Identification of a remarkably long-lived azoalkane triplet state

Optically Active Epoxy Diols by Titanium-Catalyzed Oxidation of Enantiomerically Enriched Hydroperoxy and Hydroxy Homoallylic Alcohols

“…By photooxygenation of the alcohols 1, the hydroperoxy alcohols 2 were conveniently obtained (Scheme 2). As already described in the literature [7] , in this reaction the (Z)allylic alcohols 1 afford the (S*,S*)-hydroperoxy alcohols 2 as the main diastereomer in a high threo selectivity (d.r. Ն 92 : 8), whereas the (E)-allylic alcohols 1 react totally unselectively.…”

Triplet Energy and Lifetime of 2,3-Diazabicyclo[2.2.2]oct-1-ene

“…In summary, the triplet state of azoalkanes has until recently been highly elusive. With the recent observation [16][17][18] of phosphorescence from rigid DBH analogs, 2, and the present PAC studies, these species are now better characterized. Interesting questions remain nevertheless, such as the decay mode of flexible azoalkane triplets and the nature of the decomposing state, 3 Q.…”

“…On the basis of the present results, this conclusion appears to be erroneous. Recently, Adam and co-workers found that 2 intersystem crosses to a directly observable triplet whose lifetime is 0.65 μs . The contrast between 2 and other DBH's is striking; , for example, 3 does not intersystem cross to any appreciable extent, as judged from product ratios …”

Transient Spectroscopy of a Derivative of 2,2-Difluoro-1,3-diphenylcyclopentane-1,3-diylA Persistent Localized Singlet 1,3-Diradical

“…Unlike the related 2,2-dimethyl-substituted azoalkanes, which afford the corresponding housanes on irradiation, the preparative photolysis of azoalkane 3 in benzene, n -pentane, methylene chloride, or acetonitrile at ambient temperature led to cyclopentene 7 . However, at low temperatures in a 1:3 mixture of n -pentane and isopentane, signals for not only 7 but also housane 5 were observed by 19 F (565 MHz) NMR spectroscopy .…”