(Invited) Multichromophoric Perylenediimide-Silicon Phthalocyanine-C60 System As an Artificial Photosynthetic Analogue

Abstract

Sequential photoinduced energy transfer followed by electron transfer and the formation of charge separated states, which are primary events of natural photosynthesis, have been demonstrated in a newly synthesized multichromophoric covalently linked triad, PDI-SiPc-C60. The triad was comprised of a perylenediimide (PDI) that primarily fulfils antenna functionality and electron acceptor; silicon phthalocyanine (SiPc) as an electron donor; and fulleropyrrolidine (C60) as a second electron acceptor. The multi-step convergent synthetic procedure developed here produced good yields of the triad and control dyads, PDI-SiPc and SiPc-C60. The structure and geometry of the newly synthesized donor-acceptor systems were established from spectral, computational and electrochemical studies with the help of appropriate control compounds. Ultrafast energy transfer from 1PDI* to SiPc in the case of PDI-SiPc and PDI-SiPc-C60 was witnessed. Energy level diagram established from spectral and electrochemical data suggested formation of two types of charge separated states, viz., of PDI-SiPc•+-C60 •- and PDI•--SiPc•+-C60 from the 1SiPc* in the triad; and that generation of the latter is energetically more favourable. However, photochemical studies involving femtosecond transient spectroscopy revealed formation of PDI-SiPc•+-C60 •- as a major charge separation product. This observation has been rationalized to the spatial closeness of C60 compared to PDI in the triad. The charge separated state lasted for a few nanoseconds prior to populating the 3SiPc* state during charge recombination.[1] AcknowledgmentsThis work was supported by the Spanish Ministry of Economy and Competitiveness (Mineco) of Spain (CTQ2014-55798-R to ASS), Generalitat Valenciana (Prometeo 2012/010 to ASS) and National Science Foundation (Grant No. 1401188 to FD).