Robust Inclusion Complexes of Crown Ether Fused Tetrathiafulvalenes with Li+@C60 to Afford Efficient Photodriven Charge Separation

Mustafa Supur, Yuki Kawashima, Karina R. Larsen, Kei Ohkubo, Jan O. Jeppesen, Shunichi Fukuzumi

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Inclusion complexes of benzo- and dithiabenzo-crown ether functionalized monopyrrolotetrathiafulvalene (MPTTF) molecules were formed with Li+@C60 (1Li+@C60 and 2Li+@C60). The strong complexation has been quantified by high binding constants that exceed 106M-1 obtained by UV/Vis titrations in benzonitrile (PhCN) at room temperature. On the basis of DFT studies at the B3LYP/6-311G(d,p) level, the orbital interactions between the crown ether moieties and the π surface of the fullerene together with the endohedral Li+ have a crucial role in robust complex formation. Interestingly, complexation of Li+@C60 with crown ethers accelerates the intersystem crossing upon photoexcitation of the complex, thereby yielding 3(Li+@C60)∗, when no charge separation by means of 1Li+@C60∗ occurs. Photoinduced charge separation by means of 3Li+@C60∗ with lifetimes of 135 and 120 μs for 1Li+@C60 and 2Li+@C60, respectively, and quantum yields of 0.82 in PhCN have been observed by utilizing time-resolved transient absorption spectroscopy and then confirmed by electron paramagnetic resonance measurements at 4 K. The difference in crown ether structures affects the binding constant and the rates of photoinduced electron-transfer events in the corresponding complex.

Original languageEnglish
Pages (from-to)13976-13983
Number of pages8
JournalChemistry - A European Journal
Volume20
Issue number43
DOIs
StatePublished - 20 Oct 2014

Bibliographical note

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

Keywords

  • donor-acceptor systems
  • electron transfer
  • fullerenes
  • inclusion
  • tetrathiafulvalene

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