A series of Salen-type homodinuclear lanthanide complexes and their slow magnetic relaxation in Dy2 and Ho2

A series of homodinuclear lanthanide complexes, namely, [Ln(2)(L)(2)(MeOH)(2)(NO3)(2)] [Ln = Gd (1), Tb (2), Dy (3), and Ho (4)], were synthesized by the reaction of Salen-type ligand, namely N, N '-bis(5-bromosalicylidene)ethane-1,2-diamine (H2L), with lanthanide salts in methanol and acetonitrile solution. The two Ln(III) ions in 1-4 are linked by two O-phenoxo atoms of two L2- ligands to build a dinuclear skeleton. The eight-coordinate Ln(III) center adopts a triangular dodecahedron geometry of D-2d symmetry. Theoretical calculations revealed that antiferromagnetic interactions exist in those complexes. Dynamic magnetic properties studies indicate that the Dy-2 complex behaves as a single-molecule magnet with an anisotropy barrier of U-eff approximate to 47.68 K and a pre-exponential factor tau(0) = 3.17 x 10(-6) s under a zero applied field, whereas the Ho-2 complex exhibits a fast tunneling relaxation process that is rationalized through ab initio calculations.