Paper MI-FrM5
The Densest Iron Coordination Network Based on Carboxylate Ligands

Friday, November 13, 2009, 9:40 am, Room C1

Over the last decade there has been a tremendous effort in order to create new kinds of supramolecular organic nanostructures on surfaces, with the prospect of possible catalytic, electronic, optical or magnetic applications. In particular, a lot of attention has been paid to metalorganic coordination networks (MOCNs), with the idea of creating functional metallo-supramolecular arrays on surfaces which combine the properties of their constituent metal ions and ligands.

Following this approach, the chemisorption of small molecules with ending carboxylic acids on metal surfaces has been extensively studied and deprotonation of the acid groups to produce carboxylate groups described [1]. These deprotonated groups can interact strongly with both metal surfaces and metal adatoms (either intentionally deposited or already existing as a 2D background gas that results from the emission of atoms from low coordination sites such as steps and kinks). This metal-to-carboxylate interaction, when properly addressed, leads to the formation of regular patterns of MOCNs. We have deposited oxalic acid, i.e. the smallest possible molecule with two carboxylic groups (C2O4H2), on non magnetic Cu(100) surfaces, both clean and with a small pre-deposited amount of Fe. Scanning Tunnelling Microscopy (STM) shows that moderate annealing of these systems lead to the formation of two different, new MOCNs: a rectangular copper-oxalate network, and a honeycomb iron-oxalate network, where the regularly spaced Fe spins have the smallest distance (5.2 Å) reported up to date, making the Fe-oxalate MOCN a promising system for an in-depth study of their magnetic properties.

[1] S. Stepanov, N. Lin, J. V. Barth, J. Phys.: Condens. Matter 20 (2008) 184002.