Robust Inclusion Complexes of Crown Ether Fused Tetrathiafulvalenes with Li+@C60 to Afford Efficient Photodriven Charge Separation |
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| Authors: | Dr Mustafa Supur Yuki Kawashima Dr Karina R Larsen Dr Kei Ohkubo Prof Jan O Jeppesen Prof Shunichi Fukuzumi |
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| Affiliation: | 1. Department of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA, JST, Suita, Osaka 565‐0871 (Japan), Fax: (+81)?6‐6879‐7370;2. Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230, Odense‐M (Denmark);3. Department of Bioinspired Science, Ewha Womans University, Seoul 120‐750 (Korea) |
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| Abstract: | 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 106 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 1Li+@C60* occurs. Photoinduced charge separation by means of 3Li+@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. |
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| Keywords: | donor– acceptor systems electron transfer fullerenes inclusion tetrathiafulvalene |
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