Macrocycle supported dinuclear lanthanide complexes with different β-diketonate co-ligands displaying zero field single-molecule magnetic behaviour

Three different sets of isomorphous dinuclear Gd/Dy complexes, [Ln(2)(L')(acac)(4)]center dot 2H(2)O center dot 2CH(3)CN (Ln = Gd (1(Gd)) and Dy (2(Dy)); acac = acetylacetonate), [Ln(2)(L')(tfac)(4)] (Ln = Gd (3(Gd)) and Dy (4(Dy)); tfac = trifluoroacetylacetonate), and [Ln(2)(L')(hfac)4] (Ln = Gd (5(Gd)) and Dy (6(Dy)); hfac = hexafluoroacetylacetonate), where H2L' is a new Ln-assisted in situ generated macrocyclic ligand from acyclic Schiff base HL, derived from a condensation reaction of 2,6-diformyl-4-methylphenol and N,N-dimethyldipropylenetriamine, have been synthesized by the reaction of lanthanide nitrates with ligand HL in the presence of different beta-diketonate co-ligands. Structural analysis revealed that the lanthanide ions in these complexes are all eight-coordinated in a square antiprismatic geometry with D-4d symmetry. Magnetic measurements of these complexes revealed that the magnetic interaction between Gd3+ ions is antiferromagnetic, while Dy3+ ions are ferromagnetically coupled in dimetallic complexes, and the detailed analysis of Gd analogues discloses the significant influence of the different beta-diketonate co-ligands on the magnitude of the magnetic interactions. All three Dy complexes exhibit zero field single-molecule magnet behaviour with energy barriers varying in the close range 60.1-62.8 K. The orientation of the magnetic axes and crystal structural parameters were critically analysed to establish magneto-structural correlations in three Dy-based SMMs to gain an in depth understanding of the magnetic dynamics in these systems.