Abstract:The evidence of Mcannot be doubted any more under certain experimental conditions so I raise the question about H-; is it stable in the solutions and does it absorb light as Na-, K-, etc., do? During electrolysis in, e.g., ether between two sodium electrodes, will sodium dissolve at the cathode forming anions or at the anode forming cations or on both sides?Comment: Pulse radiolysis should be done in connection with polarography to get other than optical evidence for Mformation; it also would yield redox poten… Show more
“…On the basis of the G value of e sol - , ε esol - (1300 nm) and ε BP · - (1300 nm) were estimated to be 1.8 × 10 4 and 3.5 × 10 2 M -1 cm -1 , respectively. The ε BP •- (1300 nm) is 2.8% of that at 655 nm, which is a reasonable value from the viewpoint of spectrum shape of BP •-34,35,48,49 and e sol - , ,,, supporting the reliability of the fitting results.…”
Section: Resultssupporting
confidence: 68%
“…In this paper, we adopted biphenyl (BP) as the scavenger of e sol - and of its precursor, because BP has been widely used in radiation chemistry and its radical anion (BP •- ) has strong photo absorption at around 408 and 655 nm, of which extinction coefficients are 40 000 and 12 500 M -1 cm -1 , respectively. ,,, For a comprehensive study on the reactivity of e sol - , it is of significant help to measure and analyze the formation of BP •- at 408 and 655 nm and decay of e sol - at infrared (IR). While the absorption maximum of e sol - is reported to be at 2.1 μm, ,,, its broad absorption is stretched to visible region. Because of a technical reason, 1300 nm was taken as the probe wavelength for the decay of e sol - .…”
Section: Introductionmentioning
confidence: 96%
“…Radiation-initiated reactions and the reactivity of the generated intermediates have attracted much attention in not only the basic science of radiation chemistry but also in associated fields such as biochemistry, radiotherapy, environmental chemistry, and lithography. Solvated (or hydrated) electrons in, e.g., water, − alcohols, − ethers, − amines, ,, and ionic liquids, , have been a major class of transient species and subjected to intensive theoretical and experimental investigations in terms of structures, reactivity, radiation-induced yield, etc. Since the discovery of hydrated electrons in water by Hart et al., these kinds of short-lived species have occupied an important place in radiation chemistry.…”
The initial decrease of solvated electrons in tetrahydrofuran (THF) upon addition of biphenyl was investigated by picosecond pulse radiolysis. Transient absorption spectra derived from the biphenyl radical anion (centered at 408 and 655 nm) and solvated electrons of THF (infrared) were successfully measured in the wavelength region from 400 to 900 nm by the extension of a femtosecond continuum probe light to near-ultraviolet using a second harmonic generation of Ti:sapphire laser and a CaF2 plate. From the analysis of kinetic traces at 1300 nm considering the overlap of primary solvated electrons and partial biphenyl radical anion, C37, which is defined by the solute concentration to reduce the initial yield of solvated electrons to 1/e, was found to be 87 +/- 3 mM. The rate constant of solvated electrons with biphenyl was determined as 5.8 +/- 0.3 x 10(10) M(-1) s(-1). We demonstrate that the kinetic traces at both 408 nm mainly due to biphenyl radical anion and 1300 nm mainly due to solvated electrons are reproduced with high accuracy and consistency by a simple kinetic analysis. Much higher concentrations of biphenyl (up to 2 M) were examined, showing further increase of the initial yield of biphenyl radical anion accompanying a fast decay component. This observation is discussed in terms of geminate ion recombination, scavenging, delayed geminate ion recombination, and direct ionization of biphenyl at high concentration.
“…On the basis of the G value of e sol - , ε esol - (1300 nm) and ε BP · - (1300 nm) were estimated to be 1.8 × 10 4 and 3.5 × 10 2 M -1 cm -1 , respectively. The ε BP •- (1300 nm) is 2.8% of that at 655 nm, which is a reasonable value from the viewpoint of spectrum shape of BP •-34,35,48,49 and e sol - , ,,, supporting the reliability of the fitting results.…”
Section: Resultssupporting
confidence: 68%
“…In this paper, we adopted biphenyl (BP) as the scavenger of e sol - and of its precursor, because BP has been widely used in radiation chemistry and its radical anion (BP •- ) has strong photo absorption at around 408 and 655 nm, of which extinction coefficients are 40 000 and 12 500 M -1 cm -1 , respectively. ,,, For a comprehensive study on the reactivity of e sol - , it is of significant help to measure and analyze the formation of BP •- at 408 and 655 nm and decay of e sol - at infrared (IR). While the absorption maximum of e sol - is reported to be at 2.1 μm, ,,, its broad absorption is stretched to visible region. Because of a technical reason, 1300 nm was taken as the probe wavelength for the decay of e sol - .…”
Section: Introductionmentioning
confidence: 96%
“…Radiation-initiated reactions and the reactivity of the generated intermediates have attracted much attention in not only the basic science of radiation chemistry but also in associated fields such as biochemistry, radiotherapy, environmental chemistry, and lithography. Solvated (or hydrated) electrons in, e.g., water, − alcohols, − ethers, − amines, ,, and ionic liquids, , have been a major class of transient species and subjected to intensive theoretical and experimental investigations in terms of structures, reactivity, radiation-induced yield, etc. Since the discovery of hydrated electrons in water by Hart et al., these kinds of short-lived species have occupied an important place in radiation chemistry.…”
The initial decrease of solvated electrons in tetrahydrofuran (THF) upon addition of biphenyl was investigated by picosecond pulse radiolysis. Transient absorption spectra derived from the biphenyl radical anion (centered at 408 and 655 nm) and solvated electrons of THF (infrared) were successfully measured in the wavelength region from 400 to 900 nm by the extension of a femtosecond continuum probe light to near-ultraviolet using a second harmonic generation of Ti:sapphire laser and a CaF2 plate. From the analysis of kinetic traces at 1300 nm considering the overlap of primary solvated electrons and partial biphenyl radical anion, C37, which is defined by the solute concentration to reduce the initial yield of solvated electrons to 1/e, was found to be 87 +/- 3 mM. The rate constant of solvated electrons with biphenyl was determined as 5.8 +/- 0.3 x 10(10) M(-1) s(-1). We demonstrate that the kinetic traces at both 408 nm mainly due to biphenyl radical anion and 1300 nm mainly due to solvated electrons are reproduced with high accuracy and consistency by a simple kinetic analysis. Much higher concentrations of biphenyl (up to 2 M) were examined, showing further increase of the initial yield of biphenyl radical anion accompanying a fast decay component. This observation is discussed in terms of geminate ion recombination, scavenging, delayed geminate ion recombination, and direct ionization of biphenyl at high concentration.
“…Second, in general, the rates for electron transfer to the PAEs (eq 3b) are considerably faster compared to those for hole transfer (eq 3a). This difference reflects the considerably larger diffusion rate of . − 2 Observed rate of growth of PPE 164 radical cation in DCE/toluene (1,2-dichloroethane + 1.6 M toluene) solution as a function of concentration in repeat units (the concentration of PPE molecules is smaller by a factor of 164). The straight line best fit yields a slope of 1.6 × 10 9 M -1 s -1 per repeat unit or 1.0 × 10 11 M -1 s -1 using concentration of PPE chains.…”
Section: Resultsmentioning
confidence: 99%
“…This difference reflects the considerably larger diffusion rate of e s -. [53][54][55][56] Poly(arylene ethynylene)s are known to aggregate in solution with the degree of aggregation being dependent upon the solvent system used and the concentration of the polymer. 20,57 The pseudo-first-order growth of PPE 164 •+ as a function of polymer concentration, shown in Figure 2, is linear to a concentration of 1.35 × 10 -3 M in repeat units, suggesting that aggregation is not significant in the DCE/toluene solutions at these concentrations, which were typical of the concentrations used in the paper.…”
Two poly(arylene ethynylene)s (PAEs) that are end-capped with R-terthiophene (T 3 ) groups were prepared and structurally characterized by proton NMR, GPC, and optical spectroscopy. One of the polymers (T 3 PPE 13 ) features a backbone structure that alternates phenylene ethynylene and bis(alkoxy)phenylene ethynylene repeat units. The second T 3 end-capped polymer (T 3 PBpE 12 ) features an alternating structure with biphenylene ethynylene and bis(alkoxy)phenylene ethynylene repeats. The absorption spectra of the T 3 end-capped polymers are almost the same as those of the corresponding "parent polymers" (PPE 164 and PBpE 21 , respectively) that lack the T 3 end-groups. By contrast, whereas the fluorescence spectra of the parent polymers is dominated by a blue fluorescence with λ max ) 425 nm, the emission spectra of the end-capped polymers contains a significant contribution of a green fluorescence (λ ) 500-550 nm). This signals that the singlet exciton is efficiently trapped by the T 3 end groups. Pulse radiolysis studies were carried out on all of the poly(arylene ethynylene)s in an effort to characterize the spectra and dynamics of the cation and anion radicals of the polymers. Pulse radiolytically generated solvent holes, and solvated electrons were transferred to the PAEs at nearly diffusion controlled rates. The absorption spectra of the anion radicals of the PAEs were similar and featured two strong absorption bands, one in the visible (λ ) 600 nm) and the second in the near-IR (λ ) 1600-2000 nm). The cation radicals of the T 3 end-capped polymers also feature two absorption bands, one in the visible and the second in the near-IR. However, the spectra of the cation radicals of the T 3 end-capped polymers show important differences. Specifically, the cation radical spectra of T 3 BpE 12 and PBpE 21 are identical, which reveals that the hole is not trapped by the T 3 end-cap in the biphenylene polymer. By contrast, the cation radical absorption spectra of T 3 PPE 13 (λ max ) 640 and 1350 nm) and PPE 164 (λ max ) 600 and 1950 nm) are distinctly different. This difference suggests that the hole is localized on the T 3 end-group in T 3 PPE 13 . Bimolecular hole-transfer experiments using bithiophene (T 2 , E°o x ) 1.21 V), terthiophene (T 3 , E°o x ) 0.91 V), and quaterthiophene (T 4 , E°°o x ) 0.76 V) with PPE 164 and PBpE 21 allowed the determination of the oxidation potentials for the PAEs. The values are PPE 164 , E°o x ) 0.91 V; PBpE 21 , E°o x ) 0.85 V (all potentials vs SCE). The lower oxidation potential of the biphenylene based PAE explains why the hole is not trapped by the T 3 end-groups in T 3 BpE 12 . The dynamics of intrachain hole transfer in T 3 PPE 13 are much faster than the rate of hole transfer from the solvent, and on the basis of this result, the lower limit for intrachain hole transfer is determined to be k HT g 1 × 10 8 s -1 .
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