Synthesis and magnetothermal properties of a ferromagnetically coupled NiII–GdIII–NiII cluster

A linear trimeric cluster of molecular formula [Ni2Gd(L−)6](NO3) (1) (L− = (C14H12NO2) has been isolated with its structure determined via single crystal X-ray diffraction. Magnetic susceptibility measurements of 1 show that the nickel and gadolinium ions are coupled ferromagnetically, with a ground total spin state (S) of 11/2. Best fit spin Hamiltonian parameters obtained for 1 are J1(Ni–Gd) = +0.54 cm−1, g = 2.01. EPR measurements confirm a low magnetic anisotropy (D = −0.135 cm−1) for 1. Heat capacity determination of the magnetocaloric effect (MCE) parameters for 1 shows that the change in magnetic entropy (−ΔSm) achieves a maximum of 13.74 J kg−1 K−1 at 4.0 K, with the ferromagnetic coupling giving a rapid change in low applied fields, confirming the potential of Gd molecular derivatives as coolants at liquid helium temperature