Syntheses, structures and magnetic properties of two heterometallic carbonates: K2Li[Cu(H2O)2Ru2(CO3)4X2]·5H2O (X = Cl, Br)

Abstract

Self-assembly of Ru₂(CO₃)₄³⁻ units and Cu²⁺ ions in the presence of halogen (Cl⁻ or Br⁻) has resulted in two novel isomeric layered structural heterometallic carbonates, K₂Li[Cu(H₂O)₂Ru₂(CO₃)₄X₂]·5H₂O [X = Cl (1), Br (2)]. X-ray structural analysis reveals that complexes 1 and 2 contain a similar square-grid negative layer [Cu(H₂O)₂Ru₂(CO₃)₄X₂]_n⁵ⁿ⁻, in which each Ru₂(CO₃)₄X₂⁵⁻ unit is linked by four Jahn–Teller distorted Cu(H₂O)₂²⁺ ions in a cross mode and vice versa. The adjacent negative layers are connected by K–O, Li–O bonds, and hydrogen bonding, which led to the formation of a supramolecular 3D network structure. The two complexes show ferromagnetic coupling between the Ru₂ dimer and the Cu²⁺ ion. Detailed magnetism measurement demonstrates that complex 1 exhibits soft magnetic ordering below 2.9 K coexistent with domain movement, and complex 2 shows long-range ferromagnetic ordering below 3.8 K.