ABSTRACT
This chapter focuses on thiyl radicals associated with transition metal ions some of which are able to stabilize these radicals in biological systems. Of special interest was the reactivity of iron, cobalt, and manganese. Chromium and vanadium toxicity has been found to be related with the generation of thiyl radical intermediates. The chapter examines copper-thiolate reactions in the authors' laboratory. A common feature of ionic sulfur-centered radicals is their intense electronic absorption in the visible wavelength region. Due to this phenomenon pulse radiolysis was extensively used. In general, the measurement of thiyl radicals is monitored by means of electron paramagnetic resonance (EPR) spin trapping. 5,5-Dimethyl-1-pyrroline-N-oxide, the tetramethyl derivative tetramethylpyrroline oxide, and N-t-butyl-α-phenylnitrone are frequently used as spin traps. Direct identification of the various sulfur-centered radicals by EPR is difficult. In the case of the thiyl species the direct detection is possible under special conditions.
