐dimethylaminopyridine (DMAP) resulted in the formation of the open‐cage [PtL4]2+ compound and [Pd(DMAP)4]2+ complex. This process could then be reversed, with the reformation of the cage, upon addition of p‐toluenesulfonic acid (TsOH).

Two new ferrocene-containing [Pd2(LFc)4]4+(X−)4 (where X− = BF4− or SbF6−) self-assembled cages were synthesised from the known, rotationally flexible, 1,1′-bis(3-pyridylethynyl)ferrocene ligand (LFc). The cages were shown to bind neutral and anionic guest molecules and displayed reversible redox activity.

The self-assembly of ligands of different geometries with metal ions gives rise to metallosupramolecular architectures of differing structural types. The rotational flexibility of ferrocene allows for conformational diversity, and, as such, self-assembly processes with 1,1'-disubstituted ferrocene ligands could lead to a variety of interesting architectures. Herein, we report a small family of three bis-bidentate 1,1'-disubstituted ferrocene ligands, functionalized with either 2,2'-bipyridine or 2-pyridyl-1,2,3-triazole chelating units. The self-assembly of these ligands with the (usually) four-coordinate, diamagnetic metal ions Cu(I), Ag(I), and Pd(II) was examined using a range of techniques including H and DOSY NMR spectroscopies, high-resolution electrospray ionization mass spectrometry, X-ray crystallography, and density functional theory calculations. Additionally, the electrochemical properties of these redox-active metallosupramolecular assemblies were examined using cyclic voltammetry and differential pulse voltammetry. The copper(I) complexes of the 1,1'-disubstituted ferrocene ligands were found to be coordination polymers, while the silver(I) and palladium(II) complexes formed discrete [1 + 1] or [2 + 2] metallomacrocyclic architectures.

Molecular recognition continues to be an area of keen interest for supramolecular chemists. The investigated [M(L) ] metallo-ligands (M=Pd , Pt , L=2-(1-(pyridine-4-methyl)-1 H-1,2,3-triazol-4-yl)pyridine) form a planar cationic panel with vacant pyridyl binding sites. They interact with planar neutral aromatic guests through π-π and/or metallophilic interactions. In some cases, the metallo-ligands also interacted in the solid state with Ag either through coordination to the pendant pyridyl arms, or through metal-metal interactions, forming coordination polymers. We have therefore developed a system that reliably recognises a planar electron-rich guest in solution and in the solid state, and shows the potential to link the resultant host-guest adducts into extended solid-state structures. The facile synthesis and ready functionalisation of 2-pyridyl-1,2,3-triazole ligands through copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "click" chemistry should allow for ready tuning of the electronic properties of adducts formed from these systems.