Dodecanuclear [NiII8Ln4] clusters: rings of corner-sharing {NiII2Ln2} cubanes (Ln = Dy, Gd, Y}

The solvothermal reaction of NiCl2.6H2O with 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane, LH3, and Ln(OAc)3.4H2O in the presence of salicylaldehyde in MeOH leads to the formation of the dodecanuclear isostructural species [NiII8Ln4(L’)8(OAc)4(OH)8(H2O)4].xH2O (Ln= Dy, x=6 (1); Gd, x= 24 (2); Y, x= 10 (3); L’ = the dianion of the Schiff-base resulting from the reaction of salicylaldehyde and ethanolamine). The metallic core of the clusters describes a ring a of corner-sharing {Ni2Ln2} cubanes assembled on a central, planar rectangular {Ln4} unit. Magnetization studies conducted on complexes 1 - 3 demonstrate the presence of dominant ferromagnetic exchange at low temperatures, which is largely attributed to the Ni⋯Ni interactions. The significant magnetocaloric effect observed in the Gd analogue has been assessed through heat-capacity and magnetization measurements.