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Robust Inclusion Complexes of Crown Ether Fused Tetrathiafulvalenes with Li + @C 60 to Afford Efficient Photodriven Charge Separation
Author(s) -
Supur Mustafa,
Kawashima Yuki,
Larsen Karina R.,
Ohkubo Kei,
Jeppesen Jan O.,
Fukuzumi Shunichi
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201402449
Subject(s) - benzonitrile , chemistry , photoexcitation , crown ether , photochemistry , ether , photoinduced charge separation , charge transfer complex , stability constants of complexes , binding constant , ion , medicinal chemistry , organic chemistry , excited state , photocatalysis , binding site , biochemistry , aqueous solution , physics , nuclear physics , artificial photosynthesis , catalysis
Inclusion complexes of benzo‐ and dithiabenzo‐crown ether functionalized monopyrrolotetrathiafulvalene (MPTTF) molecules were formed with Li + @C 60 ( 1⋅ Li + @C 60 and 2⋅ Li + @C 60 ). 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 + @C 60 with crown ethers accelerates the intersystem crossing upon photoexcitation of the complex, thereby yielding 3 (Li + @C 60 )*, when no charge separation by means of 1 Li + @C 60 * occurs. Photoinduced charge separation by means of 3 Li + @C 60 * with lifetimes of 135 and 120 μs for 1⋅ Li + @C 60 and 2⋅ Li + @C 60 , 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.