Reduction of Diazonium Cation

The C-C bond formed through this process is very stable compared to say a gold-thiol bond. It can resist temperatures up to 700 K without being lost from the surface [42] and is stable in a wide potential window. A further advantage over other common surface modification techniques (e.g., self-assembly of silane monolayers on oxide) is that the process is quite fast, deposition times are usually on the order of 10 s. In contrast to the enhanced stability, formation of these layers on electrode surfaces is less controlled than for the alkanethiol system. In addition, not all the radicals generated participate in the formation of C-C bonds. It varies based on the surface condition and the substituent in the para position of 

Recently, it has also been shown that a monolayer from aryldiazonium can also be formed by attaching sUyl groups at the para position of aryldiazonium [52], which function as a barrier for the already attached aromatic groups against the attack of aryl radicals, that is, sUyl groups prevent the formation of multilayers. Aryldiazonium is functionalized with the sUyl group before electrochemical 

From multilayer to monolayer using radical scavenger 

Aryldiazonium chemistry for modifying the surface has also been utilized to prepare mixed layers of two components [21, 55]. Importantly, the ratio of the two components on the surface is dominated by the reduction potentials of the two aryl diazonium salts as distinct from their ratio in solution [8, 19, 56]. 

Considering the good stability of aryldiazonium salts, this process of modification has recently been applied to fabricate molecular junctions in molecular 

---

Fischer indole disconnection of (48) requires keto acid (49) and a substituted hydrazine (50). Keto acid (49) is a standard 1,4-dicarbonyl problem (Chapter 25). Phenylhydrazines such as (59) are made by reduction of diazonium cations derived from aromatic amines (51). 

ShuL G., C. A. Castro Ruiz, D. Rochefort, P. A. Brooksby, D. Belanger. Electrochemical functionalization of glassy carbon electrode by reduction of diazonium cations in protic ionic liquid. Electrochim. Acta 106, 2013 378-385. 

---