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Thomas W Hamann - One of the best experts on this subject based on the ideXlab platform.

  • fast low spin Cobalt Complex redox shuttles for dye sensitized solar cells
    Journal of Physical Chemistry Letters, 2013
    Co-Authors: Thomas W Hamann
    Abstract:

    A low-spin Cobalt(II) Complex, Cobalt bis(trithiacyclononane), [Co(ttcn)2]3+/2+, was investigated for use as a redox shuttle in dye-sensitized solar cells, DSSCs. This unique Cobalt Complex redox shuttle is stable, transparent, and easy to synthesize from commercial ligands and has attractive energetic and kinetic features for use in DSSCs. Initial results indicate that the overall performance is limited by recombination. Variation of the sensitizer and deposition of an ultrathin coating of alumina on nanoparticle-based TiO2 DSSC photoanodes reduced recombination, which resulted in significantly improved quantum yields. The photovoltaic behavior was compared to the current record efficiency Cobalt tris-bipyridine, [Co(bpy)3]3+/2+, redox shuttle and produced similar results. Further use of high extinction organic sensitizers with only ∼200 mV of driving force for regeneration was examined, which produced efficiencies of over 2%; importantly, regeneration is not rate-limiting in this system, thus demonstrat...

  • the end of iodide Cobalt Complex redox shuttles in dsscs
    Dalton Transactions, 2012
    Co-Authors: Thomas W Hamann
    Abstract:

    This article focuses on the promise and progress of replacing the ubiquitous triiodide/iodide electrolyte with Cobalt poly-pyridine Complex redox shuttles in dye-sensitized solar cells, DSSCs. Issues which require further research will also be presented.

Curtis P Berlinguette - One of the best experts on this subject based on the ideXlab platform.

Muting Zeng - One of the best experts on this subject based on the ideXlab platform.

  • thermal degradation kinetics of chitosan Cobalt Complex as studied by thermogravimetric analysis
    Carbohydrate Polymers, 2010
    Co-Authors: Chunyan Ou, Chaohua Zhang, Sidong Li, Lei Yang, Jingjing Dong, Xueliu Mo, Muting Zeng
    Abstract:

    Abstract The thermal degradation of chitosan–Cobalt Complex at different heating rates in nitrogen was studied by thermogravimetric analysis (TGA) in the temperature range 30–800 °C. Fourier transform-infrared (FTIR) and X-ray diffractogram (XRD) analyses were utilized to determine the micro-structure of chitosan–Cobalt Complex. The results indicate that the thermal degradation of chitosan–Cobalt Complex in nitrogen is a two-step reaction, characteristic temperatures and the maximum reaction rate of thermal degradation increase with the increment of heating rate. The kinetic parameters were determined by using Friedman and Flynn–Wall–Ozawa methods. Coats–Redfern method was used to discuss the probable degradation mechanism. The results show that activation energy of the Complex resulting from two kinetic methods has similar variable tendency, and the solid-state decomposition in the first degradation stage, which is non-spontaneous, goes to a mechanism involving nucleation and growth, Avrami–Erofeev function ( A 4 ) with integral form [−ln(1 −  α )] 4 .

  • Thermal degradation kinetics of chitosan–Cobalt Complex as studied by thermogravimetric analysis
    Carbohydrate Polymers, 2010
    Co-Authors: Chunyan Ou, Chaohua Zhang, Sidong Li, Lei Yang, Jingjing Dong, Xueliu Mo, Muting Zeng
    Abstract:

    Abstract The thermal degradation of chitosan–Cobalt Complex at different heating rates in nitrogen was studied by thermogravimetric analysis (TGA) in the temperature range 30–800 °C. Fourier transform-infrared (FTIR) and X-ray diffractogram (XRD) analyses were utilized to determine the micro-structure of chitosan–Cobalt Complex. The results indicate that the thermal degradation of chitosan–Cobalt Complex in nitrogen is a two-step reaction, characteristic temperatures and the maximum reaction rate of thermal degradation increase with the increment of heating rate. The kinetic parameters were determined by using Friedman and Flynn–Wall–Ozawa methods. Coats–Redfern method was used to discuss the probable degradation mechanism. The results show that activation energy of the Complex resulting from two kinetic methods has similar variable tendency, and the solid-state decomposition in the first degradation stage, which is non-spontaneous, goes to a mechanism involving nucleation and growth, Avrami–Erofeev function ( A 4 ) with integral form [−ln(1 −  α )] 4 .

Xiaoyan Li - One of the best experts on this subject based on the ideXlab platform.

  • imine assisted c f bond activation using low valent Cobalt compounds supported by trimethylphosphine ligands and formation of novel organic fluorides
    Dalton Transactions, 2010
    Co-Authors: Zhe Lian, Tingting Zheng, Yue Chen, Xiaofeng Xu, Xiaoyan Li
    Abstract:

    A cyclometalation reaction involving C–F bond activation at a Cobalt(I) center with an aldazine-N atom as anchoring group affords ortho-chelated Cobalt(III) Complexes containing a [C–Co–F] fragment [CoFMe(PMe3)2{(C6H3F-ortho)CHN–R}] 5–8. Under similar reaction conditions π-coordinated Cobalt(0) Complexes [Co(PMe3)3((C6H3F-ortho)CHN–R)] 12–14 were formed when [Co(PMe3)4], instead of [CoMe(PMe3)4], was applied. C–F bond activation did not occur. Carbonylation of Complexes 6–8 delivered novel organic fluorides 15–17. A proposed formation mechanism of the novel organic fluorides with demetallation and carbonylation of Complexes 6–8 by CO is discussed with experimental support. As important intermediates, an acetyl Cobalt Complex, [CoFMeCO(PMe3)2{(C6H3F-ortho)CHN–R}] 20, and a 19-electron Cobalt(0) Complex, Co(CO)3(PMe3)221, were structurally characterized. The crystal and molecular structures of Complexes 5, 6, 8, 12, 20 and 21 were determined by X-ray diffraction.

  • Synergistic Effect of a Low-Valent Cobalt Complex and a Trimethylphosphine Ligand on Selective C−F Bond Activation of Perfluorinated Toluene
    Organometallics, 2009
    Co-Authors: Tingting Zheng, Simon Durr, Udo Radius, Xiaoyan Li, Yue Chen, Klaus Harms
    Abstract:

    The aryne Cobalt Complex [Co(4-CF3-η2-C6F3)(PMe3)3] (1) was formed from the reaction of [Co(PMe3)4] and perfluorinated toluene through selective activation of two C−F bonds of perfluorotoluene. A mechanism for the formation of Complex 1 is proposed and in most parts experimentally verified. Following this mechanism, a synergistic effect of an electron-rich Cobalt(0) center and one of its trimethylphosphine ligands is responsible for the C−F activation of two carbon−fluorine bonds of perfluorotoluene. The detection of difluorotrimethylphoshphorane as the sole byproduct provides strong evidence for this mechanism. Complex [Co(4-CF3-C6F4)(PMe3)3] (4), an intermediate of the proposed mechanism to the aryne Complex, was also isolated and structurally characterized. Complex 4 transforms to Complex 1 via activation of a second C−F bond of a perfluorotolyl ligand only in the presence of trimethylphosphine in the reaction mixture. Complex 4 reacts with CO under atmospheric pressure and room temperature to give [Co...

  • synergistic effect of a low valent Cobalt Complex and a trimethylphosphine ligand on selective c f bond activation of perfluorinated toluene
    Organometallics, 2009
    Co-Authors: Tingting Zheng, Simon Durr, Udo Radius, Xiaoyan Li, Yue Chen, Klaus Harms
    Abstract:

    The aryne Cobalt Complex [Co(4-CF3-η2-C6F3)(PMe3)3] (1) was formed from the reaction of [Co(PMe3)4] and perfluorinated toluene through selective activation of two C−F bonds of perfluorotoluene. A mechanism for the formation of Complex 1 is proposed and in most parts experimentally verified. Following this mechanism, a synergistic effect of an electron-rich Cobalt(0) center and one of its trimethylphosphine ligands is responsible for the C−F activation of two carbon−fluorine bonds of perfluorotoluene. The detection of difluorotrimethylphoshphorane as the sole byproduct provides strong evidence for this mechanism. Complex [Co(4-CF3-C6F4)(PMe3)3] (4), an intermediate of the proposed mechanism to the aryne Complex, was also isolated and structurally characterized. Complex 4 transforms to Complex 1 via activation of a second C−F bond of a perfluorotolyl ligand only in the presence of trimethylphosphine in the reaction mixture. Complex 4 reacts with CO under atmospheric pressure and room temperature to give [Co...

Klaus Harms - One of the best experts on this subject based on the ideXlab platform.

  • Synergistic Effect of a Low-Valent Cobalt Complex and a Trimethylphosphine Ligand on Selective C−F Bond Activation of Perfluorinated Toluene
    Organometallics, 2009
    Co-Authors: Tingting Zheng, Simon Durr, Udo Radius, Xiaoyan Li, Yue Chen, Klaus Harms
    Abstract:

    The aryne Cobalt Complex [Co(4-CF3-η2-C6F3)(PMe3)3] (1) was formed from the reaction of [Co(PMe3)4] and perfluorinated toluene through selective activation of two C−F bonds of perfluorotoluene. A mechanism for the formation of Complex 1 is proposed and in most parts experimentally verified. Following this mechanism, a synergistic effect of an electron-rich Cobalt(0) center and one of its trimethylphosphine ligands is responsible for the C−F activation of two carbon−fluorine bonds of perfluorotoluene. The detection of difluorotrimethylphoshphorane as the sole byproduct provides strong evidence for this mechanism. Complex [Co(4-CF3-C6F4)(PMe3)3] (4), an intermediate of the proposed mechanism to the aryne Complex, was also isolated and structurally characterized. Complex 4 transforms to Complex 1 via activation of a second C−F bond of a perfluorotolyl ligand only in the presence of trimethylphosphine in the reaction mixture. Complex 4 reacts with CO under atmospheric pressure and room temperature to give [Co...

  • synergistic effect of a low valent Cobalt Complex and a trimethylphosphine ligand on selective c f bond activation of perfluorinated toluene
    Organometallics, 2009
    Co-Authors: Tingting Zheng, Simon Durr, Udo Radius, Xiaoyan Li, Yue Chen, Klaus Harms
    Abstract:

    The aryne Cobalt Complex [Co(4-CF3-η2-C6F3)(PMe3)3] (1) was formed from the reaction of [Co(PMe3)4] and perfluorinated toluene through selective activation of two C−F bonds of perfluorotoluene. A mechanism for the formation of Complex 1 is proposed and in most parts experimentally verified. Following this mechanism, a synergistic effect of an electron-rich Cobalt(0) center and one of its trimethylphosphine ligands is responsible for the C−F activation of two carbon−fluorine bonds of perfluorotoluene. The detection of difluorotrimethylphoshphorane as the sole byproduct provides strong evidence for this mechanism. Complex [Co(4-CF3-C6F4)(PMe3)3] (4), an intermediate of the proposed mechanism to the aryne Complex, was also isolated and structurally characterized. Complex 4 transforms to Complex 1 via activation of a second C−F bond of a perfluorotolyl ligand only in the presence of trimethylphosphine in the reaction mixture. Complex 4 reacts with CO under atmospheric pressure and room temperature to give [Co...