In this Letter, we report a study of two neutral organic mixed valence (MV) compounds by picosecond time-resolved transient absorption spectroscopy. It is our goal to gain insight into the charge-transfer dynamics of this type of system upon optical excitation and to determine the time scale for back electron transfer. In the non-polar solvents hexane and cyclohexane back electron transfer is unusually slow (146 and 93 ps for the two compounds in hexane). In polar and protic solvents, on the other hand, it seems to be too fast to be detectable by our setup. (c) 2005 Elsevier B.V. All rights reserved.