Solvent-Dependent Photophysical Properties of Eu(TTA)3Phen: A Comprehensive Study

The solvent dependence of the optical properties of tris(thenoyltrifluoroacetonate)(1,10-phenanthroline)europium(III) (Eu(TTA)3Phen) solution was studied in chloroform, dichloromethane, toluene, acetonitrile, acetone, N,N-dimethylformamide, dimethyl sulfoxide, and methanol. The optical properties of solid Eu(TTA)3Phen were carefully studied for comparison. The absorption spectra are dominated by ligand-centered bands, with only minor solvent-induced changes in the absorption maxima. Upon excitation into the ligand band, the emission spectra containe the characteristic narrow transition bands of europium(III), indicating efficient ligand-to-metal energy transfer. The photochemical properties of Eu(TTA)3Phen significantly depend on the solvent. Nonpolar and weakly coordinating solvents preserve longer lifetimes and higher solution quantum yields, with maxima in chloroform (14.7%) and toluene (13.7%). In contrast, methanol produces the strongest perturbation, yielding the shortest lifetime (0.364 ms), highest nonradiative rate (1427 s−1), lowest Eu(III) internal quantum yield (48.0%), and lowest photoluminescence quantum yield (4.6%). Analysis of radiative/nonradiative rates and 5D0-level formation quantum yield shows that solvent-dependent luminescence arises from changes in both the Eu3+-radiative transition efficiency and ligand-to-metal sensitization, providing design guidelines for solution-processable Eu3+ emitters.