CONFORMATIONAL DYNAMICS OF TRIRADICAL NITROXIDES AS STUDIED BY EPR

The EPR spectra of a flexible nitroxide triradical are recorded in a l arge temperature range. A detailed analysis of the spectral features i s performed and the spectra are compared with computer simulations. An excellent agreement with the experimental spectra is obtained by usin g a dynamic model based on the conformation interconversion of differe nt molecular structures, characterized by the electron exchange intera ctions between pairs of free radicals. The energy barrier for the inte rconversion process and the temperature variation of the constant for the equilibrium among the conformations have been obtained. The result s show that EPR spectra of nitroxide triradicals spin labelled polymer s could be of valuable use for studying subtle details of molecular dy namics.