Electrogenerated Chemiluminescence and Electronic States of Several Organometallic Eu(III) and Tb(III) Complexes: Effects of the Ligands

We report the electrochemical properties, and electrogenerated chemiluminescence (ECL) of eight different organometallic complexes of Eu(III) and Tb(III), Eu(dbm) ₃ phen, Eu(dbm) ₃ bath, Eu(fod) ₃ phen, Eu(tta) ₃ phen, Tb(acac) ₃ phen, Tb(acac) ₃ bath, Tb(fod) ₃ phen, and Tb(tmhd) ₃ bpy in acetonitrile, where phen, bath, and bpy are 1, 10-phenanthroline, bathophenanthroline, 2,2′-bipyridyl, respectively, and the anionic ligands, acac ⁻ , dbm ⁻ , fod ⁻ , and tta ⁻ are the enolate forms of acetylacetone, dibenzoylmethanate, 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedione, and thenoyltrifluoroacetone, respectively. The electronic states of the neutral and some charged states of the complexes were clarified with density functional theory calculations. The ECL spectra were recorded by using S ₂ O ₈ ²⁻ as a coreactant, and for all complexes, sharp ECL spectra, which are attributable to the f-f transitions, were observed. On the potential-dependent ECL spectra, broad ECLs, which were originated from the ligands, were also detected. Based on the ECL behavior and the electronic states, the mechanisms of the intraconfigurational ECL were discussed.