Relative Standard Electrode Potentials of I3−/I−, I2/I3−, and I2/I− Redox Couples and the Related Formation Constants of I3− in Some Pure and Mixed Dipolar Aprotic Solvents

Datta, Jayati; Bhattacharya, Abhijit; Kundu, Kiron K.

doi:10.1246/bcsj.61.1735

Cited by 64 publications

(30 citation statements)

References 22 publications

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“…At acidic pH, these species exist largely in the form of their corresponding acids, HI and HI 3 . Since little information was available on electrochemical properties of the different redox couples (I ‐ /I 2, I ‐ /I 3 ‐ ,I 3 ‐ /I 2 ) in iodide/iodine mixtures (30), predictions on how the ratio of iodine/iodide would affect the reduction potential of such solutions were impossible to make. Taking into account that biological samples contain variable amounts of redox‐active compounds, which may result in the consumption of iodine or iodide, different strengths and molar ratios were investigated with regard to their efficacy to convert nitrite, GSNO, and SNOAlb to NO.…”

Section: Resultsmentioning

confidence: 99%

Concomitant S‐, N‐, and heme‐nitros(yl)ation in biological tissues and fluids: implications for the fate of NO in vivo

et al. 2002

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There is growing evidence for the involvement of nitric oxide (NO) -mediated nitrosation in cell signaling and pathology. Although S-nitrosothiols (RSNOs) have been frequently implicated in these processes, it is unclear whether NO forms nitrosyl adducts with moieties other than thiols. A major obstacle in assessing the significance of formation of nitrosated species is the limited reliability of available analytical techniques for measurements in complex biological matrices. Here we report on the presence of nitrosated compounds in plasma and erythrocytes of rats, mice, guinea pigs, and monkeys under basal conditions, in immunologically challenged murine macrophages in vitro and laboratory animals in vivo. Besides RSNOs, all biological samples also contained mercury-stable nitroso species, indicating the additional involvement of amine and heme nitros(yl)ation reactions. Significant differences in the amounts and ratios of RSNOs over N- and heme-nitros(yl)ated compounds were found between species and organs. These observations were made possible by the development of a novel gas-phase chemiluminescence-based technique that allows detection of nitroso species in tissues and biological fluids without prior extraction or deproteinization. The method can quantify as little as 100 fmol bound NO and has been validated extensively for use in different biological matrices. Discrimination between nitrite, RSNOs, and N-nitroso or nitrosylheme compounds is accomplished by use of group-specific reagents. Our findings suggest that NO generation in vivo leads to concomitant formation of RSNOs, nitrosamines, and nitrosylhemes with considerable variation between rodents and primates, highlighting the difficulty in comparing data between different animal models and extrapolating results from experimental animals to human physiology.

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Section: Resultsmentioning

confidence: 99%

Concomitant S‐, N‐, and heme‐nitros(yl)ation in biological tissues and fluids: implications for the fate of NO in vivo

et al. 2002

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“…in ACN K M ¼ 4 Â 10 6 ). 24,25 The free iodine concentration in the electrolyte can be described by eqn (1) and (2); where I 2 o is the added iodine and we have dropped the ''[]'' symbols in eqn (2) for readability. We refer to the remaining uncomplexed iodine in the cell at equilibrium as ''free iodine''.…”

Section: Methodsmentioning

confidence: 99%

Managing wetting behavior and collection efficiency in photoelectrochemical devices based on water electrolytes; improvement in efficiency of water/iodide dye sensitised cells to 4%

et al. 2012

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We have fabricated Dye Sensitised Solar Cells (DSSCs) using only water as the solvent and guanidinium iodide-iodine as the redox couple that operate at 4% energy efficiency under 1-sun illumination. This result is $5 times higher than the best previously reported values. We show that it is critical to facilitate the wetting of water electrolytes into the mesoporous TiO 2 dye films, especially when using hydrophobic dyes. We show chenodeoxycholic acid to be a good surfactant for this purpose. By separate variation of iodide and iodine concentrations in series of cells we show that the optimum concentrations for water based DSSCs are quite different from those used in organic electrolytes. We argue that this is due to the much lower stability constant of tri-iodide in water, relative to organic solvent. Finally we also vary the TiO 2 thickness and pore structure to achieve the above stated efficiency.

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“…26,27 The second explanation is that the TiO 2 (e -)s are good one electron reductants, perhaps best thought of as Ti(III) trap states, that are unable to facilitate the 2e -reduction of I 3 -, which is in fact the only reaction observed for I 3 -at metallic electrodes. [28][29][30] In addition, quinone/hydroquinone redox mediators that achieved some success in the older dye sensitized literature also involve two-electron transfer. 31 Significantly, it has been known for some time that the reaction of aqueous Ti(III) ions with I 3 -is also kinetically sluggish with an activation energy of 80 kcal/ mol, Reaction 3.…”

Section: Recombinationmentioning

confidence: 99%

Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I⁻ Oxidation and I₃⁻ Photodissociation

et al. 2009

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Direct 355 or 532 nm light excitation of TBAI 3 , where TBA is tetrabutyl ammonium, in CH 3 CN at room temperature yields an iodine atom, I • , and an iodine radical anion, I 2 -• . In the presence of excess iodide, the iodine atom reacts quantitatively to yield a second equivalent of I 2 -• with a rate constant of k ) 2.5 ( 0.4 × 10 10 M -1 s -1 . The I 2 -• intermediates are unstable with respect to disproportionation and yield initial reactants, k ) 3.3 ( 0.1 × 10 9 M -1 s -1 . The coordination compound Ru(bpz) 2 (deeb)(PF 6 ) 2 , where bpz is 2,2′-bipyrazine and deeb is 4,4′-(C 2 H 5 CO 2 ) 2 -2,2′-bipyridine, was prepared and characterized for mechanistic studies of iodide photo-oxidation in acetonitrile at room temperature. Ru(bpz) 2 (deeb) 2+ displayed a broad metal-to-ligand charge transfer (MLCT) absorption band at 450 nm with ε ) 1.7 × 10 4 M -1 cm -1 . Visible light excitation resulted in photoluminescence with a corrected maximum at 620 nm, a quantum yield φ ) 0.14, and an excited state lifetime τ ) 1.75 µs from which k r ) 8.36 × 10 4 s -1 and k nr ) 5.01 × 10 5 s -1 were abstracted. Arrhenius analysis of the temperature dependent excited state lifetime revealed an activation energy of ∼2500 cm -1 and a pre-exponential factor of 10 10 s -1 , assigned to activated surface crossing to a ligand field or MLCT excited state. Steady state light excitation of Ru(bpz) 2 (deeb) 2+ in a 20 mM TBAI acetonitrile solution resulted in ligand loss photochemistry with a quantum yield of 5 × 10 -5 . The MLCT excited state was dynamically quenched by iodide with K sv ) 1.1 × 10 5 M -1 and k q ) 6.6 ( 0.3 × 10 10 M -1 s -1 , a value consistent with diffusion-limited electron transfer. Excited state hole transfer to iodide was quantitative but the product yield was low due to poor cage escape yields, φ CE ) 0.042 ( 0.001. Nanosecond transient absorption was used to quantify the appearance of two photoproducts [Ru(bpz -)(bpz)(deeb)] + and I 2 -• . The coincidence of the rate constants for [Ru(bpz -)(bpz)(deeb)] + formation and for excited state decay indicated reductive quenching by iodide. The rate constant for the appearance of I 2 -• was about a factor of 3 slower than excited state decay, k ) 2.4 ( 0.2 × 10 10 M -1 s -1 , indicating that I 2 -• was not a primary photoproduct of excited state electron transfer. A mechanism was proposed where an iodine atom was the primary photoproduct that subsequently reacted with iodide, I • + I -f I 2 -• . Charge recombination Ru(bpz -)(bpz)(deeb) + + I 2 -• f Ru(bpz) 2 (deeb) 2+ + 2I -was highly favored, ∆G o ) -1.64 eV, and well described by a second-order equal concentration kinetic model, k cr ) 2.1 ( 0.3 × 10 10 M -1 s -1 .

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Relative Standard Electrode Potentials of I3−/I−, I2/I3−, and I2/I− Redox Couples and the Related Formation Constants of I3− in Some Pure and Mixed Dipolar Aprotic Solvents

Cited by 64 publications

References 22 publications

Concomitant S‐, N‐, and heme‐nitros(yl)ation in biological tissues and fluids: implications for the fate of NO in vivo

Concomitant S‐, N‐, and heme‐nitros(yl)ation in biological tissues and fluids: implications for the fate of NO in vivo

Managing wetting behavior and collection efficiency in photoelectrochemical devices based on water electrolytes; improvement in efficiency of water/iodide dye sensitised cells to 4%

Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I⁻ Oxidation and I₃⁻ Photodissociation

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Relative Standard Electrode Potentials of I3−/I−, I2/I3−, and I2/I− Redox Couples and the Related Formation Constants of I3− in Some Pure and Mixed Dipolar Aprotic Solvents

Cited by 64 publications

References 22 publications

Concomitant S‐, N‐, and heme‐nitros(yl)ation in biological tissues and fluids: implications for the fate of NO in vivo

Concomitant S‐, N‐, and heme‐nitros(yl)ation in biological tissues and fluids: implications for the fate of NO in vivo

Managing wetting behavior and collection efficiency in photoelectrochemical devices based on water electrolytes; improvement in efficiency of water/iodide dye sensitised cells to 4%

Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I− Oxidation and I3− Photodissociation

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Visible Light Generation of Iodine Atoms and I−I Bonds: Sensitized I⁻ Oxidation and I₃⁻ Photodissociation