Stepwise Coordination Assembly Approach toward Aluminum-Lanthanide-based Compounds.

Present herein is a stepwise assembly method toward aluminum-lanthanide-based (Al-Ln) compounds. From the perspective of charge balance, polyanions are necessary to bind with Ln ions. However, the synthesis of polyanions aluminum compounds remains quite challenging. Herein, two Al4 polyanions [Al4(L)4(Cat)2]·4Hdma (AlOC-13, H3L= 2,3-dihydroxybenzoic acid, Cat = catechol, and dma = dimethylamine) and [Al4(L)4(HL)2(DMF)2]·4Hdma·0.5DMF·0.5H2O (AlOC-14, DMF = N,N-dimethylformamide) were successfully obtained under solvothermal conditions. Catechol and Hdma were generated from the in situ decarboxylation of H3L ligand and decomposition of DMF, respectively. AlOC-13 is qualified for further coordination assembly for the available vacancy coordination sites, good water solubility, and scale-up synthesis. The assembly of Al4 polyanions with equivalent Ln ions afforded a series of zigzag chain structures [LnAl4(L)4(Cat)2(DMF)2(H2O)3]·Hdma (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb) (AlOC-13-Ln). Moreover, the magnetic behavior and photoluminescence of the series of AlOC-13-Ln were also studied. AlOC-13-Dy shows obvious antiferromagnetic behavior, while AlOC-13-Tb exhibits excellent green characteristic luminescence. This study not only paves the way toward anionic aluminum clusters but also reveals their potential application in water treatment of cationic metal ions capture.