Interaction of porphine and its metal complexes with C60 fullerene:: A DFT B3LYP/LANL2MB study

We performed DFT calculations (at the B3LYP/LANL2MB theoretical level, implemented in Gaussian 03W) for the interaction of free porphine ligand and a number of its metal complexes with C-60 molecule, in order to analyze how the nature of central metal ion influences the geometry and electronic characteristics. The results were compared to our BLYP/DN (DMol3 implementation) results reported earlier. The Gaussian calculations turned to be not only less efficient in terms of time, but also failed to optimize the geometry of Mn(II)-containing systems. The interaction strength remains to be a function of the central atom, however the interaction of H2P with C60 is not weaker as compared to the metal complexes. Similarly to the BLYP/DN results, in most porphine-C-60 complexes, two closest contacts of metal are those with carbon atoms of (6, 6) bond. There are three exceptions in the present case, versus only one (VOP (.) C-60) in the previous study: the closest M-C contacts involve (5,6) bond in H2P (.) C-60, and VOP (.) C-60, and in PdP (.) C-60, Pd ion coordinates to the six-membered ring. The interaction with C-60 influences the porphine geometry, and its change depends on the central atom. The most striking feature (apparently an artifact) was found for H2P (.) C-60, where H2P molecule stretches along the axis connecting two opposite meso-C atoms and shrinks in the perpendicular direction. The central metal ions interact stronger with C-60 than the atoms belonging to the porphine ligand do. As a result, in all complexes except for VOP (.) C-60 and MnCIP (.) C60, the metal is located between the macrocyclic plane and C-60. The changes in electrostatic potential and spin density distribution, HOMO and LUMO shape are discussed as well.