%0 Journal Article %J Journal of Physical Chemistry B %D 2004 %T Diamagnetic clusters of paramagnetic endometallofullerenes: A solid-state MAS NMR study %A Koltover, V. K. %A Logan, J. W. %A Heise, H. %A Bubnov, V. P. %A Estrin, Y. I. %A Kareev, I. E. %A Lodygina, V. P. %A Pines, A. %K complexes %X

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.

%B Journal of Physical Chemistry B %V 108 %P 12450-12455 %8 Aug 19 %@ 1520-6106 %G English %U ://WOS:000223289500027 %N 33 %M WOS:000223289500027 %! Diamagnetic clusters of paramagnetic endometallofullerenes: A solid-state MAS NMR study %R Doi 10.1021/Jp048610z