Hyperfine interactions between unpaired electrons and framework atoms in aluminosilicate sodalites containing paramagnetic Na-4(3+) clusters: A Si-29 and Al-27 MAS NMR study

First NMR evidence is presented for hyperfine interactions between unpaired electrons and the framework atoms in alkali-metal doped zeolites by the Al-27 and Si-29 MAS NMR spectra of aluminosilicate sodalites loaded with paramagnetic Na-4(3+) clusters which show up to seven resonances with characteristic down-field shifts caused by Fermi contact interactions between the unpaired electrons of the sodium clusters and the Al and Si atoms of the sodalite framework.