The electron self-exchange rates of ZnTPP and its corresponding pi radical cation were determined in three solvents with different electrostatic properties at room temperature by EPR spectroscopy. The radicals were produced electrochemically in a flow system. To analyze the data ENDOR experiments where performed in order to obtain experimental values for the hydrogen hyperfine-splitting. The findings correspond to basic predictions from Marcus theory. (C) 2014 Elsevier B.V. All rights reserved.