Phenoxyl radicals were synthesized having heterocyclic substituents in the 4-position. Electron spin resonance spectroscopy shows spin density can be modulated by delocalization onto the heterocycle structure, to the extent that some of the largest spin density bearing sites in 3 and 4 lies in the heterocycle, not in the phenoxyl ring.
The title diradical was synthesized and investigated by ESR and UV−vis spectroscopy. It was found
to have a lifetime of weeks even in the presence of oxygen, and even survives brief heating in
toluene up to about 60 °C. In the UV−vis spectrum, the diradical showed reversible thermochromic
behavior in the −10 to 50 °C range. In the ESR spectrum, hyperfine analysis showed nearly isolated
behavior by the phenoxyl and nitroxide spin carrying units. Upon warming, additional, broad lines
appeared at the expense of the lower temperature lines. This temperature behavior was reversible
over the 0 to 50 °C range, so long as the raised temperatures were not maintained for long time
periods. The spectral behavior is interpreted as being due to temperature-dependent conformational
effects on the exchange coupling between the spin carrying units, i.e., J-modulated exchange
behavior.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.