Adsorption Structure of Cobalt Tetraphenylporphyrin on Ag(100)

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 nm 2 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.