Self-assembly, interlocking, interconversion and anion-binding catalysis in phenoxazine-based Pd<sub>2</sub>L<sub>4</sub> and Pd<sub>4</sub>L<sub>8</sub> coordination cages.

Hong, Qiong-Yan; Huang, Bin; Wu, Meng-Xiang; Jiang, Jun-Yao; Yang, Hai-Bo; Zhao, Xiao-Li; Clever, Guido H; Shi, Xueliang · Nat Commun · 2025

basic_science · Level V

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Abstract

Interpenetration is a phenomenon frequently encountered in self-assembled Pd<sub>2</sub>L<sub>4</sub>-type coordination cages, while the mechanism of the interpenetration process remains unclear. Here we show the synthesis and solvent-mediated interconversion of highly soluble phenoxazine-based monomeric cage 1 and corresponding interlocked dimer 2. We succeed in the isolation and single-crystal structure analysis of both 1 and 2 with the same guest anion by changing the solvents utilized in self-assembly. The monomeric-to-dimeric cage conversion occurs by heating in weakly coordinating solvents, while dimeric-to-monomeric cage conversion takes place through a disassembly and reassembly process in strongly coordinating solvents at low concentration or by the addition/removal of competing ligand. The interconversion may be driven by the distinct thermodynamic stabilities of 1 and 2 in different solvents. Additionally, Cl<sup>-</sup> anions template the interpenetration of 1 because of the strong chloride binding affinity of 2 which could serve as an anion-binding catalyst for the C-Cl bond cleavage.