Spontaneous Hierarchical Assembly of Crown Ether-like Macrocycles into Nanofibers and Microfibers Induced by Alkali-Metal and Ammonium Salts.

Schiff base macrocycle 1, which has a crown ether like central pore, was combined with different alkali-metal and ammonium salts in chloroform, resulting in one-dimensional supramol. aggregates. The ion-induced self-assembly was studied with solid-state NMR spectroscopy, transmission electron microscopy (TEM), SEM, and at. force microscopy (AFM). It was found that the lengths and widths of the superstructures depend on the cation and counter-anion of the salts. Among the salts being used, Na+ and NH4+ ions with BF4- ions showed the most impressive fibrous structures that can grow up to 1 μm in diam. and hundreds of microns in length. In addn., the size of the fibers can be controlled by the evapn. rate of the solvent. A new macrocycle with bulky triptycenyl substituents that prevent supramol. assembly was prepd. and did not display any nanofibers with alkali-metal ions in chloroform when studied with TEM. [on SciFinder(R)]