Lanthanide Metal–Organic Frameworks Assembled from Unexplored Imidazolylcarboxylic Acid: Structure and Field-Induced Two-Step Magnetic Relaxation

A series of 3D homologous metal–organic frameworks, [M­(H0.5L)2] [M = Dy (1), Ho (2), Yb (3), Sm (4), Gd (5), and Y (6); H2L = 5-(1H-imidazol-1-yl)­isophthalic acid], were isolated. In these complexes, the metal centers behave as hexacoordinated environments with distorted octahedral geometries, which is unusual in the lanthanide series, linking to each other and producing a fascinating 3D architecture. Magnetically, 1 features a field-driven dual-magnetic relaxation, which is rarely observed in high-dimensional coordination polymers. Analysis on the dilution sample (1@Y) and ab initio calculation unveil that the thermally assisted slow relaxation is mostly caused by the single-ion magnetism of DyIII itself.