Synthesis and characterization of some fulleride compounds by electrocrystallization of C60

Electrocrystallization of C60 in organic solvents gave some single crystals of fulleride compounds, MXC60(solvent)y (M=PPN, Li, Na, K). The crystal of C60−• anion radical salt of PPN+ (PPN=N[P(C6H5)3]2) belongs to monoclinic system with space group of C2/c. C60 is surrounded by bulky PPN cation and crystal solvent (monochlorobenzene) and has no short C···C contact between neighbouring C60 anion radicals. Crystals of alkali-metal(Li, Na, K) C60 compounds are isomorphic and have hexagonal unit cells. The four-probe d.c. resistivity measurements demonstrated the metallic nature of NaXC60(THF)y(x∼0.4, y-2.2) with the room-temperatur conductivity being 50 Scm−1. Around 170 K the conductivity increased quite rapidly and reached as high as 1000 Scm−1. This metal-metal transition is accompanied with the shortening of the lattice dimensions.