Oxidation of hydroquinones by a nonheme iron(IV)-oxo species

Nehru, Kasi; Jang, Yukyeong; Oh, Sunok; Dallemer, F.; Nam, Wonwoo; Kim, Jinheung

doi:10.1016/j.ica.2007.12.027

Cited by 22 publications

(12 citation statements)

References 40 publications

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“…By taking the 0–0 transition energy E 00 ( E 00 = 1240/λ onset ) value as 2.38 eV (the onset absorption value is 521 nm for Ru in (GO/RuL) 1 film), the energy of LUMO of RuL in the film, E LUMO , was calculated to be −3.58 eV (−1.16 V vs NHE) with respect to the vacuum energy level according to eqs and by using an energy of −4.74 eV for SCE with respect to the zero vacuum level E HOMO .25em ( eV ) = prefix− 4.74 − E onset ( ox ) normalΔ E 00 = E LUMO − E HOMO = 1240 / λ onset The energy of ITO electrode’s conduction band, the working function value of GO, the reduction potentials of O 2 and K 3 Fe(CN) 6 , and the oxidation potential of H 2 Q are taken to be +0.2 (4.7 eV below the vacuum level), +0.3 (4.8 eV below the vacuum level), −0.26, +0.36,and +1.1 V vs NHE, respectively. By using of above-mentioned energy level values, the energy level diagram was thus constructed, and the proposed cathodic photocurrent generation mechanism is depicted in Scheme .…”

Section: Resultsmentioning

confidence: 99%

Layer-by-Layer Assembly of Graphene Oxide and a Ru(II) Complex and Significant Photocurrent Generation Properties

2013

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The multilayer films were fabricated by layer-by-layer electrostatically coassembling graphene oxide and a ruthenium complex of [Ru(bpy)2L](ClO4)2 {L = 2-(2,6-di(pyridin-2-yl)pyridine-4-yl)-1H-imidazo[4,5-f]-1,10-phenanthroline} and characterized using UV-vis absorption spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and cyclic voltammetry. The dependence of redox properties and cathodic photocurrents on the number of layers deposited and the photocurrent generation mechanism and polarity were studied in detail. The homogeneous growth and close packing of the two film-forming components, linear relationships of the dark cyclic voltometry peak currents and photocurrents vs number of layers deposited, and large cathodic photocurrent density of 4.1 μA/cm(2) for a four-layer film make this novel hybrid thin film promising applications ranging from molecular photovoltaic and photocatalytic molecular devices to photoelectrochemical sensing.

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Section: Resultsmentioning

confidence: 99%

Layer-by-Layer Assembly of Graphene Oxide and a Ru(II) Complex and Significant Photocurrent Generation Properties

2013

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“…29 As yet underrepresented in biological research, other polypyridyl ligands, including the pentadentate ligands Bn-TPEN and N4Py, have been used to produce iron(IV)-oxo species, also known as ferryls, that mimic the structure and reactivity of non-heme iron enzymes found in nature. 30,31 In addition to their ability to oxidize organic substrates, [32][33][34][35][36][37][38][39][40] recent progress from our laboratory has shown that such biomimetic ferryls can be used to oxidize the amino acid backbone and side chains with substantial selectivity. 41,42 Despite all that is known about the polypyridyl ligands in Fig.…”

Section: Introductionmentioning

confidence: 99%

Iron-binding and mobilization from ferritin by polypyridyl ligands

Jackson

Kodanko

2010

Metallomics

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Polypyridyl ligands were investigated for their ability to bind and mobilize iron(ii) from ferritin in aqueous solution. Association constants with iron(ii) (pFe(II)) were determined for the pentadentate ligands N4Py (pFe(II) = 14.4) and Bn-TPEN (pFe(II) = 13.7) using a competition method with the hexadentate ligand TPEN (pFe(II) = 14.6, 0.1 M KNO(3)). Ferrous complexes were formed using the polypyridyl ligands and ferritin as the sole iron source in the presence of reductant. The observed rates of iron mobilization from ferritin were dependent on reductant and were higher in the presence of ascorbate than dithiothreitol. TPEN, N4Py and Bn-TPEN demonstrated comparable and in some cases faster rates and higher levels of iron mobilization when compared to the iron(ii) chelator 1,10-phenanthroline, particularly at low concentrations of chelator.

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“…When H 2 O was replaced by D 2 O, the H 2 evolution rate became slower, as shown in Figures and S14, to afford the kinetic deuterium isotope effect (KIE = 2.0). In the presence of D 2 O, the protons of Cl 4 QH 2 are exchanged rapidly with D 2 O to produce Cl 4 QD 2 and H 2 O . In such a case, the KIE may result from the dissociation of a proton from Cl 4 QH 2 •+ or from hydrogen atom transfer (or PCET) from Cl 4 QH • to [Co II (dmgH) 2 pyCl] − .…”

Section: Resultsmentioning

confidence: 99%

Photocatalytic Hydrogen Evolution from Plastoquinol Analogues as a Potential Functional Model of Photosystem I

et al. 2020

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The recent development of a functional model of photosystem II (PSII) has paved a new way to connect the PSII model with a functional model of photosystem I (PSI). However, PSI functional models have yet to be reported. We report herein the first potential functional model of PSI, in which plastoquinol (PQH 2 ) analogues were oxidized to plastoquinone (PQ) analogues, accompanied by hydrogen (H 2 ) evolution. Photoirradiation of a deaerated acetonitrile (MeCN) solution containing hydroquinone derivatives (X-QH 2 ) as a hydrogen source, 9mesityl-10-methylacridinium ion (Acr + -Mes) as a photoredox catalyst, and a cobalt(III) complex, Co III (dmgH) 2 pyCl (dmgH = dimethylglyoximate monoanion; py = pyridine) as a redox catalyst resulted in the evolution of H 2 and formation of the corresponding p-benzoquinone derivatives (X-Q) quantitatively. The maximum quantum yield for photocatalytic H 2 evolution from tetrachlorohydroquinone (Cl 4 QH 2 ) with Acr + -Mes and Co III (dmgH) 2 pyCl and H 2 O in deaerated MeCN was determined to be 10%. Photocatalytic H 2 evolution is started by electron transfer (ET) from Cl 4 QH 2 to the triplet ET state of Acr + -Mes to produce Cl 4 QH 2•+ and Acr • -Mes with a rate constant of 7.2 × 10 7 M −1 s −1 , followed by ET from Acr • -Mes to Co III (dmgH) 2 pyCl to produce [Co II (dmgH) 2 pyCl] − , accompanied by the regeneration of Acr + -Mes. On the other hand, Cl 4 QH 2•+ is deprotonated to produce Cl 4 QH • , which transfers either a hydrogen-atom transfer or a proton-coupled electron transfer to [Co II (dmgH) 2 pyCl] − to produce a cobalt(III) hydride complex, [Co III (H)(dmgH) 2 pyCl] − , which reacts with H + to evolve H 2 , accompanied by the regeneration of Co III (dmgH) 2 pyCl. The formation of [Co II (dmgH) 2 pyCl] − was detected by electron paramagnetic resonance measurements.

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Oxidation of hydroquinones by a nonheme iron(IV)-oxo species

Cited by 22 publications

References 40 publications

Layer-by-Layer Assembly of Graphene Oxide and a Ru(II) Complex and Significant Photocurrent Generation Properties

Layer-by-Layer Assembly of Graphene Oxide and a Ru(II) Complex and Significant Photocurrent Generation Properties

Iron-binding and mobilization from ferritin by polypyridyl ligands

Photocatalytic Hydrogen Evolution from Plastoquinol Analogues as a Potential Functional Model of Photosystem I

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