On the assignment of 19F MAS NMR spectra of fluoroaluminates using through-space spectral edition of 19F–27Al and 19F–19F connectivities

Charlotte Martineau (1, 2, 3) , Christophe Legein (1, 2, 3) , Jean-Yves Buzaré (1, 3, 4) , Franck Fayon (1, 5)

1 FRMN-SHC - Fédération RMN du Solide à Hauts Champs
2 LdOF - Laboratoire des oxydes et fluorures
3 IRIMMFUM - Institut de recherche en ingénierie moléculaire et matériaux fonctionnels de l'université du Maine
4 LPEC - Laboratoire de physique de l'état condensé
5 CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation

Advantages and limitations of 19F–27Al and 19F–19F dipolar-based 2D NMR experiments for 19F MAS spectra assignments of fluoroaluminates are presented. In beta-BaAlF5, combination of 2D MAS 19F–27Al CP-HETCOR and 19F–19F DQ-SQ NMR correlation experiments allows complete unambiguous assignment of the ten poorly resolved resonances of same relative intensities of the 19F MAS NMR spectrum. The gain in resolution of the 19F MAS 2D spectrum compared to a 1D spectrum is evidenced, allowing distinction of the two shared-fluorine resonances of Ba3Al2F12. Limitations of the 19F MAS DQ-SQ NMR experiment are shown for Ba3Al2F12 and for alpha-CaAlF5. For beta-BaAlF5 and Ba3Al2F12, final line assignments question those previously established from 19F isotropic chemical shift calculations, which demonstrate that such experiments are essential for correct line assignments and assessment of calculation results.

Domaines: Matériaux

Charlotte Martineau, Christophe Legein, Jean-Yves Buzaré, Franck Fayon. On the assignment of 19F MAS NMR spectra of fluoroaluminates using through-space spectral edition of 19F–27Al and 19F–19F connectivities. Physical Chemistry Chemical Physics, 2009, 11, pp.950-957. ⟨10.1039/b812091a⟩. ⟨hal-00357596⟩