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Author: Tkachov, Roman × DDC: 540 × WGL Institute: IPF ×

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Now showing 1 - 3 of 3
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    AB- Versus AA+BB-Suzuki Polycondensation: A Palladium/Tris(tert-butyl)phosphine Catalyst Can Outperform Conventional Catalysts
    (Weinheim : Wiley-VCH, 2020) Zhang, Kenan; Tkachov, Roman; Ditte, Kristina; Kiriy, Nataliya; Kiriy, Anton; Voit, Brigitte
    A Pd/Pt-Bu3 catalyst having bulky, electron-rich ligands significantly outperforms conventional “step-growth catalysts” Pd(PPh3)4 and Pd(Po-Tol3)3 in the Suzuki polycondensation of the AB-type arylene-based monomers, such as some of the substituted fluorenes, carbazoles, and phenylenes. In the AA+BB polycondensation, Pd/Pt-Bu3 also performs better under homogeneous reaction conditions, in combination with the organic base Et4NOH. The superior performance of Pd/Pt-Bu3 is discussed in terms of its higher reactivity in the oxidative addition step and inherent advantages of the intramolecular catalyst transfer, which is a key step joining catalytic cycles of the AB-polycondensation. These findings are applied to the synthesis of a carbazole-based copolymer designed for the use as a hole conductor in solution-processed organic light-emitting diodes. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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    Copolymerization of zinc-activated isoindigo- and naphthalene-diimide based monomers: an efficient route to low bandgap π-conjugated random copolymers with tunable properties
    (Cambridge : RSC Publ., 2016) Karpov, Yevhen; Maiti, Jatindranath; Tkachov, Roman; Beryozkina, Tetyana; Bakulev, Vasiliy; Liu, Wei; Komber, Hartmut; Lappan, Uwe; Al-Hussein, Mahmoud; Stamm, Manfred; Voit, Brigitte; Kiriy, Anton
    The present work aims at the extension of the scope of a recently discovered polycondensation of AB-type anion-radical monomers. To this end, we investigate the polymerization of isoindigo-based monomer and its copolymerization with the naphthalenediimide-based monomer. Although polycondensations of parent naphthalenediimide- and perylenediimide-based monomers involve chain-growth mechanism, we found that the corresponding isoindigo-based monomer polymerizes in a step-growth manner under the same reaction conditions. In contrast to Stille, Suzuki and direct arylation polycondensations which require prolonged stirring at high temperatures, the polymerization approach we employed in this study proceeds fast at room temperature. It was found that near statistical copolymerization of isoindigo-based anion-radical monomers with corresponding naphtalenediimide-based monomers proceeds smoothly resulting in a library of copolymers with varying composition and properties depending on the ratio of the monomers.
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    Polyethenetetrathiolate or polytetrathiooxalate? Improved synthesis, a comparative analysis of a prominent thermoelectric polymer and implications to the charge transport mechanism
    (Cambridge : RSC Publ., 2018) Tkachov, Roman; Stepien, Lukas; Grafe, Robert; Guskova, Olga; Kiriy, Anton; Simon, Frank; Reith, Heiko; Nielsch, Kornelius; Schierning, Gabi; Kasinathan, Deepa; Leyens, Christoph
    1,1,2,2-Ethenetetrathiolate (ett4-) coordination polymers, such as poly[Kx(Ni-ett)], have been known for decades for their excellent thermoelectric properties. However in reality, ett4- is neither a "true" comonomer which participates in the polymerization, nor represents a "true" repeat unit of the target polymer. Indeed, poly[K2(Ni-ett)], which is formally the product of Ni-induced polymerization of ett4-, has a poor conductivity and needs to be oxidized to show attractive thermoelectric characteristics. The polymerization and oxidation processes are poorly controllable which causes irreproducibility of the polymer properties. To improve the synthesis reproducibility, we studied polymerization of potassium tetrathiooxalate (K2tto), the convenient synthesis of which was developed in our recent work. Because K2tto is the "true monomer", and not its precursor, a high quality product is reproducibly formed simply by mixing K2tto with NiCl2 at room temperature. The procedure does not require additional components (bases), or special conditions (prolonged heating), which are usually needed for the preparation of this polymer from the monomer precursor 1,3,4,6-tetrathiapentalene-2,5-dione (TPD). Furthermore, as tto2- is formally the product of two-electron oxidation of ett4-, the poorly controllable oxidation process is avoided and poly[Ni-tto] almost free from K is directly formed upon the complexation of Ni2+ and tto2-. Thus-obtained poly[Ni-tto] possesses conductivity in the range of 27-47 S cm-1 and a Seebeck coefficient in the range of -38 to -55 μV K-1, which are superior thermoelectric properties compared to poly[Kx(Ni-ett)] samples obtained by the previously reported methods. Redox and structural properties of poly[Ni-tto] were compared with those of poly[Kx(Ni-ett)] obtained by the reported methods. Furthermore, DFT calculations were performed to shed more light on generally promising properties of this class of materials. Particularly, possible packing models have been predicted for polymers, and the molecular dynamics simulations have been used to simulate the molecular arrangements under ambient conditions.