Linear Tetranuclear Lanthanide Cymantrenecarboxylates with Diethylene Glycol Ligand: Synthesis, Magnetism, and Thermolysis

Exchange reactions of LnCl₃ and CymCO₂K in aqueous‐organic medium in the presence of diethylene glycol (DEG) bring about isostructural tetranuclear cluster complexes with linear core, [Ln₄(CymCO₂)₁₂(O(CH₂CH₂OH)₂)₂(H₂O)₄] ⋅ 2THF (Ln=Nd (1), Gd (2), Tb (3), Dy (4), Ho (5); Cym=(η⁵‐C₅H₄)Mn(CO)₃). The complexes have centrosymmetric structure and contain two types of Ln³⁺ coordination centers. Thermal decomposition of the complexes under argon and air atmospheres was studied; in the latter case it brings about mixed oxides LnMn₂O₅ as one of the products. The complexes 1–5 were characterized by dc‐ and ac‐magnetic measurements. Complexes of Nd, Gd, and Dy exhibit the properties of single‐molecule magnets (SMMs) with remagnetization barriers Δ_eff/k_B of 14 K for 1 under 2500 Oe dc‐field, 13 K for 2 under 1500 Oe dc‐field, and with two barriers, 18 and 19 K, for 4 in zero field. The presence of field‐induced slow relaxation of the magnetization detected for the complex 2 is a rare case for Gd complexes.