Kuck, Stefan; Brede, Jens; Scarfato, Alessandro; Hoffmann, Germar; Wiesendanger, Roland; May, Sven; Kloeckner, Jan-Peter; Prosenc, Marc Germany
Salens are quadratic planar Schiff-Base Complexes with an inner metallic ion (M). Deposited on a surface this metallic ion is freely accessible from the top and ideally suited for investigations by local probe techniques. Here we will present first STM/STS experiments on Salens with the focus on the role of the central metallic ion (M = Co, Cu, Ni, Zn). For this purpose we deposited Salens via molecular beam epitaxy on metallic and insulating surfaces in ultra-high vacuum. The experiments were performed in a home-built variable-temperature scanning tunneling microscope working at temperatures between 17 K and 500 K. We studied the orientation of the Salens on the surfaces in dependence of the preparation temperature and identified HOMO and LUMO states. Whereas the temperature drives the molecular orientation on the surface as well as its conformation self-assembling is not observed. We will discuss the electronic structure in dependence of the central metallic ion as manifested in the topology.