Lanthanide mixed-ligand complexes of the [Ln(CAPh)3(Phen)] and [LaxEu1−x(CAPh)3(Phen)] (CAPh = carbacylamidophosphate) type. A comparative study of their spectral properties

Abstract

A series of complexes Ln(Pip)₃(Phen) (Ln(III) = La, Ce–Nd, Sm–Lu, Y; HPip (CAPh type ligand) = 2,2,2-trichloro-N-(dipiperidin-1-yl-phosphoryl)acetamide, Phen = 1,10-phenanthroline) has been synthesized. The lanthanum(III) doped europium(III) complexes ([La_xEu_1−x(Pip)₃(Phen)], x = 0.99, 0.95, 0.50) have been obtained by the co-crystallization method. The complexes have been characterized by means of X-ray diffraction, IR, ¹H and ³¹P-NMR and absorption spectroscopy. Emission and excitation luminescence spectra were recorded at 295 and 77 K. The lifetime values (τ) for the emission of all europium complexes were determined. The ⁵D₀ luminescence quantum efficiency is 73–89%. The symmetries of the nearest europium surrounding in pure and doped complexes were evaluated from the Stark splitting of ⁵D₀–⁷F_J transitions. Crystal structures of [Ln(Pip)₃(Phen)] (Ln = Nd (1), Eu (2) and Tb (3)) have been determined. Lattice parameters of the [Ln(Pip)₃(Phen)] (Ln = Tb, Yb) and the doped [La_xEu_1−x(Pip)₃(Phen)] (x = 0.99, 0.95, 0.50) complexes have been measured. The presence of four polymorphs within a number of rare earth elements has been estimated: two in triclinic (Ln1 = La, Nd; Ln2 = Eu), one in the monoclinic (Ln3 = Tb) and one in the rhombic (Ln4 = Tb, Yb) symmetry. Complex 3 can be obtained in two crystal modifications: monoclinic and orthorhombic ones.