Synthesis and Luminescent Properties of Novel Europium(III) Heterocyclic β‐Diketone Complexes with Lewis Bases: Structural Analysis Using the Sparkle/AM1 Model

Abstract

AbstractTris(β‐diketonato)europium(III) complexes of general formula [Eu(TPI)3·L], with chelating ligands such as 3‐phenyl‐4‐(4‐toluoyl)‐5‐isoxazolone (HTPI) and adduct‐forming reagents [L = H2O, tri‐n‐octylphosphane oxide (TOPO), triphenylphosphane oxide (TPhPO), 1,10‐phenanthroline], have been synthesized and characterized by elemental analysis and FT‐IR, 1H NMR, and photoluminescence spectroscopy. The coordination geometries of the complexes were calculated using the Sparkle/AM1 (Sparkle model for the calculation of lanthanide complexes within the Austin model 1) model. The ligand–Eu3+ energy‐transfer rates were calculated using a model of intramolecular energy transfer in lanthanide coordination complexes reported in the literature. The room‐temperature PL spectra of the europium(III) complexes are composed of the typical Eu3+ red emission, assigned to transitions between the first excited state (5D0) and the multiplet (7F0–4). The results clearly show that the substitution of water molecules by TOPO leads to greatly enhanced quantum yields (i.e., 1.3 % vs. 49.5 %) and longer 5D0 lifetimes (220 vs. 980 μs). This can be ascribed to a more efficient ligand‐to‐metal energy transfer and a less efficient nonradiative 5D0 relaxation process. The theoretical quantum yields are in good agreement with the experimental quantum yields, which highlights that the present theoretical approach can be a powerful tool for the a priori design of highly luminescent lanthanide complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)