Noncovalent 1:2 Complex of meso-Tetraphenylporphine with C60 Fullerene: A Density Functional Theory Study

We performed DFT calculations of noncovalent 1:2 complex of meso-tetraphenylporphine H2TPP with fullerene C-60, using PW91, PBE and BLYP functionals of general gradient approximation (GGA), as well as PWC and VWN functionals of local density approximation (LDA) implemented in the DMol3 module of Materials Studio. The computed geometries were compared to the experimental ones obtained previously by X-ray analysis of rhombohedral and monoclinic H2TPP+C-60 crystalline complexes. The covalent bond lengths and angles within H2TPP are best reproduced by BLYP; PWC and VWN are least precise. LDA functionals better perform for dihedral angles. PWC and VWN are the best functionals in reproducing the experimental separations between H2TPP and C-60: the LDA-calculated N(H2TPP) center dot center dot center dot C(C-60) distances are of about 2.9-3.0 angstrom, whereas the experimental values are 3.0-3.1 angstrom. Next are PW91 and PBE functionals, giving N(H2TPP) center dot center dot center dot C(C-60) distances of ca. 3.4-3.6 angstrom. BLYP produced the separations of around 4.7 angstrom, which are inconsistent with both X-ray data and the results obtained with other functionals. Of OFT methods incorporated into DMol3 module and tested in this study, PWC and VWN functionals were concluded to be most adequate, and BLYP to be least recommended to study noncovalent interactions of porphyrins with carbon nanoclusters (fullerenes and carbon nanotubes).