Chemically modified fullerene derivatives as photosensitizers in photodynamic therapy: a first-principles study.

The first-principles density functional theory (DFT) and its time-dependent approach (TD-DFT) are used to characterize the electronic structures and optical spectra properties of five chemically modified fullerenes. It is revealed that the metal fullerene derivatives possess not only stronger absorption bands in visible light regions than organically modified fullerene but also the large energy gaps (ΔE(S-T) > 0.98 eV) between the singlet ground state and the triplet state, which imply their significant aspect of potential candidates as a photosensitizer. We have found that a new metal-containing bisfullerene complexes (Pt(C(60) )(2) ), with the extended conjugated π-electrons, much degenerate orbitals and a uniform electrostatic potential surface, behave more pre-eminent photosensitizing properties than other examined fullerene derivatives.