Noncovalent complexes of Ih-C80 fullerene with phthalocyanines

The noncovalent interactions of I-h-C-80 fullerene with free-base and 3d transition M(II) phthalocyanines (where M = Mn, Fe, Co, Ni, Cu, Zn) were studied at the PBE-D/DNP level of density functional theory. The optimized complex geometries, formation energies and electronic parameters were analyzed and compared to those reported previously for similar dyads with C-60. In the complexes with I-h-C-80, the central metal atom (as well as one H atom of H2Pc) is always coordinated to a C-6:6:6 atom of C-80 cage, exhibiting only one general interaction pattern. The shortest (MCC80)-C-... and (NCC80)-C-... distances are notably longer than in dyads with C-60,C- and the distortion of Pc macrocycle is less significant. In none of C-80-based dyads the formation of new coordination bonds by metal atoms was observed. The bonding strength for Pc-C-80 dyads varies approximately to the same degree of 20kcal/mol as for their Pc-C-60 analogues, however negative formation energies for Pc-C-80 dyads are on average by 5-6kcal/mol lower than for their C-60 analogues. While in closed-shell Pc-fullerene systems HOMO is usually found totally on Pc molecule, in the case of C-80-based dyads only a minor HOMO fraction can be detected for some dyads on Pc, with the major one always distributed over fullerene cage. As a result, the calculated HOMO-LUMO gap energies turn to be very low, around 0.1eV. Analysis of spin density plots revealed that H2Pc+C-80, NiPc+C-80 and ZnPc+C-80 dyads behave as closed-shell systems, like similar noncovalent complexes of Pcs with C-60.