Rare-Earth Complexes of Ferrocene-Containing Ligands: Visible-Light Excitable Luminescent Materials

The ferrocene-derivatives bis(ferrocenyl-ethynyl)-1,10-phenanthroline (Fc2phen) and ferrocenoyltrifluoroacetone (Hfta)
have been used to synthesize ferrocene-containing rare-earth β-diketonate complexes. The complexes [Ln(tta)3(Fc2phen)] and [Ln(fta)3(phen)] (where Ln = La, Nd, Eu, Yb) show structural similarities to the tris(2-thenoyltrifluoroacetonate)(1,10-phenanthroline)lanthanide(III) complexes, [Ln(tta)3(phen)]. The coordination number
of the lanthanide ion is 8, and the coordination sphere can be described as a distorted dodecahedron. However,
the presence of the ferrocene moieties shifts the ligand absorption bands of the rare-earth complexes to longer
wavelengths so that the complexes can be excited not only by ultraviolet radiation but also by visible light of
wavelengths up to 420 nm. Red photoluminescence is observed for the europium(III) complexes and near-infrared
photoluminescence for the neodymium(III) and ytterbium(III) complexes. The presence of the ferrocene groups
makes the rare-earth complexes hydrophobic and well-soluble in apolar organic solvents.