A CF3-substituted diphosphine dioxide ligand that enhances both photoluminescence intensity and solubility of Eu(III) complexes

Abstract

The author developed the di(3-trifluoromethylphenyl)[3-(dioctylphosphinyl)propyl]phosphine oxide (DPDO-mCF3) ligand in order to prepare Eu(III) complexes with high photoluminescence intensity and solubility. By coordinating the DPDO-mCF3 ligand to Eu(III), photoluminescence intensities were increased to 6.4 and 4.3 times those of tris(4,4,5,5,6,6,6-heptafluoro-1-(2-naphthyl)-1,3-hexanedionato)europium(III) (Eu(III)(hfnh)3; 4) and tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III) (Eu(III)(fod)3; 5), respectively. Coordination of the DPDO-mCF3 ligand also increased the asymmetry ratio, total photoluminescence quantum yield (ΦTOT), and absorbance of Eu(III) complexes. ΦTOT of Eu(III)(hfnh)3(DPDO-mCF3) (1) was 0.60 in ethyl acetate at a concentration of 1 × 10−3 mol/L and 0.82 in the solid state. In addition, ΦTOT of Eu(III)(fod)3(DPDO-mCF3) (2) is 0.39 in ethyl acetate at a concentration of 1 × 10−3 mol/L and 0.56 in the solid state. Solid-state quantum yields were larger than solution-state quantum yields across a wide wavelength region. Furthermore, the solubility of 2 in 2,3-dihydrodecafluoropentane (54 μmol/g) was far higher than that of 5 (7.2 μmol/g). DPDO-mCF3 is thus an innovative ligand for Eu(III) complexes, and Eu(III) complexes bearing a DPDO-mCF3 ligand are promising candidates for many applications, including LED devices, secure media, and sensing devices.