Multi-Stimuli-Responsive Interconversion between Bowl- and Capsule-Shaped Self-Assembled Zinc(II) Complexes

摘要

Self-assembled metal—organic architectures have great potential to undergo major structural changes into different architectures. Such molecular transformation is widely applicable to responsive systems like drug delivery and allosteric catalysis. A great number of metal—organic architectures responsive to a specific stimulus have been reported so far. However, interconversion between a pair of distinct metal—organic structures in response to multiple stimuli is rarely reported despite its high versatility. Herein we report multi-stimuli-responsive interconversion between a bowl-shaped and a capsule-shaped self-assembled Zn~(II) complexes, [Zn~(II)_4L_3X_6] and [Zn~(II)_4L_4], respectively, which were found to form in equilibrium from porphyrin-based ligand L and Zn~(II) ions with different stoichiometry. Specifically, this interconversion was induced by four distinct external stimuli: exogenous ligands, Brønsted base/acid, solvents, and guest molecules. The mechanisms of the interconversion system are discussed in detail focusing on the species included in the equilibria. Thus, these findings would provide a helpful clue to design principles for multi-stimuli-responsive systems with functional versatility.