Lanthanide(III) Complexes with 4,5-Bis(diphenylphosphinoyl)-1,2,3-triazolate and the Use of 1,10-Phenanthroline As Auxiliary Ligand

New lanthanide complexes with 4,5-bis(diphenyl)phosphoranyl-1,2,3-triazolate (L −), LnL3·nH2O (1− 8) and LnL3(phen)·nH2O (9−16) (Ln = La, Ce, Nd, Sm, Eu, Gd, Tb, Er), have been prepared and spectroscopically characterized. The structures of LnL3 · nH2O (Ln = La, Ce, Nd, Sm and Gd) were determined by X-ray crystallography. The metal centers exhibit a distorted trigonal dodecahedron coordination environment with two symmetrically O,O-bidentate ligands and one unsymmetrically O,N- ligand attached to the metal; two oxygen atoms from neighboring dimethyl sulfoxide (DMSO) molecules complete the coordination sphere. This unsymmetrical ligand coordination behavior was also identified in solution through 31P{1H} NMR studies. Photoluminescence spectroscopy experiments in CH2Cl2 for both types of complexes containing Eu(III) (6, 14) and Tb(III) (7, 15) exhibit strong characteristic red and green emission bands for Eu(III) and Tb(III), respectively. Furthermore, NdL3 (phen)·5H 2O (11) displays emission in the near-infrared spectral region (4F3/2 → 4F9/2 at 872 nm and 4F3/2 → 4F11/2 at 1073 nm). The complexes containing 1,10-phenantroline exhibit higher quantum yields upon excitation at 267 nm, indicating that this auxiliary ligand promotes the luminescence of the complexes; however, luminescence lifetimes (τ) in this case are shorter than those of the LnL3·nH2O series.