STEREOCHEMICAL PATTERNS IN BROMOFULLERENES C60BR2 TO C60BR12

The stabilities of different isomers of C60Brn have been calculated for n = 2 to 12. A general stereochemical pattern which emerges is the tendency to form strings created by the edge sharing of C6Br2 hexagonal faces. Stable structures are formed if these strings form loops, thereby eliminating string ends, which may involve the creation of C6Br3 hexagonal faces. A particularly stable structure is formed at C60Br6 in which the loop forms a C10Br6 fragment with a pentagonal pyramidal arrangement of six bromine atoms. Two isomers of C60Br12 are also particularly stable. One isomer contains two of these Br-6 pentagonal pyramids on opposite sides of the molecule, and the ether isomer contains a single large loop wrapped around the middle of the molecule.