Validation of the inverted adsorption structure for free-base tetraphenyl porphyrin on Cu(111).

Utilising normal incidence X-ray standing waves we rigourously scrutinise the "inverted model" as the adsorption structure of free-base tetraphenyl porphyrin on Cu(111). We demonstrate that the iminic N atoms are anchored at near-bridge adsorption sites on the surface displaced laterally by 1.1 +/- 0.2 angstrom in excellent agreement with previously published calculations.