Kondo resonances are a very precise measure of spin-polarized transport through magnetic impurities. However, the Kondo temperature, indicating the thermal range of stability of the magnetic properties, is very low. By contrast, we find for iron phthalocyanine a Kondo temperature in spectroscopic measurements which is well above room temperature. It is also shown that the signal of the resonance depends strongly on the adsorption site of the molecule on a gold surface. Experimental data are verified by extensive numerical simulations, which establish that the coupling between iron states and states of the substrate depends strongly on the adsorption configuration.

Adsorption behavior of iron(II) phthalocyanine (FePc) on Au(111) surface at submonolayer coverage has been investigated using low-temperature scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. At the initial adsorption stage, FePc molecules prefer to adsorb on terrace dispersedly as isolated adsorbates because of the stronger molecule−substrate interaction than the lateral intermolecular interaction. Two different configurations of FePc on Au(111) surface are resolved on the basis of STM image analysis and are further identified by DFT calculations. When increasing molecule coverage, the intermolecular interaction becomes more important. The FePc molecules assemble to dimers, trimers, and short chains and even peculiar porous hexamers with two configurations. At a saturated coverage, highly ordered FePc monolayer with only one configuration of FePc is observed. The results indicate that the adsorption behavior of FePc on Au(111) is governed by a coverage-dependent competition between molecule−substrate and intermolecular interactions.

Growth behavior of iron(II) phthalocyanine (FePc) molecules on Au(111) surface at the initial stage is studied with low-temperature scanning tunneling microscopy. The FePc molecules are separately adsorbed on the face-centered cubic and the hexagonal close-packed regions at the submonolayer regime, indicating that the molecular adsorption is greatly affected by the molecule−substrate interaction. At the monolayer regime, the molecules can form a close-packed ordered structure. When the FePc goes further to the second layer, the unit cell of the formed molecular superstructure shifts compared with the unit cell of the first layer. Comparison of the growth behavior between the FePc and the CoPc also is made to understand the growth difference within the family of the phthalocyanine (Pc) molecules. And it is found that the central metal atom of the metal Pc makes a main contribution to the shift. Our results are helpful for understanding the growth of the Pc molecule family and controlling the related physical properties.