Innovative and stable catalysts can be designed within the framework of a biomimetic approach, thus embedding an active single metal atom in a tetra-pyrrolic cage. From the surface science point of view, an in situ and operando characterization of heme-like, simplified model systems may represent a challenge. Besides investigations at cryogenic temperature, a thorough atomic-level experimental understanding is indeed not straightforward so far, due to the near-ambient pressure conditions that are necessary to yield a significant interaction of the active core with gas  phase molecules at room temperature. By exploiting non-linear laser spectroscopy, access to the vibronic properties of interfaces is possible under realistic operative conditions, thus allowing the investigation of 2D metal-organic supported systems.

Self-assembled 2D layers of metal-N 4 complexes deposited on single crystal terminations and on supporting templates will be described, with a specific focus on the interaction of the single metal atom centers with small gas-phase molecules. IR-Vis Sum Frequency Generation spectroscopy, combined with other surface characterization techniques and with ab initio calculations, provides a detailed insight into geometry and chemical behavior of the layers, including also electronic properties and excitons dynamics.