Next Issue
Volume 4, May
Previous Issue
Volume 4, March
ijms-logo

Journal Browser

Journal Browser

Int. J. Mol. Sci., Volume 4, Issue 4 (April 2003) – 5 articles , Pages 158-248

  • 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 Readerexternal link to open them.
Order results
Result details
Select all
Export citation of selected articles as:
Article
The Effect of Substituents on Indirect Nuclear Spin-Spin Coupling Constants: Methan- and Ethanimine, Methanal- and Ethanaloxime
Int. J. Mol. Sci. 2003, 4(4), 231-248; https://0-doi-org.brum.beds.ac.uk/10.3390/i4040231 - 04 Apr 2003
Cited by 26 | Viewed by 8304
Abstract
Ab initio calculations of the spin-spin coupling constants have been carried out for methan- and ethanimine, methanal- and ethanaloxime at the level of the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes (SOPPA(CCSD)) using the aug-cc-pVTZ-J basis sets. Previously [...] Read more.
Ab initio calculations of the spin-spin coupling constants have been carried out for methan- and ethanimine, methanal- and ethanaloxime at the level of the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes (SOPPA(CCSD)) using the aug-cc-pVTZ-J basis sets. Previously we have shown that this method can reproduce quantitatively the coupling constants for methanimine; our new results for methanal- and ethanaloxime agree also very well with the measured couplings. A study of both purely geometrical and substituent effects on all coupling constants in the title compounds is presented. Analyzing the four contributions to the coupling constants we find that the stereoelectronic effect of the nitrogen lone pair on the one-bond C-H and C-C couplings as well as the corresponding effect for the geminal N-H and N-C couplings is affected strongly by the -OH substituent. For the one-bond C-N couplings we observe that the orbital paramagnetic (OP) contribution is comparable to the Fermi Contact (FC) contribution but opposite in sign and that the spin-dipolar (SD) term amounts to between 40% and 85% of the total coupling constants. Changes in the total one-bond C-N couplings caused by the -OH substituent are also almost entirely due to SD contribution. Full article
Show Figures

Figure 1

Article
Electric Field Effects on 2JHH Spin-Spin Coupling Constants
Int. J. Mol. Sci. 2003, 4(4), 218-230; https://0-doi-org.brum.beds.ac.uk/10.3390/i4040218 - 04 Apr 2003
Cited by 9 | Viewed by 6363
Abstract
Some calculations of the electric field derivative of the spin-spin coupling constant on molecules in the series CH3F, CH3Cl, CH3Br, CH3I, CH4, CH3Li, CH3Na and CH3K have [...] Read more.
Some calculations of the electric field derivative of the spin-spin coupling constant on molecules in the series CH3F, CH3Cl, CH3Br, CH3I, CH4, CH3Li, CH3Na and CH3K have been presented. The data is broken down into the 4 terms of the Ramsey theory: Fermi contact (FC); diamagnetic spin-orbit (DSO); paramagnetic spinorbit (PSO) and spin-dipolar (SD). The FC term is seen to dominate all the calculated Js and their derivatives presented here. The situation where the FC term does not dominate in other molecules is discussed as a contrast. Full article
Article
Electronic Mechanisms of Intra and Intermolecular J Couplings in Systems with C-H···O Interactions
Int. J. Mol. Sci. 2003, 4(4), 203-217; https://0-doi-org.brum.beds.ac.uk/10.3390/i4040203 - 04 Apr 2003
Cited by 13 | Viewed by 9331
Abstract
Correlation effects on the change of 1J(CH) couplings in model systems I:NCH...H2O and II:CH4...H2O as a function of the H...O distance are discussed. RPA and SOPPA results follow a similar trend in system II. In system [...] Read more.
Correlation effects on the change of 1J(CH) couplings in model systems I:NCH...H2O and II:CH4...H2O as a function of the H...O distance are discussed. RPA and SOPPA results follow a similar trend in system II. In system I RPA values decrease monotonously as the H...O distance decreases, while SOPPA ones exhibit flat maximum near equilibrium. Such different behavior is ascribed to the π-transmitted component. Intermolecular couplings at the equilibrium geometry of I are analyzed by means of the CLOPPA approach. The larger absolute value of 2hJ(CO) compared to 1hJ(HO) is found to arise from contributions involving a vacant LMO localized in the C-H...O moiety. Full article
Show Figures

Figure 1

Article
Through-Space Spin-Spin Coupling In Acetylenic Systems. Ab Initio and DFT Calculations
Int. J. Mol. Sci. 2003, 4(4), 193-202; https://0-doi-org.brum.beds.ac.uk/10.3390/i4040193 - 04 Apr 2003
Cited by 7 | Viewed by 7011 Show Figures

Figure 1

Article
Extension of the Karplus Relationship for NMR Spin-Spin Coupling Constants to Nonplanar Ring Systems: Pseudorotation of Tetrahydrofuran
Int. J. Mol. Sci. 2003, 4(4), 158-192; https://0-doi-org.brum.beds.ac.uk/10.3390/i4040158 - 04 Apr 2003
Cited by 48 | Viewed by 6466 Show Figures

Figure 1

Previous Issue
Next Issue
Back to TopTop