Photoexcitation of a Light-Harvesting Supramolecular Triad: A Time-Dependent DFT Study

We present the first time-dependent density functional theory (TDDFT) calculation on a light-harvestingtriad carotenoid-diaryl-porphyrin-C60. Besides the numerical challenge that the ab initio study of the electronicstructure of such a large system presents, we show that TDDFT is able to provide an accurate description ofthe excited-state properties of the system. In particular, we calculate the photoabsorption spectrum of thesupramolecular assembly, and we provide an interpretation of the photoexcitation mechanism in terms of theproperties of the component moieties. The spectrum is in good agreement with experimental data, and providesuseful insight on the photoinduced charge-transfer mechanism which characterizes the system.