Synthesis and fluorescence studies on novel complexes of Tb(III) and Eu(III) with 4-(9H-carbazol-9-yl) benzoic acid

The complexes of Tb(III), Eu(III) with 4-(9H-carbazol-9-yl) benzoic acid (p-CZBA) have been synthesized, and the compositions and structural characteristics of them have been performed by the element analysis, infrared spectra, thermal analysis, 1H NMR and fluorescence spectra. Their compositions are Tb(p-CZB)3(H2O)2 and Eu(p-CZB)3(H2O)2, respectively. Photoluminescence measurements indicated that p-CZBA itself is a blue emitter under UV radiation. When the effective energy transfer from the organic ligand to the central Tb3+ ions occurs in the binary complex, strong and characteristic green emission appears due to the 5D4 → 7Fj transitions of the 4f electrons of the central Tb3+ ions. The Tb(III) binary complex is an excellent green-light-emitter, and would be considered as a candidate material for organic light-emitting devices (OLEDs). Eu(p-CZB)3(H2O)2 hardly has fluorescence property, this is because the energy of the triplet state of the ligand is not matchable with the energy of the lowest excited state of Eu3+.