Calixarenes 3a (R = OMe) and 3b (R = NO 2 ) with 5,17bis[4-(4-substituted-phenyl)azo] and 25,27-bisoxymethyltetrazole groups were synthesized by 1,3-dipolar cycloaddition of oxyacetonitrile azocalixarenes 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 Ca 2+ , whereas 3b (with p-nitrophenylazo substituent) showed color changes toward Ca 2+ , Ba 2+ , and Pb 2+ . Job plot experiments revealed 1:1 binding stoichiometry for each of the complexes, The association constants for 3ȧCa 2+ , 3b-Ca 2+ , 3b-Ba 2+ , and 3ḃPb 2+ were determined by Benesi-Hildebrand plots. On the basis of 1 H NMR titration results, Ca 2+ was bound to the two partially deprotonated hydroxy azophenol groups and one of the two tetrazole groups of 3a and 3b.
- Inclusion compounds
- Nitrogen heterocycles