New phosphinate ligand synthesis and its effect on optical properties of the europium β-diketonate complex

The synthesis and characterization of a new organic ligand monooctyldiphenylphosphinate (L) is described, as well as a new Eu3+ diketonate complex[Eu(tta)3(L)2] (tta = thenoyltrifluoracetone). The ligand (L) was formed by substitution reaction (80% yield) and characterized by uni- and bi-dimensional 1H, 13C and 31P NMR experiments, to confirm its molecular structure. The coordination of (L) to Eu3+ in the complex[Eu(tta)3(L)2] was confirmed by FT-IR spectra. The emission spectra present the same profile when excited in Eu3+ or in the ligands, suggesting an energy transfer from ligands to Eu3+ ions. The emission spectra of the precursor[Eu(tta)3(H2O)2], and[Eu(tta)3(L2)] present bands arising from f-f intra-configurational transitions. The only 5D0-7F0 transition shows the presence of at least one site without symmetry center. The FWHM of such transition is 7 cm-1 and 57 cm-1 for[Eu(tta)3(H2O)2] and[Eu(tta)3(L)2] complexes, respectively. This widening is provided by the presence of large groups around Eu3+ ion. The calculated intensity parameters Ω2 and Ω4 show that the interaction features between center-ion and ligand are different; the small value of Ω4is related to long range effects of alkyl chain. The Langmuir isotherms of this ligand and complex have been investigated although their hydrolysis in water subphase does not allow stable monolayers (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)