Properties of noncovalent tetraphenylporphine⋯C60 dyads as studied by different long-range and dispersion-corrected DFT functionals

Abstract

The noncovalent dyad of tetraphenylporphine and C₆₀ fullerene (H₂TPP⋯C₆₀) and the tetraphenylporphine dimer (H₂TPP⋯H₂TPP) were studied by density functional theory (DFT), using functionals that incorporate empirical dispersion correction (DFT-D), functionals that use a long-range correction (LC) scheme, a hybrid functional (B3LYP) and a highly parametrized empirical exchange–correlation functional (M05-2X). The results were compared to X-ray structures and interaction energies reported in previous experimental and theoretical studies. It was found that B3LYP and CAM-B3LYP functionals fail to reproduce the X-ray structures and binding energies of the TPP⋯C₆₀ system. DFT-D functionals overestimated the π⋯π energy interactions for both systems, however, the optimized structures agree well with those observed experimentally. The LC-BLYP functional predicts geometries similar to X-ray structures; nevertheless, due to the lack of correction in the dispersion energy, the predicted energies for both model systems are low. On the other hand, the M05-2X functional exhibited the best performance. Both the structures and binding energies calculated with M05-2X are consistent with experimental and theoretical evidence reported by other authors, as well as with our experimental results obtained by means of atomic force microscopy on H₂TPP thin films grown on the HOPG/C₆₀ substrate by physical vapor deposition.