Structural Tuning and Sensitization of Uranyl Phosphonates by Incorporation of Countercations into the Framework

Abstract

By the introduction of terephthalic acid, tetramethylammonium chloride, and Zn2+ ions, three new uranyl triphosphonates with varying crystal structures, namely, [H3O]­[(UO2)2­(HL)]·​H2O (1), [NMe4]­[(UO2)2­(HL)­(H2O)]·​H2O (2), and [(UO2)3­Zn­(H2L)2­(H2O)2]·​3H2O (3), where H6L = benzene-1,3,5-triyltris­(methyl­ene) triphosphonic acid, have been successfully synthesized and characterized by means of powder and single crystal XRD, IR, EA, TGA, UV–vis, and luminescence. These three compounds all possess three-dimensional framework structures with hydrium, tetramethylammonium, and Zn2+ as the respective countercations. The uranium­(VI) center luminescence of compounds 1 and 2 is completely quenched. However, the incorporation of Zn2+ into the matrix of uranyl phosphonate in the case of compound 3 results in the emerging of the typical intense vibronic emissions of U­(VI), demonstrating that zinc phosphonate can behave as sensitizer of uranyl phosphonates. The quenching and sensitization mechanism were also discussed.

Luminescent uranium–thiophene dicarboxylate frameworks supported by transition-metal–organic cations: dimensionality and luminescence control in uranyl speciation

“…20,28 In d-block metal complexes with the formula [ML 3 ] 2+ (M = Ni 2+ , Fe 2+ , Co 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Ag + , etc., L = N-bearing ligands), counterions have been incorporated into UOFs for the tuning of functional properties such as magnetism and emission through the antenna effect or d-f sensitization. 29,30 Interpenetration in UOFs can improve their structural stabilities, the achievement of the interpenetrated network is still challenging. 31 In the present work, we have combined d-block metal complex cations [ML 3 ] 2+ (M = Cu 2+ , Zn 2+ , and Cd 2+ , L = phenanthroline) with a uraniumIJVI)-TDC honeycomb-like layer to generate three novel UOFs with a 1-D neutral chain and 2-D non-interpenetrated and interpenetrated layers, i.e.…”

Variability of Uranyl Carboxylates from Rigid Terophenyldicarboxylic Acid Ligands

“…As a result, uranyl coordination compounds favor one-dimensional (1D) chains or two-dimensional (2D)-layered crystal structures. Therefore, the design of novel UOFs is mainly centered around the organic linker, such as the functionalization of carboxylic and phosphonic acid ligands. − Flexible or semirigid ligands possess more freedom to coordinate with uranyl cations − and can offset the coordination geometry limitation, but the resulting compounds are usually subject to poor stability, which is an important issue with regard to practical application. On the contrary, UOFs assembled from rigid ligands are usually expected to be robust but suffer from clumsy coordination modes.…”