Series of Uranyl-4,4′-biphenyldicarboxylates and an Occurrence of a Cation–Cation Interaction: Hydrothermal Synthesis and in Situ Raman Studies

Abstract

Three uranium(VI)-bearing materials were synthesized hydrothermally using the organic ligand 4,4'-biphenyldicarboxylic acid: (UO2)(C14O4H8) (1); [(UO2)2(C14O4H8)2(OH)]·(NH4)(H2O) (2); (UO2)2(C14O4H8)(OH)2 (3). Compound 1 was formed after 1 day at 180 °C in an acidic environment (pH(i) = 4.03), and compounds 2 and 3 coformed after 3 days under basic conditions (pH(i) = 7.95). Coformation of all three compounds was observed at higher pH(i) (9.00). Ex situ Raman spectra of single crystals of 1-3 were collected and analyzed for signature peaks. In situ hydrothermal Raman data were also obtained and compared to the ex situ Raman spectra of the title compounds in an effort to acquire formation mechanism details. At pH(i) = 4.00, the formation of 1 was suggested by in situ Raman spectra. At an increased pH(i) (7.90), the in situ data implied the formation of compounds 1 and 3. The most basic conditions (pH(i) = 9.00) yielded a complex mixture of phases consistent with that of increased uranyl hydrolysis.

Probing the Influence of N‐Donor Capping Ligands on Supramolecular Assembly in Molecular Uranyl Materials

“…One must acknowledge, however, the complex influence of concentration, temperature, and pressure on observed condensation products. Previous studies have shown that multiple species are observed in hydrothermal systems at the complete range of pH values,11,59 thus our results may be a manifestation of any number of variables. Evaluating the basicity of the capping ligands is inconclusive and does not account for the consistency in the pH values of the solutions used to synthesize 1 – 6 (Table 2).…”

Uranyl Ion Complexes with 1,1′-Biphenyl-2,2′,6,6′-tetracarboxylic Acid: Structural and Spectroscopic Studies of One- to Three-Dimensional Assemblies

“…The simplest symmetrically disubstituted species, 1,1′-biphenyl-4,4′-dicarboxylic acid, has been shown to give a two-dimensional (2D) assembly analogous to that obtained with 1,4-benzenedicarboxylic acid, 2g a different 2D assembly comprising additional hydroxide ligands, and even a three-dimensional (3D) framework. 3 Another 3D architecture was obtained with 1,1′-biphenyl-2,2′-dinitro-4,4′-dicarboxylic acid, 4 while with 1,1′-biphenyl-3,3′,4,4′-tetracarboxylic acid, two carboxylic acid groups are uncoordinated, and the coordination polymer formed is onedimensional (1D). 5 A few examples have been reported also with polycarboxylates based on bipyridyl 5 or terphenyl 6 platforms.…”

Zero-, mono- and diperiodic uranyl ion complexes with the diphenate dianion: influences of transition metal ion coordination and differential UVI chelation

“…The diphenyl/biphenyl skeleton is one among the many carboxylate-bearing organic platforms which have been used in the synthesis of uranyl-organic complexes, coordination polymers and frameworks. [1][2][3][4][5] Most occurrences of this platform involve the linear 4,4ʹ-diphenyldicarboxylate ligand, [6][7][8][9][10] which has provided access to several novel systems, among which may be mentioned complexes displaying U=O-U oxo-bonding, 7 polycatenation, 8 or single-crystal-to-singlecrystal phase transitions 10 (polycatenation was also reported with the related 2,2ʹ-bipyridine-5,5ʹ-dicarboxylate ligand 11 ). With two more carboxylate groups, 3,3ʹ,4,4ʹdiphenyltetracarboxylate was also used and allowed formation of a triperiodic framework.…”

“…In these ligands with the lowest  values, the  dihedral angles are larger than in the other ligands of the same complexes [40.1(3)-65.9(3)° versus 16.6(5)-27.0(4)°], these differences in geometry being probably necessary for accommodation of the Ag + and H2NMe2 + cations. Mode 2 chelation of uranyl, present in 1 and 6-9, has no similar effect since the  angles are in the range of 64.03(16)-82.89(12)°, while the  angles vary within the large range of 9.6(9)-74.55(17)°; except in complex 6, this coordination mode is associated to diverse bridging or mode 1 chelation, by only one(8) or the two carboxylate groups(1,7,9). In the more than 300 crystal structures containing coordinated or free, neutral, mono-or dianionic forms of H2dip reported in the CSD, the  dihedral angles vary over all the possible range, from 0 to 90°, while the  angle does not reach values below 38°.…”