Single molecule magnet behavior and magnetic refrigeration of four tetranuclear lanthanide (Ln = GdIII, TbIII, DyIII) clusters

Four tetranuclear lanthanide clusters: {[Gd4(L1)6(tmhd)4(μ3-OH)2]·2CH3CN} (1), {[Tb4(L1)6(tmhd)4(μ3-OH)2]·4CH3CN} (2), {[Dy4(L1)6(tmhd)4(μ3-OH)2]·CH3CN} (3) and {[Gd4(L2)6(tmhd)4(μ3-OH)2]·8CH3CN·2CH2Cl2} (4) were fabricated by employing two Schiff based ligands (HL1 = 5-((4-ethylbenzylidene)amino)quinolin-8-ol and HL2 = 5-(([1,1′-biphenyl]-4-ylmethylene)amino)quinolin-8-ol). Interestingly, the cores of compounds 1–4 are nearly structurally identical. The core of the compounds contains a tetranuclear arrangement of LnIII ions, which is held together by two pyramidal μ3-OH− ions and six μ2 phenol hydroxyl oxygen atoms derived from six ligands. Magnetic studies indicated that 1 and 4 exhibit a cryogenic magnetic refrigeration property (maximum −ΔSm = 18.02 J K−1 kg−1 for 1, and 15.47 J K−1 kg−1 for 4, ΔH = 7 T at 2.0 K), whereas compound 3 exhibits a slow relaxation of magnetization with an energy barrier (Ueff/kB) of 83.1 K and τ0 = 4.18 × 10−8 s.