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

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.