A kinetic study of the one electron oxidation of substituted ferrocenes (FcX: X = H, COPh, COMe, CO(2)Et, CONH(2), CH(2)OH, Et, and Me(2)) by a series of N-oxyl radicals (succinimide-N-oxyl radical (SINO), maleimide-N-oxyl radical (MINO), 3-quinazolin-4-one-N-oxyl radical (QONO) and 3-benzotriazin-4-one-N-oxyl radical (BONO)), has been carried out in CH(3)CN. N-oxyl radicals were produced by hydrogen abstraction from the corresponding N-hydroxy derivatives by the cumyloxyl radical. With all systems, the rate constants exhibited a satisfactory fit to the Marcus equation allowing us to determine self-exchange reorganization energy values (lambda(NO)center dot(/NO)-) which have been compared with those previously determined for the PINO/PINO(-) and BTNO/BTNO(-) couples. Even small modification of the structure of the N-oxyl radicals lead to significant variation of the lambda(NO)center dot(/NO)- values. The lambda(NO)center dot(/NO)- values increase in the order BONO