Synthesis, electrochemistry and spectroscopy of lanthanide(III) homodinuclear complexes bridged by polyazine ligands

Six new complexes [Eu(tta)(3)](2)bpm, [Er(tta)(3)](2)bpm, [Tb(tta)(3)](2)bpm, [Er(tta)(3)](2)dpp, Pr(tta)(3)bpm and Nd(tta)3bpm (tta = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, bpm = 2,2'-bipyrimidine, dpp = 2,3-bis(2-pyridyl)pyrazine) were prepared and studied. The electronic absorption spectra of the complexes display pi ->pi* transitions in the UV region. Cyclic voltarnmetry of the complexes show an irreversible reduction followed by a reversible reduction both associated with the tta ligand. Eu(III) reduction in the homodinuclear [Eu(tta)(3)](2)bpm complex occurs as an irreversible reduction at less negative potentials than the tta-based reductions. Emission spectra of the Eu(III) and Tb(III) 'bimetallics are typical of this type of bonding motif with ligand centered (tta) absorptions resulting in 4f-4f transitions in the visible and near infrared region. (c) 2005 Elsevier B.V. All rights reserved.