After confirming the identity of the species formed in the two diazotization procedures, both dC12TEMPO batches were electrochemically reduced for grafting onto glassy carbon electrodes. Cyclic voltammetry experiments performed in solutions containing either dC12TEMPOtBuONO/BF3 or dC12TEMPONOBF4 (see SI-4 for details), along with optimization studies, guided the synthesis of TEMPOfunctionalized monolayers via chronoamperometry (15 min at -0.4 V). Since dC12TEMPOtBuONO/BF3 partially contains non-electroactive TEMPO-X species, a post-treatment step with lutidine, a base required for the TEMPO retro-disproportionation reaction , was necessary before analyzing the modified surfaces (see SI-5 for details). The functionalized electrodes were then characterized in a CH2Cl2/nBu4NPF6 electrolyte solution (Figure ). The cyclic voltammogram recorded on the surface modified with the compound dC12TEMPOtBuONO/BF3 (red solid line, Figure ) clearly shows a significantly higher intensity compared to the surface modified with dC12TEMPONOBF4 (blue solid line, Figure ). Integration of the voltammetric peak for the red curve yields a surface concentration of 3.0 ± 0.3 × 10 -10 mol.cm -2 , while integration of the blue curve yields a surface concentration of 1.2 ± 0.2 × 10 -10 mol.cm -2 (values averaged over 10 measurements). These results indicate that the amount of species immobilized on the surface depends on the procedure used to convert the aniline derivative (Scheme 1, compound 6) into the diazonium compound dC12TEMPO. This dependence is likely influenced by the redox state of the TEMPO moiety.