[Study on synthesis and fluorescence characterization of europium and terbium complexes of 1-(5-(2-hydroxyphenyl)-3-methyl-4,5-dihydropyrazol-1-yl) ethanone].

Six solid complexes(TbL3 x 2H2O, TbL2 (phen) x H2O, TbL2 (TPPO), EuL3 x 2H2O, EuL2 (phen) x 2H2O and EuL2 (TPPO) x 2H2O) have been synthesized based on the pyrazole ligand(HL)(phen = 1,10-phenanthroline, TPPO = Tri-phenylphosphine oxide, HL=1-(5-(2-hydroxyphenyl)-3-methyl-4,5-dihydropyrazol-1-yl) ethanone). These complexes were characterized by elemental analysis, IR spectra, and fluorescence spectra. The IR spectra indicated that all complexes exhibited the characteristic peaks of asymmetric stretching vibration v (C=O) and symmetric stretching vibration v (C=N) peaks. The C=O stretching band at 1,644 cm(-1) of HL molecule shifted to lower band in the complexes. The O-H band at 3,072 of the HL ligand is also shifted to lower band. All these shifts indicated that carbonyl group, O-H and C=N take part in coordinating with the rare-earth ion in the form of bridging tridentate. The excitation and emission spectra of the six complexes were determined at room temperature and the results show that EuL2 (Phen) x 2H2O and TbL2 (Phen) X 2H2O display the strongest relative fluorescence intensity with the excited bands at 310 and 320 nm, respectively. Meanwhile, the emission intensities of Eu3+ and Tb3+ complexes were greatly sensitized by phen.