Complexation of free-base and 3d transition metal(II) phthalocyanines with fullerene C60: A dispersion-corrected DFT study

We performed a systematic comparative theoretical study of noncovalent interactions of free-base H2Pc and a series of 3d transition metal(II) phthalocyanines (where the transition metals included manganese, iron, cobalt, nickel, copper and zinc) with fullerene C-60, by employing a DFT technique accounting for vdW interactions (PBE GGA functional with a dispersion correction by Grimme). We observed four different types of Pc interaction with fullerene cage, depending on central metal atom. Upon complexation with C-60, the macrocyclic plane undergoes distortion in all cases, to a different degree. Some correlation was observed between the calculated formation energies for Pc-fullerene complexes and intermolecular separations in them, where stronger binding is generally associated with shorter (MCC60)-C-... and (NCC60)-C-... distances. Despite of considerable differences in the structure of Pc-fullerene complexes, the latter do not exhibit notable variations in the distribution of electrostatic potential, contrary to spin density plots for open-shell species. Similarly, HOMO and LUMO distribution can vary within some limits.