Seminars Archive

1D self-organization of molecular nanostructures at surfaces: metal-organic and chiral chains.

Abstract
Joint DEMOCRITOS/ELETTRA/TASC seminar Abstract: Several advantages characterize the use of molecules as building blocks in the self-organized functionalization of surfaces: non-covalent interactions that allow to operate near equilibrium conditions where self-correction is active; directional interactions that intrinsically produce well-defined geometries and long-range periodicities; the possibility of manipulating organization and functionality by chemical design. In this talk I will present two examples of this way of engineering nanostructures, with increasing complexity of the fundamental building blocks. Coordination bonding employing metal atoms as nodes and organic molecules as linkers has been proven to be particularly successful in the fabrication of three-dimensional metal-organic coordination networks with specific magnetic, electronic, or catalytic properties. The translation of these concepts to surfaces will be discussed with a special focus on the employment of benzenepolycarboxylic acids as basic molecular units. In particular I will show that the templating role of the substrate can be exploited to fabricate one-dimensional metal-organic coordination chains on Cu(110). By changing the nature of the metallic centers also functional nanostructures with promising nanomagnetic properties can be obtained. A deep insight into their atomistic and electronic structure is provided by comparing highly resolved scanning tunneling microscopy (STM) measurements with density functional theory (DFT) calculations. The formation of biological macromolecules is based on the polymerization of amino acids in the form of peptidic chains. Here I will discuss the surface deposition of the simplest peptide composed by two identical amino acids. The Di-L-phenylalanine molecule (L-Phe-L-Phe) forms one-dimensional homochiral supramolecular structures through self-organization. Its co-deposition with the mirror imaged stereoisomer di-D-phenylalanine (D-Phe-D-Phe) results in a chiral phase separation. By exploiting the atomic-level imaging capabilities of STM, the 2D chiral recognition process is followed in real time. The stereoselectivity of the process is evidenced by STM and rationalized on the basis of DFT calculations.