Cooperative recognition of a copper cation and anion by a calix[4]arene substituted at the lower rim by a ß-amino-a,ß-unsaturated ketone

Annamalai Senthilvelan, I. Ting Ho, Kai Chi Chang, Gene Hsiang Lee, Yi Hung Liu, Wen-Sheng Chung*

*Corresponding author for this work

Research output: Contribution to journalArticle

100 Scopus citations

Abstract

We report herein a new ditopic calix[4]arene receptor 25,27-bis{[4-amino-4- ( 1 -naphthyl) -2-oxo-3-butenyl]oxy}-26,28-dihydroxycalix[4]arene (2) for the simultaneous complexation of anionic and cationic species. The host molecule 25,27-bis{[3-(l-naphthyl)-5-isoxazolyl]methoxy}-26,28-dihydroxycalix[4]arene (1) was synthesised first and was followed by a [Mo(CO)6]mediated ring-opening reaction to give the target receptor 2. The binding properties of ligands 1 and 2 towards metal ions in CH3CN were investigated by UV/Vis and fluorescence spectroscopies. The results showed that both Iigands 1 and 2 were highly selective for Cu11 ions. Upon titration with CuII, the fluorescence of 1 was severely quenched, whereas 2 showed strong fluorescence enhancement because the metal ions help to lock the conformation of the fluorophores. During the complexation of 2 with CuII, the CuII was reduced to Cu1 by the free phenolic OH of 2, whereas the phenol was oxidised by CuII after which it assisted in the trapping of CuI. Ditopic behaviour was observed for the complex 2»CuI, which showed further enhancement of its fluorescence intensity upon complexation with anions such as acetate or fluoride.

Original languageEnglish
Pages (from-to)6152-6160
Number of pages9
JournalChemistry - A European Journal
Volume15
Issue number25
DOIs
StatePublished - 15 Jun 2009

Keywords

  • Calixarenes
  • Dipolar reactions
  • Ditopic receptor
  • Fluorescence
  • Inclusion compounds

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