Two-Dimensional Ketone-Driven Metal-Organic Coordination on Cu(111).

Ada Della Pia,Davide Bonifazi,Massimo Riello,Tim S Jones,Giovanni Costantini,Alessandro De Vita,Daphne Stassen,James Lawrence

doi:10.1002/chem.201600368

Ada Della Pia, Davide Bonifazi + Show 6 more

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https://doi.org/10.1002/chem.201600368

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Abstract

Two‐dimensional metal–organic nanostructures based on the binding of ketone groups and metal atoms were fabricated by depositing pyrene‐4,5,9,10‐tetraone (PTO) molecules on a Cu(111) surface. The strongly electronegative ketone moieties bind to either copper adatoms from the substrate or codeposited iron atoms. In the former case, scanning tunnelling microscopy images reveal the development of an extended metal–organic supramolecular structure. Each copper adatom coordinates to two ketone ligands of two neighbouring PTO molecules, forming chains that are linked together into large islands through secondary van der Waals interactions. Deposition of iron atoms leads to a transformation of this assembly resulting from the substitution of the metal centres. Density functional theory calculations reveal that the driving force for the metal substitution is primarily determined by the strength of the ketone–metal bond, which is higher for Fe than for Cu. This second class of nanostructures displays a structural dependence on the rate of iron deposition.

Highlights

Surface-based two-dimensional (2D) metal–organic nanostructures (MOS) are planar and highly ordered networks formed by the coordination of metal centres to tailored functional groups of organic ligands
The inter-row distance between these features is 10.3 Æ 0.4 , corresponding to four substrate lattice spacings. We identify these protrusions as Cu adatoms bound by the strongly electron-accepting ketone groups and incorporated in metal–organic rows, composed of alternating PTO molecules and Cu adatoms
The ketone groups are expected to capture the free copper adatoms that are available at room temperature, similar to what was previously observed for other strong electron-acceptor molecules.[8,13b,c,25] The metal–organic rows display a secondary organisation level as they are linked together to form extended islands, most probably stabilised by weaker van der Waals interactions

Summary

Introduction

Surface-based two-dimensional (2D) metal–organic nanostructures (MOS) are planar and highly ordered networks formed by the coordination of metal centres to tailored functional groups of organic ligands. Bonifazi Namur Research College (NARC) and Department of Chemistry University of Namur (UNamur), 5000 (Belgium) states of the metal centres is relatively straightforward in three-dimensional (3D) metal–organic frameworks, but more problematic for their 2D counterparts This is true for polarisable, typically metallic, substrates that can effectively screen charged adsorbates,[7] and may contribute to the charge transfer.[1,8] 2D-MOS can be built under ultrahigh vacuum conditions by codepositing molecules and alkali,[8,9] transition,[10] rare earth[11] and/or post-transition metal atoms.[12] such 2D arrangements are often formed by the incorporation of ‘free’ substrate atoms that are thermally released from step edges and kink sites of metallic surfaces (known as adatoms)[8,13] or atoms pulled out of the substrate during the molecular binding process.[14] The geometric arrangement of the resulting assemblies depends on the symmetry and reconstruction of the surface,[10a,15] the choice of metal centres,[10a,16] and the nature and position of the relevant molecular functional groups[12,16b] that bind to the metal centres and define the nodes of the resulting network. Pyrene-4,5,9,10-tetraone (PTO)[24] (Figure 1) is an ideal molecular candidate for 2D MOS formation, since its equatorial bidentate ketone moieties provide the oxidative potential necessary to stabilise defined oxidation

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Conclusion