title: Chromogenic azo-coupled calix[4]arenes.
abstract: 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.
authors.affiliation: Department of Chemistry, Konyang University, Nonsan 320-711, Korea. jongskim@konyang.ac.kr
authors.forename: Jong Seung
authors.initials: JS
authors.lastname: Kim
authors.forename: Ok Jae
authors.initials: OJ
authors.lastname: Shon
authors.forename: Jae Kwang
authors.initials: JK
authors.lastname: Lee
authors.forename: Soo Heon
authors.initials: SH
authors.lastname: Lee
authors.forename: Jong Yeol
authors.initials: JY
authors.lastname: Kim
authors.forename: Ki-Min
authors.initials: KM
authors.lastname: Park
authors.forename: Shim Sung
authors.initials: SS
authors.lastname: Lee