Crystal Chemistry of Uranyl Carboxylate Coordination Networks Obtained in the Presence of Organic Amine Molecules

Abstract

AbstractThree uranyl isophthalates (1,3‐bdc) and two uranyl pyromellitates (btec) of coordination‐polymer type were hydrothermally synthesized (200 °C for 24 h) in the presence of different amine‐based molecules [1,3‐diaminopropane (dap) or dimethylamine (dma) originating from the in situ decomposition of N,N‐dimethylformamide]. (UO2)2(OH)2(H2O)(1,3‐bdc)·H2O (1) is composed of inorganic tetranuclear cores, which are linked to each other through the isophthalato ligand to generate infinite neutral ribbons, which are intercalated by free H2O molecules. The compounds (UO2)1.5(H2O)(1,3‐bdc)2·0.5H2dap·1.5H2O (2) and UO2(1,3‐bdc)1.5·0.5H2dap·2H2O (3) consist of discrete uranyl‐centered hexagonal bipyramids connected to each other by a ditopic linker to form a single‐layer network for 2 or a double‐layer network for 3. The protonated diamine molecules are located between the uranyl–organic sheets and balance the negative charge of the layered sub‐networks. The phase (UO2)2O(btec)·2Hdma·H2O (4) presents a 2D structure built up from tetranuclear units, which consist of two central sevenfold coordinated uranium centers and two peripheral eightfold coordinated uranium centers. The connection of the resulting tetramers through the pyromellitate molecules generates an anionic layerlike structure, in which the protonated dimethylammonium species are inserted. The compound UO2(btec)·2Hdma (5) is also a lamellar coordination polymer, which contains isolated eightfold coordinated uranium cations linked through pyromellitate molecules and intercalated by protonated dimethylammonium species. In both phases 4 and 5, the btec linker has non‐bonded carboxyl oxygen atoms, which preferentially interact with the protonated amine molecules through a hydrogen‐bond network. The different illustrations show the structural diversity of uranyl–organic coordination polymers with organic amine molecules as countercations.