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Using multi frequency electron paramagnetic resonance (EPR) it was possible to determine the inherent fine structure (FS) interaction of nitrogen encapsulated in a C70 cage. Confinement of N@C70 in single wall carbon nanotubes (SWNT) of rather wide diameter does not significantly influence this value. The transition between isotropic molecular tumbling and immobilization was found to occur at about 170 K in both matrices, indicating that the hindrance potential is quite small in both cases.

Since endohedral fullerenes exhibit unique features there is growing demand for their production and purification in high quality and quantity. This work shows how the chromatographic enrichment process can be optimized, for the separation of N@C60 and N@C70 from their respective empty parent compounds.

Well resolved EPR spectra of P@C60 in solution have been recorded, proving that the encased phosphorus atoms are in their quartet spin ground state. The isotropic hyperfine interaction is increased by a factor of 2.5 compared with the values measured for free atoms. An analysis of spin relaxation data reveals that fluctuating zero field splitting (ZFS) interaction induced by collision-induced deformations of the carbon shell constitutes the dominant relaxation mechanism. The variance of the time fluctuating ZFS interaction is about a factor of 10 larger than that observed for N@C60 under identical conditions. Values for the correlation time of the deformation of the fullerene cage range from 5ps to 32 ps in the temperature interval 190-300 K in toluene.

C60 is photochemically reduced in the presence of tetraphenylborate anion to C60 −. The primary products A and B are characterized with narrow EPR lines (< 0.1 mT), and then, consecutively, radical C with a 3 mT wide EPR line is observed, which correlates with the formation of a sediment.

The analysis of the electron spin echo decay function shows an exceptionally good quasi one dimensional behaviour for the electron spin diffusion.

The possibility of applying ENDOR in studies of hyperfine interactions in stable biradicals in liquid solution has been explored. The ENDOR spectra of two phenoxy biradicals are reported. Attempts to record ENDOR of some nitroxide and verdazyl biradicals were unsuccessful. The general structure of biradicals spectra and the relaxation processes which may affect the ENDOR effect are briefly discussed.

The E.S.R. spectrum of the o-dimesitoylbenzene anion-alkali cation radical shows unusually large isotropic alkali hyperfine splitting constants. We report a solution ENDOR study of this radical in which both alkali (85,87Rb) and proton ENDOR spectra were recorded. Both the alkali and proton intensities showed a strong dependence on the metal ion nuclear spin quantum number of the E.S.R. line being saturated. This dependence is attributed to strong flip-flop cross-relaxation induced by modulation of the isotropic alkali hyperfine splitting. The powder E.S.R. spectrum of the complex reveals a small anisotropy of the Rb hyperfine splitting tensor. This indicates a small metal non-s-contribution to the half-filled molecular orbital, which is consistent with the observed relaxation behaviour and the small g shift. The intensity variations in the alkali and proton ENDOR spectra were used to determine the relative signs of all hyperfine splitting constants, and the absolute signs of the hyperfine splitting const...