title: Selective molecular recognition by nanoscale environments in a supported iridium cluster catalyst.
abstract: The active sites of enzymes are contained within nanoscale environments that exhibit exquisite levels of specificity to particular molecules. The development of such nanoscale environments on synthetic surfaces, which would be capable of discriminating between molecules that would nominally bind in a similar way to the surface, could be of use in nanosensing, selective catalysis and gas separation. However, mimicking such subtle behaviour, even crudely, with a synthetic system remains a significant challenge. Here, we show that the reactive sites on the surface of a tetrairidium cluster can be controlled by using three calixarene-phosphine ligands to create a selective nanoscale environment at the metal surface. Each ligand is 1.4 nm in length and envelopes the cluster core in a manner that discriminates between the reactivities of the basal-plane and apical iridium atoms. CO ligands are initially present on the clusters and can be selectively removed from the basal-plane sites by thermal dissociation and from the apical sites by reactive decarbonylation with the bulky reactant trimethylamine-N-oxide. Both steps lead to the creation of metal sites that can bind CO molecules, but only the reactive decarbonylation step creates vacancies that are also able to bond to ethylene, and catalyse its hydrogenation.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California at Berkeley, Berkeley, California 94720, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Okrut
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California at Berkeley, Berkeley, California 94720, USA.
authors.forename: Ron C
authors.initials: RC
authors.lastname: Runnebaum
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California at Berkeley, Berkeley, California 94720, USA.
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Ouyang
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, California 95616, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, California 95616, USA.
authors.forename: Ceren
authors.initials: C
authors.lastname: Aydin
authors.affiliation: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Son-Jong
authors.initials: SJ
authors.lastname: Hwang
authors.affiliation: Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487, USA.
authors.forename: Shengjie
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California at Berkeley, Berkeley, California 94720, USA.
authors.forename: Olayinka A
authors.initials: OA
authors.lastname: Olatunji-Ojo
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California at Berkeley, Berkeley, California 94720, USA.
authors.forename: Kathleen A
authors.initials: KA
authors.lastname: Durkin
authors.affiliation: Department of Chemistry, The University of Alabama, Tuscaloosa, Alabama 35487, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Dixon
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, California 95616, USA.
authors.forename: Bruce C
authors.initials: BC
authors.lastname: Gates
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California at Berkeley, Berkeley, California 94720, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Katz
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