Harnessing entropy to heal polymers

Peroxyl radicals have a key role in the degradation of volatile organics in the atmosphere, as well as the oxidation of cellular lipids and other integral biomolecules. The excited electronic (B) state of alkylperoxyl radicals is dissociative and lies reliably in the ultraviolet region. Arylperoxyl radicals, on the other hand, are predicted to have a dissociative state accessible within the visible spectrum. To date, however, there have been no resolved room-temperature spectra of these species or any characterisation of the photoproducts of the B state of an arylperoxyl. The research groups led by Dr Adam Trevitt and Professor Stephen Blanksby at the University of Wollongong have now reported the controlled synthesis and isolation in vacuo of charge-tagged phenylperoxyl radicals that were then subjected to photodissociation action spectroscopy (Maccarone A.T., Kirk B.B., Hansen C.S., Griffiths T.M., Olsen S., Trevitt A.J., Blanksby S.J. J. Am. Chem. Soc. 2013, 135, 9010−14). Using their approach, the authors observed a broad absorbance feature centred firmly in the visible spectrum with the photoproducts clearly identified as resulting from losses of molecular and atomic oxygen. These findings suggest that the photo-activation of arylperoxyl radicals in the troposphere, which yields atomic oxygen, could feed into the production of tropospheric ozone independently of the well-known NOx cycle. Lights, peroxyls, action spectroscopy!