High-Frequency EPR study of spin and molecular dynamics in organic disordered systems

Up today organic paramagnetics are studied by EPR mainly at frequencies not higher then 10 GHz. However, it is difficult to obtain a correct information on the nature and dynamics of paramagnetic centers in the system under study due to low spectral resolution and second-order effects at these EPR wavebands. The sensitivity and informativity of the method was proved to increase considerably at 2-mm waveband EPR. The transition to this registration band allows one to obtain more additional information on various properties of condensed systems, including spin relaxation and dynamics. The present report summarizes the basic aspects of an investigation at 2-mm waveband EPR of paramagnetic centers with different mobility in various solid-state organic systems of lowed dimensionality, triphenylamine fullerene complex and polyaniline as an example. High-frequency EPR technique accompanied by the steady-state spin-packets saturation, spin label and saturation transfer methods was used for determination of all magnetic resonance parameters, both spin relaxation and spin diffusion rates and macromolecular dynamics in the organic disordered systems. The mechanisms of spin motion in the systems are discussed as well.