The photoinduced cleavage of aryl pinacols

Davidson, R. S.; Younis, F. A.; Wilson, R.

doi:10.1039/c29690000826

Cited by 8 publications

(1 citation statement)

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“…As the figure shows, H 1,8 are polarized weakly in absorption, H 3,6 weakly in emission, and H 2,7 and H 4,5 strongly in absorption. The radical that must result from such a hydrogen abstraction, the 9-hydroxyanthryl radical, possesses a spin density distribution that is characterized by large and approximately equal hyperfine coupling constants for H 1,8 and H 3,6 , and small ones for H 2,7 and H 4,5 ; from Hückel arguments it follows that the former two must be negative and the latter two positive. This would lead to large polarizations of one phase for H 1,8 and H 3,6 , and smaller polarizations of the opposite phase for H 2,7 and H 4,5 .…”

Section: Resultsmentioning

confidence: 99%

Sensitized Photolysis of Iodonium Salts Studied by CIDNP. Solvent Dependence and Influence of Lipophilic Substituents

1999

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The sensitized photoreactions of diphenyliodonium salt and four of its technically relevant derivatives bearing lipophilic substituents were investigated by pseudo-steady-state and time-resolved CIDNP experiments. Singlet (naphthalene, diphenylanthracene, dimethylanthracene) and triplet (xanthone, thioxanthone, Michler's ketone) sensitizers were used in a variety of solvents (acetonitrile, dimethyl sulfoxide, dimethylformamide, methanol, chloroform, tetrahydrofurane, diethylene glycol dimethyl ether, dioxane, toluene). Under all conditions, the primary step leading to CIDNP was found to be electron transfer from the excited sensitizer *Sens to the onium cation On+. All spin-polarization effects could be explained consistently within the framework of radical pair theory (S−T0-type CIDNP). Pair substitution, i.e., the transformation of the primary radical pairs RP 1 into secondary pairs RP 2 ( where Ph• is the phenyl or an aryl radical) plays a key role for the CIDNP effects and even leads to a field dependence of the polarization phases for the system diphenyliodonium cation/naphthalene in dioxane. Decreasing solvent polarity causes an increase of the rate RP 1 → RP 2. The introduction of a long lipophilic side chain into the onium salt has the same effect, presumably owing to self-solvation.

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Section: Resultsmentioning

confidence: 99%