Novel Topology in Semiconducting Tetrathiafulvalene Lanthanide Metal-Organic Frameworks

Tetrathiafulvalene tetrabenzoate (TTFTB) and several lanthanide ions self-assemble into metal-organic frameworks (MOFs) that exhibit a novel topology, a (3,3,3,6,6)-coordinated net, which features an unusual ligand coordination mode and stacking motif. The Yb and Lu MOFs are electrically conductive, with pellet conductivity values of 9(7) × 10⁻⁷ and 3(2) × 10⁻⁷ S/cm, respectively. The crystallographically-determined bond lengths indicate partial oxidation of the ligand, with close S ⋅ ⋅ ⋅ S contacts between ligands providing likely charge transport pathways in the material. Magnetometry reveals temperature-independent paramagnetism, consistent with the presence of ligand-based radicals, as well as weak antiferromagnetic coupling between Yb³⁺ centers. These results illustrate the diversity of MOF structures and properties that are accessible with the TTFTB ligand owing to its electroactive nature, propensity for intermolecular interactions, and conformational flexibility.