Time-resolved total internal reflection fluorometry of ternary europium(III) complexes formed at the liquid/liquid interface

Abstract

The formation of ternary europium(III) complexes with 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (Htta) and 4,7-diphenyl-1,10-phenanthroline disulfonate (bps) formed at the toluene/water interface was studied by time-resolved total internal reflection fluorescence spectrometry. The fluorescence decay profile of the interfacial complexes was fitted to the double-exponential decay function with the lifetimes of 22±8 and 203±34 µs, which proved the existence of two different species. Dependence of the fluorescence intensity of each species on the ligand concentrations suggested the formation of Eu(tta)₂bps^- (long lifetime) and Eu₂(tta)₂(bps)₂ (short lifetime) at the interface. The anomalously short lifetime of the binuclear complex was discussed in terms of a ligand–metal charge transfer state.