Noncovalent Interaction of Graphene with Heterocyclic Compounds: Benzene, Imidazole, Tetracene, and Imidazophenazines

Noncovalent functionalization of graphene with organic molecules offers a direct route to multifunctional modification of this nanomaterial, leading to its various possible practical applications. In this work, the structures of hybrids formed by linear heterocyclic compounds such as imidazophenazine (F1) and its derivatives (F2-F4) with graphene and the corresponding interaction energies are studied by using the DFT method. Special attention is paid to the hybrids where the attached molecule is located along the graphene zigzag (G_ZZ) and armchair (G_AC) directions. The interaction energies corresponding to the graphene hybrids of the F1-F4 compounds for the two directions are found to be distinct, while tetracene (being a symmetrical molecule) shows a small difference between these binding energies. It is found that the back-side CH₃ and CF₃ groups have an important influence on the arrangements of F1 derivatives on graphene and on their binding energies. The contribution of the CF₃ group to the total binding energy of the F3 molecule with graphene is the largest (3.4 kcal mol^-1) (the G_ZZ direction) while the CH₃ group increases this energy of F2 only by 2.0 kcal mol^-1 (the G_AC direction). It is shown that replacing the carbons with other atoms or adding a back-side group enables one to vary the polarizability of graphene.