Interplay between metal-free phthalocyanine molecules and Au(110) substrates

Metal-free phthalocyanine (Pc) molecules adsorbed on the Au(110) surface have been studied both experimentally (STM, LEED) and with density functional calculations. A strong interaction between substrate and adsorbate is observed. On the one hand, a clear template effect of the anisotropic substrate is observed: already at low coverages, the Pc molecules adsorb in various typical row patterns. On the other hand, the molecular adsorption modifies the substrate: at coverages higher than 0.25 monolayers, the usual (1 × 2) reconstruction is converted to a (1 × 3) reconstruction. First principle DFT calculations yield adsorption geometries that agree with the measured STM images and adsorption energies in the range of 2–3 eV. The adsorption leads to covalent and van der Waals interactions between adsorbate and substrate and is accompanied by a considerable charge transfer.