Percástegui EG, Mosquera J, Ronson TK, Plajer AJ, Kieffer M, Nitschke JR. Waterproof architectures through subcomponent self-assembly.
Chem Sci 2018;
10:2006-2018. [PMID:
30881630 PMCID:
PMC6385555 DOI:
10.1039/c8sc05085f]
[Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Accepted: 12/12/2018] [Indexed: 11/21/2022] Open
Abstract
Construction of metal–organic containers that are soluble and stable in water can be challenging – we present diverse strategies that allow the synthesis of kinetically robust water-soluble architectures via subcomponent self-assembly.
Metal–organic containers are readily prepared through self-assembly, but achieving solubility and stability in water remains challenging due to ligand insolubility and the reversible nature of the self-assembly process. Here we have developed conditions for preparing a broad range of architectures that are both soluble and kinetically stable in water through metal(ii)-templated (MII = CoII, NiII, ZnII, CdII) subcomponent self-assembly. Although these structures are composed of hydrophobic and poorly-soluble subcomponents, sulfate counterions render them water-soluble, and they remain intact indefinitely in aqueous solution. Two strategies are presented. Firstly, stability increased with metal–ligand bond strength, maximising when NiII was used as a template. Architectures that disassembled when CoII, ZnII and CdII templates were employed could be directly prepared from NiSO4 in water. Secondly, a higher density of connections between metals and ligands within a structure, considering both ligand topicity and degree of metal chelation, led to increased stability. When tritopic amines were used to build highly chelating ligands around ZnII and CdII templates, cryptate-like water-soluble structures were formed using these labile ions. Our synthetic platform provides a unified understanding of the elements of aqueous stability, allowing predictions of the stability of metal–organic cages that have not yet been prepared.
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