Evidence for electron charge transfer in the polyvinylpyrrolidone-C60 system as seen from ESR spectra

At ambient temperature the polyvinylpyrrolidone-C60 system shows an ESR signal with g = 2.0003 comparable with a previously reported g value of the C60−1 anion radical. The ESR spectrum taken at 10 K exhibits a typical anisotropic signal, which indicates that the anion radical underwent a static Jahn-Teller distortion. The electron charge transfer from polyvinylpyrrolidone to C60 may account for the observed features.