Heterometallic 3d-4f {Co2Gd4} phosphonates: New members of the potential magnetic cooler family

Abstract

Three new heterometallic phosphonate complexes with a novel 3d-4f metal core {Co2Gd4} were isolated. The reactions between CoCl2, GdCl3, ligand sodium salts, and 2,2′-bipyridine in methanol solution lead to new unexpected 3d-4f heterometallic complexes, [Na2CoIII2Gd4(L)6(bpy)2(OR)2]·nSolv (L = SAA3- (1), BSAA3- (2), and NAA3- (3); bpy = 2,2′-bipyridine; OR = OH and OMe; Solv = H2O and MeOH), composed of a rare case of two magnetically independent oxygen bridged Gd2O2 dinuclear units, which are separated by O-P-O bridges. According to the BVS calculations and measured magnetic properties, only CoIII ions are present in the obtained complexes. The magnetic properties of the compounds 1-3 were studied and the entropy changes for the designation of the magnetocaloric effect were calculated. The largest value for the magnetic entropy change -ΔSM of 20 J kg-1 K-1 for complex 1 has been found for Tav = 2.25 K and Hf = 5 T. © 2019 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.