Adsorption energies of porphyrins on MgO(100): An experimental benchmark for dispersion-corrected density-functional theory

Abstract

Using temperature-programmed desorption, adsorption energies of metallotetraphenylporphyrins were measured and used as a benchmark for dispersion-corrected density-functional theory calculations. Experimentally, simple Redhead analysis was used to extract monolayer adsorption energies for cobalt, zinc and magnesium 5,10,15,20-tetraphenyl porphyrin on MgO(100) thin films grown on Ag(100), where the prefactor for desorption was calculated by transition-state theory. Magnesium exhibits the highest experimental adsorption energy of 217 kJ/mol, while zinc and cobalt have adsorption energies of 193 and 186 kJ/mol, respectively. Using density-functional theory with a modified Grimme D3 scheme resulted in calculated adsorption energies of 209, 171 and 174 kJ/mol. The trend and even the absolute values of the experiment and the theory are in good agreement. Additionally, the calculations allow us to break down the different contributions to the adsorption energies, showing the interplay of van der Waals interactions, chemical bonds and deformation energies.