| 초록 |
A bent-shaped bipyridine ligand containing a dendritic aliphatic side chain has been synthesized as a ligand and complexed with silver ion through a self-assembling process. The resulting complexes were observed to self-assemble into supramolecular structures that differ significantly as a function of the counter-anion size in the solid state. The secondary structure of a cationic coordination chain appears to be dependent on the size of the counter-anion. As the size of anion increases, the secondary structure of the coordination chain changes, from a helical chain, via a dimeric cycle, to a zig-zag chain in the solid state. Interestingly, dilute solutions of the complexes exhibiting a helical structure in aqueous solvents undergo spontaneous gelation. Also, we observe counteranion-mediated sol-gel interconversion in aqueous solution of cationic coordination polymers driven by conformational change from folded helical chains to an unfolded random coil conformation with counteranion exchange. These results represent a significant example that size change of the entrapped guest in self-assembling system can provide a useful strategy to create stimuli-responsive smart nanomaterials with functions that can be produced at any time on demand.
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