Synthesis, characterization and fluorescent properties of lanthanide complexes with two aryl amide ligands

Abstract

Two aryl amide ligands, N-(p-tolyl)-2-(quinolin-8-yloxy)acetamide (L¹ ) and N-(4-chlorophenyl)-2-(quinolin-8-yloxy)acetamide (L² ), were synthesized. With these ligands, two series of lanthanide(III) complexes were prepared, Ln(L ⁿ )₂(NO₃)₃ (n = 1, 2; Ln = La, Sm, Eu, Gd, Dy), and characterized by the elemental analyses, molar conductivity, ¹H NMR spectra, IR spectra and TG-DTA. The fluorescence properties of the complexes and the triplet state energies of the ligands were studied in detail. In addition, the quantum yields of both Eu(III) complexes and Eu(L⁰)₂(NO₃)₃ [where L⁰ is N-(phenyl)-2-(quinolin-8-yloxy)acetamide] 1 were calculated. The results indicate that among the lowest triplet energies (T) of the three ligands, that of L² is most suitable to the resonance level (⁵D₁) of Eu(III) ion. Furthermore, Eu(L²)₂(NO₃)₃ has the highest fluorescence intensity and quantum yield of the three Eu(III) complexes.

Keywords:

• Lanthanide complexes
• Aryl amide
• Synthesis
• Fluorescence properties
• Triplet state energy

Acknowledgements

This work is supported by the National Science Foundation of China (20431010). The authors are also grateful to the Instrumental Analysis and Research Center of Lanzhou University and State Key Laboratory of Applied Organic Chemistry for providing instrumentation facilities.