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

Four tetranuclear lanthanide clusters: {[Gd-4(L-1)(6)(tmhd)(4)(mu(3)-OH)(2)]center dot 2CH(3)CN} (1), {[Tb-4(L-1)(6)(tmhd)(4)(mu(3)-OH)(2)]center dot 4CH(3)CN} (2), {[Dy-4(L-1)(6)(tmhd)(4)(mu(3)-OH)(2)]center dot CH3CN} (3) and {[Gd-4(L-2)(6)(tmhd)(4)(mu(3)-OH)(2)]center dot 8CH(3)CN center dot 2CH(2)Cl(2)} (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 Ln(III) ions, which is held together by two pyramidal mu(3)-OH- ions and six mu(2) phenol hydroxyl oxygen atoms derived from six ligands. Magnetic studies indicated that 1 and 4 exhibit a cryogenic magnetic refrigeration property (maximum -Delta S-m = 18.02 J K-1 kg(-1) for 1, and 15.47 J K-1 kg(-1) for 4, Delta H = 7 T at 2.0 K), whereas compound 3 exhibits a slow relaxation of magnetization with an energy barrier (U-eff/k(B)) of 83.1 K and tau(0) = 4.18 x 10(-8) s.