High-field nuclear magnetic resonance of thallium in zeolites

✍ Scribed by Christopher J. Groombridge; Eric N. Coker; Lovat V. C. Rees

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 776 KB
• Volume: 31
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260311207

✦ Synopsis

Abstract

Thallium‐205 NMR is reported for several zeolite samples (A, X and Y; hydrated and dehydrated) with thallium(I) exchanged for sodium. Detection at high field (7.05 T) clarifies the spectrum appearance, and it is seen that chemical shift anisotropy (CSA) dominates some of the band shapes. The large CSAs dictate that the spectrum is recorded piecewise by a frequency‐stepped spin‐echo integral (FUSSI) method. Magic‐angle sample spinning has been observed to give only a very minor line‐narrowing effect. Threefold‐coordinated zeolite A Tl^+^ sites adjacent to six‐membered rings [Tl(1) and Tl(3)] are both assigned to a resonance which has large CSA (δ~iso~ 1183, δδ—1842), while the remaining zeolite A site [Tl(2)] gives an isotropic line shape (δ~iso~ 300). Dehydrated zeolite X gives an isotropic peak (δ~iso~ 854) which is assigned to the double six‐ring Tl(I), and a broader anisotropic resonance which is tentatively attributed to supercage Tl(III). Data for dehydrated zeolite Y indicate that this has a disordered cation distribution.