A Family of Heterobimetallic Cubes Shows Spin-Crossover Behaviour Near Room Temperature

Using 4-(4'-pyridyl)aniline as a simple organic building block in combination with three different aldehyde components together with metal(II) salts gave three different Fe8 Pt6 -cubes and their corresponding Zn8 Pt6 analogues by employing the subcomponent self-assembly approach. Whereas the use of zinc(II) salts gave rise to diamagnetic cages, iron(II) salts yielded metallosupramolecular cages that show spin-crossover behaviour in solution. The spin-transition temperature T1/2 depends on the incorporated aldehyde component, giving a construction kit for the deliberate synthesis of spin-crossover compounds with tailored transition properties. Incorporation of 4-thiazolecarbaldehyde or N-methyl-2-imidazole-carbaldehyde yielded cages that undergo spin-crossover around room temperature whereas the cage obtained using 1H-4-imidazolecarbaldehyde shows a spin-transition at low temperatures. Three new structures were characterized by synchrotron X-ray diffraction and all structures were characterized by mass spectrometry, NMR and UV/Vis spectroscopy.

Multi-functional, Low Symmetry Pd2 L4 Nanocage Libraries*

Although many impressive metallo-supramolecular architectures have been reported, they tend towards high symmetry structures and avoid extraneous functionality to ensure high fidelity in the self-assembly process. This minimalist approach, however, limits the range of accessible structures and thus their potential applications. Herein is described the synthesis of a family of ditopic ligands wherein the ligand scaffolds are both low symmetry and incorporate exohedral functional moieties. Key to this design is the use of CuI -catalysed azide-alkyne cycloaddition (CuAAC) chemistry, as the triazole is capable of acting as both a coordinating heterocycle and a tether between the ligand framework and functional unit simultaneously. A common precursor was used to generate ligands with various functionalities, allowing control of electronic properties whilst maintaining the core structure of the resultant cis-Pd2 L4 nanocage assemblies. The isostructural nature of the scaffold frameworks enabled formation of combinatorial libraries from the self-assembly of ligand mixtures, generating a statistical mixture of multi-functional, low symmetry architectures.

Better Together: Functional Heterobimetallic Macrocyclic and Cage-like Assemblies

Metallosupramolecular chemistry has attracted the interest of generations of researches due to the versatile properties and functionalities of oligonuclear coordination complexes. Quite a number of different discrete cages were investigated, mostly consisting of only one type of ligand and one type of metal cation. Looking for ever more complex structures, heterobimetallic complexes became more and more attractive, as they give access to new structural motifs and functions. In the last years substantial success has been made in the design and synthesis of cages consisting of more than one type of metal cations, and a rapidly growing number of functional materials has appeared in the literature. This Minireview describes recent developments in the field of discrete heterometallic macrocycles and cages focusing on functional materials that have been used as host‐systems or as magnetic, photo‐active, redox‐active, and even catalytically active materials.

An Extensive Family of Heterometallic Titanium(IV)-Metal(III) Rings with Structure Control through Templates

A family of heterometallic [Cat][Ti_x MO_(x+1 )(O₂ C^t Bu)_2x+2 ] rings is reported where Cat=a secondary or tertiary alkyl ammonium ion, x=7, 8 or 9, and M=Fe^III , Ga^III , Cr^III , In^III and Al^III . The structures are regular polygons with eight, nine or ten vertices with each edge bridged by an oxide and two pivalates. The size of the ring formed is controlled by the alkylammonium cation present. In each case a homometallic by-product is found [Cat][Ti_x O_(x+1 )(O₂ C^t Bu)_2x-1 ].

Controlled Orthogonal Self-Assembly of Heterometal-Decorated Coordination Cages

Multiple orthogonal coordinative interactions were utilized to construct heterometal-decorated tetrahedral cages from in situ formed trinuclear Zr^IV clusters through the combination with other metal ions such as Cu^II or Pd^II . Through effective use of the hard/soft acid/base principle, the orthogonal self-assembly process of Zr-bpydc-CuCl₂ (H₂ bpydc=2,2-bipyridine-5,5-dicarboxylic acid) can be finely controlled using three strategies: post-synthetic metallization, a stepwise metalloligand approach, or a one-pot reaction.