Structures and stabilities of C60(OH)4 and C60(OH)6 fullerenols

The quantum chemical investigation of C-60(OH)(4) and C-60(OH)(6) isomers have been carried out at the MNDO, AMI and PM3 semiempirical molecular orbital levels. The relative energies of these fullerenol isomers have been calculated. For C-60(OH)(4) fullerenol, cis-l isomer obtained exclusively from 1,2-additions to the adjacent 6,6 ring fusions is the lowest energy structure. For C-60(OH)(6), the most energetically preferred structure results from 1,2- and 1,4-addition to a cyclohexatriene in the carbon cage, which places two double bonds into 6,5 ring fusions. This result suggests that the localization of double bonds into 6,5 ring fusion is not necessarily unfavorable. The most likely structures of C-60(SO4)(n) (n = 1-6) were found out, and the most probable structures of fullerenols C-60(OH)(2n) (n = 1-6) synthesized by hydrolysis of these precursors were generated, via reaction mechanism considerations. Since there are many different methods to synthesize fullerenols, the experimentally obtained fullerenols are not expected to be necessarily the most energetically preferred structures, the considerations of the reaction mechanism or kinetic factors should be more important. (C) 2000 Elsevier Science B.V. All rights reserved.