Preferential precipitation of C70 over C60 with p-halohomooxacalix[3]arenes.

Preferential precipitation of C70 from a toluene solution of C60 and C70 was accomplished with p-trihalohomooxacalix[3]arenes (1(3).X.X.X) prepared by the reductive coupling of diformylphenols. Heavy halogens, Br and/or I, are essential at the para position of 1(3).X.X.X for obtaining good yields and selectivities. C70 with up to 92% purity was obtained after the preferential precipitation.