Design, synthesis and photophysical studies of an emissive, europium based, sensor for zinc

Abstract

The synthesis of the probe complex Eu·L and photophysical studies in aqueous media are described. Eu·L is designed to be luminescently responsive to Zn^II in the presence of a competitive ionic mixture at pH 7.4. The structure of the complex is based upon a carboxylate functionalised azamacrocycle and possesses a chromophoric bis-picolyl unit for binding Zn^II. The effect on both ligand fluorescence and Eu^III phosphorescence was investigated in the presence and absence of Zn^II. The study revealed that binding Zn^II increased the intensity of ligand fluorescence and modulated the inner sphere hydration number of Eu^III (q increases from 0 to 2). This modulation in coordination environment induced pronounced changes in the form of the steady state spectra allowing the presence of Zn^II to be signalled by both changes in emission intensity and lifetime.