Highly luminescent, neutral, nine-coordinate lanthanide(III) complexes

Using a simple ligand design, we have prepared neutral, nine-coordinate lanthanide complexes that exclude water from the inner coordination sphere, thus leading to high emission quantum yields and long excited-state lifetimes. The complexes form in high synthetic yields (49-87%) by simply mixing the ligand and the lanthanide. Visible luminescence from EuIII (Φ = 60 %, τ = 2.2 ms) and TbIII (Φ = 7 %, τ = 0.2 ms) and near-infrared luminescence from YbIII (Φ = 0.7%), NdIII and Er III were observed in acetonitrile and CH2Cl2 at room temperature. In addition, the GdIII complex was prepared to gain information about the triplet state of the ligand.