Proton-coupled electron transfer across benzimidazole bridges in bioinspired proton wires

Odella, Emmanuel; Mora, Sabrina; Wadsworth, Brian L.; Goings, Joshua J.; Gervaldo, Miguel; Sereno, Leonides; Groy, Thomas L.; Gust, Devens; Moore, Thomas A.; Moore, Gary F.; Hammes‐Schiffer, Sharon; Moore, Ana L.

doi:10.1039/c9sc06010c

Cited by 23 publications

(37 citation statements)

References 38 publications

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“…41 This phenomenon has also appeared in previously reported analogous BIP derivatives where the proton translocation could be extended even up to ∼16 Å without affecting the chemical or the electrochemical reversibility of the PhO • / PhOH redox couple. 21,23 In contrast, compound 3 is chemically irreversible at low scan rates, which is frequently observed in electrochemical oxidations of phenols in the absence of a proximal basic site to serve as a proton acceptor. 42,43 The change in the chemical reversibility arising from breaking a hydrogen-bond network is similar to that observed in previously studied systems.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…20,21 On the other hand, when the ΔpK a between the benzimidazole and the presumptive TPA is unfavorable (i.e., the TPA is less basic than the benzimidazole), the proton translocation process is limited to one-electron, one-proton transfer (i.e., an E1PT process), and the final PCET product detected is the corresponding benzimidazolium ion. 20 It also has been shown that protons can be translocated through a bridge containing two benzimidazole units to a TPA (−CH 2 NEt 2 , Cy-imine, or Ph OMe imine), 23 enabling an E3PT process to take place. Indeed, a detailed study of E2PT-and E3PT-based systems illustrates the contribution of the electronic structure of the bridge to the negative ΔG for the MPCET process.…”

Section: ■ Introductionmentioning

confidence: 99%

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Role of Intact Hydrogen-Bond Networks in Multiproton-Coupled Electron Transfer

et al. 2020

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The essential role of a well-defined hydrogen-bond network in achieving chemically reversible multiproton translocations triggered by one-electron electrochemical oxidation/reduction is investigated by using pyridylbenzimidazole−phenol models. The two molecular architectures designed for these studies differ with respect to the position of the N atom on the pyridyl ring. In one of the structures, a hydrogen-bond network extends uninterrupted across the molecule from the phenol to the pyridyl group. Experimental and theoretical evidence indicates that an overall chemically reversible two-protoncoupled electron-transfer process (E2PT) takes place upon electrochemical oxidation of the phenol. This E2PT process yields the pyridinium cation and is observed regardless of the cyclic voltammogram scan rate. In contrast, when the hydrogen-bond network is disrupted, as seen in the isomer, at high scan rates (∼1000 mV s −1 ) a chemically reversible process is observed with an E 1/2 characteristic of a one-proton-coupled electron-transfer process (E1PT). At slow cyclic voltammetric scan rates (<1000 mV s −1 ) oxidation of the phenol results in an overall chemically irreversible two-proton-coupled electron-transfer process in which the second proton-transfer step yields the pyridinium cation detected by infrared spectroelectrochemistry. In this case, we postulate an initial intramolecular proton-coupled electron-transfer step yielding the E1PT product followed by a slow, likely intermolecular chemical step involving a second proton transfer to give the E2PT product. Insights into the electrochemical behavior of these systems are provided by theoretical calculations of the electrostatic potentials and electric fields at the site of the transferring protons for the forward and reverse processes. This work addresses a fundamental design principle for constructing molecular wires where protons are translocated over varied distances by a Grotthuss-type mechanism.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Role of Intact Hydrogen-Bond Networks in Multiproton-Coupled Electron Transfer

et al. 2020

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“…60 Then, both protons and electrons were transferred to the adsorbed oxygen, which called proton-coupled electron transfer (PCET). 61 After PCET, the ORR follows. A higher concentration of protons on N-doped graphene-shell surface, compared to bare carbon, act as a driving force to push the ORR toward the direct four-electron reduction.…”

Section: Materials Advances Accepted Manuscriptmentioning

confidence: 99%

N-Doped few-layer graphene encapsulated Pt-based bimetallic nanoparticles via solution plasma as an efficient oxygen catalyst for the oxygen reduction reaction

et al. 2021

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“…In particular, the new band at 1651 cm -1 corresponds to the large component of the protonated imine group stretching, which is a distinctive IR marker displayed by other BIP derivatives bearing a substituted imine group as the TPA. 12,22,42 This is evidence that an E2PT product is being formed upon phenol oxidation. Computational spectra (Fig.…”

Section: B Amentioning

confidence: 85%