A two-dimensional EPR nutation study on excited multiplet states of fullerene linked to a nitroxide radical

Photoexcited states of 3,4-fulleropyrrolidine-2-spiro-4′-[2′,2′,6′,6′- tetramethyl]piperidine-1′-oxyl (1) were studied by the two-dimensional (2D) EPR nutation method in toluene glass. 2D nutation spectra were observed by varying a pulse length of the first microwave pulse in the spin echo experiment. Three kinds of nutation frequencies were obtained from analyses of the 2D spectra and assigned to those of the excited quartet and doublet states on the basis of the fictitious spin-1/2 theory. The obtained EPR parameters such as g-values, hyperfine coupling constants, and zero-field splittings were discussed in terms of the spin Hamiltonian for doublet and quartet states.