Theoretical investigation of metalated and unmetalated pyrphyrins immobilized on Ag(111) surface

Investigations of interactions between macrocyclic molecules and metal surfaces are crucial for emerging technologies, such as chemical and biological sensors, molecular electronics, read/write/erase memory, and magnetism. Thus, understanding the organic molecule and metal interface gains considerable importance. In this respect, we investigate a relatively unexplored porphyrin-related macrocycle, named as Pyrphyrin (Pyr), on Ag(111) surface by means of density functional theory. Our results show that main contribution to the adsorption energy is the dispersive contribution arising due to the interactions between the molecules and the surface. Optimal coordination of two cyano Ns and Co atoms (for CoPyr) to the surface Ag atoms determine preferred adsorption sites. Cyano ends of the Pyr molecule act as anchoring groups and enhances the stability of the complex by bending towards the Ag(111) surface. Cobalt incorporation into the Pyr core, on the other hand, further increases the adsorption strength by contribution of the attractive interactions between Co and Ag atoms. Selected molecular orbital representations of the complexes reveal the extension of orbitals located on Co and/or on two cyano N towards surface Ag atoms, thus, hybridization between molecular and surface states upon adsorption are confirmed.