Azafullerene C59N, a stable free radical substituent in crystalline C60

Solid solutions of C59N azafullerene in C60 with concentrations of 10−5 to 10−4 were produced in large quantities in an electric gas discharge tube. C59N is a stable monomeric substituent molecule in crystalline C60. The isotropic 14N and 13C hyperfine coupling constants measured by electron spin resonance (ESR) are characteristic of the extent of delocalization of the charge over the cage and are a sensitive test of electronic structure calculations. The C59N reorientational activation energy measured below the face centered cubic (fcc) to simple cubic (sc) transition is 2300 K. This value is similar to that of the matrix C60 molecules, indicating that C59N–C60 intermolecular interactions are weak.