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Metalloprotein Electronics
Published in Sergey Edward Lyshevski, Nano and Molecular Electronics Handbook, 2018
Andrea Alessandrini, Paolo Facci
The relative simplicity of the outer-sphere electron transfer reaction promoted the development of theoretical efforts towards the prediction of electron transfer rate constants. In what follows, we will recall only the basic ideas referring the interested reader to one of the numerous works reviewing the topic [8–12].
Electrostatic bending and outer-sphere intervalence transfer in a flexible ligand-bridged ruthenium(III)-iron(II) complex
Published in Journal of Coordination Chemistry, 2018
Juan S. Aguirre-Araque, Reginaldo C. Rocha, Henrique E. Toma
These electrostatic forces promote a close approximation of the metal centers in such systems, allowing for IT between Ru(III) and Fe(II) to occur upon visible/near-IR absorptions that produce their characteristic colors. The charge-transfer behavior resulting from these outer-sphere associations can be described in terms of the Marcus–Hush theory [12, 13], typically corresponding to classes I or II for weakly coupled mixed-valence complexes [13, 14]. Photoinduced outer-sphere electron transfer can also be observed in donor-acceptor systems such as those formed by N-heterocyclic cations and pentacyanidoferrate(II) complexes [15] and even in simple mixtures of iodine with inorganic anions, as shown by Meyerstein over 50 years ago [16].
Electrochemical reduction of halogenated organic contaminants using carbon-based cathodes: A review
Published in Critical Reviews in Environmental Science and Technology, 2023
Jacob F. King, William A. Mitch
However, oxygenated functional groups are believed to catalyze reductive dehalogenation reactions in some cases when adsorption of contaminants results in formation of complexes with the oxygenated functional groups, enabling inner-sphere electron transfer to occur in addition to outer-sphere transfer. Chemisorption of TCE to C–O− groups on BDD electrodes was proposed to catalyze reductive dechlorination of TCE to form acetate and chloride (Mishra et al., 2008). The observed activation barrier was four-fold lower than that predicted by density functional theory (DFT) simulations for outer-sphere electron transfer but concurred with DFT simulations of an inner-sphere electron transfer via a complex between a deprotonated hydroxyl functional group on BDD and TCE. Catalysis can also be evidenced by a shift toward more positive potentials at which peak cathodic currents (Ep,c) are observed during cyclic voltammetry experiments, indicating a decline in the energy barrier for reduction (Durante et al., 2009; Isse, Berzi, et al., 2009; Isse, Mussini, et al., 2009; Isse, Sandona, et al., 2009). For example, catalysis was observed using Ag electrodes for reductive dehalogenation of halogenated alkanes, alkenes, benzyl chloride and brominated or iodinated aromatics, but not chlorinated aromatics (Durante et al., 2009; Y.-F. Huang et al., 2010; Isse et al., 2006; Isse, Berzi, et al., 2009; Isse, Mussini, et al., 2009; Isse, Sandona, et al., 2009; Klymenko et al., 2014; A. Wang et al., 2010), suggesting inner-sphere electron transfer after the formation of adducts between the halogenated organic and the electrode surface (Zhang et al., 2005).
Silver deposition optimization process on ultrananocrystalline diamond applied to nitrate reduction
Published in Environmental Technology, 2021
Silvia Sizuka Oishi, Andrea Boldarini Couto, Edson Cocchieri Botelho, Neidenei Gomes Ferreira
Ferri/ferrocyanide is an outer sphere electron transfer reaction and it is sensitive to the state of carbon surface [5]. Therefore, diamond surface changes after anodic treatment at different times was characterized by cyclic voltammetry in the presence 1 mmol L-1 Fe(CN)6−3/-4 in 0.5 mol.L-1 H2SO4 to study the surface reactivity as shown in Figure 2(a). B-UNCD/RVC electrode without treatment is quasi-reversible with a potential difference between the anodic and cathodic peaks (ΔEp) of ∼70 mV for this redox couple where the number of electron transfer is equal to 1.0. In this sweeping rate (10 mV s-1), for electrode after 10 min of oxidation, the behaviour continues quasi-reversible with ΔEp at around 130 mV, while for electrodes after 20 and 30 min of oxidation the anodic peak disappears, which indicates a deterioration in their electron transfer rate. In addition, the longer the anodic treatment time, the greater the current response associated with the increase of the electrode surface area as well as the surface oxygen functional groups. For anodic treatment, the first stage of oxidation in BDD is the discharge of water with the formation of hydroxyl radicals that will produce later oxygen, ozone, hydrogen peroxide or participate in diamond corrosion [27,28]. It should be taken into account that the vitreous carbon matrix is also exposed to oxidation as its presence composed the majority of the binary composite. Therefore, the termination of B-UNCD surface with oxygen functional groups and the contribution of the carbonaceous substrate influence the reaction kinetics and explain the irreversible electrochemical behaviour in ferrocyanide after 20 and 30 min of B-UNCD/RVC electrode oxidation.