Structures and stabilities of C-60(OH)(4) and C-60(OH)(6) fullerenols

The quantum chemical investigation of C-60(OH)(4) and C-60(OH)(6) isomers h ave been carried out at the MNDO, AMI and PM3 semiempirical molecular orbit al levels. The relative energies of these fullerenol isomers have been calc ulated. 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 structu re. For C-60(OH)(6), the most energetically preferred structure results fro m 1,2- and 1,4-addition to a cyclohexatriene in the carbon cage, which plac es two double bonds into 6,5 ring fusions. This result suggests that the lo calization of double bonds into 6,5 ring fusion is not necessarily unfavora ble. The most likely structures of C-60(SO4)(n) (n = 1-6) were found out, a nd the most probable structures of fullerenols C-60(OH)(2n) (n = 1-6) synth esized by hydrolysis of these precursors were generated, via reaction mecha nism considerations. Since there are many different methods to synthesize f ullerenols, 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.