Luminescent properties and CH3COO− recognition of europium complexes with different phenanthroline derivatives as second ligands

Six novel europium complexes with phenanthroline derivatives as fluorescence sensor have been prepared, and their structures were characterized by FT-IR, UV–vis, 1H NMR, 13C NMR, ESI-MS, and element analysis. All complexes exhibited long luminescent lifetime and high luminescent quantum efficiency (η). Among these complexes, the complex (a) exhibited the lowest luminescent quantum efficiency and shortest lifetime, which was attributed to the presence of OH oscillators in the corresponding ligand HPIP. Spectroscopic studies, including UV–vis, PL and 1H NMR spectra, showed that these sensors exhibited striking spectra changes in response to CH3COO− due to hydrogen bonding interaction of imidazolyl NH groups, aromatic and phenanthroline ringʹs protons with CH3COO−. Particularly, europium complexes (e) and (f) have a remarkable color changes (from transparent to light-yellow), and hence they were convenient to detect the CH3COO− with them by naked eye in DMSO solution.