Relativistic effects on nuclear magnetic shieldings of CHnX 4-n and CHXYZ (X, Y, Z = H, F, Cl, Br, I)
Nuclear magnetic shieldings of both carbon and hydrogen atoms of haluro methyl molecules are highly influenced by the substitution of one or more hydrogen by halogen heavy atoms. We applied the linear response elimination of small components, LRESC, formalism to calculate such shieldings and learn w...
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2012
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00219606_v137_n21_p_Melo http://hdl.handle.net/20.500.12110/paper_00219606_v137_n21_p_Melo |
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paper:paper_00219606_v137_n21_p_Melo2023-06-08T14:44:21Z Relativistic effects on nuclear magnetic shieldings of CHnX 4-n and CHXYZ (X, Y, Z = H, F, Cl, Br, I) Atomic numbers Carbon and hydrogens Electronic mechanisms Halogen atoms Heavy atoms Inverse halogen dependence Linear response Logarithmic dependence Model compound Nuclear magnetic shieldings Rate of increase Relativistic correction Relativistic effects Small components Spin orbits Atoms Bromine Bromine compounds Chlorine compounds Hamiltonians Hydrogen Magnetic shielding Paramagnetism Chlorine Nuclear magnetic shieldings of both carbon and hydrogen atoms of haluro methyl molecules are highly influenced by the substitution of one or more hydrogen by halogen heavy atoms. We applied the linear response elimination of small components, LRESC, formalism to calculate such shieldings and learn whether including only few terms is enough for getting quantitative reproduction of the total shieldings or not. First, we discuss the contribution of all leading relativistic corrections to σ(C), in CHX2I molecular models with X = H, F, and Cl, and show that spin-orbit (SO) effects are the main ones. After adding the SO effects to the non-relativistic (NR) results, we obtain ∼ 97 (93) of the total LRESC values for σ(C) (σ(H)). The magnitude of SO terms increases when the halogen atom becomes heavier. In this case, such contributions to σ(C) can be extrapolated as a function of Z, the halogen atomic number. Furthermore, when paramagnetic spin-orbit (PSO) contributions are also considered, we obtain results that are within 1 of the total LRESC value. Then we study in detail the main electronic mechanisms involved to contribute C and H shieldings on CHnX4 - n (n = 1, 3), and CHXYZ (X, Y, Z = F, Cl, Br, I) model compounds. The pattern of σ(C) for all series of compounds follows a normal halogen dependence (NHD), though with different rate of increase. A special family of compounds is that of CHF2X for which σnr(C) follows an inverse halogen dependence though the total shielding have a NHD due to the SO contributions. For the series CH3X (X = F, Cl, Br and I), we found that σSO ∼ ZX2.53. Another important finding of this work is the logarithmic dependence of σSO(C) with the substituent atomic number: ln σSO(C) = AX aX Z Y for both family of compounds CH2XY and CHX2Y. We also performed four-component calculations using the spin-free Hamiltonian to obtain SO contributions within a four-component framework. © 2012 American Institute of Physics. 2012 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00219606_v137_n21_p_Melo http://hdl.handle.net/20.500.12110/paper_00219606_v137_n21_p_Melo |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Atomic numbers Carbon and hydrogens Electronic mechanisms Halogen atoms Heavy atoms Inverse halogen dependence Linear response Logarithmic dependence Model compound Nuclear magnetic shieldings Rate of increase Relativistic correction Relativistic effects Small components Spin orbits Atoms Bromine Bromine compounds Chlorine compounds Hamiltonians Hydrogen Magnetic shielding Paramagnetism Chlorine |
| spellingShingle |
Atomic numbers Carbon and hydrogens Electronic mechanisms Halogen atoms Heavy atoms Inverse halogen dependence Linear response Logarithmic dependence Model compound Nuclear magnetic shieldings Rate of increase Relativistic correction Relativistic effects Small components Spin orbits Atoms Bromine Bromine compounds Chlorine compounds Hamiltonians Hydrogen Magnetic shielding Paramagnetism Chlorine Relativistic effects on nuclear magnetic shieldings of CHnX 4-n and CHXYZ (X, Y, Z = H, F, Cl, Br, I) |
| topic_facet |
Atomic numbers Carbon and hydrogens Electronic mechanisms Halogen atoms Heavy atoms Inverse halogen dependence Linear response Logarithmic dependence Model compound Nuclear magnetic shieldings Rate of increase Relativistic correction Relativistic effects Small components Spin orbits Atoms Bromine Bromine compounds Chlorine compounds Hamiltonians Hydrogen Magnetic shielding Paramagnetism Chlorine |
| description |
Nuclear magnetic shieldings of both carbon and hydrogen atoms of haluro methyl molecules are highly influenced by the substitution of one or more hydrogen by halogen heavy atoms. We applied the linear response elimination of small components, LRESC, formalism to calculate such shieldings and learn whether including only few terms is enough for getting quantitative reproduction of the total shieldings or not. First, we discuss the contribution of all leading relativistic corrections to σ(C), in CHX2I molecular models with X = H, F, and Cl, and show that spin-orbit (SO) effects are the main ones. After adding the SO effects to the non-relativistic (NR) results, we obtain ∼ 97 (93) of the total LRESC values for σ(C) (σ(H)). The magnitude of SO terms increases when the halogen atom becomes heavier. In this case, such contributions to σ(C) can be extrapolated as a function of Z, the halogen atomic number. Furthermore, when paramagnetic spin-orbit (PSO) contributions are also considered, we obtain results that are within 1 of the total LRESC value. Then we study in detail the main electronic mechanisms involved to contribute C and H shieldings on CHnX4 - n (n = 1, 3), and CHXYZ (X, Y, Z = F, Cl, Br, I) model compounds. The pattern of σ(C) for all series of compounds follows a normal halogen dependence (NHD), though with different rate of increase. A special family of compounds is that of CHF2X for which σnr(C) follows an inverse halogen dependence though the total shielding have a NHD due to the SO contributions. For the series CH3X (X = F, Cl, Br and I), we found that σSO ∼ ZX2.53. Another important finding of this work is the logarithmic dependence of σSO(C) with the substituent atomic number: ln σSO(C) = AX aX Z Y for both family of compounds CH2XY and CHX2Y. We also performed four-component calculations using the spin-free Hamiltonian to obtain SO contributions within a four-component framework. © 2012 American Institute of Physics. |
| title |
Relativistic effects on nuclear magnetic shieldings of CHnX 4-n and CHXYZ (X, Y, Z = H, F, Cl, Br, I) |
| title_short |
Relativistic effects on nuclear magnetic shieldings of CHnX 4-n and CHXYZ (X, Y, Z = H, F, Cl, Br, I) |
| title_full |
Relativistic effects on nuclear magnetic shieldings of CHnX 4-n and CHXYZ (X, Y, Z = H, F, Cl, Br, I) |
| title_fullStr |
Relativistic effects on nuclear magnetic shieldings of CHnX 4-n and CHXYZ (X, Y, Z = H, F, Cl, Br, I) |
| title_full_unstemmed |
Relativistic effects on nuclear magnetic shieldings of CHnX 4-n and CHXYZ (X, Y, Z = H, F, Cl, Br, I) |
| title_sort |
relativistic effects on nuclear magnetic shieldings of chnx 4-n and chxyz (x, y, z = h, f, cl, br, i) |
| publishDate |
2012 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00219606_v137_n21_p_Melo http://hdl.handle.net/20.500.12110/paper_00219606_v137_n21_p_Melo |
| _version_ |
1768544896582418432 |