The anisotropic properties of liquid crystals (LC) are the key factor in reducing photoinduced intramolecular electron transfer (IET) rates in donor-spacer-acceptor systems. A rate reduction by 3-4 orders of magnitude in LCs, as compared to normal isotropic liquids, enables to apply submicrosecond EPR spectroscopy to these reactions. We attribute this remarkable effect to the existence of a potential barrier, known as the nematic potential, which characterizes the anisotropic nature of the nematic LC. This nematic potential slows the rotational correlation time of,the liquid crystalline solvent molecule dipoles. Since IET is coupled to the solvent motion, slowing the rotational correlation time reduces the IET rate. Moreover, in all cases examined, the solvent (LC) dynamics control the IET rate over the entire nematic phase, thus suggesting that the reaction dynamics is brought into the solvent-controlled adiabatic limit.