Structure and vibrational IR spectra of a UCl4⋅2DMSO complex

Abstract

UDC 539.19 Structural models are designed and spectral characteristics are computed based on DFT calculations for a complex of uranium tetrachloride with two molecules of dimethylsulfoxide (UCl 4 ⋅2DMSO). The calculations were carried out using a B3LYP hybrid functional in the LANL2DZ effective core potential approximation for the uranium atom and a cc-pVDZ all-electron basis set for all other atoms. Two structural variants were found for the complex. In the first of them, which is more stable, DMSO molecules are coordinated to the central uranium atom through oxygen atoms whereas in the second one, whose energy is 225 kJ/mol higher, the coordination proceeds through sulfur atoms. The obtained spectral characteristics are analyzed and compared with experimental data. Spectral features that are characteristic of the complexation process are identified. The adequacy of the proposed models and the agreement between calculation and experiment are demonstrated.Introduction. Dimethylsulfoxide (DMSO) occupies a special place among polar organic solvents containing C=O, S=O, or P=O electron-donating groups and; consequently, tending to form coordination complexes. In contrast with dimethylformamide (DMF), hexamethylphosphoramide (HMPA), and other compounds, DMSO can coordinate to the central metal atom in certain instances not only through the O atom but also through the S atom [1][2][3][4][5]. The latter type of coordination is accompanied by a short-wavelength shift of the S=O stretching vibrational frequency whereas coordination of the former type shifts the frequency to longer wavelength. Thus, the spectral position of this vibrational frequency can act as a highly reliable signature of the complex structure.Herein structural variants of the complex of UCl 4 with two DMSO molecules are discussed based on quantum-chemical calculations of the electronic structure and an analysis of previously obtained IR spectra [6,7]. Such complexes provide an example of polymerization involving organic and inorganic ligands and, in particular, can serve as a model for uranium complexation. Their spectral and structural characteristics can be used for the preparation of uranium oxides that are used in nuclear energy.Experimental and Calculations. IR absorption spectra of pure DMSO and UCl 4 ⋅2DMSO pressed into KBr pellets [6], suspended in a mineral-oil mull [7] for the middle IR region, or pressed into a polymeric matrix [6] for the long-wavelength region were recorded on a Vertex 70 spectrophotometer (Bruker) in the ranges 400-4000 cm

Chemical bonding in Uranium‐based materials: A local vibrational mode case study of Cs 2UO 2Cl 4 and UCl 4 crystals

“…The first can be easily assigned to the asymmetric stretching of the system, where two bonds U–Cl are elongated, while the other two become shorter. This is in line with a number of experimental and theoretical studies, where this is reported in a window comprised between 320 and 350 cm 101–103 . When we transition to the periodic system (green) this peak undergoes a strong redshift, where it is shifted to 96 cm due to the strongly hindered stretching of the bonds induced by the crystalline structure, as each chlorine is shared between two Uranium atoms.…”

“…This is in line with a number of experimental and theoretical studies, where this is reported in a window comprised between 320 and 350 cm À1 . [101][102][103] When we transition to the periodic system (green) this peak undergoes a strong redshift, where it is shifted to 96 cm À1 due to the strongly hindered stretching of the bonds induced by the crystalline structure, as each chlorine is shared between two Uranium atoms. The opposite trend can be observed for the peak at 78 cm À1 (blue) which corresponds to the bending of the molecule and it undergoes a strong blueshift when we move to the solid state structure at 255 cm À1 .…”

“…The first peak resides within the 340-360 cm À1 range, corresponding to both the symmetric (shoulders at 341 cm À1 ) and asymmetric (peak at 357 cm À1 ) stretching modes. [101][102][103] The second peak, discernible in the bending vibrations, emerges within the 50-100 cm À1 region. The analysis of the Raman spectra of the crystalline structure (green), once more, reveals a strong redshift of the stretches and a comparable blueshift of the bendings, both due to the restrained motion allowed by the lattice structure.…”

Comparative studies on Graphite and Carbon Black powders, and their dispersions

“…This analysis seems to prove that DMSO solvent is a better surfactant than DMF solvent which is similar to interpretations done by previous researchers [49][50][51][52]. Thus, DMSO has an unique property to coordinate with the central atom in certain instances not only through the O atom but also via the S atom [53].…”

Quantum Chemical Analysis of Uranium Trioxide Conformers

“…The hybrid exchange-correlation functional B3LYP was also used in all calculations [25][26][27]. The approximation used in the calculations was also successful for modeling the structure and vibrational spectra of U-containing compounds (UO 2 Cl 2 , UCl 4 , and their complexes) [28,29]. LMOs were constructed by the Edmiston and Ruedenberg method [30].…”