| C60Mu radicals have been studied by transverse field muon spin resonance (TF-μSR), muon level-crossing spectroscopy (μLCR), and radio-frequency muon spin resonance (RF-μSR). 13C hyperfine coupling constants of the C60Mu radical were measured by μLCR, using a dilute solution of 99% enriched 13C60 in decalin. The signs as well as the magnitudes of the hyperfine constants were determined. The results range from 52.6 MHz to −25.4 MHz and support those calculations which predict an extended distribution of unpaired electron spin density in radical adducts of fullerenes. The muon hyperfine constant (Aμ) in C60Mu had previously been mete only for powder samples of C60. RF-μSR was used to determine the A, in dilute solution. A value of 330.9 ± 0.2 MHz was found, 2.0% larger than for the powder. In TF-μSR, of solution samples, signals arise only from the exohedral muonium adduct, C60Mu. In RF-μSR, two distinct species can be detected using powder C60, encapsulated muonium (Mu@C 60) as well as the exohedral adduct. Mu@C60 is characterized by an Aμ close to the vacuum value, whereas C60Mu has an Aμ value typical of a carbon-centred organic radical.; Four of the five possible isomeric C60Mu radicals have been detected by TF-μSR, in a C70 powder sample at 298 K. Their assignment is based on the results of semi-empirical MNDO calculations. There are significant changes in intensity and lineshape of the signals at low temperature.; A study of the kinetics of fullerenyl radical formation was performed, using dilute solutions of C60 in cyclohexane. By the muonium decay rate method, the rate constant was determined to be diffusion limited, being of the order 1011 M−1s−1 .; Using the first available fullerene derivative, C61H 2, a study of the effect of structure modification on radical formation was performed. Both encapsulated muonium and the exohedral adduct were observed. Derivitization resulted in little change to the internal electronic environment, whereas a broad range of coupling constants for the exohedral adduct was observed due to the number of nonequivalent addition sites.; Muonium addition to pyrene was investigated by both TF-μSR and μLCR Two hydropyrenyl radicals are produced and easily detected while a third is formed in low abundance. Muon and proton hyperfine constants were experimentally died and compared with semi-empirical and ab initio calculations. It was concluded that the radicals are cyclohexadienyl type, with Mu adding only to those carbon atoms which can assume a tetrahedral configuration without distorting the planar carbon skeleton of pyrene.; The first observation of an a-muonium substituted radical resembling the methyl radical is reported. Using TF-μSR, the CHMuSi(CH3) 3 radical was observed, having an Aμ of 187.6(2) MHz. This result is compared to literature values for the proton analogue and the isotope effect is discussed. |
