Novel 1,3-alternate calixazacrowns having an azo chromophoric pendent group were synthesized, and their 1,3-alternate conformations were confirmed by X-ray crystal structure. In view of the hypsochromical UV band shifting upon cation complexation, azo-coupled calixazacrown-5 (3) showed the most selective shifting with alkali and alkaline metal ions. In addition, 3 revealed K+ ion selectivity not only due to the size comparability between the K+ ion and the azacrown-5 loop but also due to a significant K+-π interaction between the two aromatic rings and the K+ ion. The UV band shifting is also dependent on the lipophilicity of the species of counteranion used.
ASJC Scopus subject areas
- Organic Chemistry