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

Abstract

The reaction of the 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 dicarboxylate (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. All MOFs except 2-Tb exhibit slow magnetic relaxation under an applied dc field. 1-Dy and 2-Dy show field-induced single-molecule magnet (SMM) behaviour with energy barriers (U_eff) of 30.77 K (τ₀ = 5.23 × 10⁻⁸) and 26.41 K (1.04 × 10⁻⁸ s), respectively.