Synthesis, characterization and ion recognition studies of lower rim 1,3-di{rhodamine} conjugate of calix[4]arene

Abstract

An amido-linked rhodamine conjugate of calix[4]arene, L has been synthesized and characterized. Metal ion recognition properties of L have been studied by emission and absorption techniques with 14 different metal ions including the transition ones. Results show that, L exhibits ratiometric emission intensity towards Hg²⁺, Fe²⁺, Fe³⁺, Cu²⁺, Pb²⁺ and Zn²⁺. Composition of the complex formed in the solution has been found to be 1:2 (L:M^n + ), based on the Job’s plot. The L can also act as a chemosensor for Hg²⁺ through naked eye detection. Fluorescence quenching observed at 485 nm follows an order, Hg²⁺ > > Fe³⁺ ~ Cu²⁺ > Zn²⁺ > Pb²⁺ > Ca²⁺, while the enhancement observed at 580 nm follows, Hg²⁺ > > Fe²⁺ ~ Pb²⁺ > Zn²⁺. Mode of interaction of Mn +  with L is by the ring opening of spirolactam moiety.