A series of water soluble RE(III) complexes: Synthesis,characterization, photophysical property and sensing activity towards Cr(III)

In this paper, four water soluble rare-earth(III) fluorescent chemosensors, Na₃RE(PDA)₃ (PDA = pyridine-2,6-dicarboxylic acid, and RE = Sm, Eu, Tb, Dy), are synthesized and characterized. Their excitation and emission spectra, fluorescence responses towards Cr(III), quenching mechanism, oxygen and thermal sensitivity of the complexes are systemically studied. The emission intensity and the excited state lifetimes of the four complexes decrease with increasing concentration of trivalent chromium (Cr(III)). Their sensing behavior towards Cr(III) is investigated by fluorescence spectroscopy. Results suggest that Na₃Dy(PDA)₃ exhibits highest sensitivity and linear spectral response towards Cr(III) (Stern–Volmer constant = 0.461 × 10⁷ L/mol, linearity = 0.996). It is note worthy that oxygen has little effect on the emission of Na₃RE(PDA)₃ complexes. These important advantages make themselves promising candidates to be utilized in actual applications.