The voltammetry of trans-stilbene, triphenylethene, and tetraphenylethene has been investigated in DMF/ toluene mixtures containing Bu4NBF4 as a function of the electrolyte concentration, solvent composition and substrate concentration. The voltammetric data show that all three ethenes undergo reduction in two le(-) steps but the separation of the potentials for the two steps depends substantially on the medium as well as the structure of the ethenes. The behavior can be understood in terms of ion pairing phenomena.