Experimental and Theoretical Electron Paramagnetic Resonance (EPR) Study on the Temperature-Dependent Structural Changes of Methylsulfanylmethane

Abstract: Methylsulfonylmethane (or dimethyl sulfone), a naturally produced and vitally important organosulfur compound in living organisms, was irradiated with gamma rays, and the produced radicals were investigated using electron paramagnetic resonance spectroscopy at different temperatures. The structure and behavior of the radical changed when the temperatures varied. The hyperfine splitting of the CH₃ group was small, and the ³³S splitting was relatively high between 80 and −50 °C. When the temperature was between −50 and −160 °C, the ³³S splitting became small and the CH₃ splitting was higher. However, the group kept rotating; therefore, only the isotropic splitting values were measured, and the g-values were anisotropic. When the temperature decreased below −180 °C, the CH₃ group stopped rotating, and the hydrogen splitting values became nonequivalent due to an inhomogeneous electron distribution. The observed structures can be explained by referring to both the experimental and theoretically calculated values reported.