Exploring the RIDEr ligation at supported PORPHyrins using a combined theory and experiment atomic-scale approach_RIDEPORPH

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Metalloporphyrins represent a class of functional molecules that interfere in numerous biological processes. They are present in hemoglobin and mediate the transport of respiratory gases. Using scanning tunneling microscopy, the experimental team at TU Munich recently showed that in the adsorbed state the porphyrin macrocycle adopts a characteristic saddle-shape deformation. Moreover, exploring the porphyrin's response to gaseous species, the studies demonstrate that there exist two adsorption sites for CO, which could be identified by the comparison with ab-initio calculations from the theoretical team at Lyon. Indeed, the carbonyl adducts are located sideways at the saddle, similar to the positioning of the legs of a rider. The saddle-shape conformation presumably represents a key factor in this scenario, which hypothesis the present project will examine in detail. A primordial question to be investigated by a systematic approach is whether this unprecedented bonding mode can be similarly invoked for related environments. The Lyon and Munich teams identified four constituent chemical parameters that can be individually varied to differentiate their intrinsic effect on the existence or non-existence of the rider ligation mode: (i) the conformation of the porphyrin macrocycle, (ii) the nature of the gaseous adduct, (iii) the type of the metal center and (iv) the reactivity of the substrate. The research strategy relies on molecular imaging and manipulation experiments at Munich interpreted with the help of atomistic calculations in Lyon.