Modulating single-molecule magnet behavior towards multiple magnetic relaxation processes through structural variation in Dy4 clusters†
Three Dy4 clusters, [Dy4(tmhd)8(L)2(CH3OH)2]·CH3OH (1), [Dy4(hfac)8(L)2(DMF)2]·C7H16 (2) and [Dy4(dbm)6(L)2(μ3-OH)2]·CH2Cl2 (3) (tmhd = 2,2,6,6-tetramethyl-3,5-heptanedione, hfac = hexafluoroacetylacetonate, dbm = 1,3-diphenyl-1,3-propanedione, HL = 2-[(2-(hydroxyimino)propanehydrazide)methyl]), have been successfully synthesized by using three different β-diketonate salts (Dy(tmhd)3·2H2O, Dy(hfac)3·2H2O, and Dy(dbm)3·2H2O) to react with HL and by changing the solvent. The X-ray structural analysis shows that four DyIII ions in clusters 1 and 2 are linearly arranged; however, cluster 3 contains one Dy4 center with a rhombus-shaped arrangement. The different structures of three Dy4 clusters were profoundly affected by these minor changes in β-diketonate or a change in the solvent. Magnetic studies reveal that Dy4 clusters 1–3 exhibit different single-molecule magnet (SMM) behaviors under a zero dc field. 1 and 2 display slow magnetic relaxation behaviors with effective energy barriers ΔE/kB = 1.44 K for 1 and ΔE/kB = 50.96 K for 2, while for 3, two distinct slow magnetic relaxation processes are observed, with effective energy barriers ΔE/kB = 40.45 K for the fast relaxation process and ΔE/kB = 113.63 K for the slow relaxation process. This study shows that the β-diketonate coligands play an important role in modulating molecular structures and further affecting the magnetic dynamics of the lanthanide clusters towards multiple magnetic relaxation processes.