Diamagnetic clusters of paramagnetic endometallofullerenes: A solid-state MAS NMR study

TitleDiamagnetic clusters of paramagnetic endometallofullerenes: A solid-state MAS NMR study
Publication TypeJournal Article
Year of Publication2004
AuthorsKoltover V.K, Logan J.W, Heise H., Bubnov V.P, Estrin Y.I, Kareev I.E, Lodygina V.P, Pines A
JournalJournal of Physical Chemistry B
Volume108
Issue33
Pagination12450-12455
Date PublishedAug 19
ISBN Number1520-6106
Accession NumberWOS:000223289500027
Keywordscomplexes
Abstract

Solid powder samples of complexes of the endometallofullerenes (EMF) La@C-82 and Y@C-82 with hexamethylphosphoramide (HMPA) were studied by magic-angle spinning (MAS) NMR. We have obtained well-resolved P-31 NMR spectra and C-13 NMR spectra for both La-EMF/HMPA and Y-EMF/HMPA and La-139 spectra for the La-EMF/HMPA. The (31)p measurements on La-EMF/HMPA and Y-EMF/HMPA have revealed considerable chemical shifts of (31)p signals relative to pure HMPA. Two-dimensional exchange P-31 experiments revealed that HMPA molecules at different sites in the EMF/HMPA complex do not change positions at a time scale of up to 1 s. Both EMF samples demonstrate a vast chemical shift range for 31p of the bound HMPA molecules. In addition, the La-EMF/HMPA exhibits the enormous spreading of the chemical shifts for La-139. The experimental results suggest that paramagnetic La@C-82 and Y@C-92 in the solid state form clusters (nanoparticles) in which the exchange coupling of the EMF takes place with quenching of the most electron spins.

URL<Go to ISI>://WOS:000223289500027
DOI10.1021/Jp048610z
Short TitleDiamagnetic clusters of paramagnetic endometallofullerenes: A solid-state MAS NMR study
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