Lanthanide(III) Complexes Based on Tris(2-pyridyl)phosphine Oxide: First Examples

A series of mononuclear complexes [Ln(Py3PO)2(NO3)3] · 1.5Me2CO (Ln = Sm, Eu, Gd, Tb, Dy) and [Ln(Py3PO)(TTA)3] (Ln = Eu, Tb; TTA‒ is thenoyltrifluoroacetonate ion) based on tris(2-pyridyl) phosphine oxide (Py3PO) is synthesized and studied. In the synthesized compounds, Py3PO acts as the N,O-chelate ligand resulting in the formation of coordination polyhedra N2O8 and NO7 of the Ln atom in complexes [Ln(Py3PO)2(NO3)3] · 1.5Me2CO and [Ln(Py3PO)(TTA)3], respectively. The complexes of Sm3+, Eu3+, Tb3+ and Dy3+ ions exhibit lanthanide-centered photoluminescence in the solid phase at 300 K. The energy of the T1 triplet level of Py3PO is determined to be 21 900 cm‒1 from the ligand-centered phosphorescence spectrum of the Gd(III) complex at 77 K. Among the complexes with the NO3‒ ions, Py3PO exhibits the highest sensibilizing ability toward Tb3+, whereas the ligand environment in the complexes with the TTA‒ ions most efficiently sensibilizes the Eu3+ ion luminescence.