Structural and magnetic properties of mixed Co–Ln (Ln = Nd, Sm, Eu, Gd and Ho) diethyleneglycolate complexes

Abstract

New hybrid compounds LnCoCl(deg)₂ (deg = diethyleneglycolate; Ln = Nd, Sm, Eu, Gd and Ho) have been synthesized by mixing cobalt and rare earth cations in a boiling diethyleneglycol (degH₂) medium. Their crystallographic structures have been ab initio solved from synchrotron powder diffraction data. They consist of edge sharing tetrameric sub-units [(Ln₂Co₂)(deg)₄(Cl)₂] forming 1D infinite chains along the c parameter of a monoclinic unit cell (SG = C2/c). The five- and seven-coordination of Co²⁺ and Ln³⁺ cations inferred from the crystallographic results is confirmed by UV-visible absorption and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. In the LnCoCl(deg)₂ (Ln = Nd, Sm, Eu, Gd, Ho) series, weak antiferromagnetic superexchange interactions have been evidenced, between high spin Co²⁺ and Ln³⁺ orbitally degenerate cations. These materials are considered as potential precursors for the simultaneous reduction of Co–Ln-glycolate species into bimetallic nanoparticles by the polyol process.