Electron Paramagnetic Resonance of Some Sulfur and Selenium Compounds

A number of organic compounds containing sulfur or selenium are known to be useful as antioxidants or radio-protective agents because of their reactivity with free radicals. We have studied the electron paramagnetic resonance (EPR) of some aliphatic and aromatic sulfide and disulfide compounds and their selenium analogs uv-irradiated at λ=2537 Å in order to characterize and compare the free radicals produced. The irradiation and the EPR measurements were carried out at liquid nitrogen temperature. The EPR spectra obtained for these compounds fall into four categories characteristic of the four types of radical species found—alkyl radicals, benzyl-type radicals, sulfur radicals, and selenium radicals. The selenium radical, which has not been previously observed, exhibits an asymmetric spectrum having an axially symmetric g factor, with g⊥=2.08 and g∥=2.12.