Transmission mechanisms of NMR long-range J(13C,19F) scalar couplings in 1-F,4-X-cubanes: a DFT and experimental study
| Autor: | Nicholas J. Head, Ernesto Díez, Rubén H. Contreras, Angel L. Esteban, Ernest W. Della |
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| Rok vydání: | 2006 |
| Předmět: |
Coupling constant
Range (particle radiation) Scalar (mathematics) Biophysics chemistry.chemical_element Condensed Matter Physics Symmetry (physics) Crystallography chemistry Computational chemistry Group (periodic table) Order (group theory) Physical and Theoretical Chemistry Molecular Biology Carbon Natural bond orbital |
| Zdroj: | Molecular Physics. 104:485-492 |
| ISSN: | 1362-3028 0026-8976 |
| DOI: | 10.1080/00268970500276499 |
| Popis: | In order to get insight into transmission mechanisms of the title spin–spin coupling constants, nJ(C, F1) couplings (n = 4, 5) were calculated at the DFT-B3LYP-6-311-G**/EPR-III level, and couplings were measured in 9 members of the series 1-F,4-X-cubanes, where the α atom of the X group is a carbon atom. Hyperconjugative interactions were evaluated within the NBO approach, using the same level of theory as that employed for calculating spin–spin coupling constants. The unusual 4J(C4,F1) spin–spin coupling constants known in 1-F,4-X-cubanes are rationalized in this work as originating mainly due to two factors, namely, (i) the strong σ-hyperconjugative interactions involving as donors the cage C–C bonds; (ii) the particular arrangement of cage bonds not involving either the C1 or the C4 carbon atoms, C i and C j . For linear X substituents, the direction F1–C1··· C4–X is a three-fold symmetry axis and there are six C i –C j equivalent cage bonds, which are involved in (C i –C j )→(C1–F1)* and (C i –C j ... |
| Databáze: | OpenAIRE |
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