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Andrzej Rajca - One of the best experts on this subject based on the ideXlab platform.

  • radical cation and neutral radical of aza thia 7 helicene with somo homo energy level inversion
    Journal of the American Chemical Society, 2016
    Co-Authors: Ying Wang, Hui Zhang, Maren Pink, Arnon Olankitwanit, Suchada Rajca, Andrzej Rajca
    Abstract:

    We report a relatively persistent, open-shell aza-thia[7]helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at Anodic Peak Potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent ne...

  • Radical Cation and Neutral Radical of Aza-thia[7]helicene with SOMO–HOMO Energy Level Inversion
    2016
    Co-Authors: Ying Wang, Hui Zhang, Maren Pink, Arnon Olankitwanit, Suchada Rajca, Andrzej Rajca
    Abstract:

    We report a relatively persistent, open-shell aza-thia[7]­helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]­helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]­helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]­helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at Anodic Peak Potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent neutral aminyl radical. Structure of the aza-thia[7]­helicene is supported by NMR, IR, X-ray crystallography, and cyclic voltammetry. The radical cation and neutral radical are characterized by EPR and UV–vis-NIR spectroscopies. DFT computations of the radical cation and neutral radical predict the SOMO–HOMO energy level inversion, which is supported experimentally by electrochemical data for the radical cation

Wen-ta Tsai - One of the best experts on this subject based on the ideXlab platform.

  • Effect of selective dissolution on fatigue crack initiation in 2205 duplex stainless steel
    Corrosion Science, 2007
    Co-Authors: Wen-ta Tsai
    Abstract:

    The effect of selective dissolution on fatigue crack initiation of 2205 duplex stainless steel (DSS) was investigated in this study. In mixed sulfuric and hydrochloric acid aqueous solution, there existed two distinctly separated Anodic Peaks in the active-to-passive transition region of the polarization curve. Either ferritic or austenitic phase was selectively dissolved at each characteristic Anodic Peak Potential. Under sinusoidal cyclic loading condition, however, selective dissolution did not assist fatigue crack initiation instead resulting in the elimination of stress concentration site in the selectively dissolving phase. As a consequence, under selective dissolution condition, fatigue crack initiated in the phase while its dissolution rate was lower with respect to the other constituent phase in the duplex stainless steel. The microstructural evolution of the corrosion fatigue crack initiation in 2205 DSS in the mixed sulfuric and hydrochloric acid solution is highlighted in this investigation.

  • effect of electrolyte composition on the active to passive transition behavior of 2205 duplex stainless steel in h2so4 hcl solutions
    Corrosion Science, 2006
    Co-Authors: C J Lin, Wen-ta Tsai
    Abstract:

    Abstract Selective dissolution could occur in duplex stainless steels (DSSs) due to the difference in chemical composition between the two constituent phases. In this study, the effect of H 2 SO 4 /HCl composition on the selective dissolution behavior was investigated. The results indicated that there were two distinct Peaks appeared in the active-to-passive transition region in the polarization curve. The Peak appeared at a lower Potential region was associated with the preferential dissolution of ferrite phase while that for austenite at a higher Potential. In the concentration ranges of 0.25–2 M of H 2 SO 4 and 0.25–2 M of HCl, the magnitude of the Peak Anodic current density and the resolution between these two Peaks greatly depended on the composition of H 2 SO 4 /HCl. However, the Anodic Peaks corresponding to the respective dissolutions of ferrite and austenite became less distinguishable when the concentrations of HCl exceeded 1.2 M. Image analysis using scanning electron microscopy (SEM) was performed to confirm the selective dissolution of each constituent phase after potentiostatic polarization at the respective Anodic Peak Potential.

  • Selective corrosion in duplex stainless steel
    Corrosion 2003, 2003
    Co-Authors: Wen-ta Tsai, Kuen-ming Tsai, Changjian Lin
    Abstract:

    In duplex stainless steel, the two constituent phases, namely ferritic (a) and austenitic (7) phases, have different crystal structure and chemical composition. They may thus exhibit different corrosion resistances in aqueous environment. In this investigation, an electrochemical technique with spatial resolution was employed to measure the Potential difference between these two constituent phases in 2205 duplex stainless steel. Image analyzing techniques were also used to examine the preferential corrosion between a and 7 phases. The experimental results showed that ferrite had a higher Potential than austenite in 0.01 M NaC1 solution. In 2M H2SO4 + xM HC1 solution, two distinct Peaks appeared in the Anodic polarization curve in the passive-to-active transition region. Preferential corrosion occurred in the ferrite phase at a lower Anodic Peak Potential, while in austenite at a higher Anodic Peak Potential.

Ying Wang - One of the best experts on this subject based on the ideXlab platform.

  • radical cation and neutral radical of aza thia 7 helicene with somo homo energy level inversion
    Journal of the American Chemical Society, 2016
    Co-Authors: Ying Wang, Hui Zhang, Maren Pink, Arnon Olankitwanit, Suchada Rajca, Andrzej Rajca
    Abstract:

    We report a relatively persistent, open-shell aza-thia[7]helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at Anodic Peak Potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent ne...

  • Radical Cation and Neutral Radical of Aza-thia[7]helicene with SOMO–HOMO Energy Level Inversion
    2016
    Co-Authors: Ying Wang, Hui Zhang, Maren Pink, Arnon Olankitwanit, Suchada Rajca, Andrzej Rajca
    Abstract:

    We report a relatively persistent, open-shell aza-thia[7]­helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]­helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]­helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]­helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at Anodic Peak Potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent neutral aminyl radical. Structure of the aza-thia[7]­helicene is supported by NMR, IR, X-ray crystallography, and cyclic voltammetry. The radical cation and neutral radical are characterized by EPR and UV–vis-NIR spectroscopies. DFT computations of the radical cation and neutral radical predict the SOMO–HOMO energy level inversion, which is supported experimentally by electrochemical data for the radical cation

Arnon Olankitwanit - One of the best experts on this subject based on the ideXlab platform.

  • radical cation and neutral radical of aza thia 7 helicene with somo homo energy level inversion
    Journal of the American Chemical Society, 2016
    Co-Authors: Ying Wang, Hui Zhang, Maren Pink, Arnon Olankitwanit, Suchada Rajca, Andrzej Rajca
    Abstract:

    We report a relatively persistent, open-shell aza-thia[7]helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at Anodic Peak Potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent ne...

  • Radical Cation and Neutral Radical of Aza-thia[7]helicene with SOMO–HOMO Energy Level Inversion
    2016
    Co-Authors: Ying Wang, Hui Zhang, Maren Pink, Arnon Olankitwanit, Suchada Rajca, Andrzej Rajca
    Abstract:

    We report a relatively persistent, open-shell aza-thia[7]­helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]­helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]­helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]­helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at Anodic Peak Potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent neutral aminyl radical. Structure of the aza-thia[7]­helicene is supported by NMR, IR, X-ray crystallography, and cyclic voltammetry. The radical cation and neutral radical are characterized by EPR and UV–vis-NIR spectroscopies. DFT computations of the radical cation and neutral radical predict the SOMO–HOMO energy level inversion, which is supported experimentally by electrochemical data for the radical cation

Maren Pink - One of the best experts on this subject based on the ideXlab platform.

  • radical cation and neutral radical of aza thia 7 helicene with somo homo energy level inversion
    Journal of the American Chemical Society, 2016
    Co-Authors: Ying Wang, Hui Zhang, Maren Pink, Arnon Olankitwanit, Suchada Rajca, Andrzej Rajca
    Abstract:

    We report a relatively persistent, open-shell aza-thia[7]helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at Anodic Peak Potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent ne...

  • Radical Cation and Neutral Radical of Aza-thia[7]helicene with SOMO–HOMO Energy Level Inversion
    2016
    Co-Authors: Ying Wang, Hui Zhang, Maren Pink, Arnon Olankitwanit, Suchada Rajca, Andrzej Rajca
    Abstract:

    We report a relatively persistent, open-shell aza-thia[7]­helicene with cross-conjugated electron-rich π-system. The singly occupied molecular orbital (SOMO) energy levels of both radical cation and neutral radical of the [7]­helicene are below the highest occupied molecular orbital (HOMO) energy levels, thereby violating the Aufbau principle. The aza-thia[7]­helicene is prepared from β-hexathiophene by a three-step one-pot reaction, in which the pyrrole ring is constructed by two consecutive C–N bond formations. Chemical oxidation converts the helicene to its radical cation, while in the presence of base (Cs2CO3), the oxidation gives neutral aminyl radical, likely via proton dissociation from the aminium radical cation with a low pKa. Reaction of the aza-thia[7]­helicene with NaH provides the corresponding anion, which shows characteristic cyclic voltammetry wave at Anodic Peak Potential Epa ≈ +0.2 V. Chemical oxidation of the anion with ferrocenium hexafluorophosphate at room temperature gives persistent neutral aminyl radical. Structure of the aza-thia[7]­helicene is supported by NMR, IR, X-ray crystallography, and cyclic voltammetry. The radical cation and neutral radical are characterized by EPR and UV–vis-NIR spectroscopies. DFT computations of the radical cation and neutral radical predict the SOMO–HOMO energy level inversion, which is supported experimentally by electrochemical data for the radical cation