The phenoxyl radical 1. of a vitamin E analogue, generated by the reaction of 2,2,5,7,8-pentamethylchroman-6-ol (1H) with 2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DPPH.) or galvinoxyl (G.), was significantly stabilized by the presence of Mg2+. Addition of Mg2+ into a solution of 1. resulted in a red shift of the absorption band of 1. as well as a decrease in the g value of the EPR spectrum of 1., indicating a complex formation between 1. and Mg2+. The complexation between the phenoxyl radical and Mg2+ significantly retards the disproportionation reaction of 1. by electronic repulsion between the metal cation and a generated organic cation (1+), leading to stabilization of the organic radical species. No effect of Mg2+ on the rate of hydrogen atom transfer from 1H to DPPH. or to G. was observed, suggesting that the hydrogen-transfer reaction between 1H and DPPH. or G. proceeds via a one-step hydrogen atom transfer mechanism rather than electron-transfer followed by proton transfer.
|Number of pages||5|
|Journal||Journal of the Chemical Society. Perkin Transactions 2|
|State||Published - 2002|