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The Lander molecule (C90H98) consists of a long polyaromatic molecular wire and four lateral di-tert-butyl-phenyl spacer groups, designed to maintain the molecular wire parallel above the substrate. It represents a model system for investigating the electronic contacts of a molecular wire to a nanoscale metallic electrode. In this article, some recent manipulation experiments of single Lander molecules by low temperature scanning tunneling microscopy (LT-STM) are presented. The selective adsorption of the molecule, the molecule-induced reconstruction of copper substrates, and their application to the investigation of contacts between molecules and nanostructures or between molecules are discussed. Manipulation experiments are reported, where the molecular wire part of a Lander molecule is contacted to a monoatomic step and to a two-atom-wide metallic nanostructure. The contact is characterized by the apparent height of the contact point in STM images and, in case of the Cu(111) substrate, by the perturbation observed in the electronic standing wave patterns. [ABSTRACT FROM AUTHOR]

Abstract: On a metal–molecule–metal nanojunction, the scanning tunneling microscope (STM) scans at the precise location of the electronic metal–molecule interaction permit a measurement of the contact conductance G 0. The conversion curve between the change in the STM contrast Δh due to this interaction and G 0 is presented for a series of conjugated molecular wires. At chemisorption distances, the two-valued character of the G 0(Δh) function is discussed, indicating experimental ways to evaluate G 0 as a function of Δh for different metal–molecule interaction ranges. [Copyright &y& Elsevier]