Noncovalent complexes of Ih−C80 fullerene with phthalocyanines

Abstract

ABSTRACTThe noncovalent interactions of Ih−C80 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 C60. In the complexes with Ih−C80, the central metal atom (as well as one H atom of H2Pc) is always coordinated to a C6:6:6 atom of C80 cage, exhibiting only one general interaction pattern. The shortest M…CC80 and N…CC80 distances are notably longer than in dyads with C60, and the distortion of Pc macrocycle is less significant. In none of C80-based dyads the formation of new coordination bonds by metal atoms was observed. The bonding strength for Pc–C80 dyads varies approximately to the same degree of 20 kcal/mol as for their Pc–C60 analogues, however negative formation energies for Pc–C80 dyads are on average by 5–6 kcal/mol lower than for their C60 analogues. While in closed-shell Pc–fullerene systems HOMO is usually found totally on Pc molecule, in the case of C80-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 0.1 eV. Analysis of spin density plots revealed that H2Pc+C80, NiPc+C80 and ZnPc+C80 dyads behave as closed-shell systems, like similar noncovalent complexes of Pcs with C60.