The geometries, electronic structures, polarizabilities and hyperpolarizabilities, and UV–vis
spectra of metallophthalocyanine dyes and metallophthalocyanine–fullerene supramolecules
are investigated by using density functional theory (DFT) and time dependent density
functional theory (TD-DFT) calculations. The results reveal that the metal and the tertiary
butyl groups of the dyes are electron donors, and the phthalocyanine rings are electron
acceptors. The electron donating power of (La) is significantly greater than that of (Sc).
For dyes, the highest occupied molecular orbitals (HOMOs) are p orbitals localized over
the phthalocyanine rings, away from the tertiary butyl groups, and the lowest unoccupied
molecular orbitals (LUMOs) are p⁄ orbitals localized over the central metal atoms. The
HOMOs of the dyes fall within the (TiO2)60 and Ti38O76 band gaps, and support the issue
of typical interfacial electron transfer reaction. The resulting potential drop of the supramolecule
LaPc.C60 increases by ca. 22.86% under the effect of the tertiary butyl groups. This
significant increase in the potential drop indicates that the tertiary butyl complexes could
be a better choice for the robust operation of the molecular rectifiers. The introduction of
metal atom and tertiary butyl groups to the phthalocyanine moiety leads to a stronger
response to the external electric field, and induces higher photo-to-current conversion efficiency.
This also shifts the absorption in the dyes and makes them potential candidates for
harvesting light in the entire visible and near IR region for photovoltaic applications. It is
also observed that the high spin state complex Sc(4)Pc could not be a potential candidate
for harvesting light in the former region of spectrum.