GIAO-CHF study of magnetic shielding tensors of carbon and nitrogen nuclei in cyano groups

Jackowski, Karol; Molchanov, Sergey; Gryff‐Keller, Adam

doi:10.1016/s0166-1280(99)00309-7

Cited by 8 publications

(3 citation statements)

References 22 publications

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“…The 13 C chemical shift data for halogenobenzenes have been taken from the free-access database, whereas the data for aliphatic halides, , CH 3 HgCCH, PhHgCH3, PhHgCl, Hg(CH 3 ) 2 , Hg(C 2 H 5 ) 2 , and C 2 H 5 HgCl have been found in the indicated literature sources. The 13 C NMR chemical shifts for PhHgCCH and PhHgPh have been measured as part of this work.…”

Section: Experimental and Computational Detailsmentioning

confidence: 99%

The Influence of a Presence of a Heavy Atom on ¹³C Shielding Constants in Organomercury Compounds and Halogen Derivatives

Wodyński

Gryff‐Keller

Pecul

2013

J. Chem. Theory Comput.

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(13)C nuclear magnetic resonance shielding constants have been calculated by means of density functional theory (DFT) for several organomercury compounds and halogen derivatives of aliphatic and aromatic compounds. Relativistic effects have been included through the four-component Dirac-Kohn-Sham (DKS) method, two-component Zeroth Order Regular Approximation (ZORA) DFT, and DFT with scalar effective core potentials (ECPs). The relative shieldings have been analyzed in terms of the position of carbon atoms with respect to the heavy atom and their hybridization. The results have been compared with the experimental values, some newly measured and some found in the literature. The main aim of the calculations has been to evaluate the magnitude of heavy atom effects on the (13)C shielding constants and to check what are the relative contributions of scalar relativistic effects and spin-orbit coupling. Another object has been to compare the DKS and ZORA results and to check how the approximate method of accounting for the heavy-atom-on-light-atom (HALA) relativistic effect by means of scalar effective core potentials on heavy atoms performs in comparison with the more rigorous two- and four-component treatment.

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Section: Experimental and Computational Detailsmentioning

confidence: 99%

The Influence of a Presence of a Heavy Atom on ¹³C Shielding Constants in Organomercury Compounds and Halogen Derivatives

Wodyński

Gryff‐Keller

Pecul

2013

J. Chem. Theory Comput.

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“…5 It seems that the existing NMR data on acetylene are still not sufficiently accurate. On the other hand, acetylene as a small molecular system is attractive for ab initio calculations, [6][7][8][9][10][11][12][13][14][15][16][17][18][19] among which are those intended to test new computational methods for determining nuclear shielding and spin-spin coupling constants. 8,20,21 The latter data should be compared with the NMR measurements for an isolated C 2 H 2 molecule, and such results can be obtained only in the gas phase.…”

Section: Introductionmentioning

confidence: 99%

Nuclear Magnetic Shielding and Spin−Spin Coupling of 1,2-¹³C-Enriched Acetylene in Gaseous Mixtures with Xenon and Carbon Dioxide

et al. 2000

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13 C and 1 H NMR spectra have been measured for 1,2-13 C-acetylene at low density in binary mixtures with xenon and carbon dioxide gases as the solvents. It was found that both the chemical shifts and the 1 J(CC) coupling constant of 13 C 2 H 2 were linearly dependent on the solvent density. The appropriate NMR parameters for an isolated 13 C 2 H 2 molecule were determined, together with the coefficients responsible for the solutesolvent molecular interactions. The 13 C NMR measurements were extended to solutions of 1,2-13 C-acetylene in liquid solvents. All of the 13 C gas-to-solution shifts were found to be positive (deshielding effects), and the 1 J(CC) coupling constant in liquid acetone was diminished by more than 5% in comparison with the value of 174.78 Hz observed in the gas phase.

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“…13 C Chemical Shifts. The GIAO−PBE0/6-311++G(2df, pd) calculated 13 C chemical shifts for mono- (R−CNN−H and H−CNN−R) and disubstituted (R−CNN−R) nitrilimines, nitriles (R−C⋮N), acetylenes (R−C⋮C−H), and allenes (RHCCCH 2 ), with substituents H, BH 2 , CH 3 , NH 2 , OH, and F, are given in Table along with available experimental data. , The calculated values are in very good agreement with the experimental 13 C chemical shifts, with a maximum error of only 2 ppm. Moreover, the effect of methyl substitution, which causes the carbon nucleus in both nitriles and acetylenes to become deshielded by 8 ppm, is reproduced.…”

Section: Resultsmentioning

confidence: 99%

Characterizing Nitrilimines with Nuclear Magnetic Resonance Spectroscopy. A Theoretical Study

2007

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The 13C chemical shifts in selected nitrilimines, nitriles, acetylenes, allenes, and singlet carbenes have been calculated using density-functional theory [PBE0/6-311++G(2df,pd)] and the gauge including atomic orbital (GIAO) method. The effects of substitution on the 13C chemical shifts in nitrilimines, R1-CNN-R2, have been examined. The carbon nucleus is generally found to be deshielded by substituents in the order CH3 < NH2 < OH < F. Comparison with nitriles, acetylenes, and allenes shows that this effect is related to the presence of the cumulated functionality, C=N=N. Terminal N-substitution is found to have a larger effect than C-substitution due to a large increase in chemical shielding anisotropy. The electronic structure of nitrilimines has recently been shown to possess a carbene component whose resonance contribution varies widely with substitution, and, as previously reported, insight into the electronic structure can be gained by an analysis of the shielding tensor, especially for carbenes. Accordingly, the components of the diagonalized 13C shielding tensor for nitrilimines and stable singlet carbenes have been examined. This analysis suggests that diaminonitrilimine, H2N-CNN-NH2, may be a stable carbene, and, to the best of our knowledge, it would be the first acyclic, unsaturated stable carbene ever reported. Finally, a detailed analysis of the 13C chemical shifts shows that an increase in the dipolar character of nitrilimines induces a shielding at the carbon nucleus, while an increase in allenic or carbenic character tends to cause a deshielding.

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GIAO-CHF study of magnetic shielding tensors of carbon and nitrogen nuclei in cyano groups

Cited by 8 publications

References 22 publications

The Influence of a Presence of a Heavy Atom on ¹³C Shielding Constants in Organomercury Compounds and Halogen Derivatives

The Influence of a Presence of a Heavy Atom on ¹³C Shielding Constants in Organomercury Compounds and Halogen Derivatives

Nuclear Magnetic Shielding and Spin−Spin Coupling of 1,2-¹³C-Enriched Acetylene in Gaseous Mixtures with Xenon and Carbon Dioxide

Characterizing Nitrilimines with Nuclear Magnetic Resonance Spectroscopy. A Theoretical Study

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GIAO-CHF study of magnetic shielding tensors of carbon and nitrogen nuclei in cyano groups

Cited by 8 publications

References 22 publications

The Influence of a Presence of a Heavy Atom on 13C Shielding Constants in Organomercury Compounds and Halogen Derivatives

The Influence of a Presence of a Heavy Atom on 13C Shielding Constants in Organomercury Compounds and Halogen Derivatives

Nuclear Magnetic Shielding and Spin−Spin Coupling of 1,2-13C-Enriched Acetylene in Gaseous Mixtures with Xenon and Carbon Dioxide

Characterizing Nitrilimines with Nuclear Magnetic Resonance Spectroscopy. A Theoretical Study

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The Influence of a Presence of a Heavy Atom on ¹³C Shielding Constants in Organomercury Compounds and Halogen Derivatives

The Influence of a Presence of a Heavy Atom on ¹³C Shielding Constants in Organomercury Compounds and Halogen Derivatives

Nuclear Magnetic Shielding and Spin−Spin Coupling of 1,2-¹³C-Enriched Acetylene in Gaseous Mixtures with Xenon and Carbon Dioxide