Combination of covalent and hydrogen bonding in the formation of 3D uranyl-carboxylate networks

Four compounds containing uranyl cation [UO2]2+ have been synthesized hydrothermally by reacting uranyl acetate and uranyl nitrate with various N/O donor ligands. The structure of all compounds was elucidated by single crystal X-ray diffraction study. Compound [(UO2)(6-methylnicotinato)3](H3O)·4H2O (1) is a discrete complex (0D), that gives rise in the crystal to hydrophilic channels, while [(UO2)(OH)(μ2-3-pyridylpropionato)]n (2) and [(UO2)(H2O)(μ3-4,4′-oxybis(benzoato)]n (3) show the formation of 1D coordination polymers. Moreover, oxalate anions, formed in situ by using 5-methylisophthalic or 2,3-pyrazinedicarboxylic acid as reactant ligands, gave rise to a 2D coordinating network [(UO2)2(μ2-oxalate)(μ2-OH)2(H2O)2]n·nH2O (4). All the complexes expanded their dimensionality to 3D through hydrogen bonds.