Methylaminated potassium fulleride, (CH₃NH₂)K ₃C₆₀: Towards hyperexpanded fulleride lattices

Co-intercalation of methylamine molecules into the cubic K₃C₆₀ lattice affords the fulleride (CH₃NH₂)K₃C₆₀, which was characterized by Raman and MAS ¹³C and ¹H NMR spectroscopy. The high-resolution synchrotron X-ray powder diffraction technique was employed to determine its crystal structure at ambient temperature. We find that CH₃NH₂ bonds to K+ ions residing in the pseudo-octahedral interstices, thereby providing an efficient and facile route to hyperexpanded close-packed strongly anisotropic fulleride lattices, while retaining the electronic contact between the C₆₀^3- anions. Preliminary evidence for the occurrence of a transition to an antiferromagnetic state at low temperature is also presented, consistent with the proximity of the present system to the metal-insulator boundary of the electronic phase diagram of C₆₀^3- fullerides.