Phases for the azafullerides ${\mathrm{Rb}}_x{\mathrm{C}}_{59}\mathrm{N}$

Using in situ Raman spectroscopy and resistance measurements we demonstrate the existence of a whole family of azafulleride ${\mathrm{Rb}}_x{\mathrm{C}}_{59}\mathrm{N}$ phases. Six phases with $x=1,2,3,4,5,6\mathrm{}$ were identified from a detailed spectroscopic study of the intercalation physics and chemistry. Intriguingly, the most stable phases were observed for ${\mathrm{RbC}}_{59}\mathrm{N},$ ${\mathrm{Rb}}_2{\mathrm{C}}_{59}\mathrm{N},$ and ${\mathrm{Rb}}_4{\mathrm{C}}_{59}\mathrm{N}$ whereas minimum resistance was observed for ${\mathrm{Rb}}_3{\mathrm{C}}_{59}\mathrm{N}.$ This supports a strong localization of the extra charge density introduced by the nitrogen substitution for all stable phases. These findings together with the observation that the dimer dissociates before ${\mathrm{RbC}}_{59}\mathrm{N}$ is formed allowed us to get insight into the effects of cage distortion and chemical doping as well as into the electronic properties of fullerene intercalation compounds.