The Stepwise Formation of {Gd4} Clusters with Magnetocaloric Effect, Accompanied by In Situ Condensation Cyclization Reactions

Abstract

Accompanied by condensation cyclization reactions in solvothermal conditions, three Gd(III) tetranuclear clusters {[Gd4(Lx)2(μ3-OH)2(NO3)2(Ac)6]} (x = 1, 2, and 3 for 1, 2, and 3, respectively) were isolated and characterized, wherein, L1–3 were in situ synthesized from bis[3-(pyridin-2-yl)-1H-1,2,4-triazole-5-yl]methane (bptm), 5-bptm (bis[3-(5-methylpyridin-2-yl)-1H-1,2,4-triazole-5-yl]methane), and 4-bptm (bis[3-(4-methylpyridin-2-yl)-1H-1,2,4-triazole-5-yl]methane) in the presence of GdIII ions, respectively. The step-by-step formation process (bptm → L1 → Gd1(L1)1 → Gd2(L1)1 → Gd2(L1)2 → Gd3(L1)2 → Gd4(L1)2) of the tetranuclear clusters in 1 was tracked by mass spectrometry technology. The study of their magnetic properties showed that 1–3 displayed significant magnetocaloric effects with the −ΔSm values of 29.25–29.64 J K–1 kg–1.