Submonolayer growth of H2-phthalocyanine on Ag(111)

Abstract

We present a comprehensive study of structural and electronic properties of the adsorbate system H 2 -phthalocyanine (H 2 Pc) on Ag(111). A comparison with copper-phthalocyanine (CuPc) on Ag(111) allows us to elucidate the impact of the central metal atom in the molecule on the adsorbate-substrate interaction. This metal atom is one fundamental parameter which can be changed in order to modify the properties of phthalocyanine molecules, and therefore its influence on the adsorption behavior is highly relevant. From high-resolution electron diffraction, we obtained a phase diagram for submonolayer coverages which turns out to be similar to that of CuPc/Ag(111). The most striking difference is a higher stability of a commensurate phase, indicating a stronger and more adsorption site-specific bonding of the H 2 Pc molecules. Furthermore, ultraviolet photoelectron spectroscopy and x-ray standing waves prove chemisorptive interaction between molecules and substrate and a significant bending of the molecules with the nitrogen atoms approaching the surface. We conclude that the attractive interaction of metal-phthalocyanine molecules with Ag (111) is mainly mediated by the aromatic body of the molecule (the tetraazaporphyrin ring in particular) rather than by the central metallic atom which (in the case of CuPc) already shows Pauli repulsion.

Surface chemistry of porphyrins and phthalocyanines

“…1.9), which were closer to the substrate than the C atoms, according to NIXSW (see Section 4. 1.4 and Tables 2 and 4) [333]. This commensurate phase, which was observed at medium coverages and low temperature, had the same unit cell as the commensurate phase of CuPc/Ag(1 1 1) (see this section above).…”

“…The behaviour of submonolayer 2HPc on Ag(1 1 1) was very similar to that of CuPc (see above) with a disordered 2D gas-like low-coverage phase, in which the molecules are isolated from each other [333]. At higher submonolayer coverages, 2HPc formed a series of ordered structures with point-on-line coincidence.…”

“…In the case of complexes with non-planar gas-phase structure, additional information about the orientation (metal-up or metaldown) is obtained. Most of the related studies were performed with the normal-incidence X-ray standing wave (NIXSW) technique [329], which was applied to SnPc/Ag(1 1 1) [196][197][198][199], CuPc on Cu(1 1 1) [233], Ag(1 1 1) [197,231,330] [332], 2HPc/Ag(1 1 1) [333], CoPc/Ag (1 1 1) [199], and PbPc/Ag(1 1 1) [199]. In addition, photoelectron diffraction (PED) has been used for the structural analysis of SnPc/Ag(1 1 1) [334] and (O)VPc/Au(1 1 1) [335].…”

Heteromolecular metal–organic interfaces: Electronic and structural fingerprints of chemical bonding

“…The other system includes different metal-phthalocyanines (MePc) as, e.g., CuPc, SnPc or PbPc on the Ag(1 1 1) surface. Both families of molecules have been intensively studied within the last two decades [8,9,[13][14][15][16][17][18][19][20][21][22][23][24][25].…”

On-surface synthesis of a two-dimensional porous coordination network: Unraveling adsorbate interactions

“…In particular, experimental studies on the molecule-substrate bonding distances, which provide the points of reference for adequate theoretical modeling, are rare-in contrast to the numerous experimental studies on single molecule adsorption [15,16] and 2D molecular layers based on intermolecular interactions different than metal coordination [17][18][19][20][21][22][23][24][25][26]. However, these data are crucial for understanding molecule-substrate interactions and of interest for determining possible distortions from the planar geometry of surface-confined 2D MOFs.…”