CCSD(T) calculation of NMR chemical shifts: consistency of calculated and measured 13C chemical shifts in the 1-cyclopropylcyclopropylidenemethyl cation

Stanton, John F.; Gauß, Jürgen; Siehl, Hans Ullrich

doi:10.1016/0009-2614(96)01077-9

Cited by 54 publications

(51 citation statements)

References 14 publications

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“…(3) A consistent reproduction of all 13 C chemical shifts, including the partially positively charged C‐4, is only possible at the MP2 level. The last conclusion confirms for our class of cations, the protonated alkylpyrroles, what previously has been found for smaller cations such as allyl, vinyl,, dienyl, or even adamantly cations . HF and DFT at least with the B3LYP functional fail for unsaturated carbocations .…”

Section: Resultssupporting

confidence: 90%

“…However, common to the large benchmark data sets that have been used in these studies is that cations are almost absent. In addition, results from the studies dedicated to organic cations have shown that accurate predictions of the chemical shifts pose a special challenge to the theoretical methods, sometimes demanding high‐level ab initio methods such as coupled cluster theory –,. In this report we present the results of a computational study of the chemical shifts or nuclear magnetic shielding constants for three protonated alkylpyrroles.…”

Section: Introductionmentioning

confidence: 98%

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Computational Prediction of ¹H and ¹³C NMR Chemical Shifts for Protonated Alkylpyrroles: Electron Correlation and Not Solvation is the Salvation

et al. 2018

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Prediction of chemical shifts in organic cations is known to be a challenge. In this article we meet this challenge for α‐protonated alkylpyrroles, a class of compounds not yet studied in this context, and present a combined experimental and theoretical study of the 13C and 1H chemical shifts in three selected pyrroles. We have investigated the importance of the solvation model, basis set, and quantum chemical method with the goal of developing a simple computational protocol, which allows prediction of 13C and 1H chemical shifts with sufficient accuracy for identifying such compounds in mixtures. We find that density functional theory with the B3LYP functional is not sufficient for reproducing all 13C chemical shifts, whereas already the simplest correlated wave function model, Møller–Plesset perturbation theory (MP2), leads to almost perfect agreement with the experimental data. Treatment of solvent effects generally improves the agreement with experiment to some extent and can in most cases be accomplished by a simple polarizable continuum model. The only exception is the NH proton, which requires inclusion of explicit solvent molecules in the calculation.

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Section: Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 98%

Computational Prediction of ¹H and ¹³C NMR Chemical Shifts for Protonated Alkylpyrroles: Electron Correlation and Not Solvation is the Salvation

et al. 2018

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“…In a similar manner to Stanton et al, 25 we compare the experimental NMR spectrum with the computed GIAO-SCF, GIAO-LDA, GIAO-B3LYP GGA 0.05 , and GIAO-CCSD͑T͒ spectra for the 1-cyclopropylcyclopropylidenemethyl-cation in Fig. 1 was found to be in good agreement with experiment͒.…”

Section: Resultsmentioning

confidence: 54%

Nuclear shielding constants by density functional theory with gauge including atomic orbitals

Helgaker

Wilson

Amos

et al. 2000

The Journal of Chemical Physics

108

115

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Recently, we introduced a new density-functional theory ͑DFT͒ approach for the calculation of NMR shielding constants. First, a hybrid DFT calculation ͑using 5% exact exchange͒ is performed on the molecule to determine Kohn-Sham orbitals and their energies; second, the constants are determined as in nonhybrid DFT theory, that is, the paramagnetic contribution to the constants is calculated from a noniterative, uncoupled sum-overstates expression. The initial results suggested that this semiempirical DFT approach gives shielding constants in good agreement with the best ab initio and experimental data; in this paper, we further validate this procedure, using London orbitals in the theory, having implemented DFT into the ab initio code DALTON. Calculations on a number of small and medium-sized molecules confirm that our approach produces shieldings in excellent agreement with experiment and the best ab initio results available, demonstrating its potential for the study of shielding constants of large systems.

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“…To successfully determine the chemical shifts for cations, second order Møller-Plesset perturbation theory (MP2) or Coupled Cluster theory are often the only methods that give results close to experimental data. [6][7][8][9] A recent study on protonated alkylpyrroles employing both DFT with the B3LYP functional and MP2 with various different solvent models concluded that B3LYP did not provide results in sufficient agreement with experimental results in contrast to MP2. 10 However, for larger compounds like, for example, oligomers of alkylpyrroles MP2 calculations are still computationally too demanding for routine applications, which makes it necessary to find cheaper alternatives.…”

Section: Introductionmentioning

confidence: 99%

“…The methods and protocols suggested for calculations of chemical shifts, which is mostly density functional theory (DFT), often give large errors for cations of organic molecules. To successfully determine the chemical shifts for cations, second order Møller–Plesset perturbation theory (MP2) or Coupled Cluster theory are often the only methods that give results close to experimental data 6–9 . A recent study on protonated alkylpyrroles employing both DFT with the B3LYP functional and MP2 with various different solvent models concluded that B3LYP did not provide results in sufficient agreement with experimental results in contrast to MP2 10 .…”

Section: Introductionmentioning

confidence: 99%

The best density functional theory functional for the prediction of ¹H and ¹³C chemical shifts of protonated alkylpyrroles

et al. 2021

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The prediction of 13C chemical shifts can be challenging with density functional theory (DFT). In this study 39 different functionals and three different basis sets were tested on three neutral alkylpyrroles and their corresponding protonated species. The calculated shielding constants were compared to experimental data and results from previous calculations at the MP2. We find that the meta‐hybrid functional TPSSh with either the Pople style basis set 6‐311++G(2d,p) or the polarization consistent basis set pcSseg‐1 gives the best results for the 13C chemical shifts, whereas for the 1H chemical shifts it is the TPSSh functional with either the 6‐311++G(2d,p) or pcSseg‐2 basis set. Including an explicit solvent molecule hydrogen bonded to NH in the alkylpyrroles improves the results slightly for the 13C chemical shifts. On the other hand, for 1H chemical shifts the opposite is true. Compared to calculations at the MP2 level none of the DFT functionals can compete with MP2 for the 13C chemical shifts but for the 1H chemical shifts the investigated DFT functionals are shown to give better agreement with experiment than MP2 calculations.

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CCSD(T) calculation of NMR chemical shifts: consistency of calculated and measured 13C chemical shifts in the 1-cyclopropylcyclopropylidenemethyl cation

Cited by 54 publications

References 14 publications

Computational Prediction of ¹H and ¹³C NMR Chemical Shifts for Protonated Alkylpyrroles: Electron Correlation and Not Solvation is the Salvation

Computational Prediction of ¹H and ¹³C NMR Chemical Shifts for Protonated Alkylpyrroles: Electron Correlation and Not Solvation is the Salvation

Nuclear shielding constants by density functional theory with gauge including atomic orbitals

The best density functional theory functional for the prediction of ¹H and ¹³C chemical shifts of protonated alkylpyrroles

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CCSD(T) calculation of NMR chemical shifts: consistency of calculated and measured 13C chemical shifts in the 1-cyclopropylcyclopropylidenemethyl cation

Cited by 54 publications

References 14 publications

Computational Prediction of 1H and 13C NMR Chemical Shifts for Protonated Alkylpyrroles: Electron Correlation and Not Solvation is the Salvation

Computational Prediction of 1H and 13C NMR Chemical Shifts for Protonated Alkylpyrroles: Electron Correlation and Not Solvation is the Salvation

Nuclear shielding constants by density functional theory with gauge including atomic orbitals

The best density functional theory functional for the prediction of 1H and 13C chemical shifts of protonated alkylpyrroles

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Computational Prediction of ¹H and ¹³C NMR Chemical Shifts for Protonated Alkylpyrroles: Electron Correlation and Not Solvation is the Salvation

Computational Prediction of ¹H and ¹³C NMR Chemical Shifts for Protonated Alkylpyrroles: Electron Correlation and Not Solvation is the Salvation

The best density functional theory functional for the prediction of ¹H and ¹³C chemical shifts of protonated alkylpyrroles