The Chemistry, Kinetics, and Mechanisms of Triplet Carbene Processes in Low-Temperature Glasses and Solids

Abstract

In the early 1960s, Closs and Hutchison at the University of Chicago(1) and Trozzolo and Wasserman(2) at Bell Laboratories demonstrated the utility of matrix isolation EPR spectroscopy in the study of triplet carbenes. Triplet carbenes are, of course, highly reactive intermediates formed upon photolysis of diazo compounds or diazirines. As such, they cannot be isolated and analyzed by conventional methods as can kinetically stable species. By photochemically preparing a carbene in a rigid matrix at low temperature, one hopes to impart a long lifetime (minutes to hours) to the species of interest, thereby enabling its characterization by EPR spectroscopy. These rigid matrices are easily prepared by simply freezing a solution of, for example, a diazo precursor in a suitable solvent to 77 K.