Photochemical electron transfer reactions on a picosecond time scale have been studied in two covalently-linked donor-acceptor systems. The first molecule is a chlorophyll-porphyrin-quinone triad that closely mimics photosynthetic charge separation by undergoing picosecond electron transfer in low temperature glasses to yield a radical ion pair that lives for 2 ms and exhibits spin-polarization. The second molecule is an electron donor-acceptor-donor molecule, consisting of two porphyrin donors rigidly attached to opposite ends of the two-electron acceptor N,N'-diphenyl- 3,4,9,1O-perylenebis(dicarboximide). This molecule acts as a light intensity dependent molecular switch on a picosecond time scale.