Journal of Physical Chemistry B, Vol.108, No.50, 19228-19232, 2004
Isolation and characterization of C60F38 center dot loss of aromaticity on F-2 addition to C60F36
From the product of fluorination of [60]fullerene with a mixture of MnF3 and K2NiF6 at 485 degreesC we have isolated two isomers of C60F38. Both elute more rapidly than the isomers of C60F36 and are obtained in lower yields. The amount of the less rapidly eluting isomer was sufficient for F-19 NMR characterization, which gave a 38 line spectrum showing the isomer to have C-1 symmetry. The structure has been identified from detailed analysis of the spectrum, and it is found to be one of the isomers predicted (DFT) to have the lowest heat of formation. This isomer and the other low energy alternatives are formed by F-2 addition to one of the isolated double bonds of C60F36, accompanied by tautomerism of one of the benzenoid rings. The consequent loss of aromaticity may account for the low yield relative to that of C60F36. The compound is not on the pathway to the formation of C60F48, providing further information that rearrangement occurs during stepwise addition from C60F2, to C60F48. Calculations of dipoles of the feasible structures indicate the features that create dipole differences.