Photo-physical behavior as chemosensor properties of anthracene-anchored 1,3-di-derivatives of lower rim calix[4]arene towards divalent transition metal ions

Abstract

Anthracene anchored 1,3-di-derivatives of lower rim p-tert-butyl-calix[4]arene were synthesized and characterized. These derivatives were subjected to the binding studies with the divalent metal ions, viz., Mg²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ using fluorescence and absorption spectra. The imine moiety that is in conjugation with the anthryl unit is responsible for quenching the fluorescence in the absence of metal ion, however, in the presence of Fe²⁺ and Cu²⁺, the spectra showed very high enhancement in fluorescence intensity indicating that the lone pair present on the imine-N is involved in the metal ion binding and as a result the photo-induced electron transfer is prevented. Based on the photo-physical studies, it has been found that the anthracene derivative that is coupled with the calix[4]arene unit through an imine bond acts as a chemosensor for Fe²⁺ and Cu²⁺. The fluorescence studies are further augmented by the absorption spectra.