Analytical Sciences

Abstract − Analytical Sciences, 27(12), 1249 (2011).

Enhancement of the Luminescence Efficiency of Europium(III) Tris(β-diketonato) Complex in Organic Media by Quaternary Ammonium Salts with Anionic Ligands
Hajime KATANO,* Kohei UEMATSU,* and Toshihide TSUKATANI**
*Department of Bioscience, Fukui Prefectural University, Eiheiji, Fukui 910-1195, Japan
**Research and Development Division, Nicca Chemical, Co. Ltd., Bunkyo, Fukui 910-8670, Japan
Benzyldimethyltetradecylammonium (BA14+) salts with anionic ligands (X), such as bis(2-ethylhexyl)sulfosuccinate, bis(2-ethylhexyl)phosphate (BEHP), and benzotriazole (BTA) anions, were prepared. These salts were soluble in various organic solvents. The luminescence emission spectra of organic solutions of a red luminescent, tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octadionato)europium(III) complex in the presence of the BA14X’s were recorded. The emission intensity of the Eu(III) complex was increased remarkably by the addition of BA14X (X = BEHP and BTA). This effect can be attributed to the formation of 1:1 X-adducts of the Eu(III) complex, in which the asymmetry of the ligand field is increased so as to enhance the emission efficiency of the 5D05F2 transition. The enhancement effect by BA14X was higher than that of charge-neutral ligands, such as tri-n-octylphosphine oxide and 1,10-phenanthroline, which have been used as second ligands to enhance the emission efficiency of tris(β-diketonato)europium(III) complexes.