Controlling the supramolecular assembly of redox active dendrimers at molecular printboards by scanning electrochemical microscopy

Redox-active ferrocenyl (Fc)-functionalized poly(propylenimine) (PPI) dendrimers solubilized in aqueous media by complexation of the Fc end groups with β-cyclodextrin (βCD) were immobilized at monolayers of βCD on glass (“molecular printboards”) via multiple host−guest interactions. The directed immobilization of the third-generation dendrimer−βCD assembly G3-PPI−(Fc)16−(βCD)16 at the printboard was achieved by supramolecular microcontact printing. The redox activity of the patterned dendrimers was mapped by scanning electrochemical microscopy (SECM) in the positive feedback mode using [IrCl6]3- as a mediator. Local oxidation of the Fc−dendrimers by the microelectrode-generated [IrCl6]2- resulted in an effective removal of the Fc−dendrimers from the host surface since the oxidation of Fc to the oxidized form (Fc+) leads to a concomitant loss of affinity for βCD. Thus, SECM provided a way not only to image the surface, but also to control the binding of the Fc-terminated dendrimers at the molecular printboard. Additionally, the electrochemical desorption process could be monitored in time as the dendrimer patterns were gradually erased upon multiple scans