Stereochemistry of nucleic acids and their constituents. XXI. The crystal and molecular structure of bis-(4-aminoimidazole-5-carboxamidoxime)copper(II) perchlorate, a degradation product of adenine N ¹-oxide

Sequestering uranium from seawater: binding strength and modes of uranyl complexes with glutarimidedioxime

“…The O=U=O moiety is perfectly 35 linear and symmetrical, with an angle of 180° and typical U=O distances of 1.7846 Å. between the calculated and the experimental is small (0.013 and 0.018 Å, respectively) and within the accuracy of typical DFT calculations. For the equatorial U-O 1 , U-O 2 and U-N 3 bonds, the differences between the calculated and the experimental are -0.034, 0.066, and 0.128 Å, larger than those that can be explained 10 by the uncertainties of DFT geometry optimization. Crystal packing effects, if there are any, could probably be the reason for such relatively large differences.…”

“…Optical absorption spectra of U(VI) in the presence of 10 glutarimidedioxime and carbonate were collected to further illustrate the competition between glutarimidedioxime and carbonate. As shown in Figure 8, 37,38 and for H 2 A and UO 2 (HA)A -from this work (Table 2), the enthalpy of reaction (2) is calculated to be +16.7 kJ/mol.…”

“…Pale brown crystals of the 1:2 (metal:ligand) complex, UO 2 (HA) 2 (H 2 O), were obtained by slow evaporation from 1 mL solution containing 1.0 mM UO 2 2+ and 2.0 mM H 2 A at pH 6-7. Representative crystals were mounted on the goniometer and crystallographic data were collected on the 10 Small-Crystal Crystallographic Beamline 11.3.1 at the Advanced Light Source of Lawrence Berkeley National Laboratory (LBNL), using the Bruker APEX II CCD diffractometer of  rotation with narrow frames at a wavelength of 0.77490 Å. Intensity data were collected within one hour using Bruker Apex 15 2 software.…”

“…The reason for the failure probably lies in the fact 10 that we were monitoring the absorption spectra of the ligand. The absorption spectra of the ligand in different U(VI) complexes, such as UO 2 HA + , UO 2 A, UO 2 (HA) 2 , UO 2 HA 2 -, and UO 2 A 2 2-, may be too similar to be distinguished from each other.…”

“…Crystal structures of some 50 amidoxime complexes with transition metals (Co, Ni, Cu, Mo and Pt) have confirmed the formation of such chelate complexes. [7][8][9][10][11][12][13][14] However, the amidoxime ligand was found to be monodentate in the crystals of two amidoxime complexes with UO 2…”