Redox Systems with Sulphur-Centered Species

Armstrong, David A.

doi:10.1007/978-1-4684-5874-9_29

Cited by 6 publications

(6 citation statements)

References 17 publications

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“…radicals with C U ( I I ) ( P~~S -)~ are Cu(1)-penicillamine complexes. In contrast to the above results with P e n s radicals, the production of .COz-radicals via reactions [6], [7], [I 11, and [12] at pH 12 in lop4 M C U ( I I ) ( P~~S - The level of Cu(I1) complex at the photostationary state then rises. However, reaction [15] was negligible at pH 10 with 4 X M total PenSH.…”

Section: Co Y-radiolysiscontrasting

confidence: 59%

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Radical reductions of Cu(II)-penicillamine complexes: Evidence for a Cu(II)-disulphide anion intermediate

Mezyk¹,

Armstrong²

1991

Can. J. Chem.

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Can. J. Chem. 69, 533 (1991).In basic solution Cu(I1) ions form plana!: complexes of stoichiometry Cu(II).L2 with penicillamine molecules, where both the nitrogen and sulphur atoms of the thiol [(NH2)CH(COz-)C(CH3)zS-] are involved in the coordination. The rates of reduction of this complex by the formate radical and the thiyl radical of penicillamine have been measured by pulse radiolysis.The rate constant for reaction [14] has been found to be 1.For the thiyl radical, which is not inherently reducing, reduction must involve the PenS:.SPen-anion complexUnder the conditions of this study, ([Pens-] -lo-' M , pH = 10.0), this anion exists in free solution equilibrium with Pens.A systematic study of the dependence of the overall reduction rate on [Pens-] showed that the reaction proceeded rapidly even when the PenS:.SPen-concentration was negligibly small. This finding can be explained by the formation of an internal PenS:.SPen-anion from the reaction of free Pens. with one of the Pens-ligands of the Cu(I1) complex:and the subsequent rapid transfer of an electron to Cu(l1):Analysis of the results gave k2 = 2.9 * 0.3 X 10' M-' s-' and k3 = 3.4 0.4 X 10' M-' s -' .

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Section: Co Y-radiolysiscontrasting

confidence: 59%

“…radicals are moderately strong one-electron oxidizing agents, with E O ( R~. / R S -) = 0.77 V (7). For typical alkaline conditions with thiol concentrations of M, however, they are in equilibrium with the uu * bonded RS : .…”

Section: Introductionmentioning

confidence: 99%

Radical reductions of Cu(II)-penicillamine complexes: Evidence for a Cu(II)-disulphide anion intermediate

Mezyk¹,

Armstrong²

1991

Can. J. Chem.

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“…Using pulse radiolysis techniques, it has been shown that thyil radicals oxidize phenothiazine drugs (Eox < 0.8 V).s9 The reduction potential of thyil radicals has been estimated to be 0.84 V. 58 The possible role of solution charge transfer complex formation which has been suggested previously6' is illustrated by the colour change observed when benzidine and phenothiazine were dissolved in NBA prior to analysis. The resulting mass spectra showed almost complete matrix suppression, perhaps indicating the significant presence of pre-formed ions in solution.…”

Section: M" Formation and Dehalogenation Inhibiting Tendencies Of Matmentioning

confidence: 98%

Beam‐induced dehalogenation in LSIMS: Effect of halogen type and matrix chemistry

Théberge

Bertrand

1995

J. Mass Spectrom.

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The LSIMS beam-induced dehalogenation of several 4-halo-phenylalanine methyl esters (I, Br, CI, F) was investigated and compared to that of atrazine using 12 different matrix compounds including diethyl phthalate for which the empirical electron affinity was known. The extent of dehalogenation, induced by a one-electron reduction process, is in agreement with the leaving group ability of the corresponding halogens~(1 > Br > CI > F) and the dehalogenation inhibiting efficiency of the matrices. The latter is rationalized in terms of electron scavenging capacity and matrix structural features relating to that capacity. The extent of dehalogenation observed for 4-1-phenylalanine methyl ester is similar to that of atrazine, a chlorinated compound, which indicates that the halogen effect is not overwhelming in determining the extent of dehalogenation. The bracketing of matrix reduction potential was attempted based on the propensity of the matrices to induce M+' formation from analytes of known oxidation potentials. The ability of matrices to induce M" formation parallels their dehalogenation and reduction inhibiting efficiencies. The last observation underlines the importance of matrix redox properties in effecting or inhibiting beam-induced processes, be they reductive or oxidative.

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“…The photochemistry of sulfur radical ions in liquids and solutions receives increasingly attention because they contribute to important oxidation−reduction processes in atmospheric sulfur cycle, solution chemistry and biochemistry. − For instance, sulfur-centered intermediates involved in electron-transfer reactions act as a reducing agent, source of oxidant thiyl radicals, and may participate to S−S bond making/bond breaking in macromolecules . With organic sulfur compounds, the detection of short-lived electronic states provides some important basis for the microscopic investigation of elementary redox reactions. , The one-electron reduction of sulfur compounds yields the formation of a odd-electron bond inside nascent sulfur-centered radical anions (RS∴SR - ). − Neat liquid dimethyl sulfide (DMS, CH 3 SCH 3 ), the simplest of the thioethers, represents a paradigm for the short-time investigation of disulfide radicals anions characterized by the presence of a two-center three-electron bond (2c/3e bond). From femtosecond UV photoionization experiments of pure liquid DMS, it has been observed that, immediately after an electron photodetachment from a lone pair of sulfur atoms, a short-lived odd-electron bonded intermediate participates, via an efficient electron attachment process , to the subpicosecond formation of a disulfide radical anion CH 3 S∴SCH 3 - (eq 1a,b).…”

Section: Introductionmentioning

confidence: 99%

Femtosecond Probing of a 2c/3e Disulfide Bond Making in Liquid Phase

2002

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The subpicosecond ultraviolet observation of a sulfur−sulfur bond making (2σ/1σ* bond) is carried out in pure liquid dimethyl sulfide at 294 K. The early stages of a disulfide bonded radical formation (CH3S∴SCH3 -) are characterized by a nonlinear λ max red shift of the absorption spectrum. In the temporal range 0−1600 fs, the red shift of 0.31 ± 0.1 eV is analyzed in the framework of a change of the 2σ/1σ* transition due to a lowering of the 2c,3e S−S bond strength and/or a destabilization of the σ lone pair during the demethylation process.

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Redox Systems with Sulphur-Centered Species

Cited by 6 publications

References 17 publications

Radical reductions of Cu(II)-penicillamine complexes: Evidence for a Cu(II)-disulphide anion intermediate

Radical reductions of Cu(II)-penicillamine complexes: Evidence for a Cu(II)-disulphide anion intermediate

Beam‐induced dehalogenation in LSIMS: Effect of halogen type and matrix chemistry

Femtosecond Probing of a 2c/3e Disulfide Bond Making in Liquid Phase

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