The first crystal structure of a monomeric phenoxyl radical: 2,4,6-tri-tert-butylphenoxyl radical

Manner, Virginia W.; Markle, Todd F.; Freudenthal, J.; Roth, Justine P.; Mayer, James M.

doi:10.1039/b712872j

Cited by 149 publications

(177 citation statements)

References 36 publications

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“…(3). A related stable 2,4,6-tri-tert-butylphenoxyl radical (2,4,6-t Bu 3 C 6 H 2 O Å ) has been isolated in the solid state and structurally characterized [28]. The structural data and theoretical calculations indicated substantive delocalization of the single electron to the ortho-and para-carbons stabilizing the radical.…”

Section: Charge-transfer Oxidation-reduction Of Uranyl(vi) and Phenolmentioning

confidence: 99%

Investigation of charge-transfer absorptions in the uranyl UO22+(VI) ion and related chemical reduction of UO22+(VI) to UO2+(V) by UV–Vis and electron paramagnetic resonance spectroscopies

Sun

Kolling

Mazagri

et al. 2015

Inorganica Chimica Acta

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a b s t r a c tThe uranyl UO 2 2+ (VI) cation (hydrated) exhibited strong charge-transfer absorptions at 350-400 nm in aqueous solutions containing bromide and iodide. The charge-transfer absorptions originate from a single-electron transfer from a halide anion to the uranium(VI) valence shell. Their intensities (represented by absorbance at 375 nm) were found to be directly proportional to molar concentrations of the halide (bromide or iodide) and UO 2 2+ in solution, respectively, showing the nature of a bimolecular interaction in the charge-transfer absorption transition. The absorptions were also greatly enhanced by sulfuric acid, and their intensity (absorbance at 375 nm) increased linearly as a function of the acid molarity. An electron paramagnetic resonance (EPR) study has indicated that the charge-transfer also took place slowly in the dark, resulting in appreciable thermal chemical reduction of diamagnetic UO 2 2+ (VI) (hydrated) to paramagnetic UO 2 + (V) (hydrated) (g = 2.08) by bromide and iodide. In the presence of sulfuric acid, CH 3 SOCH 3 (DMSO) was shown by EPR to undergo a charge-transfer oxidation by UO 2 2+(VI) to a stable CH 3 SOCH 2 Å (DMSO Å ) radical (singlet, g = 2.01), and UO 2 2+ (VI) was reduced to UO 2 + (V). A possible mechanism for this oxidation-reduction has been proposed. The charge-transfer absorption transition (350-400 nm) between UO 2 2+ (VI) and phenol (PhOH) in acetone was observed and characterized. A chemical oxidation-reduction of UO 2 2+ (VI) [in the form of U VI O 2 (acetone) 5 2+] and PhOH in acetone was found by EPR to give UO 2 + (V) [in the form of U V O 2 (acetone) 5 + ] and a stable phenoxyl (PhO Å ) radical (singlet, g = 2.00) via a simultaneous charge-transfer and deprotonation pathway.

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Section: Charge-transfer Oxidation-reduction Of Uranyl(vi) and Phenolmentioning

confidence: 99%

Investigation of charge-transfer absorptions in the uranyl UO22+(VI) ion and related chemical reduction of UO22+(VI) to UO2+(V) by UV–Vis and electron paramagnetic resonance spectroscopies

Sun

Kolling

Mazagri

et al. 2015

Inorganica Chimica Acta

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“…However, their stability is markedly improved when the positions ortho to the carbonyl groups are alkylated. 114 The radical anions of molecules 91À95 (Chart 34) all exhibit highly structured intervalence absorption bands indicative of class III behavior, while 96 À displays an unstructured Gaussian-shaped near-infrared absorption band that this is in line with class II behavior. 47 For the five fully delocalized systems, ln(E op ) depends linearly on the number of bridging σ-bonds between the terminal oxygen atoms with β n = 0.3 ( Figure 8), but absolute values for H AB were not reported, due to the prior observation that the simple two-state model is inadequate for estimation of electronic couplings in class III systems (see above).…”

Section: Chart 29mentioning

confidence: 99%

Organic Mixed Valence

2011

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“…112 We were concurrently working on less biomimetic iron complexes with three biimidazoline or three bipyrimidine ligands (Figure 10c,d). 113 The oxidized/deprotonated forms of these complexes can activate weak C–H and O–H bonds, and the reduced/protonated complexes will react with phenoxyl radicals (e.g., 2,4,6-tri- tert -butylphenoxyl 114 ) to give the corresponding phenols and the oxidized/deprotonated congener. These Fe III systems are very mild oxidants, and are able to oxidize weak C-H bonds only because they are fairly strong bases.…”

Section: B Non-heme Ironmentioning

confidence: 99%

Moving Protons and Electrons in Biomimetic Systems

Warren

Mayer

2015

Biochemistry

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An enormous variety of biological redox reactions are accompanied by changes in proton content at enzyme active sites, in their associated cofactors, in substrates/products, and between protein interfaces. Understanding this breadth of reactivity is an ongoing chemical challenge. A great many workers have developed and investigated biomimetic model complexes to build new ways of thinking about the mechanistic underpinnings of such complex biological proton-coupled electron transfer (PCET) reactions. Of particular importance are those model reactions that involve transfer of one proton (H+) and one electron (e–), equivalently transfer of a hydrogen atom (H•). In this Current Topic Article we review key concepts in PCET reactivity, and describe important advances in biomimetic PCET chemistry, with special emphasis on research that has enhanced efforts to understand biological PCET reactions.

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The first crystal structure of a monomeric phenoxyl radical: 2,4,6-tri-tert-butylphenoxyl radical

Abstract: Crystals of the 2,4,6-tri-tert-butylphenoxyl radical have been isolated and characterized by X-ray diffraction, and calculations have been performed that give the distribution of spin density in the radical.

Cited by 149 publications

References 36 publications

Investigation of charge-transfer absorptions in the uranyl UO22+(VI) ion and related chemical reduction of UO22+(VI) to UO2+(V) by UV–Vis and electron paramagnetic resonance spectroscopies

Investigation of charge-transfer absorptions in the uranyl UO22+(VI) ion and related chemical reduction of UO22+(VI) to UO2+(V) by UV–Vis and electron paramagnetic resonance spectroscopies

Organic Mixed Valence

Moving Protons and Electrons in Biomimetic Systems

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