89003-96-3Relevant academic research and scientific papers
Photocyclization of Aryl Halides. Part 4. 5-(2-Halogenophenyl)-1,3-diphenyl-Δ2-pyrazolines. Predissociation and Electron Transfer between Intramolecular but Separate Chromophores
Grimshaw, James,Silva, A. Prasanna de,
, p. 1679 - 1686 (2007/10/02)
Photoreaction of 5-(2-iodophenyl)-1,3-diphenyl-Δ2-pyrazoline proceeds by simple bond homolysis from the S1deg state to give 1,3,5-triphenylpyrazoline and 2-phenylpyrazolophenanthridine in a ratio which depends on the hydrogen atom donor ability of the hydrocarbon solvent.The quantum yield for decomposition of the iodo-compound depends on the viscosity of the hydrocarbon solvent and on the temperature.The corresponding chloro- and bromo-compounds as well as the 3-iodo- and 4-iodo-phenyl compounds are photostable.Consideration of these facts and the complementary fluorescence data suggest a mechanism of interchromophoric predissociation to an n?* state.However, examples are given where there is a smaller electron donor-acceptor energy gap between the two chromophores so that photoreaction occurs by an electron transfer pathway.
