  Charge transport processes in disordered complex media are accompanied by
anomalously slow relaxation for which usually a broad distribution of
relaxation times is adopted. To account for those properties of the
environment, a standard kinetic approach in description of the system is
addressed either in the framework of continuous-time random walks (CTRW) or
fractional diffusion. In this paper the power of the CTRW approach is
illustrated by use of the probabilistic formalism and limit theorems that allow
to predict the limiting distributions of the paths traversed by charges and to
derive effective relaxation properties of the entire system of interest.
Application of the method is discussed for non-exponential electron-transfer
processes controlled by dynamics of the surrounding medium.
