Modulating single-molecule magnet behaviors of Dy4III clusters through utilizing two different β-diketonate coligands

In search of simple approaches to rationally modulate the single-molecule magnet behaviors in polynuclear lanthanide clusters, a new system containing two structurally closely related rhombus-shaped Dy4 clusters, Dy4(tmhd)4L6(μ3-OH)2·5CH3CN (1) and Dy4(acac)4L6(μ3-OH)2 (2) (HL = 5-(4-ethyoxylbenzylidene)-8-hydroxylquinoline, Htmhd = 2,2,6,6-tetramethyl-3,5-heptanedione and Hacac = acetylacetonate), have been obtained by employing two dysprosium β-diketonate salts to react with a bidentate Schiff base ligand (HL). The two Dy4 clusters have similar structures and possess a structure in which four Dy3+ ions remain in a perfect plane with a rhombus-shaped geometric construction. Dynamic magnetic analysis revealed different single-molecule magnet (SMM) behaviors occurs in 1 and 2. Under zero direct-current (dc) field, 1 displays typical SMMs behavior with ΔE/kB = 39.6 K and τ0 = 2.1 × 10−6 s. However, for 2, a peculiar feature of the χ″ versus temperature curves is that more than two peaks that are frequency-dependent are revealed, indicating the occurrence of multifold relaxation processes that lead to two ΔE/kB (31.3 K and 81.6 K) and pre-exponential factors (τ0 = 3.1 × 10−6 s, τ0 = 2.2 × 10−7 s).