title: Controlling the supramolecular assembly of redox-active dendrimers at molecular printboards by scanning electrochemical microscopy.
abstract: Redox-active ferrocenyl (Fc)-functionalized poly(propylenimine) (PPI) dendrimers solubilized in aqueous media by complexation of the Fc end groups with beta-cyclodextrin (betaCD) were immobilized at monolayers of betaCD on glass ("molecular printboards") via multiple host-guest interactions. The directed immobilization of the third-generation dendrimer-betaCD assembly G3-PPI-(Fc)16-(betaCD)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 [IrCl(6)](3-) as a mediator. Local oxidation of the Fc-dendrimers by the microelectrode-generated [IrCl(6)](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 betaCD. 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.
authors.affiliation: Laboratories of Supramolecular Chemistry and Technology and Molecular Nanofabrication, MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands.
authors.forename: Christian A
authors.initials: CA
authors.lastname: Nijhuis
authors.forename: Jatin K
authors.initials: JK
authors.lastname: Sinha
authors.forename: Gunther
authors.initials: G
authors.lastname: Wittstock
authors.forename: Jurriaan
authors.initials: J
authors.lastname: Huskens
authors.forename: Bart Jan
authors.initials: BJ
authors.lastname: Ravoo
authors.forename: David N
authors.initials: DN
authors.lastname: Reinhoudt
mesh_terms: D050091:Dendrimers / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011126:Polypropylenes / Q000737:chemistry; D047392:beta-Cyclodextrins / Q000737:chemistry
chemical_list: D050091:Dendrimers; D005296:Ferrous Compounds; D011126:Polypropylenes; D047392:beta-Cyclodextrins; C443641:poly(propyleneimine); C031215:betadex