STM studies on double- and triple-decker porphyrin and phthalocyanine complexes

Properly designed double- and triple-decker porphyrin and/or phthalocyanine complexes assemble themselves into ordered higher-order structures on substrate surfaces. One of the macrocyclic ligands adsorbs on the surface almost always in a face-on fashion on highly oriented pyrolytic graphite and Au(111) surfaces as revealed by means of scanning tunnelling microscopy. For example, well-ordered oriented monolayer assemblies of single-molecule magnets were fabricated. In some cases, the vertical orientation, that is, which ligand adsorbs on the surface, can be controlled by applied potentials. The rotational libration of the top ligand with respect to the adsorbed bottom ligand and hence to the surface has been visualised for a double-decker porphyrin with a molecular beacon. The electronic, magnetic and dynamic properties of double- and triple-decker complexes bode well for the development of molecular devices.