Gadolinium, terbium and europium complexes containing dibenzoylmethane and carbazole-functionalized 2-(2-pyridyl)-benzimidazole: Structural and spectroscopic characterization

Lanthanide complexes of the form Ln(DBM) 3 (Cz-PBM) (where Ln   =   Gd(III), Tb(III) and Eu(III); DBM   =   dibenzoylmethane and Cz-PBM   =   (4-(9 H -carbazol-9-yl)phenyl)methyl-2-(2′-pyridyl)benzimidazole) have been successfully synthesized and characterized. The crystal structures of the Gd(III) and Tb(III) complexes were determined by single-crystal X-ray analysis. The results reveal that in the complexes the central metal ions assume a square antiprismatic geometry and are octa-coordinated by six oxygen atoms from DBM ligands and two nitrogen atoms from the Cz-PBM ligand. Under excitation with ultraviolet light, the Eu(III) complex exhibited a strong red emission, but the Tb(III) complex did not show the characteristic emissions of the Tb 3+ ion. The results show that the ligands favor energy transfers to the emitting energy level of Eu 3+ .