A family of lanthanide metal-organic frameworks based on a redox-active tetrathiafulvalene-dicarboxylate ligand showing slow relaxation of magnetisation and electronic conductivity.

The reaction of redox-active tetrathiafulvalene ligand and lanthanide ions is an important approach to prepare photo-electro-magnetic multifunctional metal-organic framework materials. A series of isostructural lanthanide metal-organic frameworks (Ln-MOFs) based on the in-situ generated tetrathiafulvalene dicarboxylic (TTF-DC) ligand, {[Ln4(TTF-DC)6(DMF)4(H2O)2]·4DMF}n (Ln = Gd (1-Gd), Tb (1-Tb), Dy (1-Dy) and Er (1-Er)), was synthesized and characterized. These Ln-MOFs display tunable redox-active properties and semiconductor performance, and their electronic conductivities have been significantly improved after oxidation. There are ferromagnetic interactions in 1-Tb, 1-Dy, 1-Er and the corresponding oxidized analogues, 2-Tb, 2-Dy and 2-Er. All compounds except 2-Tb exhibit slow magnetic relaxation under applied dc field. 1-Dy and 2-Dy show the field-induced single-molecule magnets (SMMs) behaviour with energy barriers (Ueff) of 30.77 K (τ0 = 5.23×10−8) and 26.41 K (1.04×10−8 s), respectively.