Stabilization of Free Radicals and Reactive Molecules in Cavities of the Water Clathrate Lattice

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Abstract
Experimental methods are described for placing free radicals and reactive molecules in cavities of the water clathrate lattice. When located at cavity sites, diffusion and recombination of the active species is markedly reduced up to relatively high temperatures. The experimental procedure begins with the synthesis of water clathrates of H2S, CH3SH, and C2H5SH. Ultraviolet photolysis of CH3SH and C2H5SH produces H atoms which diffuse away leaving the CH3S and C2H5S radicals trapped in the cavities. The H atoms react with other guest molecules to produce additional stabilized radicals and H2. Photolysis of H2S clathrates is more complex, producing probably S2 as the stabilized species. The presence of the active species is monitored by diffuse reflectance spectrophotometry. Temperatures at which stabilization is achieved extend to —20°C and above, thus exceeding the range attainable by other matrix isolation techniques for small reactive molecules.