Catalysis of Photoinduced Electron Transfer Reactions

Fukuzumi, Shunichi; Itoh, Shinobu

doi:10.1002/9780470133569.ch3

Cited by 19 publications

(7 citation statements)

References 186 publications

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“…Although acid catalysis has been demonstrated for chemical reactions involving two-electron pathways, explosive growth in the general area of (single) electron-transfer chemistry has been witnessed in the past decade. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] Electron transfer (ET) from electron donors (D) to electron acceptors (A) is accelerated by binding acids including Brønsted acids and metal ions (e.g., Sc 3+ ) acting as Lewis acids to one-electron reduced species of A. Such acceleration of rates of ET by acids is not called acid catalysis, because acids are consumed in acid-promoted electron transfer (APET) reactions.…”

Section: Introductionmentioning

confidence: 99%

“…This concept is more general than that by Johannes Nicolaus Brønsted, who defined that an acid is a molecule that can donate protons. Although acid catalysis has been demonstrated for chemical reactions involving two‐electron pathways, explosive growth in the general area of (single) electron‐transfer chemistry has been witnessed in the past decade 15–31 . Electron transfer (ET) from electron donors (D) to electron acceptors (A) is accelerated by binding acids including Brønsted acids and metal ions ( e.g ., Sc 3+ ) acting as Lewis acids to one‐electron reduced species of A.…”

Section: Introductionmentioning

confidence: 99%

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Acid Catalysis via Acid‐Promoted Electron Transfer

Fukuzumi

Lee

Nam

2020

Bulletin Korean Chem Soc

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This feature article focuses on acid catalysis in various redox reactions of not only organic compounds but also metal complexes, in particular metal-oxygen complexes via acid-promoted electron transfer (APET). On the other hand, proton-coupled electron transfer (PCET) has been extensively studied in relation with important biological PCET reactions such as O 2 reduction in respiration and water oxidation in photosynthesis. Because PCET is normally defined as simultaneous electron and proton transfer from the same substrate, acid-promoted electron transfer using external acids is called APET in this article. Various types of chemical transformations exhibiting acid catalysis via APET discussed in this article include C C bond formation, C H bond oxidation, aromatic hydroxylation, and oxygen atom transfer reactions such as sulfoxidation and epoxidation reactions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Acid Catalysis via Acid‐Promoted Electron Transfer

Fukuzumi

Lee

Nam

2020

Bulletin Korean Chem Soc

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“…Metal ions play a critical role in modulating ET reactions in biological processes 19. A variety of enzymes use the specific properties of metal ions to modulate ET (For example, Zn(II) can influence ET by altering the conformation of a local protein domain, thereby limiting protein motions which are necessary for efficient ET in the photosynthetic bacterial reaction center) 20–24.…”

Section: Introductionmentioning

confidence: 99%

“…The presence of metal ions can alter the essential properties of electron donors and acceptors, the electron donor‐acceptor distance, and the surrounding of the catalytic center 26(b). The role of metal ion modulation of PCET is not as well understood as in ET, where a variety of metal‐containing enzymes are involved in controlling ET processes in biological redox systems 19, 20, 28(a). There are few investigations of the role of metal ions on PCET in biocatalysis 28.…”

Section: Introductionmentioning

confidence: 99%

Effect of metal ions on radical type and proton‐coupled electron transfer channel: σ‐Radical vs π‐radical and σ‐channel vs π‐channel in the imide units

et al. 2009

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The mechanism of proton transfer (PT)/electron transfer (ET) in imide units, and its regulation by hydrated metal ions, was explored theoretically using density functional theory in a representative model (a nearly planar and cisoid complex between uracil and its N(3)-dehydrogenated radical, UU). In UU (sigma-radical), PT/ET normally occurs via a seven-center, cyclic proton-coupled sigma-electron sigma-channel transfer (PC(sigma)E(sigma)T) mechanism (3.8 kcal/mol barrier height) with a N(3)-->N(3') PT and an O(4)-->O(4') ET. Binding of hydrated metal ions to the dioxygen sites (O(2)/O(2') or/and O(4)/O(4')) of UU may significantly affect its PT/ET cooperative reactivity by changing the radical type (sigma-radical <--> pi-radical) and ET channel (sigma-channel <--> pi-channel), leading to different mechanisms, ranging from PC(sigma)E(sigma)T, to proton-coupled pi-electron sigma-channel transfer (PC(pi)E(sigma)T) to proton-coupled pi-electron pi-channel transfer (PC(pi)E(pi)T). This change originates from an alteration of the ordering of the UU moiety SOMO/HDMO (the singly occupied molecular orbital and the highest doubly occupied molecular orbital), induced by binding of the hydrated metal ions. It is a consequence of three associated factors: the asymmetric reactant structure, electron cloud redistribution, and fixing role of metal ions to structural backbone. The findings regarding the modulation of the PT/ET pathway via hydrated metal ions may provide valuable information for a greater understanding of PT/ET cooperative mechanisms, and an alternative way for designing imide-based molecular devices, such as molecular switches and molecular wires.

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“…9 Such a strong binding of Sc(OTf) 3 with the radical anions of electron acceptors results in ET from electron donors to acceptors even though photoinduced intramolecular ET is energetically impossible in the absence of metal ion. 10,11 The elongation of the CS state lifetime of D-A linked dyads has been achieved by the addition of metal ions. 12,13 However, there has so far been no report on formation of the CS state of D-A dyads using fullerene as an electron donor in the presence of metal ions.…”

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confidence: 99%