Physisorption of benzene derivatives on graphene: Critical roles of steric and stereoelectronic effects of the substituent

A series of benzene derivatives with different substituents adsorbed on graphene was investigated using a density-functional tight-binding method with a dispersion correction. Compared to benzene, the derivative with either an electron-withdrawing or -donating substituent exhibits stronger physisorption. Moreover, the steric size of the substituent is important in determining the adsorption strength, while the direction and the number of H atoms in the substituent affect the electron transfer from graphene. NBO analysis reveals that the stereoelectronic effect of the conjugation between the substituent and the benzene ring strongly influences the π⋯π interaction region between the molecule and graphene. The findings can deepen the understanding of the interaction between an aromatic molecule and graphene as well as the corresponding adsorption mechanism.