Synthesis, Characterization, and Luminescence Properties of Eu³⁺ 3‐Phenyl‐4‐(4‐toluoyl)‐5‐isoxazolonate Based Organic‐Inorganic Hybrids

Abstract

Abstract Organic‐inorganic hybrids incorporating Eu(TPI) 3 · 3H 2 O or Eu(TPI) 3 · 2TOPO [where TPI and TOPO stand for 3‐phenyl‐4‐(4‐toluoyl)‐5‐isoxazolone and tri‐ n ‐octylphosphane oxide, respectively] were synthesized either by acetic acid solvolysis or a conventional hydrolysis sol‐gel route. The host framework of these materials, named as di‐ureasil, consists of a siliceous skeleton grafted, through urea cross‐linkages, to both ends of poly(ethylene oxide) chains. The resulting Eu 3+ ‐based di‐ureasils were characterized by X‐ray diffraction and Fourier transform mid‐IR, 29 Si and 13 C NMR, and photoluminescence spectroscopy. The room‐temperature photoluminescence (PL) spectra of the Eu 3+ ‐based di‐ureasils display the typical Eu 3+ red emission, assigned to transitions between the first excited state ( 5 D 0 ) and the ground multiplet ( 7 F 0–4 ). Enhanced 5 D 0 quantum efficiency ( η = 13 % vs. 32 %) and a longer lifetime ( τ = 0.30 vs. 0.42 ms) was noticed for the hybrid incorporating the Eu(TPI) 3 · 3H 2 O complex, compared with the undoped complex. The enhancement is explained by the coordination ability of the organic counter part of the host structure, which is strong enough to displace the water molecules of the Eu(TPI) 3 · 3H 2 O complex from the Eu 3+ neighborhood in the hybrids. On the other hand, a decrease in the 5 D 0 quantum efficiency ( η = 76 % vs. 61 %) and lifetime ( τ = 0.98 vs. 0.75 ms) was noticed for the hybrid incorporating the Eu(TPI) 3 · 2TOPO complex, relative to the undoped complex, probably because of an increase in the nonradiative transition probability. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)