화학공학소재연구정보센터
Journal of the American Chemical Society, Vol.122, No.49, 12174-12185, 2000
A color-switching molecule: Specific properties of new tetraaza macrocycle zinc complex with a facile hydrogen atom
Unsymmetrical aza macrocycle and its zinc complex, which were designed with the aim pf exhibiting the hybrid properties of planar and nonplanar macrocycles, were newly synthesized and showed the attractive property of being color-switching molecules. The colors of the solutions, which contain these compounds with a facile hydrogen atom, can be controlled easily by changing the solvent or the acid and base system. The color of the solution containing the free base macrocycle was orange. Importantly, the color of the solution containing the zinc complex of macrocycle depended on the solvent; the solution of zinc complex, which was formed in dichloromethane, showed colorless, and the solutions of acetonitrile and methanol showed yellow and red, respectively. The color of the solution containing the zinc complex was changed by the addition of acids or bases, and the transformation between the colors of the solutions was reversible. This color-switching phenomenon is considered to be related to the change of the conjugation system with the positional change of a facile hydrogen atom on the aza-macrocycle. This facile hydrogen atom would arise from the unsymmetry and the distorted nonplanarity of the macrocyclic ring. Furthermore, this new macrocycle exhibited a high selectivity for binding of lithium ion among alkali and alkaline earth metal ions, and the color of its solution changed from orange to colorless with the formation of lithium complex.