Analysis of intermolecular interactions of -perfluoroalkanes with circumcoronene using dispersion-corrected DFT calculations: comparison with those of -alkanes.

Understanding the interactions between the adsorbate and substrate is critical in basic and advanced scientific fields, including the formation of well-organised nanoarchitectures self-assembly on surfaces. In this study, the interactions of -alkanes and -perfluoroalkanes with circumcoronene were studied using dispersion-corrected density functional theory calculations as models of their adsorption on graphite. The interactions of -perfluoroalkanes with circumcoronene were significantly weaker than those of the corresponding -alkanes, the calculated adsorption energies of -perfluorohexane and -hexane were -9.05 and -13.06 kcal mol, respectively. The dispersion interactions were the major source of attraction between circumcoronene and the adsorbed molecules. Larger steric repulsion of -perfluoroalkanes compared to those of -alkanes increased their equilibrium distances from circumcoronene and decreased the dispersion interactions, resulting in weaker interactions. The interactions between two adsorbed -perfluorohexane molecules and those of -hexane molecules were -2.96 and -2.98 kcal mol, respectively, which are not negligible in the stabilisation of adsorbed molecules. The geometries of adsorbed -perfluoroalkane dimers revealed that the equilibrium distance between two -perfluoroalkane molecules did not match the width of the six-membered rings in circumcoronene, in contrast to that between -alkanes. The lattice mismatch also destabilised the adsorbed -perfluoroalkane dimers. The difference in the adsorption energy between flat-on and edge-on orientations of -perfluorohexane was smaller than that of corresponding -hexane.