The aim of this proposal is the study of the dynamics of electron transfer. This process is ubiquitous in biological (photosynthetic reaction, respiratory chain), physical (conductor materials ) and chemical systems. Initially, we will interest in gas phase electron transfer systems but the longer term target is to model the electron transfer in solid state. The hybrid MM.VB (Molecular Mechanics - Valence Bond) method that allows for non-adiabatic dynamics simulations on large systems, will be extend to the electron transfer processes. The methodological developments involve the derivation of the VB model and new parameterizations based on CASSCF computations. This will be followed by "on the fly dynamics" simulations on molecular systems of experimental and theoretical Interest. A large amount of data is available for several radical ions. Some of them can be viewed as simple models for solid state electron transfers (recently the MM- YB type approach has been extended to the solid state).The goal of the project is to establish new methodology that can be used to model electron transfer processes. In a future work, the method could be used in a different framework where the MM part will be replaced by a force field of biological relevance.