Investigation of free radicals in clathrate hydrates using electron paramagnetic resonance spectroscopy

Gas hydrates (or clathrate hydrates) are well-defined crystalline structures that consist of a host lattice of hydrogen-bonded water molecules partially or fully loaded with guest molecules. Guest molecules are located in the cavities formed by water molecules. In this research, the double hydrates of a thiol and another organic compound were synthesized in a gas handling system constructed in our lab. A UV diode was used to irradiate the sample hydrates mounted in an EPR spectrometer in order to produce isolated hydrogen atoms and other free radicals inside the hydrate cavities. Hydrogen atoms can diffuse freely between cages above the diffusion temperature and react with the organic molecules in other cages to produce organic radicals which can be detected by EPR. In this research, the temperature at which hydrogen radicals can be stabilized inside the cavities is determined. This is important because gas hydrates are being considered as a future storage material for hydrogen molecules.