Neutral Peptide Biradicals Formed by Dissociative Electron Transfer

Burns, Colin; Rochelle, Lakecia; Forbes, Malcolm D. E.

doi:10.1021/ol0160452

Cited by 15 publications

(12 citation statements)

References 19 publications

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“…In the first, photoinduced ET leads to formation of a transient intermediate in which the aryl bromide acceptor is transformed into its radical anion. 38 The ET reaction fits nicely with reaction 3 of Scheme 9 and with the known reductive behavior of aryl bromides. 10 C-Br bond cleavage eventually yields the aryl radical together with bromide ion.…”

Section: Homolytic and Heterolytic Cleavagessupporting

confidence: 71%

“…We have already described two cases of photoinduced DETs in which the spacer length was varied (Scheme 11). In both reactions, either the efficiency of exchange interactions within the biradical, as studied by time resolved electron paramagnatic resonance, 38 or the cyclization yield 39 were found to be functions of the chain length. In both cases, the spacers were rather flexible.…”

Section: Electronic Coupling and Det Ratesmentioning

confidence: 99%

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Intramolecular dissociative electron transfer

Antonello

Maran

2005

Chem. Soc. Rev.

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Dissociative electron transfers (ET) are reactions in which the ET is associated with the cleavage of a sigma bond. Although a rather satisfactory amount of information is currently available on the intermolecular and heterogeneous dissociative ET reactions, less is known for the corresponding intramolecular processes, despite the relevance of these reactions in both chemistry and biochemistry. This tutorial review focuses on the most recent developments in this area, with particular emphasis on the reactions occurring in well-defined Donor-Spacer-Acceptor molecular systems. The goal is to provide the reader with the essential background to understand and possibly predict the feasibility and rates of these reactions, as well as to stimulate the application of the intramolecular dissociative ET concepts and related issues to still unexplored molecular systems.

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Section: Homolytic and Heterolytic Cleavagessupporting

confidence: 71%

Section: Electronic Coupling and Det Ratesmentioning

confidence: 99%

Intramolecular dissociative electron transfer

Antonello

Maran

2005

Chem. Soc. Rev.

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“…The value of λ can be estimated as ≤6-10 Å. 20,21 The lifetime of first excited electronic states in polypeptides is of the order of nanoseconds, with much longer lifetimes for high Rydberg states. 22 This is enough for single-bond cleavage.…”

Section: Vibrational Vs Electronic Excitationmentioning

confidence: 99%

Electronic Excitation Gives Informative Fragmentation of Polypeptide Cations and Anions

Haselmann

Budnik

Kjeldsen

et al. 2002

Eur J Mass Spectrom (Chichester)

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A Fourier transform mass spectrometer is a versatile instrument with a range of available fragmentation techniques. Comparison of polypeptide fragmentation patterns revealed that the techniques involving electronic excitation, such as hot-electron-capture dissociation (HECD) and electron-detachment dissociation (EDD), are even more informative than vibrational excitation (VE) techniques such as collisional activation. For dications of the peptide KIMHASELMANN, 11 eV HECD cleaved all inter-residue links in at least two places, with up to five fragments characterizing each link. For dianions of the same molecule, VE produced only one backbone cleavage whereas EDD gave ten, including five internal cleavage fragments. This is consistent with the general postulate that homogeneous electronic excitation yields more types of cleavage than near-equilibrium processes such as VE.

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“…Our laboratory has a long-standing interest in the kinetic and magnetic properties of functionalized biradicals in free solution (1)(2)(3)(4)(5). The bulk of our work has focused on flexible biradical structures such as polymethylene chains (6), but some semirigid spacers have also been investigated (7).…”

Section: Introductionmentioning

confidence: 99%

Electron Spin Exchange in Linked Phenothiazine–Viologen Charge Transfer Complexes Incorporated in “Through‐Ring” (Rotaxane) α‐Cyclodextrins

Yonemura

Forbes

2015

Photochem & Photobiology

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A series of covalently bound phenothiazine (PHZ) donor and methylviologen (V) acceptor compounds with polymethylene chain spacers (C8 , C10 , C12 ) were incorporated in a "through-ring" (rotaxane) fashion to α-cyclodextrin (α-CD) hosts such that the alkyl chains were fully extended, with the donor and acceptor on opposite sides of the α-CD cylinder. Photoexcitation of the PHZ unit induces electron transfer from the PHZ first excited triplet state to the V moiety, forming a biradicaloid charge-separated state. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy at the X-band and Q-band microwave frequencies was used to investigate the spin exchange interaction, J, in these biradicaloids. Simulation of the spectra using a "static" model for spin-correlated radical pairs allows extraction of the J values, which are negative in sign and have absolute values range from 2 to 1000 Gauss. Comparison of the PHZn V (n = 8, 10, 12) spectra to those obtained using phenyl ether spacers indicates that π-bonds may assist the electronic coupling. The results are discussed in terms of through-bond vs through-space electronic coupling mechanisms.

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Neutral Peptide Biradicals Formed by Dissociative Electron Transfer

Cited by 15 publications

References 19 publications

Intramolecular dissociative electron transfer

Intramolecular dissociative electron transfer

Electronic Excitation Gives Informative Fragmentation of Polypeptide Cations and Anions

Electron Spin Exchange in Linked Phenothiazine–Viologen Charge Transfer Complexes Incorporated in “Through‐Ring” (Rotaxane) α‐Cyclodextrins

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