From Isolated Molecular Complexes to Extended Networks: Synthesis and Characterization of Thorium Furanmono- and Dicarboxylates

Aqueous reactions of thorium chloride and furanmono- and dicarboxylate ligands including 2-furoate (2FA), 3-furoate (3FA), and 2,5-furandicarboxylate (2,5FDC) yielded four Th(IV) phases that exhibit diverse structural chemistry ranging from isolated molecular units to 3D topologies. [Th(2FA)(4)](n)(Th-1) and [Th(3FA)(4)](n)(Th-2) consist of isostructural ligand bridged 1D chains. The compounds exhibit wide stability, forming at temperatures of 20-120 degrees C and pH ca. 1-4. Using the bifunctional ligand 2,5FDC a stark difference is observed; Th-2(2,5FDC)(4)(H2O)(10)center dot 2H(2)O (Th-3) is built from relatively rare ligand-bridged molecular complexes.Th-3similarly exhibits broad synthetic stability, forming over 20-100 degrees C and pH 1.8-6. At higher temperatures; however, [Th(2,5FDC)(2)(H2O)(2)](n)(Th-4), which adopts an extended 3D network is observed. The structures were determined by single-crystal X-ray diffraction and further characterized via Raman and IR spectroscopy as well as thermogravimetric analysis. Overall, the work highlights the role of organic ligands in the stabilization of unique Th structural units.