Multi‐functional, Low Symmetry Pd2L4 Nanocage Libraries

• Published in: Chemistry : a European journal Vol. 27; no. 13; pp. 4454 - 4460
• Main Author: Lewis, James E. M.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-03-2021; John Wiley and Sons Inc
• Subjects: Alkynes; Assembly; asymmetrical; cages; Chemistry; Combinatorial analysis; Combinatorial libraries; combinatorial library; Cycloaddition; Libraries; Ligands; metallo-supramolecular; Metallography; Scaffolds; self-assembly; Symmetry; Triazoles
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202005363

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‐Pd2L4 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.
Symmetry is over: A family of functionalised, asymmetric ditopic ligands was synthesised from a common precursor. Each ligand was capable of self‐assembling with PdII ions to selectively form low‐symmetry cis‐Pd2L4 nanocages. Due to the isostructural nature of the ligand framework, multiple ligands were able to be combined to generate combinatorial libraries containing heteroleptic, multi‐functional, low symmetry nanocages.