Adsorption Structure of Cobalt Tetraphenylporphyrin on Ag(100)

Abstract

Using a combination of LEED, high-resolution XPS, XSW, and NEXAFS, we have studied the adsorption of cobalt­(II) 5,10,15,20-tetraphenyl­porphyrin (CoTPP) on Ag(100) at 300 K. In agreement with previous studies on Ag(111), we find a charge transfer from the silver surface to the porphyrin molecule, reducing the metal center. At high coverages we observe a square-shaped 1.41 × 1.41 nm2 adsorption structure, which becomes more open at lower coverages. Because of the superior energy resolution of the Diamond i09 beamline, we are able to resolve a low-binding-energy shoulder in the C 1s spectrum, originating from the lower carbon atoms in the rotated phenyl rings. This is confirmed by XSW measurements, which also gives the adsorption heights of the other atoms in the molecule. In addition, the XSW and complementary NEXAFS measurements yield information about the rotation of the phenyl rings and the deformation of the macrocycle.

Adsorption of Phosphonic-Acid-Functionalized Porphyrin Molecules on TiO2(110)

“…For TPPP, the range of possible angles include 35°, which is the angle observed for flat-lying tetraphenyl porphyrin molecules because of their saddle-shape distortion, with two opposing pyrrole rings pointing upward and the other two down toward the surface. 46 The distorted structure deduced from DFT can be found elsewhere. 47 It is thus entirely possible that TPPP at 0.7 ML adsorbs in a flat-lying configuration with all four phosphonic acid groups bonded to the surface.…”

Interfacial Reactions of Tetraphenylporphyrin with Cobalt‐Oxide Thin Films

“…We define 1MLa st he coverage that is left on the surface after multilayer desorption at 525 K. This coverage attenuates substrate photoelectrons with ak inetic energy of 100 eV by 50 %, and the amount of carbon is in good agreement with previously measured, densely packed, flat-lying layer of CoTPP on Ag(100) also produced from multilayer desorption. [29]…”

On-Surface Synthesis of Nonmetal Porphyrins

“…While 3d metal ions are generally positioned in or near the macrocycle plane, larger elements such as lanthanides are displaced from the molecular center (e.g., allowing for the in situ formation of double- and multidecker assemblies , ). Importantly, the interaction with the supporting surface can affect the adsorbed porphyrins’ properties, such as the molecular conformation ,,− and the oxidation state of the central atom, which is often reduced by charge transfer from the metallic substrate. − …”

“…The resulting row-type molecular arrangement, where molecules in neighboring rows show a different orientation, thus forming a 1 + 1 pattern, closely resembles the 2H-TPyP assembly on Ag(111). , The coexistence of the regular 1 + 1 pattern with similar assemblies (e.g., the 1 + 2 pattern, the 2 + 2 pattern, mixed domains) points to a subtle balance between molecule–molecule and molecule–substrate interactions guiding the assemblies. Indeed, minor modifications of TPP (e.g., Co versus the Zn center) as well as the Co-TPP coverage were reported to influence the molecular packing on Ag(100). , While a square unit cell with one molecular orientation was observed for a Zn-TPP monolayer after annealing to 500 K (α-pyr axis aligned 45° off the ⟨110⟩ directions), two molecular orientations prevail in the Co-TPP unit cell at 0.7 monolayer coverage . Additionally, recent experiments show that a kinetically trapped Zn-TPP 1 + 2 phase can be stabilized at rt .…”