Thorium and uranium diphosphonates: Syntheses, structures, and spectroscopic properties

Four new thorium and uranium diphosphonate compounds, [H3O]{Th2[C6H4(PO3)2]2F} (Thbbp-1), An2{(O3PC6H4PO3H)2[C6H4(PO3H)2]} [An=Th(IV), U(IV)] (Thbbp-2)/(U4bbp), and [(C2H5)(CH3)3N][(UO2)3(O3PC6H4PO3H)2F(H2O)] (U6bbp) have been synthesized hydrothermally using 1,4-benzenebisphosphonic acid as ligand. The crystal structures of these compounds were determined by single crystal X-ray diffraction. Thbbp-1 and Thbbp-2 contain seven-coordinate Th(IV) within ThO6F and ThO7 units with capped trigonal prismatic and capped octahedral geometries, respectively. U4bbp is isotypic with Thbbp-2. The structure of U6bbp contains U(VI) is the common seven-coordinate pentagonal bipyramid. - Graphical abstract: Coordination polyhedra and luminescence properties in thorium and uranium compounds. Highlights: ► Three-dimensional thorium and uranium complexes. ► Conversion of U(VI) to U(IV) under hydrothermal condition. ► Unusual seven-coordinate thorium complexes exhibiting capped octahedral and capped trigonal prismatic geometries.