Asymmetry in propeller-like trinuclear diphenoxo-bridged Cu^II–Ln^III–Cu^II (Ln = La, Pr, Nd) Schiff base complexes – synthesis, structure and magnetic properties

Neutral heterotrinuclear complexes 2{[Cu₂Ln(H₂L)₂(NO₃)₃]}·6CH₃OH (Ln = La (1), Nd (2)) and [Cu₂Ln(H₂L)₂(NO₃)₃]·4CH₃OH·2H₂O (Ln = Pr (3)) were obtained in the reaction of N,N′-bis(2,3-dihydroxybenzylidene)-1,3-diaminopropane (H₄L = C₁₇H₁₈N₂O₄) with the respective salts of Ln^III and Cu^II. Compounds 1–3 have similar coordination units and display asymmetry in the degree of planarity of the bridging CuO₂Ln fragments, which is unusual for Cu^II–Ln^III–Cu^II complexes. The geometry of the obtained complexes has been compared to the structural data of other 3d–4f–3d trinuclear diphenoxo-bridged complexes. The temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicate that the interaction between Cu^II and Ln^III ions is antiferromagnetic for Ln = Pr (2) and Nd (3), whereas in 1 the Cu^II–La^III pairs show no significant interaction, which is in accord with the non-magnetic nature of the ground state for lanthanum(III).