Catenierung und Aggregation von Koordinationskäfigen mit mehreren Kavitäten

Highly Efficient Self-Assembly of Heterometallic [2]Catenanes and Cyclic Bis[2]catenanes via Orthogonal Metal-Coordination Interactions

Although catenated cages have been widely constructed due to their unique and elegant topological structures, cyclic catenanes formed by the connection of multiple catenane units have been rarely reported. Herein, based on the orthogonal metal-coordination-driven self-assembly, we prepare a series of heterometallic [2]catenanes and cyclic bis[2]catenanes, whose structures are clearly evidenced by single-crystal X-ray analysis. Owing to the multiple positively charged nature, as well as the potential synergistic effect of the Cu(I) and Pt(II) metal ions, the cyclic bis[2]catenanes display broad-spectrum antibacterial activity. This work not only provides an efficient strategy for the construction of heterometallic [2]catenanes and cyclic bis[2]catenanes but also explores their applications as superior antibacterial agents, which will promote the construction of advanced supramolecular structures for biomedical applications.

Pseudo-heterolepticity in Low-Symmetry Metal-Organic Cages

Heteroleptic metal-organic cages, formed through integrative self-assembly of ligand mixtures, are highly attractive as reduced symmetry supramolecular hosts. Ensuring high-fidelity, non-statistical self-assembly, however, presents a significant challenge in molecular engineering due to the inherent difficulty in predicting thermodynamic energy landscapes. In this work, two conceptual strategies are described that circumvent this issue, using ligand design strategies to access structurally sophisticated metal-organic hosts. Using these approaches, it was possible to realise cavity environments described by two inequivalent, unsymmetrical ligand frameworks, representing a significant step forward in the construction of highly anisotropic confined spaces.

Heterotrimetallic Double Cavity Cages: Syntheses and Selective Guest Binding

A strategy for the generation of heterotrimetallic double cavity (DC) cages [Pd_nPt_mL₄]⁶⁺ (DC1: n=1, m=2; and DC2: n=2, m=1) is reported. The DC cages were generated by combining an inert platinum(II) tetrapyridylaldehyde complex with a suitably substituted pyridylamine and Pd^II ions. ¹H and DOSY nuclear magnetic resonance spectroscopy (NMR) and electrospray ionization mass spectrometry (ESIMS) data were consistent with the formation of the DC architectures. DC1 and DC2 were shown to interact with several different guest molecules. The structure of DC1, which features two identical cavities, binding two 2,6‐diaminoanthraquinone (DAQ) guest molecules was determined by single‐crystal X‐ray crystallography. In addition, DC1 was shown to bind two molecules of 5‐fluorouracil (5‐FU) in a statistical (non‐cooperative) manner. In contrast, DC2, which features two different cage cavities, was found to interact with two different guests, 5‐FU and cisplatin, selectively.

Backbone-Bridging Promotes Diversity in Heteroleptic Cages

The combination of shape-complementary bis-monodentate ligands L^A and L^B with Pd^II cations yields heteroleptic cages cis-[Pd₂ L^A ₂ L^B ₂ ] by self-sorting. Herein, we report how such assemblies can be diversified by introduction of covalent backbone bridges between two L^A units. Together with solvent and guest effects, the flexibility of these linkers can modulate nuclearity, topology, and number of cavities in a family of four structurally diverse assemblies. Ligand L^A1 , with flexible linker, reacts in CH₃ CN with its L^B counterpart to a tetranuclear dimer D1. In DMSO, however, a trinuclear pseudo-tetrahedron T1 is formed. The product of L^A2 , with rigid linker, looks similar to D1, but with a rotated ligand arrangement. In presence of an anionic guest, this dimer D2 transforms and a hexanuclear prismatic barrel P2 crystallizes. We demonstrate how controlling a ligand's coordination mode can trigger structural differentiation and increase complexity in metallo-supramolecular assembly.