Reproducible Synthesis of a Monofluorinated Trimesate: A Versatile Linking Ligand for the Construction of Lanthanide Coordination Polymers

Abstract

The synthesis of monofluorinated trimesic acid (H3mfBTC = 2‐fluoro‐1,3,5‐benzene‐tricarboxylic acid) described in the literature leads in fact to its monopotassium salt K(H2mfBTC) (1), which was identified by a single crystal structure analysis (Pc, Z = 2). It is obtained as a single‐phase product and shows good solubility in water so that from aqueous solutions fourteen new coordination polymers with LnIII cations were synthesized and structurally characterized. Depending on the size of the cations three different structure types with different water contents were observed. For LnIII = La3+ – Nd3+ and Sm3+ – Gd3+ the composition 1∞[LnIII(mfBTC)3/3(H2O)6] was found and confirmed by a structural analysis (Cc, Z = 4; CN = 9). For LnIII = Tb3+ – Ho3+ the composition 2∞[LnIII(mfBTC)3/3(H2O)3]·H2O was obtained and confirmed by X‐ray single crystal structure analysis (C2/c, Z = 8; CN = 9). Finally, for LnIII = Er3+ – Lu3+ the composition 1∞[LnIII(mfBTC)2/2(H2O)5]·2H2O was found and again confirmed by X‐ray single crystal structure analysis (P1, Z = 2; CN = 8). Subtle changes of the cationic radii lead to different coordination spheres and thus to different compositions. The thermal stability of selected compounds representing all three structure types was investigated by DTA/TGA measurements. All compounds are stable up to at least 100 °C, before the release of water molecules starts. The EuIII and TbIII compounds show the expected intense red and green luminescence.