METHOXY AND METHOXIDE ADDUCTS OF FULLERENE-60 - SEMIEMPIRICAL THEORETICAL-STUDIES

Semiempirical molecular orbital calculations utilising the AM1 approxi mation with the MOPAC program have been used to suggest the likely sta ble isomeric structures of the smaller methoxylated adducts of C-60, n amely the anions C-60(OMe)(n)(-), n = 1,3,5,7, and the neutral species C-60(OMe)(n), n = 2,4,6. While the OMe species is expected to behave similarly to the F atom in respect of its electronegativity and electr ophilicity, its greater size and asymmetric geometry influences the ro le of non-bonded interactions in determining the favoured configuratio ns and relative chemical stabilities of the respective isomers of each structure. The 'string' model which describes the localised addition pattern observed in the case of the bromine adducts, C60Br2n, for n va lues up to 12, is also appropriate in describing the stable OMe and OM e(-) adducts of C-60. The five-fold symmetric C-60(OMe)(5)(-) anion is of particular interest as it is revealed as the most stable species, in agreement with its observation as the most abundant species occurri ng in electrospray mass spectra. This suggests that metal salts of til e general type M(+)C(60)L(5)(-) may be isolable under appropriate expe rimental conditions.