First electron spin resonance identification of a nitrogen peroxy radical as intermediate in the photooxidation of 2,2,6,6-tetramethylpiperidine derivatives

ESR evidence has been obtained for the existence of a N-peroxyl radical intermediates in the conversion of 2,2,6,6-tetramethylpiperidinaminyl radical to the corresponding nitroxide. This observation is of interest for the understanding of the mechanism of photostabilization of polyolefines by tetramethylpiperidine derivatives. The species identified is the first example of a novel class of peroxy radicals characterized by the direct binding of the oxygen atom to nitrogen atom; information regarding its structure has been obtained by INDO MO calculations and by 17O ESR spectroscopy.