Cross-Fullerene Dimers [(C ₆₀ )(C ₇₀ )]: Solid-State Synthesis, Characterization and Mechanism

Abstract

Two isomers of the cross-fullerene dimer, i.e., [(C₆₀)(C₇₀)], were synthesized in the solid state, isolated by recycling high performance liquid chromatography and characterized by mass spectrometry and UV/Vis absorption spectroscopy. The observed inability to produce a similarly dimerized endohedral metallofullerene, (La@C₈₂)₂, strongly suggests the dimerization mechanism of a nucleophilic addition from the additive material to the carbon cage and at the final step of an intramolecular S_N2’ reaction that connects the two fullerene cages.

Key words

fullerene - dimerization - solid-phase synthesis - endohedral metallofullerene - reaction mechanism

References

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12

Forman, G. S.; Tagmatarchis, N.; Shinohara, H. J. Am. Chem. Soc. 2002, in press.

18

Interestingly, in a recent publication on the cross-dimerization between [60]- and [70]fullerene, (cf. ref. [6] ) the isolation of only a single isomer of [(C₆₀)(C₇₀)] was reported.

19

The two isomers of [(C₆₀)(C₇₀)] were numbered with respect to their retention times on a 5PYE column (i.e. see Figure [1] ).

23

After grinding the materials in the solid state the reaction mixture was dissolved in a mixture of toluene/o-dichlorobenzene and analyzed by high performance liquid chromatography (5PYE column, toleuene eluent, 15mL/min flow rate). A single peak was observed at a retention time of 27 min that was identified as La@C₈₂ (I) by both mass spectrometry and electron paramagnetic resonance.