Thin molecular films under model conditions are often exploited as benchmarks and case studies to investigate the electronic and structural changes occurring on the surface of metallic electrodes. Here we show that the modification of a metallic surface induced by oxygen adsorption allows the preservation of the geometry of a molecular adlayer, giving access to the determination of molecular orbital symmetries by means of near-edge x-ray absorption fine structure spectroscopy, NEXAFS. As a prototypical example, we exploited Nickel Tetraphenyl Porphyrin molecules deposited on a bare and on an oxygen pre-covered Cu(100) surface. We find that adsorbed atomic oxygen quenches the charge transfer at the metal-organic interface but, in contrast to a thin film sample, maintains the ordered adsorption geometry of the organic molecules. In this way, it is possible to disentangle π* and σ* symmetry orbitals, hence estimating the relative oscillator strength of core level transitions directly from the experimental data, as well as to evaluate and localize the degree of charge transfer in a coupled system. In particular, we neatly single out the σ* contribution associated with the N 1s transition to the mixed N 2px,y-Ni 3dx 2 -y 2 orbital, which falls close to the leading π*-symmetry LUMO resonance.

Self-metalation is ap romising route to include as ingle metal atom in at etrapyrrolic macrocycle in organic frameworks supported by metal surfaces.T he molecule-surface interaction may providet he charge transfer and the geometric distortion of the molecular plane necessary for metal inclusion. However,a tametal surface the presence of an activation barrier can represent an obstacle that cannot be compensated by ah igher substrate temperature without affecting the layer integrity.The formation of the intermediate state can be facilitated in some cases by oxygen pre-adsorption at the supporting metal surface,l ike in the case of 2H-TPP/ Pd(100). In such cases,the activation barrier can be overcome by mild annealing,y ielding the formation of desorbing products and of the metalated tetrapyrrole.W eshow here that the self-metalation of 2H-TPP at the Pd(100) surface can be promoted already at room temperature by the presence of an oxygen gas phase at close-to-ambient conditions via an Eley-Rideal mechanism.

Self-metalation is ap romising route to include as ingle metal atom in at etrapyrrolic macrocycle in organic frameworks supported by metal surfaces.T he molecule-surface interaction may providet he charge transfer and the geometric distortion of the molecular plane necessary for metal inclusion. However,a tametal surface the presence of an activation barrier can represent an obstacle that cannot be compensated by ah igher substrate temperature without affecting the layer integrity.The formation of the intermediate state can be facilitated in some cases by oxygen pre-adsorption at the supporting metal surface,l ike in the case of 2H-TPP/ Pd(100). In such cases,the activation barrier can be overcome by mild annealing,y ielding the formation of desorbing products and of the metalated tetrapyrrole.W eshow here that the self-metalation of 2H-TPP at the Pd(100) surface can be promoted already at room temperature by the presence of an oxygen gas phase at close-to-ambient conditions via an Eley-Rideal mechanism.