Water Formation for the Metalation of Porphyrin Molecules on Oxidized Cu(111)

Abstract

Herein the formation of water molecules in the intermediate step of the redox reaction of porphyrins self-metalation on O/Cu(111) is demonstrated. Photoemission measurements show that the temperature on which porphyrins pick-up a substrate metal atom on O/Cu(111) is reduced by about 185±15 K with respect to the pure Cu(111). DFT calculations clearly indicate that the formation of a water molecule is less expensive than the formation of H2 on the O/Cu(111) substrate and, in some cases, it can be also exothermic.

Deciphering complex features in STM images of O adatoms on Ag(110)

“…These results clarified several unexplained observations such as the strong disordering of the surface upon O 2 dissociation [16] and the facile route by which oxygen migrates to subsurface sites even at low temperature [27]. Along the same lines, it is also likely that the strong reduction of the barrier for metalation of porphyrins on Cu surfaces in the presence of coadsorbed oxygen [28,29] is associated with the grabbing of substrate atoms by atomic oxygen. As stressed in ref.…”

Stabilization and activation of molecular oxygen at biomimetic tetrapyrroles on surfaces: from UHV to near-ambient pressure

“…67 All these steps are facilitated by the co-presence of oxygen, nally forming water upon reaction with the central H atoms in the tetrapyrrole pocket. 8,68,69 This is the case for the self-metalation reaction of 2H-TPP molecules adsorbed on Cu(111), where the pre-oxidation of the metal termination lowers the reaction temperature by 185 AE 15 K, down to room temperature (Fig. 5e).…”

Tetrapyrroles at near-ambient pressure: porphyrins and phthalocyanines beyond the pressure gap

“…A significant core level shift allows clear distinction between the two species, contributing with adiabatic N 1s peaks at 399.8-400.3 and 397.6-398.5 eV, respectively, depending on the molecular species and on its interaction with the metal substrate. Upon metalation, the N 1s associated with the M-N 4 center grows around 398.6-398.9 eV, depending on the metal, at the expense of the former doublet [28,29,89,90,96,[100][101][102]. Local geometric information of tetrapyrroles adsorbed at surfaces can be obtained by angle-and/or energy-resolved photoemission experiments in photoelectron diffraction based approaches, allowing distinction between metalated and non-metalated molecules [84,103].…”

“…At temperatures above 550-660 K, dehydrogenation of the external moieties of the tetrapyrrole takes place, contributing in hydrogen desorption features up to 1000 K [96,104]. When the surface metalation reaction is oxygen-assisted, water is produced instead [99][100][101]. STM can be exploited as a local probe to distinguish between metalated and non-metalated Figure 15.…”