M. Sarakha et M. Bolte, TRANSFORMATION OF 2,6-DIMETHYLPHENOL PHOTOINDUCED BY EXCITATION OF [CO(NH3)(5)N-3](2+) AT 365 NM, Journal of photochemistry and photobiology. A, Chemistry, 97(1-2), 1996, pp. 87-92
Efficient induced oxidation of 2,6-dimethylphenol (DMP) occurred by ex
citation of azidopentaammine cobalt(III) at 365 nm. The presence of DM
P did not affect significantly the quantum yields. The azide radical N
-3(.), produced on irradiation, efficiently reacted with DMP to yield
phenoxyl radicals. In aerated as well as in deaerated solution, the co
upling of such radicals yielded unequivocally 3,3',5,5'-tetramethyldip
henoquinone as the predominant photoproduct. Trace concentrations of p
ara-para coupling dimer together with polyphenyl ethers were also dete
cted by mass spectrometry. The formation of the substituted diphenoqui
none in the absence of oxygen was attributed to a subsequent oxidative
pathway involving the starting Co(III) complex. No dimethyl-p-benzoqu
inone or dimethylhydroquinone was formed, suggesting that the cobalt i
ons play an important role in the observed reactions.