ESR studies on the interaction of calixarenes and free radicals

Electron spin resonance (ESR) measurements reveal that p-t-butylcalix[4]arene interacted with the radical generated by self-trapping of 2-methyl-2-nitrosopropane (MNP) as judged from the change in hyperfine coupling constants. The interaction can be ascribed to the inclusion of the radical in the calixarene, and the inclusion form is proposed. The further research indicates that the inclusion played a marked role in stabilizing short lifetime radicals, and obviously improved the efficiency of a spin trap, such as nitrosodurene (ND), in trapping the radicals.