Lower rim 1,3-di-amide-derivative of calix[4]arene possessing bis-{N-(2,2′-dipyridylamide)} pendants: a dual fluorescence sensor for Zn2+ and Ni2+

Single crystal XRD structure of the lower rim 1,3-di-amide-derivative of calix[4]arene possessing bis-{N-(2,2′-dipyridylamide)} pendants (L) exhibit two distinct binding cores, viz., N4 and O6. L was found to be selective for Zn2+ by switch-on and for Ni2+ by switch-off fluorescence by forming 1:1 complexes. The binding and the composition of the complex formed have been addressed based on steady state and time-resolved fluorescence spectroscopy in addition to the absorption and ESI MS. As L can detect Zn2+ and Ni2+ to a concentration as low as 142 and 203 ppb, respectively, L can be a very sensitive molecular probe for these ions. The coordination details of the metal ion-bound complexes have been addressed based on ab initio calculations showing that the stabilization energies are commensurate with the coordination formed.

Graphical abstractSingle crystal XRD structure of the lower rim 1,3-di-amide-derivative of calix[4]arene possessing bis-{N-(2,2′-dipyridylamide)} pendants (L) exhibits two distinct binding cores, viz., N4 and O6. L was found to be selective to Zn2+ by switch-on and to Ni2+ by switch-off fluorescence by forming 1:1 complexes, where the lowest Zn2+ and Ni2+ concentration detection limits are 142 and 203 ppb, respectively. The coordination aspects of these complexes have been addressed based on computational calculations.Figure optionsDownload full-size imageDownload as PowerPoint slide