Zheng-Hua Zhang

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

Three metal-organic frameworks (MOFs) [La(bta)(H2O)]n (1), [La(bta)(H2O)2·H2O]n (2) and [Er(bta)(H2O)2·H2O]n (3) with different structures were synthesized by reactions of 1,3,5-benzenetriacetic acid (H3bta) 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 bta3 − adopts cis, cis, cis conformation and acts as a μ6-bridge linking six lanthanum atoms to form a 2D framework; while in 2, the bta3 − has cis, trans, trans conformation and serves as a μ5-bridging ligand, which results in a 3D channel-like structure. In the case of 3, each bta3 − also adopts cis, trans, trans conformation but acts as a μ4-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 H3bta 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.

Synthesis and crystal structure of a two-dimensional silver(I)-hexamethylenetetramine coordination polymer (hmt)

A novel two-dimensional coordination polymer [Ag(µ3-hexamethylenetetramine)(H2O)](BF4) was synthesized and characterized by X-ray crystallography. It crystallized in the orthorhombic space group Pnnm with a = 15.561(7) Å, b = 10.754(5) Å, c = 6.514(3) Å, and Z = 4. Each Ag center is four-coordinated in a slightly distorted tetrahedral geometry. The structure consists of 2D wavy layers of hexagonal units; these 2D layers are further connected to form a 3D network by O-H⋯F, C-H⋯F hydrogen bonds with counter anions BF4− in the layers.