Supramolecular formation of Li+@PCBM fullerene with sulfonated porphyrins and long-lived charge separation

Yuki Kawashima, Kei Ohkubo, Hiroshi Okada, Yutaka Matsuo, Shunichi Fukuzumi

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13 Scopus citations


Lithium-ion-encapsulated [6,6]-phenyl-C61-butyric acid methyl ester fullerene (Li+@PCBM) was utilized to construct supramolecules with sulfonated meso-tetraphenylporphyrins (MTPPS4-; M=Zn, H2) in polar benzonitrile. The association constants were determined to be 1.8×105m-1 for ZnTPPS4-/Li+@PCBM and 6.2×104m-1 for H2TPPS4-/Li+@PCBM. From the electrochemical analyses, the energies of the charge-separated (CS) states were estimated to be 0.69 eV for ZnTPPS4-/Li+@PCBM and 1.00 eV for H2TPPS4-/Li+@PCBM. Upon photoexcitation of the porphyrin moieties of MTPPS4-/Li+@PCBM, photoinduced electron transfer occurred to produce the CS states. The lifetimes of the CS states were 560 μs for ZnTPPS4-/Li+@PCBM and 450 μs for H2TPPS4-/Li+@PCBM. The spin states of the CS states were determined to be triplet by electron paramagnetic resonance spectroscopy measurements at 4 K. The reorganization energies (λ) and electronic coupling term (V) for back electron transfer (BET) were determined from the temperature dependence of kBET to be λ =0.36 eV and V=8.5×10-3 cm-1 for ZnTPPS4-/Li+@PCBM and λ =0.62 eV and V=7.9×10-3 cm-1 for H2TPPS4-/Li+@PCBM based on the Marcus theory of nonadiabatic electron transfer. Such small V values are the result of a small orbital interaction between the MTPPS4- and Li+ @PCBM moieties. These small V values and spin-forbidden charge recombination afford a long-lived CS state.

Original languageEnglish
Pages (from-to)3782-3790
Number of pages9
Issue number17
StatePublished - 12 Jan 2014

Bibliographical note

Publisher Copyright:
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.


  • Charge separation
  • Electron transfer
  • Endohedral fullerenes
  • Porphyrinoids
  • Supramolecular chemistry


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