51
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Melo JI, Maldonado AF, Aucar GA. Relativistic effects on nuclear magnetic shieldings of CHnX4−n and CHXYZ (X, Y, Z = H, F, Cl, Br, I). J Chem Phys 2012; 137:214319. [DOI: 10.1063/1.4768470] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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52
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Sun Q, Xiao Y, Liu W. Exact two-component relativistic theory for NMR parameters: General formulation and pilot application. J Chem Phys 2012; 137:174105. [DOI: 10.1063/1.4764042] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
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53
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Abstract
This perspective article discusses some broadly-known and some less broadly-known consequences of Einstein's special relativity in quantum chemistry, and provides a brief outline of the theoretical methods currently in use, along with a discussion of recent developments and selected applications. The treatment of the electron correlation problem in relativistic quantum chemistry methods, and expanding the reach of the available relativistic methods to calculate all kinds of energy derivative properties, in particular spectroscopic and magnetic properties, requires on-going efforts.
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Affiliation(s)
- Jochen Autschbach
- Department of Chemistry, State University of New York at Buffalo, New York 14260-3000, USA.
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54
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Maldonado AF, Giménez CA, Aucar GA. Nuclear charge-distribution effects on the NMR spectroscopy parameters. J Chem Phys 2012; 136:224110. [DOI: 10.1063/1.4729253] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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55
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Aucar IA, Gómez SS, de Azúa MCR, Giribet CG. Theoretical study of the nuclear spin-molecular rotation coupling for relativistic electrons and non-relativistic nuclei. J Chem Phys 2012; 136:204119. [DOI: 10.1063/1.4721627] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
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56
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Ducati LC, Contreras RH, Tormena CF. Unexpected geometrical effects on paramagnetic spin-orbit and spin-dipolar 2J(FF) couplings. J Phys Chem A 2012; 116:4930-3. [PMID: 22533483 DOI: 10.1021/jp301912x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The second-rank tensor character of the paramagnetic spin-orbit and spin-dipolar contributions to nuclear spin-spin coupling constants is usually ignored when NMR measurements are carried out in the isotropic phase. However, in this study it is shown that isotropic (2)J(FF) couplings strongly depend on the relative orientation of the C-F bonds containing the coupling nuclei and the eigenvectors of such tensors. Predictions about such effect are obtained using a qualitative approach based on the polarization propagator formalism at the RPA, and results are corroborated performing high-level ab initio spin-spin coupling calculations at the SOPPA(CCSD)/EPR-III//MP2/EPR-III level in a model system. It is highlighted that no calculations at the RPA level were carried out in this work. The quite promising results reported in this paper suggest that similar properties are expected to hold for the second-rank nuclear magnetic shielding tensor.
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Affiliation(s)
- Lucas C Ducati
- Chemistry Institute, State University of Campinas, Caixa Postal 6154, 13084-971 Campinas, SP, Brazil
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Zarycz N, Aucar GA. The analysis of NMR J-couplings of saturated and unsaturated compounds by the localized second order polarization propagator approach method. J Chem Phys 2012; 136:174115. [PMID: 22583218 DOI: 10.1063/1.3697844] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Calculations of NMR J-coupling with polarization propagators are not invariant under unitary transformations at second order level of approach, second order polarization propagator approach (SOPPA). They are only invariant at first order or random phase level of approach (RPA). We performed "localized" SOPPA (Loc-SOPPA), calculations of J-couplings applying two different schemes for the localization of molecular orbitals(LMO): Foster-Boys and Pipek-Mezey. We show here that results of such Loc-SOPPA calculations are different though not much: they are less than 6% different in the worst case. Therefore it is possible to apply them with confidence in the analysis of the transmission of different coupling mechanisms within the molecule. We are able now to get reliable information on what LMOs are the most important (and so which are not important) for a given J-coupling in a molecule. This information can then be used for selecting which are the paths that should be described with the highest possible accuracy for that J-coupling calculation. A few unsaturated compounds are analyzed: ethene, trans-difluoroethene or DiF-ethene, and imine. It is shown that different lone pairs (of p(z) or p(x/y) type) are responsible for the vicinal F-F J-coupling in DiF-ethene; and also the fact that the main LP contributor is not the same for the fermi contact and the spin-dipolar mechanisms. We also studied phosphorous containing compounds such as phosphine and cis-propylene phosphine. In both cases the analysis of the main LMO contributing to one-bond P-H coupling and through-space P-C coupling were performed. The above mentioned unsaturated molecular systems have quasiinstability problems that arise at RPA level of approach. We show here that they are mostly originated in the antibonding π∗ LMO, corresponding to the C=C or C=N double bonds. We performed the analysis of the origin of quasiinstabilities for the SD mechanism. The contribution of each kind of excitation terms to SOPPA calculations were considered, meaning the main contributions by single and double excitations. It is shown that one can get more than 97% of the total electron correlation contribution when including terms that mainly contain single excitations (though double-excitation matrix elements should still be calculated).
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Affiliation(s)
- Natalia Zarycz
- Department of Physics, Northeastern University of Argentina and IMIT Institute, Avenida Libertad 5460 - Corrientes, W 3404 AAS Argentina
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58
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NMR espectroscopic parameters of HX and Si(Sn)X4 (X=H, F, Cl, Br and I) and SnBr4−nIn model compounds. Chem Phys 2012. [DOI: 10.1016/j.chemphys.2011.08.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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59
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Zarycz N, Aucar GA. Analysis of Electron Correlation Effects and Contributions of NMR J-Couplings from Occupied Localized Molecular Orbitals. J Phys Chem A 2012; 116:1272-82. [DOI: 10.1021/jp209850z] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Natalia Zarycz
- Department of Physics, Natural and Exact Science Faculty,
Northeastern University of Argentina, Corrientes, Argentina
| | - Gustavo A. Aucar
- Department of Physics, Natural and Exact Science Faculty,
Northeastern University of Argentina, Corrientes, Argentina
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61
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Cormanich RA, Moreira MA, Freitas MP, Ramalho TC, Anconi CPA, Rittner R, Contreras RH, Tormena CF. 1hJFH coupling in 2-fluorophenol revisited: is intramolecular hydrogen bond responsible for this long-range coupling? MAGNETIC RESONANCE IN CHEMISTRY : MRC 2011; 49:763-767. [PMID: 22095853 DOI: 10.1002/mrc.2838] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 08/29/2011] [Accepted: 08/31/2011] [Indexed: 05/31/2023]
Abstract
The present study shows that a hydrogen bond between the OH group and the fluorine atom is not involved in the (1h)J(FH) spin-spin coupling transmission either for 4-bromo-2-fluorophenol or 2-fluorophenol. In fact, according to a quantum theory of atoms in molecules analysis, no bond critical point is found between O-H and F moieties. The nature of the transmission mechanism of the Fermi contact term of the (1h)J(FH) spin-spin coupling is studied by analyzing canonical molecular orbitals (see J. Phys. Chem. A 2010, 114, 1044), and it is observed that virtual orbitals play only a quite minor role in its transmission. This is typical of a Fermi contact term transmitted mainly through exchange interactions owing to the overlap of proximate electronic clouds; therefore, it is suggested to identify them as (nTS)J(FH) coupling where n stands for the number of formal bonds separating the coupling nuclei. In the cases studied in this work is n = 4. Results presented in this work could provide an interesting rationalization for different experimental signs known in the current literature for proximate J(FH) couplings.
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Affiliation(s)
- Pekka Pyykkö
- Department of Chemistry, University of Helsinki, POB 55 (A. I. Virtasen aukio 1), 00014 Helsinki, Finland
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63
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Gómez SS, Aucar GA. Relativistic effects on the nuclear magnetic resonance shielding of FX (X = F, Cl, Br, I, and At) molecular systems. J Chem Phys 2011; 134:204314. [DOI: 10.1063/1.3587051] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
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64
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Melo JI, Maldonado A, Aucar GA. Relativistic effects on the shielding of SnH2XY and PbH2XY (X, Y = F, Cl, Br and I) heavy atom–containing molecules. Theor Chem Acc 2011. [DOI: 10.1007/s00214-010-0886-4] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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65
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Roukala J, Maldonado AF, Vaara J, Aucar GA, Lantto P. Relativistic effects on group-12 metal nuclear shieldings. Phys Chem Chem Phys 2011; 13:21016-25. [DOI: 10.1039/c1cp22043h] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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66
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Zarycz N, Aucar GA, Védova COD. NMR Spectroscopic Parameters of Molecular Systems with Strong Hydrogen Bonds. J Phys Chem A 2010; 114:7162-72. [DOI: 10.1021/jp1019334] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Natalia Zarycz
- Physics Department, Exact and Natural Science Faculty, Northeastern University of Argentina and Institute of Modeling and Innovation on Technology, IMIT, CONICET-UNNE
| | - Gustavo A. Aucar
- Physics Department, Exact and Natural Science Faculty, Northeastern University of Argentina and Institute of Modeling and Innovation on Technology, IMIT, CONICET-UNNE
| | - Carlos O. Della Védova
- CEQUINOR (UNLP-CONICET) and Departamento de Química, Facultad de Ciencias Exactas - Univ. Nac. de La Plata, CC962 and Laboratorio de Servicios a la Industria y al Sistema Científico (LaSeISiC), UNLP-CIC−CONICET), La Plata (CP 1900), Argentina
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