Dodecanuclear [Ni^II₈Ln₄] clusters and rings of corner-sharing {Ni^II₂Ln₂} cubanes (Ln = Dy, Gd, Y}; Magnetic and Magnetothermal properties

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 [Ni^II₈Ln₄(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 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.