4-Amino-TEMPO center dot is attached to a self-assembled monolayers of HS(CH2)(10)COOH on gold electrodes and the kinetics of the TEMPO center dot/TEMPO+ redox couple are measured over a wide range of scan rates in 1 M H2SO4. Analysis of the rate constants yields the standard rate constant (1.2 s(-1)) and the reorganization energies for TEMPO center dot (1.5 eV) and TEMPO+ (1.3 eV). These values are the first experimental measurements of reorganization energies of TEMPO center dot in aqueous solution. 2007 Elsevier B.V. All rights reserved.