Perfluoroacetylmethylmethylene and Its Quintet Radical Pair: Isolation and ESR Detection

Article abstract of DOI:10.1021/ja00411a027

Perfluoroacetylmethylmethylene (1) was produced by the photolysis of 3-diazohexafluoro-2-butanone at T<30 K.Two triplet ESR spectra were observed with relative intensities of ca. 9:1 and assigned to the cis and trans geometrical conformers of 1, respectively.These triplets are most likely the ground electronic state of 1.The relative yields of the conformers appear to be governed by the geometry of the source compound. cis-1 is kinetically more stable than trans-1 and decays at a higher temperature featuring first-order kinetics with E_a=5.0 kcal/mol, probably corresponding to triplet--->singlet intersystem crossing prior to or concertedly with a Wolff rearrangement to the ketone structure.An additional weak ESR spectrum attributed to a quintet state radical pair arising from the interaction of two triplet 1 was also observed.