Robust inclusion complexes of crown ether fused tetrathiafulvalenes with Li⁺@C₆₀ to afford efficient photodriven charge separation

Chemistry. 2014 Oct 20;20(43):13976-83. doi: 10.1002/chem.201402449. Epub 2014 Sep 11.


Inclusion complexes of benzo- and dithiabenzo-crown ether functionalized monopyrrolotetrathiafulvalene (MPTTF) molecules were formed with Li(+)@C60(1⋅Li(+)@C60 and 2⋅Li(+)@C60). The strong complexation has been quantified by high binding constants that exceed 10(6) M(-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 (1)Li(+)@C60* occurs. Photoinduced charge separation by means of (3)Li(+)@C60* with lifetimes of 135 and 120 μs for 1⋅Li(+)@C60 and 2⋅Li(+)@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.

Keywords: donor-acceptor systems; electron transfer; fullerenes; inclusion; tetrathiafulvalene.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crown Ethers / chemistry*
  • Electron Transport
  • Fullerenes / chemistry*
  • Heterocyclic Compounds / chemistry*
  • Lithium / chemistry*
  • Models, Molecular
  • Photochemical Processes


  • Crown Ethers
  • Fullerenes
  • Heterocyclic Compounds
  • Lithium
  • tetrathiafulvalene