Dipyrrolylquinoxaline-bridged hydrazones: a new class of chemosensors for copper(II)

Novel 2,3-bis(1H-pyrrol-2-yl)quinoxaline-functionalized hydrazones were prepared and characterized as new chemosensors for copper(II) ion. The binding properties of the compounds 4, 5, 6 and 7 for cations were examined by UV–vis, fluorescence spectroscopy, and linear sweep voltammetric experiments (LSV). The results indicate that a 1:1 stoichiometric complex is formed between compound 4 (or 5, 6, 7) and copper(II) ion, and the association constant is 1.3?×?10⁵ M^?1 for 4, 2.1?×?10⁶ M^?1 for 5, 4.1?×?10⁵ M^?1 for 6 and 8.0?×?10⁵ M^?1 for 7, respectively. The recognition mechanism between compound 4 (or 5, 6, 7) and metal ion was discussed based on their electrochemical properties, absorbance changes, and the fluorescence quenching effect when they interact with each other. Control experiments revealed that compound 4 (or 5, 6, 7) has a highly selective response to copper (II) ion.