Bw. Clare et Dl. Kepert, STEREOCHEMICAL PATTERNS IN BROMOFULLERENES, C60BR12 TO C60BR24, Journal of molecular structure. Theochem, 358, 1995, pp. 79-94
The stabilities of different isomers of C60Brn have been calculated fo
r n = 14-24. Two types of structure are found to be important. The fir
st type involves the linking of alternating 1,4-C6Br2 rings and 1,3-C6
Br2 rings, forming -Br-BrBr-Br- strings over the molecule. Additional
stability is achieved if the string ends are eliminated by the formati
on of cyclic strings, and particularly stable structures incorporate t
he Br-12 cycle of S-6 symmetry. The strings may branch at 1,3,5-C6Br3,
rings with the formation of polycyclic string structures, culminating
in the rhombicuboctahedral bromine pattern in C60Br24 These patterns
are related to the conformation of the Cg rings, which form shallow bo
ats in 1,4-C6Br2 and chairs in 1,3,5-C6Br3. A second important structu
ral feature is the presence of discrete Br-6 skew pentagonal pyramids,
one in C60BT6, two in C60Br12 and three in C60Br18 These results indi
cate the possibility of forming C60Br12 and C60Br18 under the appropri
ate conditions.