3-Phenyl-4-benzoyl-5-isoxazolonate Complex of Eu³⁺ with Tri-n-octylphosphine Oxide as a Promising Light-Conversion Molecular Device

Abstract

Three new europium complexes, [Eu(PBI)3.3H2O] (1), [Eu(PBI)3.2TOPO] (2), and [Eu(PBI)3.2TPPO.H2O] (3) (where HPBI, TOPO, and TPPO stand for 3-phenyl-4-benzoyl-5-isoxazolone, tri-n-octylphosphine oxide, and triphenylphosphine oxide, respectively), with different neutral ligands were synthesized and characterized by elemental analysis, Fourier transform infrared, (1)H NMR, thermogravimetric analysis, and photoluminescence (PL) 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 in terms of a model of the intramolecular energy-transfer process in lanthanide coordination compounds 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 (7F(0-4)). On the basis of emission spectra and lifetimes of the 5D0-emitting level, the emission quantum efficiency (eta) was determined. The results clearly show that the substitution of water molecules by TOPO leads to greatly enhanced quantum efficiency (i.e., 26% vs 92%) and longer 5D0 lifetimes (250 vs 1160 micros). This can be ascribed to a more efficient ligand-to-metal energy transfer and a less nonradiative 5D0 relaxation process. Judd-Ofelt intensity parameters (Omega2 and Omega4) were determined from the emission spectra for the Eu3+ ion based on the 5D0 --> 7F2 and 5D0 --> 7F4 electronic transitions, respectively, and the 5D0 --> 7F1 magnetic-dipole-allowed transition was taken as the reference. A point to be noted in these results is the relatively high value of the Omega2 intensity parameter for all of the complexes. This may be interpreted as being a consequence of the hypersensitive behavior of the 5D0 --> 7F2 transition. The dynamic coupling mechanism is, therefore, dominant, indicating that the Eu3+ ion is in a highly polarizable chemical environment.

Seven‐Coordinate Luminophores: Brilliant Luminescence of Lanthanide Complexes with C3v Geometrical Structures

“…The kr and Φff of Tb III complexes were calculated under the assumption that the emission lifetimes at 77 K (Figure 4b and 4c) were the radiative emission lifetime (τrad). [33] Tb(tmh)3(tppo) also exhibited a high Φff of 88%, a large kr (1.04×10 3 s -1 ) and a small knr (1.49×10 2 s -1 ). Hasegawa et al…”

Facile and Large-Scale Syntheses of Nanocrystal Rare Earth Metal–Organic Frameworks at Room Temperature and Their Photoluminescence Properties

“…We have focused on the lanthanide-containing MOFs because of their electronic, optical and chemical characteristics that result from the 4f electronic shells of the ions [24][25][26]. Energy transfer between the ligands and the lanthanide trivalent ion improves the overall photoluminescent properties of MOFs, which have been extensively explored in materials science [27].…”

Luminescent Europium(III) Nanoparticles for Sensing and Imaging of Temperature in the Physiological Range

“…iii) The absorption band of DNM extends into the visible part of the spectrum, [14] thus, enabling the use of small and efficient light sources such as LEDs or diode lasers. iv) The ligand trioctylphosphine oxide can increase the efficiency of ligand-to-metal energy transfer and decrease that of the nonradiative decay of the 5 D 0 electronic state, [15] thus, increasing the luminescence quantum yield of the complex. Figure 1 shows the absorption and emission spectra of Eu-DT in toluene solution.…”