Optical spectroscopy studies of the complexation of chromogenic azo-calix[4]arene with Eu3+, Ag+ and Cu2+ ions

Due to their potential applicability as selective receptors in electrochemical and/or optical sensors (optodes) a new family of chromogenic calix[4]arenes derivatives were investigated. The complexing properties of these molecules towards metallic cations and lanthanides and the photophysical properties of the formed compounds in acetonitrile solution have been studied by UV/Vis spectroscopy. The molar ratio method revealed that the stoichiometry of calix[4]arenes 1a and 1b to Eu(III) in the complex is 1 : 1. The stability constants of the complexes have been determined.