Structure and Binding Energies of the Porphine Dimer

Christian Mück-Lichtenfeld (1) , Stefan Grimme (1)

1 Organisch-Chemisches Institut

Density functional theory optimisations with GGA functionals that include an empirical correction term for the dispersion energy (denoted as -D) have been performed for the van der Waals dimer of porphine. Interaction energies have been also obtained with a recently developed double-hybrid functional (B2-PLYP-D) and at the SCS-MP2 level of theory. The preferred conformer is a parallel displaced complex (1.72 A lateral displacement) with an interplanar distance of 3.27 A. The orientation (rotation) of the two monomers has only minor effects (< 1 kcal/mol) on the binding energy ΔE, implying a certain flexibility of mutual movement around the monomer principal axes. The best estimate for ΔE is -25 kcal/mol with B2-PLYP-D. The also investigated T-shaped structures are much higher (about 15 kcal/mol) in energy. While dispersion contributions are absolutely essential for the binding of all investigated structures, the electrostatic contributions mainly determine the preferred conformations (e.g.displacement vs. rotation).

Mots clés: Physical Sciences

Christian Mück-Lichtenfeld, Stefan Grimme. Structure and Binding Energies of the Porphine Dimer. Molecular Physics, 2008, 105 (19-22), pp.2793-2798. ⟨10.1080/00268970701635543⟩. ⟨hal-00513142⟩