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Ukhanev SA, Fedorov SV, Rusakov YY, Rusakova IL, Krivdin LB. Computational protocols for the 19F NMR parameters. Part 2: Fluorobenzenes. J Fluor Chem 2023. [DOI: 10.1016/j.jfluchem.2023.110093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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2
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Sutter K, Aucar GA, Autschbach J. Analysis of Proton NMR in Hydrogen Bonds in Terms of Lone-Pair and Bond Orbital Contributions. Chemistry 2015; 21:18138-55. [DOI: 10.1002/chem.201502346] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Indexed: 11/10/2022]
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Cormanich RA, Rittner R, O'Hagan D, Bühl M. Inter- and intramolecular CF···C=O interactions on aliphatic and cyclohexane carbonyl derivatives. J Comput Chem 2015; 37:25-33. [PMID: 25903504 DOI: 10.1002/jcc.23918] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2015] [Revised: 03/23/2015] [Accepted: 03/25/2015] [Indexed: 12/18/2022]
Abstract
Weak inter- and intra- molecular C(δ+)F(δ-)···C(δ+)=O(δ-) interactions were theoretically evaluated in 4 different sets of compounds at different theoretical levels. Intermolecular CH3F···C=O interactions were stabilizing by about 1 kcal mol(-1) for various carbonyl containing functional groups. Intramolecular CF···C=O interactions were also detected in aliphatic and fluorinated cyclohexane carbonyl derivatives. However, the stabilization provided by intramolecular CF···C=O interactions was not enough to govern the conformational preferences of compounds 2-4.
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Affiliation(s)
- Rodrigo A Cormanich
- School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife KY169ST, United Kingdom.,Chemistry Institute, State University of Campinas, P.O. Box 6154, 13083-971, Campinas, SP, Brazil
| | - Roberto Rittner
- Chemistry Institute, State University of Campinas, P.O. Box 6154, 13083-971, Campinas, SP, Brazil
| | - David O'Hagan
- School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife KY169ST, United Kingdom
| | - Michael Bühl
- School of Chemistry, University of St Andrews, North Haugh, St Andrews, Fife KY169ST, United Kingdom
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Contreras RH, Llorente T, Ducati LC, Tormena CF. Revisiting NMR Through-Space JFF Spin–Spin Coupling Constants for Getting Insight into Proximate F---F Interactions. J Phys Chem A 2014; 118:5068-75. [DOI: 10.1021/jp501929t] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Rubén H. Contreras
- Department
of Physics, FCEyN, University of Buenos Aires and IFIBA-CONICET, C1053ABJ Buenos Aires, Argentina
| | - Tomás Llorente
- Department
of Physics, FCEyN, University of Buenos Aires and IFIBA-CONICET, C1053ABJ Buenos Aires, Argentina
| | - Lucas Colucci Ducati
- Institute
of Chemistry, University of Sao Paulo − USP, P.O. Box 26077, 05513-970 Sao Paulo - SP, Brazil
| | - Cláudio Francisco Tormena
- Chemistry
Institute, University of Campinas - UNICAMP, P.O. Box 6154, 13083-970 Campinas - SP, Brazil
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5
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Hierso JC. Indirect nonbonded nuclear spin-spin coupling: a guide for the recognition and understanding of "through-space" NMR J constants in small organic, organometallic, and coordination compounds. Chem Rev 2014; 114:4838-67. [PMID: 24533483 DOI: 10.1021/cr400330g] [Citation(s) in RCA: 124] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Jean-Cyrille Hierso
- Institut de Chimie Moléculaire (ICMUB, UMR-CNRS 6302), Université de Bourgogne and Institut Universitaire de France (IUF) , 9 Avenue Alain Savary, BP 47870 Dijon F-21078, France
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Contreras RH, Ferraro M, Ruiz de Azúa MC, Aucar GA. Brief Account of Nonrelativistic Theory of NMR Parameters. SCIENCE AND TECHNOLOGY OF ATOMIC, MOLECULAR, CONDENSED MATTER & BIOLOGICAL SYSTEMS 2013. [DOI: 10.1016/b978-0-444-59411-2.00002-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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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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Nath N, Lokesh, Suryaprakash N. Measurement and applications of long-range heteronuclear scalar couplings: recent experimental and theoretical developments. Chemphyschem 2012; 13:645-60. [PMID: 22302693 DOI: 10.1002/cphc.201100748] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 12/04/2011] [Indexed: 12/11/2022]
Abstract
The use of long-range heteronuclear couplings, in association with (1)H-(1)H scalar couplings and NOE restraints, has acquired growing importance for the determination of the relative stereochemistry, and structural and conformational information of organic and biological molecules. However, the routine use of such couplings is hindered by the inherent difficulties in their measurement. Prior to the advancement in experimental techniques, both long-range homo- and heteronuclear scalar couplings were not easily accessible, especially for very large molecules. The development of a large number of multidimensional NMR experimental methodologies has alleviated the complications associated with the measurement of couplings of smaller strengths. Subsequent application of these methods and the utilization of determined J-couplings for structure calculations have revolutionized this area of research. Problems in organic, inorganic and biophysical chemistry have also been solved by utilizing the short- and long-range heteronuclear couplings. In this minireview, we discuss the advantages and limitations of a number of experimental techniques reported in recent times for the measurement of long-range heteronuclear couplings and a few selected applications of such couplings. This includes the study of medium- to larger-sized molecules in a variety of applications, especially in the study of hydrogen bonding in biological systems. The utilization of these couplings in conjunction with theoretical calculations to arrive at conclusions on the hyperconjugation, configurational analysis and the effect of the electronegativity of the substituents is also discussed.
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Affiliation(s)
- Nilamoni Nath
- NMR Research Centre, Indian Institute of Science, Bangalore, India
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Favaro DC, Ducati LC, dos Santos FP, Contreras RH, Tormena CF. Stereochemical dependence of 3JCH coupling constants in 2-substituted 4-t-butyl-cyclohexanone and their alcohol derivatives. J Phys Chem A 2011; 115:14539-45. [PMID: 22060817 DOI: 10.1021/jp2083456] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Theoretical and experimental studies on (3)J(C2H6eq) NMR spin-spin coupling constants in both the 2-X-4-t-butyl-cyclohexanone (X = H, CH(3), F, Cl, and Br) and in their alcohol derivatives series are reported. Results thus found are rationalized in terms of the transmission of the Fermi contact contribution to such couplings. To this end, dependencies of (3)J(C2H6eq) couplings versus the C(2)-C(1)-C(6) angle are compared in both series for equatorial and axial X orientations. The main trend is described in terms of the rear lobes interaction. Besides, for X = halogen atom in equatorial orientation a rather strong interaction between oxygen and halogen lone pairs is observed, and its influence on (3)J(C2H6eq) couplings is discussed and rationalized in terms of different Fermi contact transmission pathways.
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Affiliation(s)
- Denize C Favaro
- Chemistry Institute, State University of Campinas, Campinas SP, Brazil
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Ghiviriga I, Zhang L, Martinez H, Contreras RH, Tormena CF, Nodin L, Dolbier WR. 19F chemical shifts, coupling constants and conformational preferences in monosubstituted perfluoroparacyclophanes. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2011; 49:93-105. [PMID: 21246624 DOI: 10.1002/mrc.2713] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Revised: 11/15/2010] [Accepted: 11/19/2010] [Indexed: 05/30/2023]
Abstract
In the process of studying the chemistry of perfluoro[2.2]paracyclophanes (PFPCs), a novel class of compounds, it became necessary to identify some disubstituted products. To achieve this goal, we characterize in this work some monosubstituted PFPCs, identifying their (19)F-(19) F coupling patterns, and establishing a methodology for the assignment of their (19)F chemical shifts. The pattern of coupling constants indicates a skewed geometry in which the upper deck moves towards or away from the substituent, depending on the substituent electron-donor character and size. Quantum chemical calculations, performed at the HF/6-311 + G(d,p)//B3LYP/EPR-III level of theory, confirmed the conformations inferred from coupling constants and reproduced well the values of the couplings. Transmission mechanisms for the FC term of four- and five-bond (19)F-(19) F couplings are discussed in detail. Understanding the conformational preferences of PFPCs and how they are reflected by the coupling constants facilitates the assignment of (19)F chemical shifts in monosubstituted PFPCs and the identification of the disubstituted products.
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Affiliation(s)
- Ion Ghiviriga
- Chemistry Department, University of Florida, Gainesville, 32611-7200, USA.
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Contreras RH, dos Santos FP, Ducati LC, Tormena CF. Difference between ²JC2H3 and ²JC3H2 spin-spin couplings in heterocyclic five- and six-membered rings as a probe for studying σ-ring currents: a quantum chemical analysis. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2010; 48 Suppl 1:S151-S158. [PMID: 21104760 DOI: 10.1002/mrc.2669] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Adequate analyses of canonical molecular orbitals (CMOs) can provide rather detailed information on the importance of different σ-Fermi contact (FC) coupling pathways (FC term transmitted through the σ-skeleton). Knowledge of the spatial distribution of CMOs is obtained by expanding them in terms of natural bond orbitals (NBOs). Their relative importance for transmitting the σ-FC contribution to a given spin-spin coupling constants (SSCCs) is estimated by resorting to the expression of the FC term given by the polarisation propagator formalism. In this way, it is possible to classify the effects affecting such couplings in two different ways: delocalisation interactions taking place in the neighbourhood of the coupling nuclei and 'round the ring' effects. The latter, associated with σ-ring currents, are observed to yield significant differences between the FC terms of (2)J(C2H3) and (2)J(C3H2) SSCCs which, consequently, are taken as probes to gauge the differences in σ-ring currents for the five-membered rings (furan, thiophene, selenophene and pyrrol) and also for the six-membered rings (benzene, pyridine, protonated pyridine and N-oxide pyridine) used in the present study.
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Affiliation(s)
- Rubén H Contreras
- Department of Physics, FCEyN, University of Buenos Aires and IFIBA-CONICET, Buenos Aires, Argentina
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Contreras RH, Gotelli G, Ducati LC, Barbosa TM, Tormena CF. Analysis of Canonical Molecular Orbitals to Identify Fermi Contact Coupling Pathways. 1. Through-Space Transmission by Overlap of 31P Lone Pairs. J Phys Chem A 2009; 114:1044-51. [DOI: 10.1021/jp908970f] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Rubén H. Contreras
- Department of Physics, FCEyN, University of Buenos Aires, and CONICET, Buenos Aires, Argentina, Department of Pharmaceutical Technology, FFyB, University of Buenos Aires, Buenos Aires, Argentina, and Organic Chemistry Department, Chemistry Institute, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil
| | - Gustavo Gotelli
- Department of Physics, FCEyN, University of Buenos Aires, and CONICET, Buenos Aires, Argentina, Department of Pharmaceutical Technology, FFyB, University of Buenos Aires, Buenos Aires, Argentina, and Organic Chemistry Department, Chemistry Institute, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil
| | - Lucas C. Ducati
- Department of Physics, FCEyN, University of Buenos Aires, and CONICET, Buenos Aires, Argentina, Department of Pharmaceutical Technology, FFyB, University of Buenos Aires, Buenos Aires, Argentina, and Organic Chemistry Department, Chemistry Institute, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil
| | - Thais M. Barbosa
- Department of Physics, FCEyN, University of Buenos Aires, and CONICET, Buenos Aires, Argentina, Department of Pharmaceutical Technology, FFyB, University of Buenos Aires, Buenos Aires, Argentina, and Organic Chemistry Department, Chemistry Institute, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil
| | - Cláudio F. Tormena
- Department of Physics, FCEyN, University of Buenos Aires, and CONICET, Buenos Aires, Argentina, Department of Pharmaceutical Technology, FFyB, University of Buenos Aires, Buenos Aires, Argentina, and Organic Chemistry Department, Chemistry Institute, University of Campinas, P.O. Box 6154, 13084-971 Campinas, São Paulo, Brazil
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Contreras RH, Llorente T, Pagola GI, Bustamante MG, Pasqualini EE, Melo JI, Tormena CF. Qualitative Study of Substituent Effects on NMR 15N and 17O Chemical Shifts. J Phys Chem A 2009; 113:9874-80. [DOI: 10.1021/jp901926p] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rubén H. Contreras
- Department of Physics, FCEyN, University of Buenos
Aires and CONICET, Buenos Aires, Argentina, Argentine National Atomic
Energy Commission, Buenos Aires Province, Argentina, and Organic Chemistry
Department, Chemistry Institute, University of Campinas, P.O. Box
6154; zip code 13084-971, Campinas, São Paulo, Brazil
| | - Tomás Llorente
- Department of Physics, FCEyN, University of Buenos
Aires and CONICET, Buenos Aires, Argentina, Argentine National Atomic
Energy Commission, Buenos Aires Province, Argentina, and Organic Chemistry
Department, Chemistry Institute, University of Campinas, P.O. Box
6154; zip code 13084-971, Campinas, São Paulo, Brazil
| | - Gabriel I. Pagola
- Department of Physics, FCEyN, University of Buenos
Aires and CONICET, Buenos Aires, Argentina, Argentine National Atomic
Energy Commission, Buenos Aires Province, Argentina, and Organic Chemistry
Department, Chemistry Institute, University of Campinas, P.O. Box
6154; zip code 13084-971, Campinas, São Paulo, Brazil
| | - Manuel G. Bustamante
- Department of Physics, FCEyN, University of Buenos
Aires and CONICET, Buenos Aires, Argentina, Argentine National Atomic
Energy Commission, Buenos Aires Province, Argentina, and Organic Chemistry
Department, Chemistry Institute, University of Campinas, P.O. Box
6154; zip code 13084-971, Campinas, São Paulo, Brazil
| | - Enrique E. Pasqualini
- Department of Physics, FCEyN, University of Buenos
Aires and CONICET, Buenos Aires, Argentina, Argentine National Atomic
Energy Commission, Buenos Aires Province, Argentina, and Organic Chemistry
Department, Chemistry Institute, University of Campinas, P.O. Box
6154; zip code 13084-971, Campinas, São Paulo, Brazil
| | - Juan I. Melo
- Department of Physics, FCEyN, University of Buenos
Aires and CONICET, Buenos Aires, Argentina, Argentine National Atomic
Energy Commission, Buenos Aires Province, Argentina, and Organic Chemistry
Department, Chemistry Institute, University of Campinas, P.O. Box
6154; zip code 13084-971, Campinas, São Paulo, Brazil
| | - Cláudio F. Tormena
- Department of Physics, FCEyN, University of Buenos
Aires and CONICET, Buenos Aires, Argentina, Argentine National Atomic
Energy Commission, Buenos Aires Province, Argentina, and Organic Chemistry
Department, Chemistry Institute, University of Campinas, P.O. Box
6154; zip code 13084-971, Campinas, São Paulo, Brazil
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Contreras RH, Provasi PF, dos Santos FP, Tormena CF. Stereochemical dependence of NMR geminal spin-spin coupling constants. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2009; 47:113-120. [PMID: 18991325 DOI: 10.1002/mrc.2359] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In this work it was sought to explore the versatility of geminal spin-spin coupling constants, (2)J(XY) SSCCs, as probes for stereochemical studies. A set of compounds, where their experimental (2)J(XY) SSCCs through the X-C-Y molecular fragment are predicted to be sensitive to hyperconjugative interactions involving either bonding or antibonding orbitals containing the C carbon atom ('coupling pathway'), were analyzed. SSCC calculations were performed for some selected examples using the second order polarization propagator approximation (SOPPA) method or within the DFT-B3LYP framework. Hyperconjugative interactions were calculated within the Natural Bond Orbital (NBO) approach. Results are condensed in two qualitative rules: Rule I(M)-hyperconjugative interactions transferring charge into the coupling pathway yield a positive increase to the Fermi contact (FC), contribution to (2)K(XY) reduced spin-spin coupling constants (RSSCC), and Rule II(M)-hyperconjugative interactions transferring charge from the coupling pathway yield a negative increase to the FC contribution to (2)K(XY) RSSCC.
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Affiliation(s)
- Rubén H Contreras
- Department of Physics, FCEyN, University of Buenos Aires and CONICET, Buenos Aires, Argentina
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Pedersoli S, Tormena CF, dos Santos FP, Contreras RH, Rittner R. Stereochemical behavior of 1JCH and 2JCH NMR coupling constants in α-substituted acetamides. J Mol Struct 2008. [DOI: 10.1016/j.molstruc.2008.04.040] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Pérez C, Suardíaz R, Ortiz PJ, Crespo-Otero R, Bonetto GM, Gavín JA, García de la Vega JM, San Fabián J, Contreras RH. On the unusual 2J(C2-H(f)) coupling dependence on syn/anti CHO conformation in 5-X-furan-2-carboxaldehydes. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2008; 46:846-850. [PMID: 18566984 DOI: 10.1002/mrc.2268] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
A remarkable difference for (2)J(C(2)-H(f)) coupling constant in syn and anti conformers of 5-X-furan-2-carboxaldehydes (X = CH(3), Ph, NO(2), Br) and a rationalization of this difference are reported. On the basis of the current knowledge of the Fermi-contact term transmission, a rather unusual dual-coupling pathway in the syn conformer is presented. The additional coupling pathway resembles somewhat that of the J(H-H) in homoallylic couplings, which are transmitted by hyperconjugative interactions involving the pi(C=C) electronic system. The homoallylic coupling pathway can be labeled as sigma*(C-H) <-- pi(C=C) --> sigma*(C-H). In the present case, this additional coupling pathway, using an analogous notation, can be labeled as sigma*(C(2)-C(C)) <-- LP(1)(O(1))...LP(2)(O(C)) --> sigma*(C(C)-H(f)) (sigma*(C(2)-C(C))) where O(1) and O(C) stand for the ring and carbonyl O atoms, respectively. This additional coupling pathway is not activated in the anti conformers since both oxygen lone pairs do not overlap.
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Affiliation(s)
- Carlos Pérez
- Departamento de Química Física, Facultad de Química, Universidad de La Habana, La Habana 10400, Cuba.
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Contreras RH, Suardíaz R, Pérez C, Crespo-Otero R, San Fabián J, García de la Vega JM. Karplus Equation for 3JHH Spin−Spin Couplings with Unusual 3J(180°) < 3J(0°) Relationship. J Chem Theory Comput 2008; 4:1494-500. [DOI: 10.1021/ct800145h] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- R. H. Contreras
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - R. Suardíaz
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - C. Pérez
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - R. Crespo-Otero
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - J. San Fabián
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - J. M. García de la Vega
- Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and CONICET, Buenos Aires, Argentina, Departamento de Química Física, Facultad de Química, Universidad de la Habana, La Habana 10400, Cuba, and Departamento de Química Física Aplicada, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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Pedersoli S, Dos Santos FP, Rittner R, Contreras RH, Tormena CF. NMR spin-spin couplings involving nuclei in the neighborhood of a carbonyl group. 3JCH couplings in alpha-substituted acetamides. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2008; 46:202-205. [PMID: 18181244 DOI: 10.1002/mrc.2158] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In this work 3JCH spin-spin coupling constants (SSCCs) for the cis- and trans-conformers for alpha-X-acetamides (X = F, Cl, Br and CN) (1-4) were studied in detail since they were found to be notably different for both conformers. These differences are rationalized as originating in the changes of the strong negative hyperconjugative interactions that take place within the carbonyl group. Such changes are found to depend not only on conformation, but also on solvent. For the cis-conformers there is a close proximity between the X-substituent and the in-plane oxygen lone pair of pure p character, which affects notably their respective negative hyperconjugative interactions. Both the efficiency for transmitting the Fermi contact (FC) term through the coupling pathway of 3JCH SSCCs and its potential as a probe to study the stereochemical properties of the XH2C group are discussed.
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Affiliation(s)
- Susimaire Pedersoli
- Physical Organic Chemistry Laboratory, Chemistry Institute, Campinas State University, C.P. 6154, 13084-971, Campinas, SP, Brazil
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Autschbach J. Analyzing molecular properties calculated with two-component relativistic methods using spin-free natural bond orbitals: NMR spin-spin coupling constants. J Chem Phys 2007; 127:124106. [PMID: 17902892 DOI: 10.1063/1.2768363] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
An analysis method for static linear response properties employing two-component (spin-orbit) relativistic density functional theory along with scalar relativistic "natural localized molecular orbitals" (NLMOs) and "natural bond orbitals" (NBOs) has been developed. The spin-orbit NLMO/NBO analysis has been applied to study the indirect spin-spin coupling (J-coupling) constants in Tl-I, PbH(4), and a dinuclear Pt-Tl bonded complex with a very large Pt-Tl coupling constant (expt.: 146.8 kHz). For Tl-I it is shown that the analysis scheme based on scalar relativistic NLMOs is applicable even if spin-orbit coupling is responsible for most of the coupling's magnitude. For PbH(4) it is shown that electron delocalization plays a much larger role for the Pb-H coupling than it is the case for the C-H coupling in methane. For the Pt-Tl complex the analysis clearly demonstrates the strong influence of the ligands on the Pt-Tl coupling constant and quantifies the effect of the delocalization of the Pt-Tl bond on the Pt-Tl coupling constant.
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Affiliation(s)
- Jochen Autschbach
- Department of Chemistry, State University of New York at Buffalo, Buffalo, New York 14260-3000, USA.
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Contreras RH, Esteban AL, Díez E, Lochert IJ, Della EW, Tormena CF. Experimental and DFT studies on the transmission mechanisms of analogous NMR JCH and JCC couplings in 1-X- and 1-X-3-methylbicyclo[1.1.1]-pentanes. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2007; 45:572-7. [PMID: 17534878 DOI: 10.1002/mrc.2009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The main aim of this work is to compare the transmission mechanisms for the Fermi contact term of spin-spin couplings, SSCCs, in series 1-X-bicyclo[1.1.1]-pentane, (1), and 1-X-3-methylbicyclo[1.1.1]pentane, (2), and from that comparison to gain insight into some subtle aspects of the FC transmission. To this end, 18 members of the latter series were isotopically enriched in (13)C at the methyl position and the following couplings were measured; 1JC3CMe, 3JC1CMe and 4JCXCMe. These three types of SSCCs in (2) are compared, respectively, with 1JC3H3, 3JC1H3 and 4JCXH in (1); these latter values were taken from previous works. Since electron delocalization plays an important role in the transmission of the FC interaction, the natural bond orbital (NBO) method is employed to quantify electron delocalization interactions within selected members of series (1) and (2). It is found that 1JC3H3 SSCCs in (1) is more efficiently transmitted than 1JC3CMe SSCCs in (2). On the other hand, 3JC1H3 and 4JCXH SSCCs in (1) are notably less efficiently transmitted than 3JC1CMe and 4JCXCMe SSCCs in (2), although substituent effects on these two SSCCs show the opposite trends. These different efficiencies are rationalized in terms of different sigma-hyperconjugative interactions in both series of compounds.
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Affiliation(s)
- Rubén H Contreras
- Department of Physics, FCEyN, University of Buenos Aires, Ciudad Universitaria, Pabellón 1 (C1428EHA) Buenos Aires, Argentina
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Cremer D, Gräfenstein J. Calculation and analysis of NMR spin-spin coupling constants. Phys Chem Chem Phys 2007; 9:2791-816. [PMID: 17538726 DOI: 10.1039/b700737j] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The analysis of NMR spin-spin coupling leads to a unique insight into the electronic structure of closed-shell molecules, provided one is able to decode the different features of the spin-spin coupling mechanism. For this purpose, the physics of spin-spin coupling is described and the way how spin-spin coupling constants (SSCCs) can be quantum mechanically determined. Based on this insight, a set of requirements is derived that guide the development of a quantum mechanical analysis of spin-spin coupling. It is demonstrated that the J-OC-PSP (=J-OC-OC-PSP: Decomposition of J into orbital contributions using orbital currents and partial spin polarization) analysis method fulfills all requirements. J-OC-PSP makes it possible to partition the isotropic indirect SSCC J or its reduced analogue K as well as the four Ramsey terms (Fermi contact (FC), spin dipole (SD), diamagnetic spin orbit (DSO), paramagnetic spin orbit (PSO)) leading to J (or K) into Cartesian components (for the anisotropic Ramsey terms SD, DSO, PSO), orbital contributions or electron interaction terms. For the purpose of decoding the spin-spin coupling mechanism, FC, SD, DSO, and PSO coupling is discussed in detail and related to electronic and bonding features of the molecules in question. The myth of empirical and semiempirical relationships between SSCCs and bonding features is unveiled. It is found that most relationships are only of limited, partly dubious value, often arising from a fortuitous cancellation of terms that cannot be expected in general. These relationships are replaced by quantum chemical relations and descriptions that directly reflect the complex electronic processes leading to spin-spin coupling.
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Affiliation(s)
- Dieter Cremer
- Department of Chemistry, University of the Pacific, 3601 Pacific Avenue, Stockton, California 95211, USA
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Provasi PF, Sauer SPA. On the Angular Dependence of the Vicinal Fluorine−Fluorine Coupling Constant in 1,2-Difluoroethane: Deviation from a Karplus-like Shape. J Chem Theory Comput 2006; 2:1019-27. [DOI: 10.1021/ct6000973] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Patricio F. Provasi
- Department of Physics, University of Northeastern, Av. Libertad 5500, W 3404 AAS Corrientes, Argentina
| | - Stephan P. A. Sauer
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
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Contreras RH, Esteban AL, Díez E, Della EW, Lochert IJ, Dos Santos FP, Tormena CF. Experimental and Theoretical Study of Hyperconjugative Interaction Effects on NMR 1JCH Scalar Couplings. J Phys Chem A 2006; 110:4266-75. [PMID: 16553380 DOI: 10.1021/jp0555201] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hyperconjugative and electrostatic interactions effects on 1J(CH) spin-spin coupling constants (SSCCs) are critically studied from both theoretical and experimental points of view. A qualitative model is used to predict how the former affect such SSCCs, while electrostatic interactions are modeled with a point charge placed in the vicinity of the corresponding sigma(CH) bond. Hyperconjugative interactions are calculated using the "natural bond orbital" approach, and using the point-charge model, it is shown how intertwined are both types of interactions. Several members of the series 1-X-bicyclo[1.1.1]pentane and 1-X-3-methylbicyclo[1.1.1]pentane are chosen as model compounds for measuring 1J(CH) SSCCs; in some of them were performed also DFT-SSCC calculations. The strained cage substrate in these series defines strong sigma-hyperconjugative interactions, making these compounds excellent examples to verify the qualitative model presented in this work. It is verified that (a) hyperconjugative interactions from the sigma(CH) bond or into the sigma(CH) antibond containing the coupling nuclei yield a decrease of the corresponding 1J(CH) SSCC and (b) hyperconjugative interactions from other bonds involving the coupling C nucleus yield an increase of that 1J(CH) SSCC.
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Affiliation(s)
- Rubén H Contreras
- Departamento de Física, FCEyN, Universidad de Buenos Aires, Ciudad Universitaria, P. 1 and CONICET (C1428EHA) Buenos Aires, Argentina
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