Next Issue
Volume 4, April
Previous Issue
Volume 4, February
 
 
ijms-logo

Journal Browser

Journal Browser

Int. J. Mol. Sci., Volume 4, Issue 3 (March 2003) – 7 articles , Pages 62-157

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
114 KiB  
Article
The Spin–Spin Coupling Constants in Ethane, Methanol and Methylamine: A Comparison of DFT, MCSCF and CCSD Results
by Magdalena Pecul and Trygve Helgaker
Int. J. Mol. Sci. 2003, 4(3), 143-157; https://doi.org/10.3390/i4030143 - 25 Feb 2003
Cited by 73 | Viewed by 11015
Abstract
The spin–spin coupling constants in ethane, methylamine, and methanol have been calculated using density-functional theory (DFT), coupled-cluster singlesand-doubles (CCSD) theory, and multiconfigurational self-consistent field (MCSCF) theory so as to benchmark the performance of DFT against high-level ab initio methods and experimental data. For [...] Read more.
The spin–spin coupling constants in ethane, methylamine, and methanol have been calculated using density-functional theory (DFT), coupled-cluster singlesand-doubles (CCSD) theory, and multiconfigurational self-consistent field (MCSCF) theory so as to benchmark the performance of DFT against high-level ab initio methods and experimental data. For each molecule, the Karplus curve has been evaluated at the three computational levels. The comparisons with ab initio methods indicate that DFT reproduces the 1J(CH), 1J(CC), and 1J(NH) one-bond couplings well but is less accurate for 1J(CN), 1J(OH), and 1J(CO). While DFT performs well for the geminal couplings 2J(HH) and 2J(CH), it tends to overestimate the vicinal 3J(HH) couplings slightly although it is sufficiently accurate for most purposes. Full article
Show Figures

Figure 1

62 KiB  
Article
Gas–Phase Studies of Spin–Spin Coupling Constants
by Karol Jackowski
Int. J. Mol. Sci. 2003, 4(3), 135-142; https://doi.org/10.3390/i4030135 - 25 Feb 2003
Cited by 33 | Viewed by 8513
Abstract
Recent results of experimental spin-spin coupling constants are reviewed and their relation to ab initio calculations is discussed. It is shown that the NMR measurements of spin-spin coupling are density dependent in the gas phase. The extrapolation to the zerodensity limit is required [...] Read more.
Recent results of experimental spin-spin coupling constants are reviewed and their relation to ab initio calculations is discussed. It is shown that the NMR measurements of spin-spin coupling are density dependent in the gas phase. The extrapolation to the zerodensity limit is required in order to obtain the Jo coupling constants which are free from intermolecular interactions. Such coupling constants can be used as the experimental standards for any comparison with the results of appropriate calculations. It is also pointed out that the effects of the rotational and vibrational motion of nuclei in a molecule can be estimated completely only by theoretical methods. Full article
Show Figures

Figure 1

121 KiB  
Article
Solvent Effects on the Indirect Spin–Spin Coupling Constants of Benzene: The DFT-PCM Approach
by Kenneth Ruud, Luca Frediani, Roberto Cammi and Benedetta Mennucci
Int. J. Mol. Sci. 2003, 4(3), 119-134; https://doi.org/10.3390/i4030119 - 25 Feb 2003
Cited by 67 | Viewed by 11330
Abstract
We present an extension of the Polarizable Continuum Model (PCM) to the calculation of solvent effects on indirect spin–spin coupling constants for Hartree–Fock wave functions and Density Functional Theory. This is achieved by implementing the PCM model for singlet and triplet linear response [...] Read more.
We present an extension of the Polarizable Continuum Model (PCM) to the calculation of solvent effects on indirect spin–spin coupling constants for Hartree–Fock wave functions and Density Functional Theory. This is achieved by implementing the PCM model for singlet and triplet linear response functions. The new code is used for calculating the solvent effects on the indirect spin–spin coupling constants of benzene. For the 1J(H13C) coupling constants, our calculated solvent shifts are in good agreement with experimental observations when geometry relaxation is taken into account. However, our results do not support the extrapolated gas-phase value for this coupling constant. A new experimentally derived 1J(H 13C) for a vibrating benzene molecule at 300 K is proposed. Full article
417 KiB  
Article
Experimental Determination of Pseudorotation Potentials for Disubstituted Cyclopentanes Based on Spin–Spin Coupling Constants
by Sergei V. Zubkov and Vyacheslav A. Chertkov
Int. J. Mol. Sci. 2003, 4(3), 107-118; https://doi.org/10.3390/i4030107 - 25 Feb 2003
Cited by 14 | Viewed by 8069
Abstract
Complete analysis of 1H-NMR spectra of trans-1,2-dichlorocyclopentane and trans-1,2-dibromocyclopentane was performed with use of our total lineshape fitting algorithm VALISA. The resulting high precision spin-spin coupling constants were then applied to the problem of conformational analysis, yielding a continuos potential of pseudorotation [...] Read more.
Complete analysis of 1H-NMR spectra of trans-1,2-dichlorocyclopentane and trans-1,2-dibromocyclopentane was performed with use of our total lineshape fitting algorithm VALISA. The resulting high precision spin-spin coupling constants were then applied to the problem of conformational analysis, yielding a continuos potential of pseudorotation for the studied compounds in CDCl3, CCl4, and CD3CN solutions. Full article
Show Figures

Figure 1

202 KiB  
Article
Solvent Effects on Nuclear Magnetic Resonance 2J(C,Hf) and 1J(C,Hf) Spin–Spin Coupling Constants in Acetaldehyde
by Daniel Zaccari, Verónica Barone, Juan E. Peralta, Rubén H. Contreras, Oscar E. Taurian, Ernesto Díez and Angel Esteban
Int. J. Mol. Sci. 2003, 4(3), 93-106; https://doi.org/10.3390/i4030093 - 25 Feb 2003
Cited by 21 | Viewed by 12921
Abstract
The known solvent dependence of 1J(Cc,Hf) and 2J(C1,Hf) couplings in acetaldehyde is studied from a theoretical viewpoint based on the density functional theory approach where the dielectric solvent effect is taken into account [...] Read more.
The known solvent dependence of 1J(Cc,Hf) and 2J(C1,Hf) couplings in acetaldehyde is studied from a theoretical viewpoint based on the density functional theory approach where the dielectric solvent effect is taken into account with the polarizable continuum model. The four terms of scalar couplings, Fermi contact, paramagnetic spin orbital, diamagnetic spin orbital and spin dipolar, are calculated but the solvent effect analysis is restricted to the first term since for both couplings it is by far the dominant contribution. Experimental trends of Δ1J(Cc,Hf) and Δ2J(C1,Hf) Vs ε (the solvent dielectric constant) are correctly reproduced although they are somewhat underestimated. Specific interactions between solute and solvent molecules are studied for dimethylsulfoxide, DMSO, solutions considering two different one-to-one molecular complexes between acetaldehyde and DMSO. They are determined by interactions of type C=O---H---C and S=O---H---C, and the effects of such interactions on 1J(Cc,Hf) and 2J(C1,Hf) couplings are analyzed. Even though only in a semiquantitative way, it is shown that the effect of such interactions on the solvent effects, of Δ1J(Cc,Hf) and Δ2J(C1,Hf), tend to improve the agreement between calculated and experimental values. These results seem to indicate that a continuum dielectric model has not enough flexibility for describing quantitatively solvent effects on spin-spin couplings. Apparently, even for relatively weak hydrogen bonding, the contribution from “direct” interactions is of the same order of magnitude as the “dielectric” effect. Full article
Show Figures

Figure 1

213 KiB  
Article
Review on DFT and ab initio Calculations of Scalar Coupling Constants
by Ibon Alkorta and José Elguero
Int. J. Mol. Sci. 2003, 4(3), 64-92; https://doi.org/10.3390/i4030064 - 25 Feb 2003
Cited by 74 | Viewed by 13191
Abstract
The present review summarizes the information available on the ab initio calculations of spin-spin nuclear coupling constants through hydrogen bonds or in van der Waals complexes. It also reports the sources of experimental data on nhJXY scalar couplings. Full article
Show Figures

Figure 1

16 KiB  
Editorial
Special Issue on Nuclear Magnetic Resonance Spin–Spin Coupling Constants — Calculations and Measurements
by Stephan P. A. Sauer
Int. J. Mol. Sci. 2003, 4(3), 62-63; https://doi.org/10.3390/i4030062 - 25 Feb 2003
Cited by 1 | Viewed by 5002
Abstract
The importance of nuclear magnetic resonance (NMR) spectroscopy for the determination of three dimensional structures of even biomolecules has again been emphasized by last years Nobel prize.[...] Full article
Previous Issue
Next Issue
Back to TopTop