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Shunichi Fukuzumi - One of the best experts on this subject based on the ideXlab platform.
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supramolecular Electron Transfer by anion binding
Chemical Communications, 2012Co-Authors: Shunichi Fukuzumi, Kei Ohkubo, Francis Dsouza, Jonathan L SesslerAbstract:Anion binding has emerged as an attractive strategy to construct supramolecular Electron donor–acceptor complexes. In recent years, the level of sophistication in the design of these systems has advanced to the point where it is possible to create ensembles that mimic key aspects of the photoinduced Electron-Transfer events operative in the photosynthetic reaction centre. Although anion binding is a reversible process, kinetic studies on anion binding and dissociation processes, as well as photoinduced Electron-Transfer and back Electron-Transfer reactions in supramolecular Electron donor–acceptor complexes formed by anion binding, have revealed that photoinduced Electron Transfer and back Electron Transfer occur at time scales much faster than those associated with anion binding and dissociation. This difference in rates ensures that the linkage between Electron donor and acceptor moieties is maintained over the course of most forward and back Electron-Transfer processes. A particular example of this principle is illustrated by Electron-Transfer ensembles based on tetrathiafulvalene calix[4]pyrroles (TTF-C4Ps). In these ensembles, the TTF-C4Ps act as donors, Transferring Electrons to various Electron acceptors after anion binding. Competition with non-redox active substrates is also observed. Anion binding to the pyrrole amine groups of an oxoporphyrinogen unit within various supramolecular complexes formed with fullerenes also results in acceleration of the photoinduced Electron-Transfer process but deceleration of the back Electron Transfer; again, this is ascribed to favourable structural and Electronic changes. Anion binding also plays a role in stabilizing supramolecular complexes between sulphonated tetraphenylporphyrin anions ([MTPPS]4−: M = H2 and Zn) and a lithium ion encapsulated C60 (Li+@C60); the resulting ensemble produces long-lived charge-separated states upon photoexcitation of the porphyrins.
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Mechanisms of metal ion-coupled Electron Transfer
Physical Chemistry Chemical Physics, 2012Co-Authors: Shunichi Fukuzumi, Kei Ohkubo, Yuma MorimotoAbstract:Redox inactive metal ions acting as Lewis acids can control Electron Transfer from Electron donors (D) to Electron acceptors (A) by binding to radical anions of Electron acceptors which act as Lewis bases. Such Electron Transfer is defined as metal ion-coupled Electron Transfer (MCET). Mechanisms of metal ion-coupled Electron Transfer are classified mainly into two pathways, i.e., metal ion binding to Electron acceptors followed by Electron Transfer (MB/ET) and Electron Transfer followed by metal ion binding to the resulting radical anions of Electron acceptors (ET/MB). In the former case, Electron Transfer and the stronger binding of metal ions to the radical anions occur in a concerted manner. Examples are shown in each case to clarify the factors to control MCET reactions in both thermal and photoinduced Electron-Transfer reactions including back Electron-Transfer reactions.
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Mechanisms of metal ion-coupled Electron Transfer
Physical chemistry chemical physics : PCCP, 2012Co-Authors: Shunichi Fukuzumi, Kei Ohkubo, Yuma MorimotoAbstract:Redox inactive metal ions acting as Lewis acids can control Electron Transfer from Electron donors (D) to Electron acceptors (A) by binding to radical anions of Electron acceptors which act as Lewis bases. Such Electron Transfer is defined as metal ion-coupled Electron Transfer (MCET). Mechanisms of metal ion-coupled Electron Transfer are classified mainly into two pathways, i.e., metal ion binding to Electron acceptors followed by Electron Transfer (MB/ET) and Electron Transfer followed by metal ion binding to the resulting radical anions of Electron acceptors (ET/MB). In the former case, Electron Transfer and the stronger binding of metal ions to the radical anions occur in a concerted manner. Examples are shown in each case to clarify the factors to control MCET reactions in both thermal and photoinduced Electron-Transfer reactions including back Electron-Transfer reactions.
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Metal ion-coupled and decoupled Electron Transfer
Coordination Chemistry Reviews, 2010Co-Authors: Shunichi Fukuzumi, Kei OhkuboAbstract:Abstract Effects of metal ions on thermal and photoinduced Electron-Transfer reactions from Electron donors (D) to Electron acceptors (A) are reviewed in terms of metal ion-coupled Electron Transfer (MCET) vs. metal ion-decoupled Electron Transfer (MDET). When Electron Transfer from D to A is coupled with binding of metal ions to A − , such an Electron Transfer is defined as MCET in which metal ions accelerate the rates of Electron Transfer. A number of examples of Electron-Transfer reactions from D to A, which are energetically impossible to occur, are made possible by strong binding of metal ions to A − in MCET. The structures of metal ion complexes with A − are also discussed in relation with the MCET reactivity. The MCET reactivity of metal ions is shown to be enhanced with an increase in the Lewis acidity of metal ions. In contrast to MCET, strong binding of metal ions to A − results in deceleration of back Electron Transfer from metal ion complexes of A − to D + in the radical ion pair, which is produced by photoinduced Electron Transfer from D to A in the presence of metal ions, as compared with back Electron Transfer without metal ions. The deceleration of back Electron Transfer in the presence of metal ions results from no binding of metal ions to A. This type of Electron Transfer is defined as metal ion-decoupled Electron Transfer (MDET). The lifetimes of CS state (D + –A − ) produced by photoinduced Electron Transfer from D to A in the D–A linked systems are also elongated by adding metal ions to the D–A systems because of the stabilization of the CS states by strong binding of metal ions to A − and the resulting slow MDET processes.
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Bioinspired Electron-Transfer Systems and Applications
Bulletin of the Chemical Society of Japan, 2006Co-Authors: Shunichi FukuzumiAbstract:Bioinspired Electron-Transfer systems including artificial photosynthesis and respiration are presented herein together with some of their applications. First, multi-step Electron-Transfer systems ...
Kei Ohkubo - One of the best experts on this subject based on the ideXlab platform.
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supramolecular Electron Transfer by anion binding
Chemical Communications, 2012Co-Authors: Shunichi Fukuzumi, Kei Ohkubo, Francis Dsouza, Jonathan L SesslerAbstract:Anion binding has emerged as an attractive strategy to construct supramolecular Electron donor–acceptor complexes. In recent years, the level of sophistication in the design of these systems has advanced to the point where it is possible to create ensembles that mimic key aspects of the photoinduced Electron-Transfer events operative in the photosynthetic reaction centre. Although anion binding is a reversible process, kinetic studies on anion binding and dissociation processes, as well as photoinduced Electron-Transfer and back Electron-Transfer reactions in supramolecular Electron donor–acceptor complexes formed by anion binding, have revealed that photoinduced Electron Transfer and back Electron Transfer occur at time scales much faster than those associated with anion binding and dissociation. This difference in rates ensures that the linkage between Electron donor and acceptor moieties is maintained over the course of most forward and back Electron-Transfer processes. A particular example of this principle is illustrated by Electron-Transfer ensembles based on tetrathiafulvalene calix[4]pyrroles (TTF-C4Ps). In these ensembles, the TTF-C4Ps act as donors, Transferring Electrons to various Electron acceptors after anion binding. Competition with non-redox active substrates is also observed. Anion binding to the pyrrole amine groups of an oxoporphyrinogen unit within various supramolecular complexes formed with fullerenes also results in acceleration of the photoinduced Electron-Transfer process but deceleration of the back Electron Transfer; again, this is ascribed to favourable structural and Electronic changes. Anion binding also plays a role in stabilizing supramolecular complexes between sulphonated tetraphenylporphyrin anions ([MTPPS]4−: M = H2 and Zn) and a lithium ion encapsulated C60 (Li+@C60); the resulting ensemble produces long-lived charge-separated states upon photoexcitation of the porphyrins.
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Mechanisms of metal ion-coupled Electron Transfer
Physical chemistry chemical physics : PCCP, 2012Co-Authors: Shunichi Fukuzumi, Kei Ohkubo, Yuma MorimotoAbstract:Redox inactive metal ions acting as Lewis acids can control Electron Transfer from Electron donors (D) to Electron acceptors (A) by binding to radical anions of Electron acceptors which act as Lewis bases. Such Electron Transfer is defined as metal ion-coupled Electron Transfer (MCET). Mechanisms of metal ion-coupled Electron Transfer are classified mainly into two pathways, i.e., metal ion binding to Electron acceptors followed by Electron Transfer (MB/ET) and Electron Transfer followed by metal ion binding to the resulting radical anions of Electron acceptors (ET/MB). In the former case, Electron Transfer and the stronger binding of metal ions to the radical anions occur in a concerted manner. Examples are shown in each case to clarify the factors to control MCET reactions in both thermal and photoinduced Electron-Transfer reactions including back Electron-Transfer reactions.
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Mechanisms of metal ion-coupled Electron Transfer
Physical Chemistry Chemical Physics, 2012Co-Authors: Shunichi Fukuzumi, Kei Ohkubo, Yuma MorimotoAbstract:Redox inactive metal ions acting as Lewis acids can control Electron Transfer from Electron donors (D) to Electron acceptors (A) by binding to radical anions of Electron acceptors which act as Lewis bases. Such Electron Transfer is defined as metal ion-coupled Electron Transfer (MCET). Mechanisms of metal ion-coupled Electron Transfer are classified mainly into two pathways, i.e., metal ion binding to Electron acceptors followed by Electron Transfer (MB/ET) and Electron Transfer followed by metal ion binding to the resulting radical anions of Electron acceptors (ET/MB). In the former case, Electron Transfer and the stronger binding of metal ions to the radical anions occur in a concerted manner. Examples are shown in each case to clarify the factors to control MCET reactions in both thermal and photoinduced Electron-Transfer reactions including back Electron-Transfer reactions.
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Metal ion-coupled and decoupled Electron Transfer
Coordination Chemistry Reviews, 2010Co-Authors: Shunichi Fukuzumi, Kei OhkuboAbstract:Abstract Effects of metal ions on thermal and photoinduced Electron-Transfer reactions from Electron donors (D) to Electron acceptors (A) are reviewed in terms of metal ion-coupled Electron Transfer (MCET) vs. metal ion-decoupled Electron Transfer (MDET). When Electron Transfer from D to A is coupled with binding of metal ions to A − , such an Electron Transfer is defined as MCET in which metal ions accelerate the rates of Electron Transfer. A number of examples of Electron-Transfer reactions from D to A, which are energetically impossible to occur, are made possible by strong binding of metal ions to A − in MCET. The structures of metal ion complexes with A − are also discussed in relation with the MCET reactivity. The MCET reactivity of metal ions is shown to be enhanced with an increase in the Lewis acidity of metal ions. In contrast to MCET, strong binding of metal ions to A − results in deceleration of back Electron Transfer from metal ion complexes of A − to D + in the radical ion pair, which is produced by photoinduced Electron Transfer from D to A in the presence of metal ions, as compared with back Electron Transfer without metal ions. The deceleration of back Electron Transfer in the presence of metal ions results from no binding of metal ions to A. This type of Electron Transfer is defined as metal ion-decoupled Electron Transfer (MDET). The lifetimes of CS state (D + –A − ) produced by photoinduced Electron Transfer from D to A in the D–A linked systems are also elongated by adding metal ions to the D–A systems because of the stabilization of the CS states by strong binding of metal ions to A − and the resulting slow MDET processes.
Yuma Morimoto - One of the best experts on this subject based on the ideXlab platform.
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Mechanisms of metal ion-coupled Electron Transfer
Physical Chemistry Chemical Physics, 2012Co-Authors: Shunichi Fukuzumi, Kei Ohkubo, Yuma MorimotoAbstract:Redox inactive metal ions acting as Lewis acids can control Electron Transfer from Electron donors (D) to Electron acceptors (A) by binding to radical anions of Electron acceptors which act as Lewis bases. Such Electron Transfer is defined as metal ion-coupled Electron Transfer (MCET). Mechanisms of metal ion-coupled Electron Transfer are classified mainly into two pathways, i.e., metal ion binding to Electron acceptors followed by Electron Transfer (MB/ET) and Electron Transfer followed by metal ion binding to the resulting radical anions of Electron acceptors (ET/MB). In the former case, Electron Transfer and the stronger binding of metal ions to the radical anions occur in a concerted manner. Examples are shown in each case to clarify the factors to control MCET reactions in both thermal and photoinduced Electron-Transfer reactions including back Electron-Transfer reactions.
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Mechanisms of metal ion-coupled Electron Transfer
Physical chemistry chemical physics : PCCP, 2012Co-Authors: Shunichi Fukuzumi, Kei Ohkubo, Yuma MorimotoAbstract:Redox inactive metal ions acting as Lewis acids can control Electron Transfer from Electron donors (D) to Electron acceptors (A) by binding to radical anions of Electron acceptors which act as Lewis bases. Such Electron Transfer is defined as metal ion-coupled Electron Transfer (MCET). Mechanisms of metal ion-coupled Electron Transfer are classified mainly into two pathways, i.e., metal ion binding to Electron acceptors followed by Electron Transfer (MB/ET) and Electron Transfer followed by metal ion binding to the resulting radical anions of Electron acceptors (ET/MB). In the former case, Electron Transfer and the stronger binding of metal ions to the radical anions occur in a concerted manner. Examples are shown in each case to clarify the factors to control MCET reactions in both thermal and photoinduced Electron-Transfer reactions including back Electron-Transfer reactions.
Tamar Seideman - One of the best experts on this subject based on the ideXlab platform.
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Photoisomerization-coupled Electron Transfer.
The Journal of chemical physics, 2020Co-Authors: Jakub K. Sowa, Emily A. Weiss, Tamar SeidemanAbstract:Photochromic molecular structures constitute a unique platform for constructing molecular switches, sensors, and memory devices. One of their most promising applications is as light-switchable Electron acceptor or donor units. Here, we investigate a previously unexplored process that we postulate may occur in such systems: an ultrafast Electron Transfer triggered by a simultaneous photoisomerization of the donor or the acceptor moiety. We propose a theoretical model for this phenomenon and, with the aid of density functional theory calculations, apply it to the case of a dihydropyrene-type photochromic molecular donor. By considering the wavepacket dynamics and the photoisomerization yield, we show that the two processes involved, Electron Transfer and photoisomerization, are in general inseparable and need to be treated in a unified manner. We finish by discussing how the efficiency of photoisomerization-coupled Electron Transfer can be controlled experimentally.
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photoisomerization coupled Electron Transfer
arXiv: Chemical Physics, 2020Co-Authors: Jakub K. Sowa, Emily A. Weiss, Tamar SeidemanAbstract:Photochromic molecular structures constitute a unique platform for constructing molecular switches, sensors and memory devices. One of their most promising applications is as light-switchable Electron acceptor or donor units. Here, we investigate a previously unexplored process that we postulate may occur in such systems: an ultrafast Electron Transfer triggered by a simultaneous photoisomerization of the donor or the acceptor moiety. We propose a theoretical model for this phenomenon and, with the aid of DFT calculations, apply it to the case of a dihydropyrene-type photochromic molecular donor. By considering the wavepacket dynamics and the photoisomerization yield, we show that the two processes involved, Electron Transfer and photoisomerization, are in general inseparable and need to be treated in a unified manner. We finish by discussing how the efficiency of photoisomerization-coupled Electron Transfer can be controlled experimentally.
Ji Sun - One of the best experts on this subject based on the ideXlab platform.
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New perspectives on long-range Electron Transfer in conformationally organized peptides and Electron-Transfer proteins: an experimental approach
Journal of Photochemistry and Photobiology A: Chemistry, 1994Co-Authors: Stephan S. Isied, Icaro Moreira, Michael Y. Ogawa, Asbed Vassilian, Bente E. Arbo, Ji SunAbstract:Abstract Intramolecular Electron-Transfer studies across a series of peptides ranging from dipeptides to longer peptides with secondary structure (such as polyproline II and a 17-amino acid α helix) have been carried out. Metal ammine and bipyridine complexes have been used as donors and acceptors in these studies. These studies show that the rate of Electron Transfer is sensitive to the peptide structure and conformation, even for dipeptide bridges. For peptides with secondary structure, the connectivity of the donor and acceptor to the peptide is also important for the observation of long-range Electron Transfer. For example, for (bpy)2RuIIL(Pro)n-apyRuIII(NH3)5 (n = 9) (bpy2,2′ bipyridine, L4-carboxy-4′-methyl-2,2′-bipyridine, apy-4-aminopyridine), an Electron Transfer rate 2 × 104 s−1 was observed, while intramolecular Electron Transfer could not be observed for the α helix bridge in (bpy)2RuIIL[α-helical peptide]-(His)2RuIII(NH3)4 (α-helical peptide Ala-Glu-(Ala)3Lys-Glu(Ala) 3Lys-His(Ala)3His-Ala). Comparative intramolecular Electron-Transfer experiments were also conducted with two cytochrome c derivatives: one modified at His 33 by [-Ru(NH3)4isn] and one modified at Met 65 by [-Fe(CN)5]. Although the His 33 and Met 65 sites are located at similar distances from the heme, and the two metal complexes possess similar reorganization energies and driving force, different rates of Electron Transfer varying by about 1000 were observed for the Electron Transfer from the heme to the metal complex. The experiments presented show that the shortest through-space distance is not always the most important determinent of the rate of Electron Transfer, and other factors such as the peptide structure and conformation and the connectivity of the donor and acceptor to the peptide bridge are very important.
