Synthesis, X-ray Crystallography, and Spectroscopic Studies of Lanthanide Complexes of Dual Donor Ligand and Transition Metal Systems

Lanthanide (III) ions are known to coordinate to various ligands while offering characteristics f-f transitions which usually display sharp emissions. However, high nuOH vibrational manifolds constitute an important non-radiative pathway that results in partial quenching of emission from lanthanide ions. In this study we attempted to follow a novel approach by coordinating the metal to selected phosphine oxides which are thought to play a double role of replacing the H2O quencher as well as acting as an effective sensitizer. Hence, several new compounds containing N-based auxiliary ligands and group 11 transitions metal complexes were crystallized and studied through x-ray crystallography, luminescence and other spectroscopic techniques. Structural analysis of [(Eu(H2O)4((Au(CN) 2)2(Terpy)] Au(CN)2·2(TPPO) (1), crystallizes in a monoclinic system with space group P21/c and unit cell parameters of a = 16.9623(3) A, b = 10.4361(19) A, c = 33.347(7) A, beta = 91.280(7) °, and V = 901.51(9) A 3. The photoluminescence studies show characteristic f-f emissions of the Eu3+ ion, with the strongest band observed at 616 nm corresponding to the 5D0 → 7F 2 transition. The excitation spectrum provides a strong band at 358 nm corresponding to the terpy ligand. Substitution of Terpy with phenanthroline derivatives were also explored which yielded crystal structures of, [(TPH)Au(CN) 2]2 (2), [(DPH)Au(CN)2)]·H 2O (3) and (DPH)Cl·3H2O (5), as well as, powders of [TbCl3(H2O)2(DPH) 2]·4H2O (6), [Eu(TPH)](CF3O 3S)3 (7). A copper complex of [Cu(DPH) 2](CF3O3S)·H2O (4) was also achieved which exhibits intense red luminescence. New understanding regarding the mode of interaction is reported as well as spectroscopic and structural data of these complexes.