Photoexcitation of Light-Harvesting C-P-C60 Triads: A FLMO-TD-DFT Study

The recently proposed linear-scaling time-dependent density functional theory (TD-DFT) [J. Chem. Theory. Comput. 2011, 7, 3643] is employed to capture more than 300 low-lying excited states for three light-harvesting C-P-C-60 triads composed of beta-carotenoid polyene (C), diaryl-based porphyrin (P), and pyrrole-fullerene (C-60). The simulated optical absorption spectra are grossly in good agreement with experimental observations. To gain insights on the structure-property relations, both top-down and bottom-up analyses of the excited states are made in terms of the underlying fragment localized molecular orbitals (FLMO). A maximum occupation method is further proposed for finding excited-state solutions of self-consistent-field equations and is applied to long-range charge-transfer states that cannot be described by TD-DFT with pure density functionals.