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Side‐on sulfur monoxide complexes of scandium, yttrium, and lanthanum difluorides [MF2(η2‐SO)] were prepared via oxidation of metal atoms by SOF2 in cryogenic matrixes. The structures of these SO complexes are determined by characteristic infrared absorptions as well as isotopic frequency ratios, and the assignments are further supported by density functional theory calculations. A doublet ground state with nonplanar Cs symmetry was established for all the complexes with side‐on SO ligands. The S−O bond lengths as well as the S−O stretching vibrational frequencies approach those of SO−, suggesting that the group 3 metal MF2(η2‐SO) complexes can be considered as (MF2)+(SO)−. Consistent with this notion, the interaction between MF2 and SO is mainly ionic with SO negatively charged by about −0.60 e, and the unpaired electron is located in the SO 3π orbital that is antibonding in character. It is highly exothermic to form MF2(η2‐SO) mediated by a single fluorine transfer MF(SOF) intermediate from the reactions of SOF2 and metal atoms. The absence of group 3 metal sulfur monoxide complexes using SO2F2 as a precursor is because the resulting complexes would require a metal center with the oxidation state higher than III. [ABSTRACT FROM AUTHOR]

In order to investigate the species in the FLiNaK–CeF3 and FLiNaK–CeF3–Li2O melts, in situ high temperature Raman spectroscopy was used with the aid of density functional theory (DFT) calculation. In molten FLiNaK, the CeF63− octahedra affected by alkali cations were identified to be the predominan species. Binuclear cerium oxyfluoride anions Ce2OF84− and Ce2OF106− were formed after adding O2− into the molten FLiNaK‐CeF3 (20 mol%) mixtures. Both of these two species were predicted to have Ce−O−Ce geometries with two CeF4/CeF5 moieties bridged by a single oxygen atom. [ABSTRACT FROM AUTHOR]

The low-frequency spectra of gallic acid (GA) and its monohydrate were investigated by terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5 to 4.5 THz. The dehydration process of GA monohydrate was monitored on-line. The kinetic mechanism of the dehydration process was analyzed depending on the THz spectral change at different temperatures. The results indicate that the diffusion of water molecule dominates the speed of the entire dehydration process. Solid-state density functional theory (DFT) calculations of the vibrational modes of both GA and its monohydrate were performed based on their crystalline structures for better interpreting the experimental THz spectra. The results demonstrate that the characterized features of GA mainly originate from the collective vibrations of molecules. And the interactions between GA and water molecules are responsible for THz fingerprint of GA monohydrate. Multi-techniques including differential scanning calorimetry and thermogravimetry (DSC-TG) and powder X-ray diffraction (PXRD) were also carried out to further investigate GA and its monohydrate. [ABSTRACT FROM AUTHOR]

• Zirconium and hafnium fluorides are present as MF 6 2– and MF 7 3– in the KF melts. • The influence of O2– on the speciation in melts has been studied by Raman and DFT. • Oxyfluorides exist in the form of MOF 5 3– with terminal oxygen structure. The influence of oxide ions on the speciation in molten KF containing ZrF 4 and HfF 4 has been studied by using Raman spectroscopy, and identification of the structures is carried out by density functional theory calculations within the polarization continuum model. Zirconium and hafnium fluorides are present as MF 6 2– and MF 7 3– (M = Zr, Hf) in the KF melts with low MF 4 concentrations, whereas MF 6 2– dominate at high MF 4 concentrations. With the addition of 3–5 mol% Li 2 O into the KF-MF 4 (10 mol%) melts, oxyfluorides in the form of MOF 5 3– were observed with characteristic terminal M O stretching bands at 775 (Zr) and 763 (Hf) cm−1. However, these oxyfluorides were not observed when 5 mol% Li 2 O was added into the KF melts with 30–40 mol% ZrF 4 and HfF 4. The formation of MOF 5 3– anion is consistent with the much lower average association energies of MF 7 3− than MF 6 2−. This makes it a lot more favourable to replace F− by O2− so as to generate MOF 5 3–, and the free F- ions released can further react with MF 6 2− to give MF 7 3−. As the Li 2 O concentration is increased to 15 mol%, the melts are no longer homogeneous and the Raman bands due to zirconium and hafnium oxides coming into exist. [ABSTRACT FROM AUTHOR]

The low-frequency vibrational property of l -phenylalanine ( l -Phe) and l -phenylalanine monohydrate ( l -Phe·H 2 O) has been investigated by terahertz time-domain spectroscopy (THz-TDS) at room and low temperature ranging from 0.5 to 4.5 THz. Distinctive THz absorption spectra of the two compounds were observed. Density functional theory (DFT) calculations based on the crystal structures have been performed to simulate the vibrational modes of l -Phe and l -Phe·H 2 O and the results agree well with the experimental observations. The study indicates that the characterized features of l -Phe mainly originate from the collective vibration of molecules. And the characterized features of l -Phe·H 2 O mainly come from hydrogen bond interactions between l -Phe and water molecules. l -Phe and l -Phe·H 2 O were also verified by differential scanning calorimetry and thermogravimetry (DSC-TG) and powder X-ray diffraction (PXRD) examinations. [ABSTRACT FROM AUTHOR]

• The structure of tantalum fluorides and oxyfluorides in molten FLiNaK was studied by Raman spectroscopy. • Density functional theory (DFT) calculations were employed to assist the assignment of the bands observed in molten salts. • The TaF 7 2− and TaF 8 3− octahedral was identified to be present in molten FLiNaK-K 2 TaF 7 mixtures. • The oxyfluorides of TaOF 5 2−, TaOF 6 3−, TaO 2 F 2 − and TaO 2 F 3 2− were formed with Li 2 O adding into the molten salts. Combined with Raman spectroscopy and theoretical calculations, the tantalum fluoride and oxyfluoride ions in molten FLiNaK were studied. Firstly, the Raman spectra of K 2 TaF 7 were recorded from 298 to 973 K and no structural evolution was observed. The coexistence of TaF 7 2– and TaF 8 3– anions was confirmed in K 2 TaF 7 and molten FLiNaK-K 2 TaF 7 mixtures. With the addition of Li 2 O (3 mol%), the terminal oxo ligands TaOF 5 2– and TaOF 6 3– were formed at the expense of TaF 7 2– and TaF 8 3– with the release of free F– ions, respectively. When the Li 2 O content increased to 13 mol%, two new oxyfluorides TaO 2 F 2 – and TaO 2 F 3 2– were observed that contained two non-bridging oxygens. As the content of Li 2 O further increased to 40 mol%, insoluble solid tantalum oxide species like β-Ta 2 O 5 was found, which indicates the transformation of intermediate oxyfluorides formed by the reaction of TaF 7 2– and TaF 8 3– fluorides with O2– in molten FLiNaK to oxides. [ABSTRACT FROM AUTHOR]

• The structure of cerium fluoride and oxyfluoride was studied by Raman and DFT. • Both LuF 5 2− and LuF 6 3− anions were identified in molten FLiNaK. • Lu 2 OF 8 4−, Lu 2 O 2 F 4 2− and Lu 2 O 2 F 6 4− anions were confirmed with the addition of Li 2 O. Combined with Raman spectroscopy and density functional theory (DFT) calculations, the micro-structures in molten FLiNaK-LuF 3 and FLiNaK-LuF 3 -Li 2 O systems were studied. Both LuF 5 2− (D 3h) and LuF 6 3− (O h) anions were identified in molten FLiNaK, and their relative content varied with the concentration of LuF 3. For regarding the affection of oxygen anion, Li 2 O was added into the molten FLiNaK-LuF 3 (20 mol%) sample. The lutecium oxyfluoride anion Lu 2 OF 8 4− was firstly formed which possesses a linear Lu O Lu geometry with two LuF 4 moieties bridged by one single oxygen atom. Further increasing the Li 2 O content to 10 mol% resulted in the formation of two species, which belonged to the Lu 2 O 2 F 4 2− and Lu 2 O 2 F 6 4− anions. When increased the concentration of Li 2 O to 20 mol%, a new species appeared which was approximate to the oxide structure. [ABSTRACT FROM AUTHOR]

The structural evolution of Li 2 BeF 4 from crystalline to molten states has been investigated by Raman spectroscopic technique with the assist of density functional theory (DFT). The experimental results of temperature-dependent Raman spectra of Li 2 BeF 4 showed that no solid-state phase transformation was taken place during heating process from 298 to 723 K. In the molten state, the structure of BeF 4 2− anion was affected by Li+ cation and environment. For the binary LiF-BeF 2 melts with varying LiF/BeF 2 ratio, the stretching bands of beryllium‑fluorine bonds in molten Raman spectra were deconvolved identified by Gaussian function. When the concentration of BeF 2 exceeding 33 mol%, the dimer Be 2 F 7 3− was formed and dominated the spectrum. It was characterized to have a linear Be–F–Be geometry with two BeF 4 moieties bridged by a single fluorine atom. A second anion Be 3 F 10 4− processing a triple chain structure formed when the content of BeF 2 increasing to 50 mol%. When the concentration of BeF 2 went beyond 60 mol%, the Raman intensity and band width gradually decreased. While the intensity and band width of Raman spectra gradually decreased with the concentration of BeF 2 exceeding to 60 mol%, which suggests that the band should be assigned to a hexatomic Be 6 F 18 6− ring which was similar to the situation in the pure BeF 2 network structure. • The structure of beryllium fluorides was studied by Raman and DFT calculations. • Different models and methods were established to simulate crystal and melt. • Fluoroberyllate species BeF 4 2−, Be 2 F 7 3−, Be 3 F 10 4−, and Be 6 F 18 6− were observed. [ABSTRACT FROM AUTHOR]