Anion-directed assembly of lanthanide coordination polymers with SMMs properties based on a dihydrazone ligand

Four new Ln(III)-based coordination polymers (CPs), [Eu(HL)Cl₂(DMF)₂]·(H₂L) (1), [Dy(HL)Cl₂(DMF)₂]·(H₂L) (2), [Er(HL)Cl₂(DMF)(CH₃OH)]·(DMF) (3) and [Yb(HL)Cl₂(DMF)(H₂O)]·(DMF) (4) (H₂L=2,6-bis[(3-methoxysalicylidene)hydrazinocarbonyl]pyridine) have been synthesized through the reaction of Ln(III) chloride and H₂L by using the vapour diffusion method. Interestingly, Cl^- as a template agent plays a vital role in the formation of the target complexes. Single-crystal X-ray diffraction studies indicate that 1 and 2 are isostructural and crystallize in triclinic space group P1, while complexes 3 and 4 are isostructural and crystallize in monoclinic space group C2/c. Variable temperature magnetization measurement (χ_MT-T) demonstrates possible antiferromagnetic interactions in complex 2. Alternating-current (ac) susceptibility measurement furthermore indicated frequency dependence for both the in-phase (χ′) and out-of-phase (χ″) components in 2, suggesting that there is a slow relaxation behavior of the magnetization, which is typical of single-molecule magnets (SMMs). This is the first time that Ln(III) CPs based on such a dihydrazone ligand has been reported so far.