Influence of fluorinated chain length on luminescent properties of Eu3+β-diketonate complexes

Five novel europium β-diketonate complexes containing a pyrazole fragment were investigated. The influence of the number of fluorine atoms in diketonate ligands on luminescent properties was analyzed. Luminescence intensity of Eu3+ complexes increases significantly when CH bonds with high oscillation energy are replaced with CF bonds with low oscillation energy as the efficiency of energy transfer is improved. Further extension of the fluorinated chain length results in a substantial decrease in non-radiative relaxation rates while the increase in luminescence decay rates is observed. The theoretical results elaborated in terms of Judd-Ofelt theory are in good agreement with the experimental data obtained by time-resolved luminescence spectroscopy.