Cycloaddition of Metal Porphines on Metal-Supported Graphene: A Computational Study

The cycloaddition reactions of iron porphine with graphene epitaxed to a series of lattice-matched and lattice-mismatched metal surfaces have been investigated by using dispersion-corrected density functional theory (DFT) calculations. Our calculations evidence the nonclassic cycloaddition with 3 pi units from graphene on specific hollow C- top C - hollow C registry areas. The most favorable cycloadduct results from an exothermic [3 + 2] process with a C2 edge of the porphine molecule. We also show that the feasibility of the cydoaddition depends on the nature of the metal below graphene: Ir is the most reactive metal, while Re is less reactive and Cu is almost inactive. The various reactivities Of epitaxial graphene can be traced back to both the energy positioning of the metal-hybridized pi states of graphene prior to the functionalization and the strengthening of the graphene metal interaction after the functionalization. Our work predicts an unanticipated way for controlled covalent functionalization of graphene-covered metal surfaces.