Tetrazoles and para-substituted phenylazo-coupled calix[4]arenes as highly sensitive chromogenic sensors for Ca 2+

Yu Jen Chen, Wen-Sheng Chung*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Scopus citations

Abstract

Calix[4]arenes 3a (R = OMe) and 3b (R = NO2) with 5,17bis[4-(4-substituted-phenyl)azo] and 25,27-bisoxymethyltetrazole groups were synthesized by 1,3-dipolar cycloaddition of oxyacetonitrile azocalix[4]arenes 2a and 2b activated with trimethylsilyl azide, UV/Vis screening of 3a and 3b with 14 metal ions showed, that 3a (with p-methoxyphenylazo substituent) was a highly chromogenic sensor to Ca2+, whereas 3b (with p-nitrophenylazo substituent) showed color changes toward Ca2+, Ba2+, and Pb2+. Job plot experiments revealed 1:1 binding stoichiometry for each of the complexes, The association constants for 3ȧCa2+, 3b-Ca2+, 3b-Ba2+, and 3ḃPb2+ were determined by Benesi-Hildebrand plots. On the basis of 1H NMR titration results, Ca2+ was bound to the two partially deprotonated hydroxy azophenol groups and one of the two tetrazole groups of 3a and 3b.

Original languageEnglish
Pages (from-to)4770-4776
Number of pages7
JournalEuropean Journal of Organic Chemistry
Issue number28
DOIs
StatePublished - Oct 2009

Keywords

  • Calixarenes
  • Cycloaddition
  • Inclusion compounds
  • Ionophores
  • Nitrogen heterocycles

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