[Pt@Pb12]2– — A challenging system for relativistic density functional theory calculations of 195Pt and 207Pb NMR parameters

2011 ◽  
Vol 89 (7) ◽  
pp. 814-821 ◽  
Author(s):  
Boris Le Guennic ◽  
Jochen Autschbach
Keyword(s):  
Density Functional ◽  
Chemical Shifts ◽  
Relativistic Effects ◽  
Magnetic Coupling ◽  
Principal Component ◽  
Density Functional Theory Calculations ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Test Case ◽  
Nmr Parameters

We report computations of NMR chemical shifts and indirect spin-spin coupling constants (J couplings) for the [Pt@Pb12]2– “superatom”. The system is strongly influenced by relativistic effects. The Pt–Pb coupling constant is predicted to be negative, with its magnitude being in reasonable agreement with experiment. Pt and Pb chemical shifts also agree reasonably well with experiment. The Pb shielding tensor is strongly anisotropic, with a large deshielding principal component dominated by magnetic coupling between frontier orbitals of the cluster that resemble atomic g orbitals. The NMR parameters are sensitive to approximations made in the computations and require the inclusion of spin-orbit coupling in the theoretical model to achieve reliable results. Computing the NMR parameters of the compact [Pt@Pb12]2– system with its many electrons proves to be a challenging test case for relativistic density functional methods.

scholarly journals Factors Governing the Chemical Stability and NMR Parameters of Uracil Tautomers and Its 5-Halogen Derivatives

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3931 ◽  
Author(s):  
Kacper Rzepiela ◽  
Aneta Buczek ◽  
Teobald Kupka ◽  
Małgorzata A. Broda
Keyword(s):  
Electrostatic Interactions ◽  
Density Functional ◽  
Chemical Shifts ◽  
Polarizable Continuum Model ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Basis Set ◽  
Basis Sets ◽  
Nmr Parameters ◽  
Solvent Model

We report on the density functional theory (DFT) modelling of structural, energetic and NMR parameters of uracil and its derivatives (5-halogenouracil (5XU), X = F, Cl, Br and I) in vacuum and in water using the polarizable continuum model (PCM) and the solvent model density (SMD) approach. On the basis of the obtained results, we conclude that the intramolecular electrostatic interactions are the main factors governing the stability of the six tautomeric forms of uracil and 5XU. Two indices of aromaticity, the harmonic oscillator model of aromaticity (HOMA), satisfying the geometric criterion, and the nuclear independent chemical shift (NICS), were applied to evaluate the aromaticity of uracil and its derivatives in the gas phase and water. The values of these parameters showed that the most stable tautomer is the least aromatic. A good performance of newly designed xOPBE density functional in combination with both large aug-cc-pVQZ and small STO(1M)−3G basis sets for predicting chemical shifts of uracil and 5-fluorouracil in vacuum and water was observed. As a practical alternative for calculating the chemical shifts of challenging heterocyclic compounds, we also propose B3LYP calculations with small STO(1M)−3G basis set. The indirect spin–spin coupling constants predicted by B3LYP/aug-cc-pVQZ(mixed) method reproduce the experimental data for uracil and 5-fluorouracil well.

Calculated NMR Parameters (Chemical Shifts and Coupling Constants) of Cyclic C4H2 and C4H4 Molecules Containing Carbene Centers, and of Some of their Boron Analoga, Using Density Functional Theory (DFT)

2004 ◽  
Vol 59 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Bernd Wrackmeyer
Keyword(s):  
Density Functional ◽  
Singlet State ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Spin Orbital ◽  
Functional Theory ◽  
Orbital Interactions ◽  
Nmr Parameters ◽  
Spin Spin Coupling

Abstract Singlet state structures of small, cyclic hydrocarbons which can result from the addition of molecular dicarbon (C2) to ethyne (HC≡CH) or ethene (H2C=CH2) have been calculated (B3LYP/6- 311+G(d,p) level of theory), and were found to contain carbene centres. Some structures of analogous boranes (replacement of the carbene centers by BH fragments) were also calculated. The computation of NMR parameters such as chemical shifts δ 13C and δ 11B, and coupling constants 1J(13C,1H), 1J(11B,1H), J(13C,13C) and J(13C,11B) shows that these data can be used for the discussion of the bonding situation. The presence of inverted carbene centers is clearly indicated by the increased 13C nuclear magnetic shielding. Scalar 13C-13C spin-spin coupling involving carbene centers are frequently dominated by spin-dipole and spin-orbital interactions.

scholarly journals RELATIVISTIC EFFECTS IN THE NMR PARAMETERS OF AMINO CHLORIDE PLATINUM COMPLEXES

2020 ◽  
Vol 2020 (1) ◽  
pp. 87-92
Author(s):  
Leonid Krivdin ◽  
Valentin Semenov ◽  
Dmitriy Samul'cev
Keyword(s):  
Density Functional ◽  
Chemical Shifts ◽  
Relativistic Effects ◽  
Platinum Complexes ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Chloride Complexes ◽  
Spin Coupling Constants ◽  
High Level ◽  
Spin Spin Coupling

Relativistic effects in geometric parameters, NMR chemical shifts, and spin-spin coupling constants involving 1H, 15N, and 195Pt nuclei in cisplatin and transplatin, the simplest representatives of the platinum amino chloride complexes, were studied by means of the high-level nonempirical calculations within the framework of the Density Functional Theory

Structural Characterization of Natural Products By Means of Quantum Chemical Calculations of NMR Parameters: New insights

2021 ◽  
Author(s):  
Fabio Luiz Paranhos Costa ◽  
Ana Carolina Ferreira de Albuquerque ◽  
Rodolfo Goetze Fiorot ◽  
Luciano Morais Lião ◽  
Lucas Haidar Martorano ◽  
...  
Keyword(s):  
Natural Products ◽  
Structural Characterization ◽  
Quantum Chemical ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Nmr Parameters ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

The calculation of NMR parameters for natural products was pioneered by Bifulco and coworkers in 2002. Since then, modelling 1H and 13C chemical shifts and spin-spin coupling constants for this...

scholarly journals Estudo do tautomerismo ceto-enólico da 7-epi-clusianona através de cálculos teóricos de deslocamentos químicos de RMN

2020 ◽  
Author(s):  
Ana Carolina Ferreira de Albuquerque ◽  
José Walkimar de Mesquita Carneiro ◽  
Fernando Martins dos Santos Junior
Keyword(s):  
Natural Products ◽  
Structural Characterization ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Chemical Shifts ◽  
Coupling Constants ◽  
Spectroscopic Techniques ◽  
Chemical Structures ◽  
Nmr Parameters

The properties of natural products, including their biological and pharmacological activities, are directly correlated with their chemical structures. Thus, a correct structural characterization of these compounds is a crucial step to the understanding of their biological activities. However, despite the recent advances in spectroscopic techniques, structural studies of natural products can be challenging. This way, theoretical calculations of Nuclear Magnetic Resonance (NMR) parameters (such as chemical shifts and coupling constants) have proven to be a powerful and low-cost tool for the aid to experimental techniques traditionally used for the structural characterization of natural products. One of the several applications of quantum-mechanical calculations of NMR parameters is the study of tautomerism. Since chemical shifts are sensitive to the tautomeric equilibrium, this technique can provide crucial informations. In this work, it was applied a protocol for theoretical calculations of ¹³C chemical shifts in order to study the tautomerism of the natural product 7-epi-clusianone, isolated from Rheedia gardneriana. This protocol consists in a Monte Carlo conformational search, followed by geometry optimization and shielding tensors calculations, both using a density functional level of theory. After comparison of theoretical and experimental data, it was possible to confirm the two tautomers present in equilibrium in the experimental solution. Furthermore, this study highlights how this theoretical protocol can be an effective method in identifying the preferred tautomeric form in solution.

scholarly journals Solid-State NMR of Spin-9/2 Nuclei 115In and 209Bi in Functional Inorganic Complex Oxides

2021 ◽  
Author(s):  
Kent Griffith ◽  
Fenghua Ding ◽  
Steven Flynn
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Density Functional ◽  
Pulse Sequence ◽  
Density Functional Theory Calculations ◽  
Coupling Constants ◽  
Site Symmetry ◽  
Quadrupole Moments ◽  
Special Equipment ◽  
Nmr Parameters

Indium and bismuth are technologically important elements, in particular as oxides for optoelectronic applications. <sup>115</sup>In and <sup>209</sup>Bi are both I = 9/2 nuclei with high natural abundances and moderately high frequencies but large nuclear electric quadrupole moments. Leveraging the quadrupolar interaction as a measure of local symmetry and polyhedral distortions for these nuclei could provide powerful insights on a range of applied materials. However, the absence of reported NMR parameters on these nuclei, particularly in oxides, hinders their use by the broader materials community. In this contribution, solid-state <sup>115</sup>In and <sup>209</sup>Bi NMR of three recently discovered quaternary bismuth or indium oxides are reported, supported by density functional theory calculations, numerical simulations, diffraction, and additional multinuclear (<sup>27</sup>Al, <sup>69,71</sup>Ga, <sup>121</sup>Sb) solid-state NMR measurements. The compounds LiIn<sub>2</sub>SbO<sub>6</sub>, BiAlTeO<sub>6</sub>, and BiGaTeO<sub>6</sub> are measured without special equipment at 9.4 T, demonstrating that wideline techniques such as the QCPMG pulse sequence and frequency-stepped acquisition can enable straightforward extraction of quadrupolar tensor information in I = 9/2 <sup>115</sup>In and <sup>209</sup>Bi even in sites with large quadrupolar coupling constants. Relationships are described between the NMR observables and local site symmetry. These are amongst the first reports of the NMR parameters of <sup>115</sup>In, <sup>121</sup>Sb, and <sup>209</sup>Bi in oxides.

scholarly journals Nuclear magnetic resonance parameters in Zn2, Cd2 and Hg2 dimers: relativistic calculations

2021 ◽  
Vol 140 (3) ◽  
Author(s):  
Katarzyna Jakubowska ◽  
Magdalena Pecul
Keyword(s):  
Density Functional ◽  
Relativistic Effects ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Shielding Constants ◽  
Nuclear Shielding ◽  
Magnetic Resonance Parameters ◽  
Internuclear Distances ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

AbstractThe potential energy curves and the NMR properties: nuclear spin–spin coupling constants and nuclear shielding constants have been calculated for Zn2, Cd2 and Hg2 dimers using density functional theory. The calculations have been carried out using the relativistic four-component Dirac–Coulomb Hamiltonian, and, in the case of energy curves, also relativistic effective core potentials. In case of NMR parameters, the relativistic effects turned out to be critically important even for the lightest dimer, Zn2. The importance of the spin–orbit coupling depends on the internuclear distance: these effects tend to be significant for short internuclear distances.

scholarly journals Solid-State NMR of Spin-9/2 Nuclei 115In and 209Bi in Functional Inorganic Complex Oxides

2021 ◽  
Author(s):  
Kent Griffith ◽  
Fenghua Ding ◽  
Steven Flynn
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Density Functional ◽  
Pulse Sequence ◽  
Density Functional Theory Calculations ◽  
Coupling Constants ◽  
Site Symmetry ◽  
Quadrupole Moments ◽  
Special Equipment ◽  
Nmr Parameters

Indium and bismuth are technologically important elements, in particular as oxides for optoelectronic applications. <sup>115</sup>In and <sup>209</sup>Bi are both I = 9/2 nuclei with high natural abundances and moderately high frequencies but large nuclear electric quadrupole moments. Leveraging the quadrupolar interaction as a measure of local symmetry and polyhedral distortions for these nuclei could provide powerful insights on a range of applied materials. However, the absence of reported NMR parameters on these nuclei, particularly in oxides, hinders their use by the broader materials community. In this contribution, solid-state <sup>115</sup>In and <sup>209</sup>Bi NMR of three recently discovered quaternary bismuth or indium oxides are reported, supported by density functional theory calculations, numerical simulations, diffraction, and additional multinuclear (<sup>27</sup>Al, <sup>69,71</sup>Ga, <sup>121</sup>Sb) solid-state NMR measurements. The compounds LiIn<sub>2</sub>SbO<sub>6</sub>, BiAlTeO<sub>6</sub>, and BiGaTeO<sub>6</sub> are measured without special equipment at 9.4 T, demonstrating that wideline techniques such as the QCPMG pulse sequence and frequency-stepped acquisition can enable straightforward extraction of quadrupolar tensor information in I = 9/2 <sup>115</sup>In and <sup>209</sup>Bi even in sites with large quadrupolar coupling constants. Relationships are described between the NMR observables and local site symmetry. These are amongst the first reports of the NMR parameters of <sup>115</sup>In, <sup>121</sup>Sb, and <sup>209</sup>Bi in oxides.

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