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Ukhanev, Stepan A.; Fedorov, Sergei V.; Krivdin, Leonid B.
doi: 10.1002/mrc.5275pmid: 35468229
The substituent α‐, β‐, and γ‐effects of the elements of the second and third periods on 19F NMR chemical shifts are evaluated including the establishment of stereochemical dependence of γ‐effect, the latter particularly important in stereochemical studies of fluorine‐containing compounds. Benchmark calculations performed for a series of 32 simple inorganic fluorine‐containing molecules demonstrated a markedly good correlation between calculated and experimental fluorine chemical shifts characterized by a mean absolute error of 22.5 ppm in the range of about 900 ppm, which corresponds to a 2.5% error in the percentage terms.
Shakirbay, Akerke; Choi, Jeong Sik; Kim, Dong Chul; Shin, Hyo Soon; Yeo, Dong Hun; Lee, Joon Hyung
doi: 10.1002/mrc.5291pmid: 35665956
In this paper, we evaluated the particle dispersion degree of alumina slurry containing a dispersant by solvent nuclear magnetic resonance (NMR) relaxation and compared it with conventional dispersion evaluation methods such as viscosity, particle size, and sedimentation height measurements. The dispersion of slurry was evaluated via numerical analysis of the transverse relaxation time (T2). The effect of the changes in different parameters of the experiment in terms of milling time, solid loading, and dispersant amount was investigated by NMR relaxation as well as conventional methods. The results of NMR relaxation measurements revealed that T2 correlates well with other dispersion evaluation methods; thus, it is an efficient technique to evaluate the dispersion of alumina slurry, specifically, when studying the effect of the change in milling time and dispersion amount.
Hussein, A. Wahab M. A.; Rekik, Najeh; Farooq, Umer; Chebaane, Saleh; Affan, Hira; Albaid, Abdelhamid; Aslam, Affia; Alfhaid, Latifah H. K.
doi: 10.1002/mrc.5293pmid: 35691917
Phosphate‐based glasses such as pure germanophosphate can be achieved at moderately low temperature by means of affordable chemical substances. Nowadays, they become more stimulating because they can be easily doped with alkali, transition metal ions, and rare earth oxides to afford the anticipated physical and/or chemical features for nanoscience applications. Herein, we report an experimental study dealing with the structure of pure germanophosphate glass samples of GeO2 prepared with different concentrations ranging from 20 up to 70 mole%. 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy has been employed to characterize the co‐formed glasses by two different glass‐forming oxides. The components of the phosphate species ( Qn) in each sample were determined by analyzing the MAS NMR spectra. Interestingly, 31P MAS NMR spectrum for each sample was found to be characteristic powder patterns of the middle units Q2. Q2 unit found herein has one oxygen atom bonded towards one germanium atom (non‐bridging) and the other two oxygens are bonding towards two phosphorus atoms (bridging) of phosphate group (PO4). The results show that Q2 split into two units, Q2I and Q2II, due to different shielding of the phosphorus nucleus provided by the next nearest neighbor atoms. The chemical shift is interpreted in terms of the structure of each building unit of the phosphate group. The results obtained herein shed light on the way how to explore the revealed structure of the prepared glasses for the development of supported catalysts. Indeed, owing to their high chemical/thermal stability, the co‐formed germanophosphate glasses obtained may prove as useful substrates for potential nanocatalysts.
Rakhmatullin, Aydar; Brusko, Vasiliy V.; Shcherbitskaya, Elmira R.; Polovov, Ilya B.; Bakirov, Rinat; Bessada, Catherine
doi: 10.1002/mrc.5294pmid: 35712821
A family of three‐ and four‐coordinated silver(I) complexes of formulas [Ag(PPh3)2L], [Ag(PPh3)L], and [AgL]n with N‐thiophosphorylated thiourea and thioamide ligands of general formula RC(S)NHP(S)(OPri)2 [R = Ph, PhNH, iPrNH, tBuNH, NH2] have been studied by solid‐state 109Ag and 31P CPMAS NMR spectroscopy. 109Ag NMR spectra have provided valuable structural information about Ag coordination, which is in good accordance with the available crystal structure data. The data presented in this work represent a significant addition to the available 109Ag chemical shifts and chemical shifts anisotropies. The silver chemical shift ranges for different P,S‐environments and coordination state were discussed in detail. The 1J(31P–107/109Ag) and 2J(31P–31P) values were determined and analyzed.
Ukhanev, Stepan A.; Fedorov, Sergei V.; Rusakov, Yuriy Y.; Rusakova, Irina L.; Krivdin, Leonid B.
doi: 10.1002/mrc.5276pmid: 35470458
All possible spin–spin coupling constants, 19F–19F, 19F–13C, and 19F–1H, of pentafluorobenzene were calculated at five different levels of theory, HF, DFT, SOPPA (CCSD), CCSD, and the SOPPA (CCSD)‐based composite scheme with taking into account solvent, vibrational, relativistic, and correlation corrections. Most corrections were next to negligible for the long‐range couplings but quite essential for the one‐bond carbon–fluorine coupling constants. Hartree–Fock calculations were found to be entirely unreliable, while DFT results were comparable in accuracy with the data obtained using the wave function‐based methods.
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