New molecules allowing long-range electron transfer and switching processes are described. The electron transfer is experimentally probed by measurement of the so-called "intervalence transition" which occurs in mixed valence binuclear coordination complexes of the general type M-L-M (M = metal site, L = bridging ligand). This allows the determination of the effective coupling parameter between metal sites. For molecular switching, we consider systems in which the bridging ligand L can be modified by an external perturbation. Several examples are presented : control by photonic perturbation with the Twisted Internal Charge Transfer (TICT) effect, control by H+ ion through a pH induced redox reaction, and control by reversible alkaline ion complexation. The final goal is to use these molecules as bridges in ultrasmall metallic structures.