Ultrafast photoinduced energy and electron transfer in multi-modular donor-acceptor conjugates

Mohamed E. El-Khouly, Channa A. Wijesinghe, Vladimir N. Nesterov, Melvin E. Zandler, Shunichi Fukuzumi, Francis D'Souza

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New multi-modular donor-acceptor conjugates featuring zinc porphyrin (ZnP), catechol-chelated boron dipyrrin (BDP), triphenylamine (TPA) and fullerene (C 60), or naphthalenediimide (NDI) have been newly designed and synthesized as photosynthetic antenna and reaction-center mimics. The X-ray structure of triphenylamine-BDP is also reported. The wide-band capturing polyad revealed ultrafast energy-transfer (k ENT=1.0×10 12 s -1) from the singlet excited BDP to the covalently linked ZnP owing to close proximity and favorable orientation of the entities. Introducing either fullerene or naphthalenediimide electron acceptors to the TPA-BDP-ZnP triad through metal-ligand axial coordination resulted in electron donor-acceptor polyads whose structures were revealed by spectroscopic, electrochemical and computational studies. Excitation of the electron donor, zinc porphyrin resulted in rapid electron-transfer to coordinated fullerene or naphthalenediimide yielding charge separated ion-pair species. The measured electron transfer rate constants from femtosecond transient spectral technique in non-polar toluene were in the range of 5.0×10 9-3.5×10 10 s -1. Stabilization of the charge-separated state in these multi-modular donor-acceptor polyads is also observed to certain level.

Original languageEnglish
Pages (from-to)13844-13853
Number of pages10
JournalChemistry - A European Journal
Issue number43
StatePublished - 22 Oct 2012


  • artificial photosynthesis
  • donor-acceptor systems
  • electron transfer
  • energy transfer
  • fullerene


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