Distortion and bonding strength of phthalocyanine molecules adsorbed on topological defects in graphene

Abstract

We studied the influence of topological defects on the bonding strength, geometries and electronic parameters for free-base H2Pc and two 3d-metal derivatives (CuPc and ZnPc) interacting with graphene sheet models. The DFT calculation results obtained for the cluster models containing isolated pentagon (5), pyracylene unit (5665) and Stone-Wales (SW) defect were compared to those for a defect-free graphene model (G). The topology of graphene surface has a strong influence on the shape of usually planar phthalocyanine molecules. While on the models of pristine and SW defect-containing graphene macrocycles remain generally flat, the presence of isolated pentagonal defects and pyracylene units in most cases induces strong distortion of phthalocyanine system, in order to increase the area of its contact with graphene sheet, and thus to provide a more efficient π-π stacking interaction between the two components. In the case of cone-shaped 5 and 5665 nanoclusters, the macrocycle distortion is more pronounced in the case of ‘endo’ as compared to ‘exo’ adsorption; in turn, it is stronger for 5665 model, which has a sharper curvature. The noncovalent bonding is strong for all the complexes studied, increasing in the order of 5665_exo <5_exo <5665_endo <5_endo < G < SW.