Structures and magnetic properties of two series of Schiff base binuclear lanthanide complexes

Until now, although there are many examples of studying the magnetic properties of Schiff base binuclear lanthanide complexes, the relationship between the structure and magnetic properties of the complexes still is worth further investigation in order to improve the magnetic properties of Schiff base lanthanide complexes. In this work, we successfully obtained two series of binuclear Ln complexes by in situ reaction of 4‐diethylaminosalicylaldehyde, benzoic hydrazide and different lanthanide salts at 80°C under solvothermal conditions, namely, [Ln2(L)3(NO3)3]·CH3CN·CH3OH·H2O [Ln = Dy (1), Ho (2), Gd (3) L = deprotonated 4‐diethylamino salicylaldehyde benzoylhydrazine], [Ln2(L)4(CH3COO)]CH3COO·CH3CN [Ln = Dy (4), Ho (5), Gd (6)]. The complex 1 contains three Schiff base ligands L, two Dy (III) ions, and three NO3−. The ligand H1L is formed by in situ Schiff base reaction with 4‐diethylaminosalicylaldehyde and benzoic hydrazide with the participation of Ln (NO3)3. When replacing Ln (NO3)3 with Ln (OAc)3, obtained three μ2‐OAc bridged binuclear Ln (III) complexes. The magnetic study showed that complex 4 exhibits field‐induced single‐molecule magnet (SMM) behavior while complex 1 does not show any SMMs behavior. In addition, we have studied the magnetocaloric effect of complexes 3 and 6, their maximum −ΔSm values are 21.37 J kg−1 K−1 and 15.32 J kg−1 K−1, respectively, under ΔH = 7 T and T = 2 K. Two series of binuclear Ln complexes were obtained, the single‐molecule magnets of Dy‐based complexes and magneto‐thermometric effects of Gd‐based were also investigated.