Ken'ichi Aoki, M. Nakagawa, T. Seki
Nov 15, 2002
Citations
0
Influential Citations
13
Citations
Journal
Bulletin of the Chemical Society of Japan
Abstract
Two ways to control the macroscopic morphology of fibrous organizates of amphoteric azopyridine carboxylic acids by tuning the strength of π–π stacking among the component molecules are presented. The self-organization of the azopyridine carboxylic acids (1–5) from aqueous solutions is governed not only by carboxyl/pyridyl hydrogen bondings, but also by dipole–dipole and π–π stacking interactions. The level of the latter could be tuned by the substituent structure at the phenyl ring. As a result, whereas leaflet crystals were formed from non-substituted derivative 1, 3 with a propyl substituent gave fibrous assemblages, and needle-like assemblages were obtained from 2, 4, and 5 with methyl, s-butyl, and ethoxy substituents, respectively. The propyl-substitution is likely to enhance an anisotropic growth rate of the intermolecular hydrogen bonds due to efficient suppression of π–π stacking among aromatic cores, leading to the appearance of microfibers with the highest aspect ratio. The second way to contro...