Search

Two LnIII complexes derived from one aromatic monocarboxylate ligand, namely [Tb2(mnba)6(H2O)4]n (1) and [Dy2(mnba)4(μ3-OH)2(H2O)]n (2) (Hmnba = m-nitrobenzoic acid), have been prepared by similar synthetic procedures and structurally characterized. Complex 1 contains two identical one-dimensional (1D) chains with the syn,syn-carboxylate as linkers, while complex 2 takes the 1D chain structure with μ3--OH and carboxylate as bridge. Magnetic studies indicate that ferromagnetic interactions between intra-chain metal centers exist in 1 and 2 and only complex 2 exhibits field-induced slow magnetic relaxation behavior.

Two dinuclear GdIII cluster complexes with the formulas [Gd2(iba)6(bipy)2] (1) and [Gd2(nic)6(H2O)4] (2) (Hiba = isobutyric acid, Hnic = nicotinic acid and bipy = 2,2´-bipyridine) have been constructed by using gadolinium oxide as GdIII ion source under hydrothermal conditions. Although both 1 and 2 exhibit dinuclear structures, the coordination fashions are totally different. In 1, the carboxylate groups of Hiba take syn-syn-μ2-η1:η1, syn-syn-μ2-η1:η2 and syn-μ-η1:η1 modes and bipy acts as the chelating ligand. While the carboxylate groups of Hnic display syn-syn-μ2-η1:η1 and syn-μ-η1:η1 modes in 2 and two water molecules take part in coordination. Magnetic studies reveal weak ferromagnetic couplings and significant magnetic entropy changes with −ΔSmmax = 29.3 J kg−1 K−1 and 27.4 J kg−1 K−1 (ΔH = 7 T), respectively.

Two Gd2 cluster complexes with the formulas of [Gd2(dnba)6(phen)2] (1) and [Gd2(Hnsa)2(nsa)2(phen)2(H2O)2] (2) (Hdnba = 3,5-dinitrobenzoic acid, H2nsa = 5-nitrosalicylic acid and phen = 1,10-phenanthroline) respectively have been successfully synthesized under hydrothermal conditions. The GdIII ions of 1 are bridged by four carboxylates with syn-syn-μ2-η1:η1 and syn-syn-μ2-η1:η2 modes, while the GdIII ions of 2 are linked by two carboxylate ligands with only syn-syn-μ2-η1:η2 mode. Magnetic studies indicate that weak antiferromagnetic and ferromagnetic interactions exist between the adjacent GdIII ions within Gd2 clusters, respectively. Complexes 1 and 2 display distinct magnetocaloric effects induced by different magnetic interactions and magnetic densities. Notably, the maximum magnetic entropy changes (−ΔSmmax) of 1 and 2 reach 16.8 J kg−1 K−1 and 22.2 J kg−1 K−1 with ΔH = 7 T at 2 K and 3.5 K, respectively.