EPR spectroscopy of radical pairs formed by the reaction of triplet dibenzocycloheptadienylidene and fluorenylidene with organic matrices at 77 K

Triplet dibenzocycloheptadienylidene (3DBC) and triplet fluorenylidene (3Fl) abstract hydrogen atoms from organic solvent matrices (MH) at 77 K to form triplet radical pairs (3RP): (Chemical Equation Presented) The radical pairs can be detected by EPR spectroscopy and are formed by both thermal and secondary photochemical reactions of the carbenes. The spectral assignments are supported by kinetic evidence as the rate of disappearance of the 3DBC spectrum is comparable to the growth of the signals attributed to the 3RP. There is also a substantial kinetic isotope effect observed upon deuteriation of the solvent matrix. The data suggest that there is a change in mechanism for carbene decay between organic matrices and their deuteriated modifications. © 1987 American Chemical Society.

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