title: Self-assembled monolayer of organic iodine on a Au surface for attachment of redox-active metal clusters.
abstract: The attachment of a bifunctional iodo-organo-phosphinate compound to gold (Au) surfaces via chemisorption of the iodine atom is described and used to chelate a redox-active metal cluster via the phosphinate group. XPS, AFM, and electrochemical measurements show that (4-iodo-phenyl)phenyl phosphinic acid (IPPA) forms a tightly bound self-assembled monolayer (SAM) on Au surfaces. The surface coverage of an IPPA monolayer on Au was quantified by an electrochemical method and found to be 0.40 +/- 0.03 nmol/cm2, roughly corresponding to 0.4 monolayers. We show that the Au/IPPA SAM, but not the underivatized Au, adsorbs Mn4O4(Ph2PO2)6 from solution by a phosphinate exchange reaction to yield Au/IPPA/Mn4O4(Ph2PO2)5 SAM. The resulting SAM is firmly bound and not removed by sonication, as confirmed by manganese XPS (Mn 2p1/2) and by AFM. Electrochemistry confirms that Mn4O4(Ph2PO2)6 is anchored on the Au/IPPA surface and that redox chemistry can be mediated between the electrode and the surface-attached complex. Mn4O4(Ph2PO2)6 contains the reactive Mn4O46+ cubane core, a redox-active bioinspired catalyst.
authors.affiliation: Department of Chemistry and PRISM, Princeton University, Princeton, NJ 08540, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Yu
authors.forename: Manish
authors.initials: M
authors.lastname: Dubey
authors.forename: Steven L
authors.initials: SL
authors.lastname: Bernasek
authors.forename: G Charles
authors.initials: GC
authors.lastname: Dismukes
mesh_terms: D004563:Electrochemistry; D004566:Electrodes; D006046:Gold / Q000737:chemistry*; D006847:Hydrocarbons, Iodinated / Q000737:chemistry*; D007462:Iodobenzenes; D017895:Manganese Compounds / Q000737:chemistry*; D008567:Membranes, Artificial; D063065:Organophosphonates / Q000737:chemistry*; D010084:Oxidation-Reduction; D010721:Phosphinic Acids / Q000737:chemistry*
chemical_list: C523650:(4-iodo-phenyl)phenyl phosphinic acid; D006847:Hydrocarbons, Iodinated; D007462:Iodobenzenes; D017895:Manganese Compounds; D008567:Membranes, Artificial; D063065:Organophosphonates; D010721:Phosphinic Acids; D006046:Gold