Interfacial Reactions of Tetraphenylporphyrin with Cobalt‐Oxide Thin Films

We have studied the adsorption and interfacial reactions of 2H‐tetraphenylporphyrin (2HTPP) with cobalt‐terminated Co 3 O 4 (111) and oxygen‐terminated CoO(111) thin films using synchrotron‐radiation X‐ray photoelectron spectroscopy. Already at 275 K, we find evidence for the formation of a metalated species, most likely CoTPP, on both surfaces. The degree of self‐metalation increases with temperature on both surfaces until 475 K, where the metalation is almost complete. At 575 K the porphyrin coverage decreases drastically on the reducible cobalt‐terminated Co 3 O 4 (111) surface, while higher temperatures are needed on the non‐reducible oxygen‐terminated CoO(111). The low temperature self‐metalation is similar to that observed on MgO(100) surfaces, but drastically different from that observed on TiO 2 (110), where no self‐metalation is observed at room temperature.