The design of the TEMPO-functionalized diazonium salt (dC12TEMPO, Scheme 1) was based on previous studies on redox-active perylenediimide- and ferrocene-based layers, formed via the reduction of aryldiazonium salts. These works demonstrated that inserting a long alkyl spacer between the redox-active moiety and the aryldiazonium group offers several key advantages for the resulting organic layer's properties. First, the films produced using this approach are stabilized by covalent bonds formed between the electrode surface and the organic molecules. Then a single molecular layer is formed, mainly due to the inhibition of electron transfer by the initial layer. The generation of reactive radicals is thus suppressed, preventing the reduction of diazonium salts at the functionalized electrode/solution interface and limiting film growth to a single monolayer. Nevertheless, electron transfer remains efficient enough to probe the immobilized redox-active groups. Furthermore, the alkyl chains enhance interactions between neighboring molecules through intermolecular Van der Waals forces.