Reflectance infrared and UV–visible spectroelectrochemical studies on a series of [Ni3(µ3-L)(µ3-I)(µ2-dppm)3][PF6] (L = CO; CNR, R = alkyl, aryl; dppm = Ph2PCH2PPh2) clusters

1996 ◽  
Vol 74 (12) ◽  
pp. 2503-2508 ◽  
Author(s):  
John Washington ◽  
Clifford P. Kubiak
Keyword(s):  
Single Electron ◽  
Band Shift ◽  
Alkyl Aryl ◽  
Specular Reflectance ◽  
Nickel Clusters ◽  
Key Words Nickel ◽  
Uv Visible ◽  
Electron Reduction ◽  
Configuration Changes ◽  
Nickel Cluster

The trinuclear nickel clusters [Ni3(µ3-L)(µ3-I)(µ2-dppm)3]+ (L = CO (1); CNR, R = CH3 (2), i-C3H7 (3), C6H11 (4), t-C4H9 (5), CH2C6H5 (6), C6H5 (7), p-C6H4I (8), p-C6H4F (9), p-C6H4CH3 (10), p-C6H4CF3 (11), p-C6H4OCH3 (12), p-C6H4CN (13), 2,6-(CH3)2C6H3 (14); dppm = Ph2PCH2PPh2) all contain a triply bridging π-acceptor (carbonyl or isocyanide) ligand. Compounds 1–14 all undergo single electron reductions over a relatively narrow range of E1/2( +/0) (−1.08 V to –1.18 V vs. SCE in acetonitrile) and are known electrocatalysts for the reduction of carbon dioxide. Specular reflectance infrared spectroelectrochemical (SEC) measurements on 1–14 indicate that the capping isocyanide or carbonyl ligand remains triply bridging (µ3,η1) upon single electron reduction. The magnitude of the ν(C≡O) or ν(C≡N) absorption band shift upon reduction is related to both the electronic and steric properties of the capping π-acceptor ligand. Spectroelectrochemical studies with UV–visible detection revealed a hypsochromic shift upon reduction of the clusters. The SEC cell and spectrometer utilized are extremely versatile and allow for data from 600 to 22 000 cm−1 to be acquired without modifying the SEC cell and making only minor configuration changes to the spectrometer. Key words: nickel, cluster, carbonyl, isocyanide, spectroelectrochemical.

Effect of NO2 substitution and solvent on UV-visible spectra, redox potentials and electron transfer mechanisms of copper β-nitrotriarylcorroles. Proposed electrogeneration of a Cu(I) oxidation state

2016 ◽  
Vol 20 (07) ◽  
pp. 753-765 ◽  
Author(s):  
Lina Ye ◽  
Zhongping Ou ◽  
Yuanyuan Fang ◽  
Yang Song ◽  
Bihong Li ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Soret Band ◽  
Redox Potentials ◽  
Nonaqueous Media ◽  
Initial Assignment ◽  
Visible Spectra ◽  
Phenyl Rings ◽  
Uv Visible ◽  
Electron Reduction ◽  
Transfer Mechanisms

Three copper triarylcorroles containing a [Formula: see text]-pyrrole nitro substituent were synthesized and characterized as to their spectral and electrochemical properties in nonaqueous media. The examined compounds are represented as [Formula: see text]-NO2(YPh)3CorCu, where Cor is the trianion of a triphenylcorrole and Y is a Cl, H or CH3 substituent at the para-position of the three meso-phenyl rings of the compound. The data from absorption spectra, electrochemistry and thin-layer spectroelectrochemistry are consistent with an initial assignment of Cu[Formula: see text]-Cor[Formula: see text] in CH2Cl2, DMF and pyridine and electrogeneration of a formal Cu(II) corrole with an unreduced macrocycle, represented as Cu[Formula: see text]-Cor[Formula: see text], after the first one-electron reduction in these solvents. The doubly reduced [Formula: see text]-nitrocorrole has a sharp Soret band at 439 nm and a well-defined Q-band at 611 nm in CH2Cl2. Similar absorption spectra are seen for the three examined doubly reduced nitrocorroles in DMF and pyridine, suggesting formation of a Cu(I) species with an unreduced macrocycle which is represented as Cu[Formula: see text]-Cor[Formula: see text]. Changes in redox potentials and absorption spectra of the nitrocorroles are examined as a function of solvent and substituents on the meso-phenyl rings of the compounds and comparisons are made between spectral and electrochemical data of the newly synthesized corroles and that of structurally related tetraarylcorroles lacking a [Formula: see text]-nitro group.

scholarly journals An electron transfer driven magnetic switch: ferromagnetic exchange and spin delocalization in iron verdazyl complexes

2018 ◽  
Vol 47 (18) ◽  
pp. 6351-6360 ◽  
Author(s):  
David J. R. Brook ◽  
Connor Fleming ◽  
Dorothy Chung ◽  
Cardius Richardson ◽  
Servando Ponce ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Spin Crossover ◽  
Large Change ◽  
Single Electron ◽  
Spin Multiplicity ◽  
Magnetic Switch ◽  
Ferromagnetic Exchange ◽  
Spin Delocalization ◽  
Electron Reduction

A single electron reduction of an iron bis(verdazyl) complex results in a large change in spin multiplicity resulting from a combination of spin crossover and exceptionally strong ferromagnetic exchange.

scholarly journals Combined Photoredox and Carbene Catalysis for the Synthesis of Ketones from Carboxylic Acids

2020 ◽  
Author(s):  
Anna Davies ◽  
keegan fitzpatrick ◽  
Rick Betori ◽  
Karl Scheidt
Keyword(s):  
Carboxylic Acids ◽  
Late Stage ◽  
Pharmaceutical Compounds ◽  
Single Electron ◽  
Photoredox Catalysis ◽  
Radical Coupling ◽  
Electron Reduction

Disclosed herein is the development of a novel single-electron reduction of acyl azoliums for the formation of ketones from carboxylic acids. Facile construction of the acyl azolium <i>in situ</i> followed by a radical-radical coupling was made possible using merged NHC-photoredox catalysis. The utility of this protocol in synthesis was demonstrated in the late-stage functionalization of a variety of pharmaceutical compounds.

scholarly journals Enzymatic single-electron reduction and aerobic cytotoxicity of tirapazamine and its 1-oxide and nor-oxide metabolites

Chemija ◽  
2018 ◽  
Vol 29 (4) ◽  
Author(s):  
Jonas Šarlauskas ◽  
Aušra Nemeikaitė-Čėnienė ◽  
Audronė Marozienė ◽  
Lina Misevičienė ◽  
Mindaugas Lesanavičius ◽  
...  
Keyword(s):  
Side Effects ◽  
Anticancer Agent ◽  
Redox Cycling ◽  
Nitroaromatic Compounds ◽  
Single Electron ◽  
Reductive Activation ◽  
Cell Nuclei ◽  
Electron Reduction ◽  
Phenylene Diamine

Aerobic cytotoxicity of 3-amino-1,2,4-benzotriazine-1,4-dioxide (tirapazamine, TPZ), a bioreductively activated hypoxia-specific anticancer agent, is responsible for TPZ side effects in chemotherapy. In order to clarify its mechanisms, we examined the aerobic cytotoxicity of TPZ and its main metabolites, 3-amino-1,2,4-benzotriazine-1-oxide and 3-amino-1,2,4-benzotriazine in murine hepatoma MH22a cells, and their reduction by NADPH:cytochrome P-450 reductase (P-450R) and ferredoxin:NADP+ reductase (FNR). Analogous studies of several quinones and nitroaromatic compounds with similar values of single-electron reduction midpoint potentials (E17) were carried out. In single-electron reduction by P-450R and FNR, the reactivity of TPZ and its monoxide was similar to that of quinones and nitroaromatics, and increased with an increase in their E17. The cytotoxicity of TPZ and its metabolites possessed a prooxidant character, because it was partly prevented by an antioxidant N,N’-diphenyl-p-phenylene diamine and desferrioxamine, and potentiated by 1,3-bis(2-chloroethyl)-1-nitrosourea. Importantly, the cytotoxicity of TPZ and, possibly, its 1-N-oxide, was much higher than that of quinones and nitroaromatics with similar values of E17 and redox cycling activities. A possible additional factor in the aerobic cytotoxicity of TPZ is its reductive activation in oxygen-poor cell nuclei, leading to the formation of DNA-damaging species similar to those forming under hypoxia.

ChemInform Abstract: PREPARATION OF β-(P′-NITROAZOXY)BENZENE AND ITS SINGLE-ELECTRON REDUCTION

1977 ◽  
Vol 8 (38) ◽  
pp. no-no
Author(s):  
V. S. SMOLYAKOV ◽  
Z. V. TODRES ◽  
A. N. USHAKOV ◽  
L. A. NEIMAN
Keyword(s):  
Single Electron ◽  
Electron Reduction

Cobalt-catalyzed asymmetric hydrogenation of enamides enabled by single-electron reduction

Science ◽  
2018 ◽  
Vol 360 (6391) ◽  
pp. 888-893 ◽  
Author(s):  
Max R. Friedfeld ◽  
Hongyu Zhong ◽  
Rebecca T. Ruck ◽  
Michael Shevlin ◽  
Paul J. Chirik
Keyword(s):  
Asymmetric Hydrogenation ◽  
Single Electron ◽  
Electron Reduction

α-Amino Radicals via Photocatalytic Single-Electron Reduction of Imine Derivatives

ACS Catalysis ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 2009-2025 ◽  
Author(s):  
Jamie A. Leitch ◽  
Thomas Rossolini ◽  
Tatiana Rogova ◽  
J. Andrew P. Maitland ◽  
Darren J. Dixon
Keyword(s):  
Single Electron ◽  
Electron Reduction

Rate of single electron reduction of Togni’s reagent

2017 ◽  
Vol 203 ◽  
pp. 218-222 ◽  
Author(s):  
Nico Santschi ◽  
Thomas Nauser
Keyword(s):  
Single Electron ◽  
Electron Reduction

Manganese(III) and manganese(IV) corroles: synthesis, spectroscopic, electrochemical and X-ray structural characterization

2005 ◽  
Vol 09 (06) ◽  
pp. 398-412 ◽  
Author(s):  
Zhongping Ou ◽  
Christoph Erben ◽  
Marie Autret ◽  
Stefan Will ◽  
Daniel Rosen ◽  
...  
Keyword(s):  
Redox Reactions ◽  
Esr Spectroscopy ◽  
Spectroscopic Characterization ◽  
Axial Ligand ◽  
X Ray Diffraction ◽  
Nonaqueous Media ◽  
X Ray ◽  
Cation Radicals ◽  
Uv Visible ◽  
Electron Reduction

The synthesis, spectroscopic characterization and electrochemistry of four Mn(III) and Mn(IV) octaethylcorroles are reported and the potentials of the Mn(III) / Mn(IV) and Mn(IV) / Mn(III) processes examined as a function of the axial ligand. The investigated compounds are represented as ( OEC ) Mn , ( OEC ) MnCl , ( OEC ) Mn ( py ) and ( OEC ) Mn ( C 6 H 5) where OEC is the trianion of octaethylcorrole. The first one-electron oxidation of ( OEC ) Mn III and ( OEC ) Mn III ( py ) in PhCN or pyridine containing 0.1 M TBAP leads to the facile formation of a Mn(IV) species while the first one-electron reduction of ( OEC ) Mn IV Cl and ( OEC ) Mn IV ( C 6 H 5) in the same two solvents leads to the Mn(III) corrole. All other redox reactions occur at the corrole macrocycle to give π-cation radicals or π-anion radicals and there is no evidence for electrogeneration of a compound with a Mn(II) oxidation state as is the case for manganese(III) porphyrins which are all easily reduced to the Mn(II) state in nonaqueous media. The products of each Mn(III)/Mn(IV) redox reaction were characterized by UV-visible and/or ESR spectroscopy and the structures of ( OEC ) MnCl , ( OEC ) Mn ( py ) and ( OEC ) Mn ( C 6 H 5) were determined by single-crystal X-ray diffraction.

scholarly journals Mechanistic Insights on Hypervalent Iodine-Mediated Styrene Hetero- and Homodimerization

2020 ◽  
Author(s):  
Aqeel A. Hussein ◽  
Ahmed Al-Yasari ◽  
Yumiao Ma
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Single Electron ◽  
Hypervalent Iodine ◽  
Functional Theory ◽  
Rate Determining Step ◽  
Before And After ◽  
Electron Reduction ◽  
Dynamics Simulations ◽  
Insight Into

A mechanistic insight into the hetero- and homodimerizations (HETD and HOMD) of styrenes promoted by hypervalent iodine reagents (HVIRs; DMP and PIDA) and facilitated by HFIP to yield all trans cyclobutanes is reported using density functional theory (DFT) calculations. The HFIP molecules lower the energy of the single electron oxidation (SEO) or initiation as a result of strong hydrogen bonding interactions that substantially stabilize the frontier orbitals before and after electron addition. The HETD or HOMD is a radically-characterized π-π stacked head-to-head stepwise [2+2] cycloaddition initiated via SEO by DMP or PIDA, respectively. DFT results supported by quasiclassical molecular dynamics simulations show that HOMD is a competing pathway to HETD although the latter is relatively faster, in accordance with experimental observations. The initiation is a rate-determining step as a thermodynamically endergonic and propagation is accomplished by radically-cationic hetero- and homodimerized intermediate as propagation is faster than single electron reduction (SER) or termination by radically-anionic HVIRs. Initiation by DMP found to be faster and less endergonic than by PIDA due to (1) the energy gap of electron transfer in a SEO step by I(V) is lower than I(III) and (2) the SOMO energy of the radical anion I(V) is lower than I(III). Furthermore, the presence of p-methoxy group is essential to underpin the SEO by which the more thermodynamically favorable SEO leads to a successful cycloaddition as the thermodynamic term represents a major contribution in the initiative barrier.

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