HIGH-FIELD NUCLEAR-MAGNETIC-RESONANCE OF THALLIUM IN ZEOLITES

Thallium-205 NMR is reported for several zeolite samples (A, X and Y; hydrated and dehydrated) with thallium(I) exchanged for sodium. Detect ion at high field (7.05 T) clarifies the spectrum appearance, and it i s seen that chemical shift anisotropy (CSA) dominates some of the band shapes. The large CSAs dictate that the spectrum is recorded piecewis e by a frequency-stepped spin-echo integral (FUSSI) method. Magic-angl e sample spinning has been observed to give only a very minor line-nar rowing effect. Threefold-coordinated zeolite A Tl+ sites adjacent to s ix-membered rings [Tl(1) and Tl(3)] are both assigned to a resonance w hich has large CSA (delta(iso) 1183, DELTAdelta -1842), while the rema ining zeolite A site [Tl(2)] gives an isotropic line shape (delta(iso) 300). Dehydrated zeolite X gives an isotropic peak (delta(iso) 854) w hich is assigned to the double six-ring Tl(I), and a broader anisotrop ic resonance which is tentatively attributed to supercage TI(III). Dat a for dehydrated zeolite Y indicate that this has a disordered cation distribution.