Double fluorescence conversion in ultraviolet and visible region for some praseodymium complexes of aromatic carboxyates

Four praseodymium complexes of aromatic carboxylates (benzoate, 4-tert-butylbenzoate, 2-benzoylbenoate, and benzimidazole-5-carboxylate) have been synthesized and characterized, whose photophysical properties have been studied with ultraviolet spectra, phosphorescence spectra, and fluorescence spectra. The fluorescent emission spectra of all praseodymium complexes show two-emission peaks under the excitation band of 245 nm at about 395 and 595 nm respectively, while one peak under 415 nm at about 595 nm, which attributed to be S-1(0) --> I-1(6) (395 nm) transition and the characteristic emission D-1(2) --> H-3(4) (595 nm) transition of Pr3+ ion. The S-1(0) --> I-1(6) transition can be ascribed as the transition of charge transfer state, and the D-1(2) --> H-3(4) can be further proved that there exists an antenna effect in the fluorescence of praseodymium with aromatic carboxylic acids. In conclusion, the praseodymium complexes systems can realize the double fluorescent conversion in both ultraviolet and visible region and can be further studied the application of this conversion.