Dispersion-Corrected Density Functional Theory Calculations of meso-Tetraphenylporphine-C₆₀ Complex by Using DMol3 Module

We performed a series of DMol3 calculations of geometry, energy and some electronic properties of the noncovalent dyad of meso-tetraphenylporphine and fullerene C₆₀ (H₂TPP-C₆₀) by applying different types of dispersion correction (as well as without it, for comparison), in order to suggest a computational methodology capable of yielding most realistic results in theoretical studies of the interactions of porphyrin-like compounds with carbon nanoclusters. The method evaluation was based on the binding energies E and the shortest intermolecular contacts N_H2TPP···C_C60. The binding energy values closely matching the best estimates reported elsewhere were –25 5 and –25.2 kcal/mol calculated with PBE GGA functional and Grimme dispersion correction, in con- junction with DNP basis set versions 3.5 and 4.4, respectively. TS-corrected PBE calculations yielded weaker binding (–19.5 and –16.1 kcal/mol for the basis set versions 3.5 and 4.4, respectively), whereas OBS-corrected PW91 functional predicted much stronger association (–43.1 and –42 6 kcal/mol, respectively). The values for closest contacts NH2TPP···C_C60, which are systematically overestimated by pure GGA functionals, were dramatically improved by applying Grimme or TS dispersion correction to PBE, and OBS correction to PW91 functional. All the resulting calculated N_H2TPP···C_C60 separations matched very well the corresponding experimental distances of about 3.0 Å, where the best results were obtained with Grimme-corrected PBE and OBS-corrected PW91. Based on the above, of GGA and LDA functionals available in DMol3 module, PBE functional along with Grimme dispersion correction can be suggested as the computational methodology most suitable for theoretical studies of the interactions of porphyrin-like compounds with larger carbon nanoclusters such as carbon nanotubes and graphene.