Electronic origin of molybdenum-95 NMR chemical shifts in molybdenum complexes. Relationship between excitation energy and chemical shift

1990 ◽  
Vol 29 (17) ◽  
pp. 3095-3097 ◽  
Author(s):  
Hiroshi Nakatsuji ◽  
M. Sugimoto ◽  
S. Saito
Keyword(s):  
Chemical Shift ◽  
Excitation Energy ◽  
Chemical Shifts ◽  
Molybdenum Complexes ◽  
Nmr Chemical Shifts

Origin of the 29Si NMR chemical shift in R3Si–X and relationship to the formation of silylium (R3Si+) ions

2020 ◽  
Vol 49 (45) ◽  
pp. 16453-16463 ◽  
Author(s):  
Winn Huynh ◽  
Matthew P. Conley
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
29Si Nmr ◽  
Surface Oxygen ◽  
Nmr Chemical Shift ◽  
Dft Methods ◽  
Nmr Chemical Shifts

The origin in deshielding of 29Si NMR chemical shifts in R3Si–X, where X = H, OMe, Cl, OTf, [CH6B11X6], toluene, and OX (OX = surface oxygen), as well as iPr3Si+ and Mes3Si+ were studied using DFT methods.

Carbon-13 chemical shifts of alkene carbons in 2-acylidene-3,5-diaryl-2,3-dihydro-1,3,4-thiadiazoles and related benzothiazoles and -selenazoles, and their relationship to other push-pull alkenes

1996 ◽  
Vol 74 (7) ◽  
pp. 1329-1334 ◽  
Author(s):  
Jennifer L. Mueller ◽  
Martin S. Gibson ◽  
J. Stephen Hartman
Keyword(s):  
Chemical Shift ◽  
Key Words ◽  
Chemical Shifts ◽  
Charge Delocalization ◽  
Nmr Chemical Shifts ◽  
Charge Polarization

Carbon-13 chemical shifts of alkene carbons are observed in the ranges 78–109 ppm (Cα) and 154–164 ppm (Cβ) for a series of 11 2-acylidene-3,5-diaryl-2,3-dihydro-1,3,4-thiadiazoles, 3 2-acylidene-3-alkyl-2,3-dihydrobenzothiazoles, and 2 2-acylidene-3-alkyl-2,3-dihydrobenzoselenazoles of known geometry, indicating appreciable charge polarization in these compounds as in other push–pull olefins. Substitution that promotes more extensive charge delocalization results in the Cα signal shifting to the higher-frequency end of the chemical shift range. The observed shifts are compared with those calculated according to the Pretsch scheme. Key words: carbon-13 NMR, chemical shifts, push–pull olefins, 1,3,4-thiadiazoles, benzothiazoles, benzoselenazoles.

Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative1H and13C NMR chemical shifts

2015 ◽  
Vol 17 (35) ◽  
pp. 23183-23194 ◽  
Author(s):  
Bogdan A. Marekha ◽  
Oleg N. Kalugin ◽  
Marc Bria ◽  
Abdenacer Idrissi
Keyword(s):  
Ionic Liquids ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Ion Association ◽  
Ion Solvation ◽  
Mixture Composition ◽  
Imidazolium Ionic Liquids ◽  
Structural Patterns ◽  
Nmr Chemical Shifts ◽  
Molecular Solvents

Competition between ion solvation and association in mixtures of imidazolium ionic liquids and molecular solvents can be systematically addressed by the analysis of relative chemical shift variation with mixture composition.

Carbon-13 nuclear magnetic resonance studies of organotellurium compounds. II. Chemical shift trends

1982 ◽  
Vol 60 (5) ◽  
pp. 596-600 ◽  
Author(s):  
Raj. K. Chadha ◽  
Jack M. Miller
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Magnetic Resonance Studies ◽  
Nmr Chemical Shifts ◽  
Organic Group ◽  
Opposite Trend ◽  
Organotellurium Compounds ◽  
C Nmr

13C nmr chemical shifts are reported for some aromatic and aliphatic tellurium compounds. For a given organic group, the shift of the C1 atom varies in the order [Formula: see text], as expected from electronegative considerations. The C2 atom experiences an opposite trend while the C3 and C4 atoms of the ring experience smaller changes. The chemical shifts of para-substituted aromatic tellurium compounds do not show additivity of contributions from the substituents.

scholarly journals An automated framework for high-throughput predictions of NMR chemical shifts within liquid solutions

2021 ◽  
Author(s):  
Rasha Atwi ◽  
Ying Chen ◽  
Kee Sung Han ◽  
Karl Mueller ◽  
Vijayakumar Murugesan ◽  
...  
Keyword(s):  
Chemical Shift ◽  
High Throughput ◽  
Chemical Shifts ◽  
Computational Techniques ◽  
Test Case ◽  
Biomolecular Systems ◽  
Nmr Chemical Shifts ◽  
Stable Species ◽  
Daunting Task ◽  
Liquid Solutions

Abstract Identifying stable speciation in multicomponent liquid solutions is of fundamental importance to areas ranging from electrochemistry to organic chemistry and biomolecular systems. However, elucidating this complex solvation environment is a daunting task even when using advanced experimental and computational techniques. Here, we introduce a fully automated, high-throughput computational framework for the accurate and robust prediction of stable species present in liquid solutions by computing the nuclear magnetic resonance (NMR) chemical shifts of molecules. The framework automatically extracts and categorizes hundreds of thousands of atomic clusters from classical molecular dynamics (CMD) simulations to identify the most stable speciation in the solution and calculate their NMR chemical shifts via DFT calculations. Additionally, the framework creates an output database of computed chemical shifts for liquid solutions across a wide chemical and parameter space. This task can be infeasible experimentally and challenging using conventional computational methods. To demonstrate the capabilities of our framework, we compare our computational results to experimental measurements for a complex test case of magnesium bis(trifluoromethanesulfonyl)imide Mg(TFSI)2 salt in dimethoxyethane (DME) solvent, which is a common electrolyte system for Mg-based batteries. Our extensive benchmarking and analysis of the Mg2+ solvation structural evolutions reveal critical factors such as the effect of force field parameters that influence the accuracy of NMR chemical shift predictions in liquid solutions. Furthermore, we show how the framework reduces the efforts of performing and managing over 300 13C and 600 1H DFT chemical shift predictions to a single submission procedure. By enabling more efficient and accurate high-throughput computations of NMR chemical shifts, our approach can accelerate theory-guided design of liquid solutions for various applications.

scholarly journals Carbon-13 NMR Chemical Shift of Methyl Group: A Useful Parameter for Structural Analysis of C-Methylated Flavonoids

2006 ◽  
Vol 1 (11) ◽  
pp. 1934578X0600101
Author(s):  
Pawan K. Agrawal ◽  
Chandan Agrawal ◽  
Shravan Agrawal
Keyword(s):  
Structural Analysis ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Nmr Chemical Shift ◽  
Methyl Group ◽  
Nmr Chemical Shifts ◽  
Nmr Study ◽  
Pterocarpus Santalinus ◽  
Group A ◽  
C Nmr

The 13C NMR resonances corresponding to the C-Me group of C-6 and/or C-8 C-methylated-flavonoids absorb between 6.7–10.0 ppm and typically between 6.7–8.7 ppm. A comparative 13C NMR study reflects that the 13C NMR chemical shifts reported for 6-hydroxy-5-methyl-3′,4′,5′-trimethoxyaurone-4-O-α-L-rhamnoside from Pterocarpus santalinus and 8-C-methyl-5,7,2′,4′- tetramethoxyflavanone from Terminalia alata are inconsistent with the assigned structures, and therefore need reconsideration.

scholarly journals Solvent-Dependent Structures of Natural Products Based on the Combined Use of DFT Calculations and 1H-NMR Chemical Shifts

Molecules ◽  
2019 ◽  
Vol 24 (12) ◽  
pp. 2290 ◽  
Author(s):  
Saima H. Mari ◽  
Panayiotis C. Varras ◽  
Atia-tul-Wahab ◽  
Iqbal M. Choudhary ◽  
Michael G. Siskos ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Natural Products ◽  
Chemical Shift ◽  
Intramolecular Hydrogen Bond ◽  
1H Nmr ◽  
Chemical Shifts ◽  
Oh Groups ◽  
X Ray ◽  
Nmr Chemical Shifts ◽  
Intramolecular Hydrogen

Detailed solvent and temperature effects on the experimental 1H-NMR chemical shifts of the natural products chrysophanol (1), emodin (2), and physcion (3) are reported for the investigation of hydrogen bonding, solvation and conformation effects in solution. Very small chemical shift of │Δδ│ < 0.3 ppm and temperature coefficients │Δδ/ΔΤ│ ≤ 2.1 ppb/K were observed in DMSO-d6, acetone-d6 and CDCl3 for the C(1)–OH and C(8)–OH groups which demonstrate that they are involved in a strong intramolecular hydrogen bond. On the contrary, large chemical shift differences of 5.23 ppm at 298 K and Δδ/ΔΤ values in the range of −5.3 to −19.1 ppb/K between DMSO-d6 and CDCl3 were observed for the C(3)–OH group which demonstrate that the solvation state of the hydroxyl proton is a key factor in determining the value of the chemical shift. DFT calculated 1H-NMR chemical shifts, using various functionals and basis sets, the conductor-like polarizable continuum model, and discrete solute-solvent hydrogen bond interactions, were found to be in very good agreement with the experimental 1H-NMR chemical shifts even with computationally less demanding level of theory. The 1H-NMR chemical shifts of the OH groups which participate in intramolecular hydrogen bond are dependent on the conformational state of substituents and, thus, can be used as molecular sensors in conformational analysis. When the X-ray structures of chrysophanol (1), emodin (2), and physcion (3) were used as input geometries, the DFT-calculated 1H-NMR chemical shifts were shown to strongly deviate from the experimental chemical shifts and no functional dependence could be obtained. Comparison of the most important intramolecular data of the DFT calculated and the X-ray structures demonstrate significant differences for distances involving hydrogen atoms, most notably the intramolecular hydrogen bond O–H and C–H bond lengths which deviate by 0.152 tο 0.132 Å and 0.133 to 0.100 Å, respectively, in the two structural methods. Further differences were observed in the conformation of –OH, –CH3, and –OCH3 substituents.

scholarly journals Accurate prediction of chemical shifts for aqueous protein structure on “Real World” data

2020 ◽  
Vol 11 (12) ◽  
pp. 3180-3191 ◽  
Author(s):  
Jie Li ◽  
Kochise C. Bennett ◽  
Yuchen Liu ◽  
Michael V. Martin ◽  
Teresa Head-Gordon
Keyword(s):  
Protein Structure ◽  
Chemical Shift ◽  
Real World ◽  
Chemical Shifts ◽  
Accurate Prediction ◽  
Data Sets ◽  
Real World Data ◽  
World Data ◽  
Nmr Chemical Shifts

UCBShift predicts NMR chemical shifts of proteins that exceeds accuracy of other popular chemical shift predictors on real-world data sets.

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