Formation of uranyl phthalate coordination polymers with unusual 2D net topologies in the presence of organic cations

Abstract

New uranyl coordination polymers have been synthesized in the presence of organic cations using phthalic acid as a linker. X-ray analysis of single crystals has shown that compounds with protonated imidazole, and 2-methylimidazole exhibit 2D layered structures. The complex (HIm)₂[(UO₂)₃{C₆H₄(COO)₂}₄]·2H₂O contains two crystallographically unique uranium atoms in penta- and hexagonal bipyramidal environments. As a result of the bridging function of the phthalate ions, infinite layers were formed. The stacking of the layers results in the formation of square channels which were filled with HIm cations. In the structure of (HMeIm)₄[(UO₂)₇{C₆H₄(COO)₂}₈(OH)₂], four crystallographically unique uranium atoms were found both in the 6- and 7-fold coordination environments. Both phthalate- and hydroxyl-ions act as bridging ligands resulting in the 2D structure. Organic cations are located between the layers. Both layered complexes exhibit unusual net topologies. In addition, a series of tetranuclear complexes were obtained that are described by the formula A₄[(UO₂)₄(μ₃-O)₂{C₆H₄(COO)₂}4]·nH₂O (where A = t-BuNH₃, C₂H₅NH₃, As(C₆H₅)₄). All complexes are characterized by IR, UV-vis, and luminescence spectroscopy. Thermal analysis of the compounds was conducted.