Fluorescence from samarium(II) iodide and its electron transfer quenching: Dynamics of the reaction of benzyl radicals with Sm(II)

The luminescence from SmI2 in THF can be readily quenched by a variety of electron accepters. In the case of organohalides, the reaction is quite fast; for example, for dichloromethane the rate constant is 2.7 x 10(8) M(-1) s(-1). Electron transfer leads to halide loss and formation of the carbon-centered radical. Ire the case of benzyl chloride, the benzyl radicals produced can be readily detected using laser flash photolysis techniques. This electron-transfer reaction has been used as a source of benzyl radicals in order to determine the rate constant for their reaction with SmI2; the value obtained is (5.3 +/- 1.4) x 10(7) M(-1) s(-1) in THF at room temperature. The effect of HMPA on the spectroscopic properties of SmI2 has also been examined.