Abstract
Both nanosecond and microsecond pulse radiolysis techniques have been used to investigate the formation of the cation and triplet state of NNN'N' tetramethyl- p-phenylenediamine (TMPD) in the radiolysis of organic liquids. In benzene solutions the triplet state of TMPD is mainly formed by energy transfer from the singlet and triplet excited states of benzene. The decay of the triplet TMPD is first order and is accompanied by delayed fluorescence. In cyclohexane and 3-methyl-pentane solutions a mixture of the triplet state and cation of TMPD are formed. The cation is formed by electron transfer from TMPD to the solvent cation, while neutralization of the TMPD cation leads to the triplet state. A significantyield of TMPD cation is formed in ethanol and isopropanol solutions. It is suggested that the cation is derived by electron transfer from TMPD to an oxidizing solvent radical ( G ≈ 1·0). The rate of electron transfer is k = (4·5±0·5) x 10 9 l mol -1 s -1 in ethanol and (5·5±1·5) x 10 9 l mol -1s -1 in isopropanol. In the absence of TMPD the oxidizing radical disappears by first-order kinetics with k = (1·7±0·5) × 10 7 s −1 in ethanol and k = (3·5±0·5) x 10 7 l mol -1 s -1 in isopropanol.
Published Version
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