Lanthanide-Organic Frameworks with Flexible Triacid Ligand: Structural Variation Under Different Reaction Conditions

Three metal-organic frameworks (MOFs) [La(bta)(H 2 O)] n (1), [La(bta)(H 2 O) 2 ·H 2 O] n (2) and [Er(bta)(H 2 O) 2 ·H 2 O] n (3) with different structures were synthesized by reactions of 1,3,5-benzenetriacetic acid (H 3 bta) with the corresponding lanthanide salts under different conditions. X-ray diffraction analyses reveal that complexes 1 and 2 have the same metal atom and ligand but different structures. In 1, each bta 3 −  adopts cis , cis , cis conformation and acts as a μ 6 -bridge linking six lanthanum atoms to form a 2D framework; while in 2, the bta 3 −  has cis , trans , trans conformation and serves as a μ 5 -bridging ligand, which results in a 3D channel-like structure. In the case of 3, each bta 3 −  also adopts cis , trans , trans conformation but acts as a μ 4 -bridge linking four erbium atoms to form a 3D channel-like framework. The results imply that the reaction conditions have great impact on the structure of MOFs, and the flexible triacid ligand H 3 bta is versatile and can adopt different conformations in the formation of MOFs. The magnetic property of complex 3 was investigated in the temperature range of 1.8–300 K.