Magnetic properties of Bis-Lanthanoates

In this study three different types of bis-lanthanoates, that exist in different phases, have been synthesised and characterised (Ln = lanthanide): 1) imidazolium lanthanide acetate – [C4Mim]2[Ln2(OAc)8] – forms a crystalline solid at room temperature, 2) phosphonium lanthanide acetate – [P666 14]2[Ln2(OAc)8] – is in a solid glassy state, and 3) phosphonium lanthanide octanoate – [P666 14]2[Ln2(Oct)8] – is an ionic liquid. X-ray diffraction of the crystalline solid 1) confirm that the Ln(III) ions form dimers, bridged by carboxyl groups, but cannot yield information about samples 2) and 3) since these lack long-range order. SQUID magnetometry studies of samples where the lanthanide is dysprosium, show that all three samples have effective magnetic moments consistent with non-interacting Ln(III) ions at room temperature, but deviate from this behaviour in the same way below 50 K, see figure. The experimentally determined magnetic susceptibility has been compared to a simple model for a system with two Dy(III) ions; the implications from these fits for the magnetic interactions and the structure of the ionic liquid and glass will be discussed.