Chromogenic azo-coupled calix[4]arenes.
Novel 1,3-alternate calix[4]azacrowns 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 calix[4]azacrown-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+-pi 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.
Kim
Jong Seung
JS
Department of Chemistry, Konyang University, Nonsan 320-711, Korea. jongskim@konyang.ac.kr
Shon
Ok Jae
OJ
Lee
Jae Kwang
JK
Lee
Soo Heon
SH
Kim
Jong Yeol
JY
Park
Ki-Min
KM
Lee
Shim Sung
SS