Calculating<scp>NMR</scp>Chemical Shifts and<i>J</i>‐Couplings for Heavy Element Compounds

Autschbach, Jochen

doi:10.1002/9780470027318.a9173

Cited by 6 publications

(5 citation statements)

References 110 publications

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“…A similar observation has been recently reported by Krivdin and co‐workers for halosilanes SiX n H 4− n 13 and for other Si complexes 14. In heavier atoms (e.g., 183 W or 195 Pt),15 such effects may amount to thousands of ppm but are partly compensated for, in the chemical shift calculation, because the reference compound is affected by roughly the same amount 16. In contrast, no such compensation occurs for 13 C atoms, because the reference compound (tetramethylsilane) is not affected.…”

Section: Introductionsupporting

confidence: 85%

“…[14] In heavier atoms (e.g., 183 Wo r 195 Pt), [15] such effectsm ay amount to thousands of ppm but are partly compensated for,i nt he chemical shift calculation, because the reference compound is affected by roughly the same amount. [16] In contrast, no such compensation occurs for 13 Ca toms, because the reference compound (tetramethylsilane) is nota ffected. Thus, even if s SO is much smaller for 13 Ca toms (see below), it needs to be calculatedi n order to attain aq uantitative prediction.…”

Section: Introductionmentioning

confidence: 99%

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Four‐Component Relativistic DFT Calculations of ¹³C Chemical Shifts of Halogenated Natural Substances

Casella

Bagno

Komorovský

et al. 2015

Chemistry A European J

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We have calculated the (13)C NMR chemical shifts of a large ensemble of halogenated organic molecules (81 molecules for a total of 250 experimental (13)C NMR data at four different levels of theory), ranging from small rigid organic compounds, used to benchmark the performance of various levels of theory, to natural substances of marine origin with conformational degrees of freedom. Carbon atoms bonded to heavy halogen atoms, particularly bromine and iodine, are known to be rather challenging when it comes to the prediction of their chemical shifts by quantum methods, due to relativistic effects. In this paper, we have applied the state-of-the-art four-component relativistic density functional theory for the prediction of such NMR properties and compared the performance with two-component and nonrelativistic methods. Our results highlight the necessity to include relativistic corrections within a four-component description for the most accurate prediction of the NMR properties of halogenated organic substances.

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Section: Introductionsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Four‐Component Relativistic DFT Calculations of ¹³C Chemical Shifts of Halogenated Natural Substances

Casella

Bagno

Komorovský

et al. 2015

Chemistry A European J

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“…The vicinity of the relatively light silicon atom to a heavier atom requires consideration of relativistic effects on its chemical shift. Generally, such so-called heavy atom effects on the light atom (HALA) include scalar or spin-free relativistic (SFR) and the often dominant spin–orbit (SO-)HALA effects − that can have a huge impact on the quality of the chemical shift calculation . Popular treatments to account for HALA effects are (SO‑)ECPs or the widely used (SO‑)ZORA , approximation.…”

Section: Results and Discussionmentioning

confidence: 99%

Comprehensive Benchmark Study on the Calculation of ²⁹Si NMR Chemical Shifts

et al. 2020

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A comprehensive and diverse benchmark set for the calculation of 29 Si NMR chemical shifts is presented. The SiS146 set includes 100 silicon containing compounds with 146 experimentally determined reference 29 Si NMR chemical shifts measured in nine different solvents in a range from −400 to +828 ppm. Silicon atoms bound to main group elements as well as transition metals with coordination numbers of 2−6 in various bonding patterns including multiple bonds and coordinative and aromatic bonding are represented. The performance of various common and specialized density functional approximations including (meta-)GGA, hybrid, and double-hybrid functionals in combination with different AO basis sets and for differently optimized geometries is evaluated. The role of scalar-relativistic effects is further investigated by inclusion of the zeroth order regular approximation (ZORA) method into the calculations. GGA density functional approximations (DFAs) are found to outperform hybrid DFAs with B97-D3 performing best with an MAD of 7.2 ppm for the subset including only light atoms (Z < 18), while TPSSh is the best tested hybrid functional with an MAD of 10.3 ppm. For 29 Si cores in the vicinity of heavier atoms, the application of ZORA proved indispensable. Inclusion of spin−orbit effects into the 29 Si NMR chemical shift calculation decreases the mean absolute deviations by up to 74% compared to calculations applying effective core potentials.

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“…27 The development of relativistic methods for the NMR shielding tensor of diamagnetic systems has been reviewed in the literature. 6,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] In pNMR, experimental data are typically obtained for light nuclei in heavy-element systems, with the NMR nuclei relatively far from the paramagnetic center. This is due to the fact that the nuclei close to the paramagnetic center relax very fast and the associated line broadening renders the NMR signals unobservable in such cases.…”

Section: Most Of the Available Relativistic Quantum-chemical Implemenmentioning

confidence: 99%

Relativistic Approximations to Paramagnetic NMR Chemical Shift and Shielding Anisotropy in Transition Metal Systems

Rouf

Mareš

Vaara

2017

J. Chem. Theory Comput.

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We apply approximate relativistic methods to calculate the magnetic property tensors, i.e., the g-tensor, zero-field splitting (ZFS) tensor (D), and hyperfine coupling (HFC) tensors, for the purpose of constructing paramagnetic nuclear magnetic resonance (pNMR) shielding tensors. The chemical shift and shielding anisotropy are calculated by applying a modern implementation of the classic Kurland-McGarvey theory ( J. Magn. Reson. 1970 , 2 , 286 ), which formulates the shielding tensor in terms of the g- and HFC tensors obtained for the ground multiplet, in the case of higher than doublet multiplicity defined by the ZFS interaction. The g- and ZFS tensors are calculated by ab initio complete active space self-consistent field and N-electron valence-state perturbation theory methods with spin-orbit (SO) effects treated via quasidegenerate perturbation theory. Results obtained with the scalar relativistic (SR) Douglas-Kroll-Hess Hamiltonian used for the g- and ZFS tensor calculations are compared with nonrelativistically based computations. The HFC tensors computed using the fully relativistic four-component matrix Dirac-Kohn-Sham approach are contrasted against perturbationally SO-corrected nonrelativistic results in the density functional theory framework. These approximations are applied on paramagnetic metallocenes (MCp) (M = Ni, Cr, V, Mn, Co, Rh, Ir), a Co(II) pyrazolylborate complex, and a Cr(III) complex. SR effects are found to be small for g and D in these systems. The HFCs are found to be more influenced by relativistic effects for the 3d systems. However, for some of the 3d complexes, nonrelativistic calculations give a reasonable agreement with the experimental chemical shift and shielding anisotropy. The influence of scalar relativity is strong for the 5d IrCp system. This mixed ab initio/DFT technique, with a fully relativistic method used for the critical HFC tensor, should be useful for the treatment of both electron correlation and relativistic effects at a reasonable computational cost to compute the pNMR shielding tensors in transition metal systems.

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CalculatingNMRChemical Shifts andJ‐Couplings for Heavy Element Compounds

Cited by 6 publications

References 110 publications

Four‐Component Relativistic DFT Calculations of ¹³C Chemical Shifts of Halogenated Natural Substances

Four‐Component Relativistic DFT Calculations of ¹³C Chemical Shifts of Halogenated Natural Substances

Comprehensive Benchmark Study on the Calculation of ²⁹Si NMR Chemical Shifts

Relativistic Approximations to Paramagnetic NMR Chemical Shift and Shielding Anisotropy in Transition Metal Systems

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CalculatingNMRChemical Shifts andJ‐Couplings for Heavy Element Compounds

Cited by 6 publications

References 110 publications

Four‐Component Relativistic DFT Calculations of 13C Chemical Shifts of Halogenated Natural Substances

Four‐Component Relativistic DFT Calculations of 13C Chemical Shifts of Halogenated Natural Substances

Comprehensive Benchmark Study on the Calculation of 29Si NMR Chemical Shifts

Relativistic Approximations to Paramagnetic NMR Chemical Shift and Shielding Anisotropy in Transition Metal Systems

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Four‐Component Relativistic DFT Calculations of ¹³C Chemical Shifts of Halogenated Natural Substances

Four‐Component Relativistic DFT Calculations of ¹³C Chemical Shifts of Halogenated Natural Substances

Comprehensive Benchmark Study on the Calculation of ²⁹Si NMR Chemical Shifts