Actinide nitrate complexes (original) (raw)
Related papers
Thermodynamics and Structure of Actinide(IV) Complexes with Nitrilotriacetic Acid
Inorganic Chemistry, 2009
Nitrilotriacetic acid, commonly known as NTA (N(CH 2 CO 2 H) 3 ), can be considered a representative of the polyaminocarboxylic family. The results presented in this paper describe the thermodynamical complexation and structural investigation of An(IV) complexes with NTA in aqueous solution. In the first part, the stability constants of the An(IV) complexes (An ) Pu, Np, U, and Th) have been determined by spectrophotometry. In the second part, the coordination spheres of the actinide cation in these complexes have been described using extended X-ray absorption fine structure spectroscopy and compared to the solid-state structure of (Hpy) 2 [U(NTA) 2 ] · (H 2 O). These data are further compared to quantum chemical calculations, and their evolution across the actinide series is discussed. In particular, an interpretation of the role of the nitrogen atom in the coordination mode is proposed. These results are considered to be model behavior of polyaminocarboxylic ligands such as diethylenetriamine pentaacetic acid, which is nowadays the best candidate for a chelating agent in the framework of actinide decorporation for the human body.
Journal of Molecular Structure
The p-xylylenediaminium bis(nitrate) compound have been synthesized and then, it was characterized by using Fourier Transform infrared (FT-IR) in the solid phase and, by using the Ultraviolet-Visible (UV-Visible) and Hydrogen and Carbon Nuclear Magnetic Resonance (1 Hand 13 C-NMR) spectra in aqueous solution and in dimethylsulfoxide solvent. In this work, two monodentate and bidentate coordination modes were considered for the nitrate ligands in both media in order to study the structural and vibrational properties of that salt. Hence, the natural bond orbital (NBO), atoms in molecules (AIM), Merz-Kollman (MK) charges, molecular electrostatic potentials (MEP) and frontier orbitals studies were performed for p-xylylenediaminium bis(nitrate) and their cation and anion species taking into account for the salt those two coordination modes for the nitrate ligands. The intermolecular interactions of this salt were also evaluated by Hirshfeld surface analysis. The B3LYP calculations performed by using the hybrid method and the 6-311G* and 6-311++G** basis sets generate monodentate and bidentate structures with C i and C 2 symmetries, respectively. The force fields and the force constants values for these two structures were also computed and their complete vibrational assignments were performed by using those both levels of theory. The strong band at 1536 cm-1 , the bands between 2754 and 2547 cm-1 and the bands between 1779 and 1704 cm-1 support clearly the presence of the dimeric species while the IR bands at 1986/1856 cm-1 could justify the presence of the bidentate species in the solid phase.
Seven coordinate complexes of metal(II) nitrates
Inorganica Chimica Acta, 1988
ESR spectra at both X and Q band are reported for manganese(R) ions doped into the seven coordinate complexes M(L)a(NOs)s (M = Co, Ni, Zn or Cd; L = pyridine or substituted pyridine). The zero field splitting parameters D and X (=E/D) are deduced. All complexes show considerable deviation from cubic symmetry, as can be expected for a seven coordinate structure. The distinctly lower D value of Ni(Mn)(pyridine)s(NO&, as compared to the analogous cobalt and zinc complex, suggests a geometry tending towards an octahedral structure. The steric hindrance by the substituent reduces the D value.
X-Ray photoelectron study of actinide (Th, U, Pu, Am) nitrates
Nuclear Technology & Radiation Protection, 2003
In this work an X-ray pho toelectron spec troscopy study of ni trates Th(NO 3 ) 4 ×4H 2 O, UO 2 (NO 3 ) 2 ×nH 2 O, Pu(NO 3 ) 4 ×nH 2 O, and Am(NO 3 ) 2 ×nH 2 O was done in the binding energy range from 0 to 1000 eV in order to draw a correlation of the fine spectral structure param e ters with the ac ti nide ions ox i da tion states, close en vi ron ment struc ture, and chem i cal bond na ture. The lin earity of the dependence of the An5f n line in tensity on the num ber n 5f of the An5f electrons was proven to remain up to the Am 3+ ion with the elec tron configura-tion{Rn 5f 6 . The spectral structure in the binding en ergy range from 0 to~15 eV was as sociated with the formation of the outer valence mo lecular orbitals due to the in teraction of the An6d-, 7s, 5f -O2p elec trons, and the fine spec tral structure in the binding en ergy range from~15 to ~50 eV -with the for mation of the in ner valence molecular orbitals due to the interaction of the An6p -O2s elec trons from the filled neigh boring atomic orbitals of actinide and oxygen in the studied com pounds. The fine structure of the core level elec tron spectra in the binding en ergy range from~50 to 1000 eV was shown to correlate with the actinide ion ox i da tion state.
The Sulfate Coordination of Np(IV), Np(V), and Np(VI) in Aqueous Solution
Inorganic Chemistry, 2009
The coordination and redox behavior of Np(IV), Np(V), and Np(VI) sulfate in aqueous solution were investigated by Np L 3 -edge extended X-ray absorption fine structure (EXAFS) spectroscopy, cyclic voltammetry, and density functional theory (DFT) calculations. The sulfate coordination mode, that is, monodentate versus bidentate, was determined by using neptunium-sulfur distances R Np-S and coordination numbers N S obtained by EXAFS spectroscopy. Np(VI) is coordinated by sulfate in the bidentate (R Np-S = 3.12 ( 0.02 Å ) and monodentate (R Np-S = 3.61 ( 0.02 Å ) modes at a low sulfate concentration of [SO 4 2-]/[NpO 2 2+ ] = 1. At higher [SO 4 2-]/[NpO 2 2+ ] ratios, bidentate coordination prevails. Approximately two bidentate sulfate groups are coordinated to Np(VI) with 2.0 M SO 4 2and at pH 1.1. Np(V) is coordinated by sulfate in the bidentate (R Np-S = 3.16 ( 0.02 Å ) and monodentate (R Np-S = 3.67 ( 0.02 Å ) modes. However, sulfate coordination is less pronounced and does not exceed one SO 4 2per Np(V) with 2.0 M SO 4 2-. The redox reaction between the Np(VI)/Np(V) couple can be basically categorized as quasi-reversible. It becomes a more irreversible character at high sulfate concentrations due to structural rearrangement of the sulfate ligands. Finally, Np (IV) also shows bidentate (R Np-S = 3.06 ( 0.02 Å ) and monodentate (R Np-S = 3.78 ( 0.02 Å ) coordination modes. The sulfate coordination increases with an increasing [SO 4 2-]/[Np 4+ ] ratio. A comparison of other tetravalent actinides shows that the monodentate sulfate coordination decreases whereas the bidentate coordination increases along the series Th(IV)-U(IV)-Np(IV). This trend was studied by DFT calculations and is discussed in terms of solvation energy and increasing number of unpaired electrons.
Journal of The American Chemical Society, 1978
- All least-squares refinements were based on the minization of Z W ,~ I F. 1 -I Fcl l p with the individual weights w, = I / U ( F . )~. Atomic scattering factors used for all nonhydrogen atoms are from Hanson, H. P.; Herman, F.; Lea, J. D.; Skillman, S. Acta Crystallogr. 1984, 17, 1040. Those for the hydrogen atoms are from Stewart, R . F.; Davidson, E. R.; Simpson, W. T. Abstract: The structures of the title compounds, Na4[M(C6H402)4]*21 HzO, M = Th, U, have been determined by single-crystal X-ray diffraction methods using counter data. These isostructural tetrakis(catecho1ato) complexes are structural archetypes for actinide-specific macrocyclic sequestering agents. The complexes have D2d molecular symmetry. The M -0 bond lengths are 2.417 (3) and 2.421 (3) 8, for Th and 2.362 (3) and 2.389 (4) 8, for U. The ring 0 -M -0 bond angles are 66.8 (1)'
Iranian Journal of Chemistry & Chemical Engineering-international English Edition, 2020
In this study, firstly, the vibrational analysis of the bidentate coordination of the title ions to a metal was theoretically performed as combined with group theoretical analysis. In the calculation, the DFT method with B3LYP functional was used at DEF2-TZVP level set and, cobalt, nickel and copper metals were taken. As expected the coordination of the ions to the metal atom lowered the symmetry and so, the splitting of degenerate modes occurred together with the appearance of IR inactive modes. The calculated frequencies for all the modes were given together with their symmetry species in tables. These results showed that all the splitting bands of the degenerate modes are nearly center-out, and if the intensity of degenerate mode is high the intensities of its splitting bands are also high or vice versa. Then, to compare, some metal complexes with bidentate and unidentate ligands were optimized and, their calculated frequencies were given together with their corresponding experim...
Theoretical structural and experimental vibrational study of niobyl nitrate
Journal of Molecular Structure, 2011
We have prepared niobyl nitrate, Nb(NO 3 ) 3 and characterized it by infrared and Raman spectroscopies. The Density functional theory (DFT) has been used to study its structure and vibrational properties. We have made a comparative work for this compound to evaluate not only the best level of theory but also the best basis set to be used to reproduce the experimental wavenumbers. These calculations gave us a precise knowledge of the normal modes of vibration taking into account the type of coordination adopted by nitrate groups of this compound as monodentate and bidentate ligands. The calculated harmonic vibrational frequencies for niobyl nitrate are consistent with the experimental vibrational spectra. An assignment of the observed spectral features is proposed. The nature of the NbAO and Nb O bonds and the topological properties of electronic charge density in the compound were systematically and quantitatively investigated by means of Natural Bond Order (NBO) and the Bader's Atoms in Molecules theory (AIM), respectively.