Cover Picture: Physical Properties of Superbulky Lanthanide Metallocenes: Synthesis and Extraordinary Luminescence of [EuII(CpBIG)2] (CpBIG=(4-nBu-C6H4)5-Cyclopentadienyl) (Chem. Eur. J. 37/2013)

Abstract

High luminescence is observed for an Eu2+ ion sandwiched between two bulky cyclopentadienyl ligands, as described by S. Harder et al. in their Full Paper on page 12272 ff. In contrast to [Eu(Cp*)2] (Cp* = pentamethylcyclopentadienyl), which hardly shows luminescence, a quantum yield of 45% is found for the europocene [Eu(CpBIG)2] (CpBIG=(4-nBu-C6H4)5-cyclopentadienyl). Magnetic susceptibility measurements, and Mössbauer as well as EXAFS spectroscopy rule out possible oxidation-state ambiguities for the lanthanide(II) metallocenes of Sm, Eu, and Yb.