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| Titel: |
Spin relaxation and magnetic shielding of 93Nb nuclei in [NbClnBr6-n]- anions |
| Auteur: |
Tarasov, V. P. Privalov, V. I. Buslaev, Yu.A. |
| Verschenen in: |
Molecular physics |
| Paginering: | Jaargang 35 (1978) nr. 4 pagina's 1047-1055 |
| Jaar: |
1978-04 |
| Inhoud: |
The temperature dependence of T1 and T2 relaxation times of 93Nb nuclei in octahedral [NbClnBr6-n]-(n = 0 to 6) complexes contained in acetonitrile solution is measured. The relaxation rate is found to be controlled by quadrupole interactions in all complexes except cis-[NbCl3Br3]-. The relaxation mechanism in cis-[NbCl3Br3]- anion depends on exchange processes associated with intramolecular cis⇆trans isomerization. Calculated values of the electric field gradient (EFG) tensor invariant gφ2 agree qualitatively with experimental values of T1,2-1. For cis-[NbCl3Br3]- gφ2 = 0. On the basis of data for T1 and T2 the assignment of resonant signals to isomers has been established. The relative chemical shift of cis and trans isomers does not correspond to that evaluated by using a pairwise additivity model. The variations of diamagnetic Δσd and paramagnetic Δσp contributions to the shielding constant of 93Nb nuclei with the composition of coordination sphere are calculated. Δσp contribution to the chemical shifts in the [NbClnBr6-n]- is shown to be about 70 per cent. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 16 van 20 gevonden artikelen
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