title: Ordered monolayers of free-standing porphyrins on gold.
abstract: The controlled attachment of chromophores to metal or semiconducting surfaces is a prerequisite for the construction of photonic devices and artificial surface-based light-harvesting systems. We present an approach to mount porphyrins in ordered monolayers on Au(111) by self-assembly and verify it, employing STM, absorption spectroscopy, and quantum chemical calculations. The usual adsorption geometry of planar chromophores, flat on the surface or densely packed edge-on, is prevented by mounting the porphyrins upright on a molecular platform. An ethynyl unit as spacer and pivot joint provides almost free azimuthal rotation of the unsubstituted porphin. However, rotation of the larger triphenylporphyrin unit is sterically restricted: because the diameter of the substituted porphyrin is larger than the distance to its next neighbors, the phenyl substituents of neigboring molecules interact by dispersion force, which leads to an alignment of the azimuthal rotators.
authors: Otto-Diels-Institute for Organic Chemistry and ‡Institute for Experimental and Applied Physics, Christian-Albrechts-University of Kiel , 24098 Kiel, Germany.
authors: Franziska L
authors: FL
authors: Otte
authors: Sonja
authors: S
authors: Lemke
authors: Christian
authors: C
authors: Schütt
authors: Nicolai R
authors: NR
authors: Krekiehn
authors: Ulrich
authors: U
authors: Jung
authors: Olaf M
authors: OM
authors: Magnussen
authors: Rainer
authors: R
authors: Herges
mesh_terms: D000327:Adsorption; D019281:Dimerization; D006046:Gold / Q000737:chemistry*; D008422:Materials Testing; D008670:Metals / Q000737:chemistry; D016252:Microscopy, Scanning Tunneling; D017785:Photons; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D012666:Semiconductors; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties
chemical_list: D008670:Metals; D011166:Porphyrins; D006046:Gold