Novel pyrazolone derivatives and corresponding europium(III) complexes: Synthesis and properties research

A series of pyrazolone derivatives ligands L1−7 were successfully synthesized and validated by 1H NMR and MS, corresponding europium complexes [EuL1−7(NO3)2]NO3·EtOAc were synthesized. Physico-chemistry properties of title complexes were determined by Elemental analysis, Molar conductance, UV absorption spectra, IR spectra and Thermogravimetric analysis. The title complexes exhibit characteristic red fluorescence of Eu3+. The effect of various substituent groups in ligands on the of title Eu3+ complexes is ordered: Cl > -Br > -OCH3 > -F > -CH3 > -H > -NO2, and [EuL6(NO3)2]NO3·EtOAc containing Cl possesses the strongest fluorescence intensity, so does fluorescence quantum yield. The electrochemical properties indicate that energy gap Eg and LUMO energy level are huge affected by substituent groups, and variation trends of LUMO energy level affected by diverse substituent groups are also different. The prepared title europium complexes have potential application prospects in the fields of photoelectric functional materials and life sciences.