The Stepwise Formation of {Gd-4} Clusters with Magnetocaloric Effect, Accompanied by In Situ Condensation Cyclization Reactions

Accompanied by condensation cyclization reactions in solvothermal conditions, three Gd(III) tetranuclear clusters {[ Gd-4(L-x)(2)( mu(3)-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 Gd-III ions, respectively. The step-by-step formation process (bptm -> L-1 -> Gd-1(L-1)(1) -> Gd-2(L-1)(1) -> Gd-2(L-1)(2) -> Gd-3(L-1)(2) -> Gd-4(L-1)(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 -Delta S-m values of 29.25-29.64 J K-1 kg(-1).