Following the Metalation Process of Protoporphyrin IX with Metal Substrate Atoms at Room Temperature

We have studied the in situ coordination reaction of porphyrin molecules, particularly protoporphyrin IX (H2PPIX), with copper substrate atoms in ultrahigh vacuum conditions with a combination of X-ray photoelectron spec- troscopy and scanning tunneling microscopy. We show that these protoporphyrin IX molecules deposited on Cu surfaces, as Cu(110) and Cu(100), form metalloprotoporphyrin IX (CuPPIX) by incorporation of Cu atoms from the surface already at room temperature. We have followed this reaction as a function of temperature and we have determined inter- mediate situations at lower temperatures where the physisorbed macrocycle rings present a tendency to establish hydrogen bonding between molecules.