16O/18O oxygen isotope exchange kinetics in MnO 4 − as probed by 55Mn NMR
- 33 Downloads
The effect of the 16O ↔ 18O substitution in the coordination sphere of permanganate anion MnO 4 − on the chemical shift of 55Mn nuclei have been studied by 17O and 55Mn NMR. Time constants τ n,k of oxygen exchange in the water–permanganate anion system have been estimated. In nearly neutral solutions (pH ≈ 6.8–7.2), the oxygen exchange time is on the order of tens of hours. Bubbling gaseous HCl through this solution for a few seconds leads to the equilibrium distribution of oxygen isotopes in the manganese coordination sphere. The observed temperature dependences of isotope-induced 55Mn NMR shifts in Mn16 O 44-n 18 O n – (n = 0–4) have been treated as a result of rovibrational averaging of Mn–O bond lengths. The change in the Mn—O bond length in caused by the 16O → 18O isotope substitution is on the order of 10–4 Å.
Keywords55Mn and 17O NMR permanganate anion isotope shifts equilibrium constants isotope exchange
Unable to display preview. Download preview PDF.
- 1.K. U. Buckler, A. R. Haase, O. Lutz, M. Muller, and A. Nolle, Z. Naturforsch. A 32, 126 (1977).Google Scholar
- 2.A. R. Haase, O. Lutz, M. Muller, and A. Nolle, Z. Naturforsch. A 31, 1427 (1976).Google Scholar
- 3.O. Lutz, W. Nepple, and A. Nolle, Z. Naturforsch. A 31, 1046 (1976).Google Scholar
- 8.C. J. Jameson and H. J. Osten, Ann. Rep. NMR Spectrosc. 17, 3 (1986).Google Scholar