title: Zinc Porphyrin Metal-Center Exchange at the Solid-Liquid Interface.
abstract: Demetalation of zinc 5,10,15,20-tetraphenylporphyrin (ZnTPP) under acidic conditions and ion exchange with Cu(2+) ions at neutral pH are both rapid reactions in the liquid medium. However, for ZnTPP monolayers adsorbed on a Au(111) surface exposed to aqueous solution, we find that, although ion exchange takes place rapidly as expected, demetalation does not occur, even at pH values as low as 0. Based on this, we conclude that metal center exchange on the surface does not proceed through a free-base porphyrin as an intermediate. Furthermore, once formed, CuTPP is stable on the surface and the reverse exchange from CuTPP to ZnTPP in the presence of Zn(2+) ions could not be achieved. The preference for copper is so strong that even an attempt to exchange adsorbed ZnTPP with Ni(2+) ions in the presence of traces of Cu(2+) yielded CuTPP rather than NiTPP.
authors.affiliation: Institute of Physical Chemistry II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Franke
authors.affiliation: Department of Inorganic, Analytical and Physical Chemistry, University of Buenos Aires, Buenos Aires, Argentina.
authors.forename: Florencia
authors.initials: F
authors.lastname: Marchini
authors.affiliation: Institute of Organic Chemistry II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Norbert
authors.initials: N
authors.lastname: Jux
authors.affiliation: Institute of Physical Chemistry II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Steinrück
authors.affiliation: Institute of Physical Chemistry II, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany. Ole.Lytken@fau.de.
authors.forename: Ole
authors.initials: O
authors.lastname: Lytken
authors.affiliation: Department of Inorganic, Analytical and Physical Chemistry, University of Buenos Aires, Buenos Aires, Argentina. fwilliams@qi.fcen.uba.ar.
authors.forename: Federico J
authors.initials: FJ
authors.lastname: Williams
keywords: ion exchange; metalation; porphyrins; solid-liquid interfaces; zinc