Large-Pore Layered Networks, Polycatenated Frameworks, and Three-Dimensional Frameworks of Uranyl Tri(biphenyl)amine/Tri(phenyl)amine Tricarboxylate: Solvent-/Ligand-Dependent Dual Regulation

In this work, we present the syntheses of four novel uranyl complexes of tri­(biphenyl)­amine tricarboxylate (L1) or triphenylamine tricarboxylate (L2), 1–4, with layered networks or three-dimensional (3D) frameworks through solvothermal/hydrothermal reactions. Using dimethylformamide (DMF) as the solvent, compound 1 ([NH₂(CH₃)₂]­[UO₂(L1)]­·3DMF) and 3 ([NH₂(CH₃)₂]­[UO₂(L2)]­·DMF) give nearly identical (6,3)-connected large-pore layered networks in spite of the slight difference in packing mode (“ABC-ABC” pattern in 1 vs “AB-AB” pattern in 3). When mixed DMF/water solvents were used, compound 2 ([NH₂(CH₃)₂]₂­[UO₂(L1)]₂­(NO₃)₂­·H₂O) with a two-dimensional (2D) + 2D → three-dimensional (3D) polycatenasted framework and compound 4 ([NH₂(CH₃)₂]­[UO₂(L2)]­·2H₂O) with a (10,3)-connected 2-fold interpenetrating 3D framework were achieved from H₃L1 and H₃L2, respectively, which might be attributed to the induction of water molecules with strong hydrogen-bonding capacity. Most remarkably, the difference between a 2D + 2D → 3D polycatenated framework and (10,3)-connected 2-fold interpenetrating 3D framework demonstrates the vital role of conformation flexibility of ligand on the final structure of uranyl compounds, which should be related to the increased amount of phenyl groups of the L1 ligand endowing its molecular skeleton more freedom and adjusting molecular conformation more easily. Their physicochemical properties were also studied by powder X-ray diffraction, thermogravimetric analysis, IR spectroscopy, and luminescence spectroscopy.