From Monolayer to Multilayer: Perylenediimide Diazonium Derivative Acting Either as a Growth Inhibitor or a Growth Enhancer.

Fine control of electrografting kinetics of diazonium salts is of paramount importance, particularly when considering the application of diazoniums for the fabrication of 2D nanomaterials. In this work, we develop controlled grafting of a perylenediimide (PDI) moiety separated with a 12-carbon aliphatic chain from aryldiazonium. The particular design of the diazonium cation synthesized for this study allows for fine tuning of the surface coverage by simple adjustment of the applied potential. Indeed, according to the potential imposed at the working electrode, the PDI moiety can either enhance the charge propagation within the growing layer or consume the diazonium salt in the bulk solution via redox cross-reaction. With this approach, the surface functionalization can be restricted to a monolayer or a multilayer in a robust and elegant manner, obeying Langmuir or first-order kinetics of electrografting, respectively. The experimental observations are supported with in situ spectroelectrochemical investigations aimed to differentiate the reduction of PDI moieties in the deposited layer and the bulk solution. A tentative mechanistic scheme is proposed, and numerical simulations are undertaken to rationalize the data.