Cryogenic matrix isolation synthesis

Similarly, the design of macroscale vapor synthesis reactions in liquids can benefit from adaptations of the techniques of cryogenic matrix isolation for studies in fluids.(33,34) For example, a significant development in the field of VS has been the discovery by Klabunde and co-workers(35) of "solvated" metal atoms for use in the preparation of uni-and bimetallic supported catalysts. It is worth examining the subject of solvated atoms in a little detail to reveal something about them and to introduce the microscale VS technique in thin, quiescent liquid films. 

Figure 7. Conversion of standard cryogenic matrix isolation equipment for use in microscale, liquid phase metal vapor synthesis and spectroscopy. Continued on next page.

Fluorodiazirines have also been used extensively as carbene photoprecursors for cryogenic matrix isolation " and laser flash photolysis studies. Photolysis of fluorophenoxydiazirine has made observation of the corresponding carbene directly observable in yet another fashion encapsulated in a hemicarcer-and. Diazirines have been used for studies in solution of carbene philicities as well as for synthesis of cyclopropanes and cyclopropenes.Of course, diazo compounds can also serve as carbene photoprecursors, but for carbenes such as difluorocarbene, the diazo precursor is either nonexistent or extremely unstable. 

However, there is another approach to low-temperature chemistry that offers much more promise for yielding product materials in useful concentrations and amounts. While in free-radical stabilization one arrests or stops chemical processes by means of a matrix isolation, in synthesis studies the observation of the chemical process becomes now the essence of the experiment. In the former area one might produce carbene (CH2) and trap it for a detailed study by a variety of techniques. Typically, in the latter area the CH2 would be pumped into a cryogenic reactor and one would observe the reactions that might occur and their rates. The kind of experiments that one may do and the nature of the results are best illustrated by looking at several current examples. 

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