Two anhydrous salts of tetrafluoroterephthalic acid (H2tF-BDC): K2tF-BDC and Rb2tF-BDC

Article abstract of DOI:10.1002/zaac.201300480

Two new anhydrous salts of tetrafluoroterephthalic acid (H ₂tF-BDC), namely K₂tF-BDC (1) and Rb₂tF-BDC (2), were synthesized and structurally characterized. The crystal structure of 1 (I2/m, Z = 2) was solved and refined from X-ray single crystal data. K ⁺ (CN = 8) is coordinated by six oxygen atoms of five different tF-BDC^2- linkers and two fluorine atoms of two of these linkers, which connect the KO₆F₂ polyhedra to a 3D network. The crystal structure of 2 (P1, Z = 1) was refined from X-ray powder diffraction data. It crystallizes in a structure type already known from Tl ₂tF-BDC. Rb⁺ (CN = 8) is also coordinated by six oxygen and two fluorine atoms. But six tF-BDC^2- linkers are involved in the coordination. Again, a 3D network is formed. Both compounds can be obtained as single-phase samples. They are not porous and stable in air. The thermal stability was investigated by DTA/TG measurements. The decomposition starts at approx. 200°C (1) and 230°C (2). Their good solubility in water makes them interesting starting materials for the synthesis of new MOFs with the perfluorinated linker tF-BDC^2-. Copyright