Gas-phase radicals in co-condensed adamantane matrix: proton splitting in the esr spectrum of the cycloheptatrienylperoxyl radical

Abstract The cycloheptatrienyl (tropenyl) radical was generated by the gas-phase pyrolysis of ditropenyl at 473–723 K and was trapped in cocondensed adamantane at 77 K. Well-resolved isotrppic ESR spectra of the tropenyl radical showed a linear temperature dependence of a iso in the range 77–226 K. The tropenylperoxyl radical was obtained if the ditropenyl pyrolysis was carried out in the presence of dioxygen. The anisotropic ESR spectrum of the tropenylperoxyl radical obtained in the adamantane matrix at 77 K was characterized by g 1 = 2.035, g 2 = 2.009, g 3 = 2.002 and a 1 = 8.4 G,† a 2 = 9.6 G and a 3 = 5.35 G. The values of g iso and a iso were found experimentally in the freely rotating radical at 130 K to be g = 2.0157 and a = 7.5 G respectively. The hyperfine coupling arises from coupling to the β-H atom via a hyperconjugative mechanism.