Synthesis and Photoinduced Intramolecular Processes of Light‐Harvesting Silicon Phthalocyanine–Naphthalenediimide–Fullerene Connected Systems

Fast moving : A new pentad (see figure) composed of silicon phthalocyanine (SiPc), as electron donor, that is connected with two units of naphthalenediimide (NDI) and fullerene C 60 , as electron acceptors, undergoes fast and efficient charge‐separation processes via the NDI and SiPc singlet excited states.Photoinduced intramolecular processes of a newly synthesized pentad composed of silicon phthalocyanine (SiPc) that is connected with two units of naphthalenediimide (NDI) and fullerene C 60 to form SiPc‐(NDI) 2 ‐(C 60 ) 2 have been studied and the results are compared with the reference compounds, namely, the SiPc‐(NDI) 2 triad and NDI‐C 60 dyad. Upon photoexcitation, the main quenching pathway in polar solvents involved electron transfer via the singlet excited states of SiPc‐(NDI) 2 ‐(C 60 ) 2 and SiPc‐(NDI) 2 , but not NDI‐C 60 for which the energy transfer is dominant. The occurrence of electron‐transfer processes of SiPc‐(NDI) 2 ‐(C 60 ) 2 and SiPc‐(NDI) 2 were studied by time‐resolved emission and transient absorption techniques and confirmed by redox measurements and molecular orbital calculations with ab initio B3 LYP/3–21G(*) methods. Fast and efficient charge‐separation processes via the singlet excited states of NDI and SiPc were monitored, followed by charge recombination to populate the C 60 and SiPc triplet states. The lifetimes of charge‐separated states were estimated as 1000 and 250 ps for SiPc‐(NDI) 2 ‐(C 60 ) 2 and SiPc‐(NDI) 2 , respectively.