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Author: Naumov, Sergej × DDC: 570 ×

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    Towards efficient initiators for two-photon induced polymerization: Fine tuning of the donor/acceptor properties
    (Cambridge : Royal Society of Chemistry, 2019) Holzer, Brigitte; Lunzer, Markus; Rosspeintner, Arnulf; Licari, Giuseppe; Tromayer, Maximilian; Naumov, Sergej; Lumpi, Daniel; Horkel, Ernst; Hametner, Christian; Ovsianikov, Aleksandr; Liska, Robert; Vauthey, Eric; Fröhlich, Johannes
    In this work we present the design, synthesis and systematic investigation of the optical properties of symmetric triphenylamine (TPA)-substituted thiophenes. The use of electron-donating (-OMe, -tBu, -Me, -TMS), -neutral (-H) or -withdrawing (-F, -CN, -SO2Me) substituents gives rise to D-A-D based two-photon absorption (2PA) chromophores. The photophysical properties of these compounds, including one-photon absorption and 2PA using two-photon-excited fluorescence, were investigated in different organic solvents with varying polarity. The maximum 2PA cross sections prove to be strongly dependent on the nature of the TPA substituent and range between ~173 GM (Goeppert-Mayer units) and 379 GM. Although most of the investigated substances also exhibit high fluorescence quantum yields, two-photon absorption screening tests of an acrylate monomer formulation revealed the efficiency of these materials as 2PA photoinitiators. These results are supported by quantum chemical calculations of the spin density distribution indicating that the mechanism of polymerization initiation using acrylate monomer is favored by strong localization of the unpaired electrons in the triplet state on the C2 carbon of the thiophene moiety. © 2019 The Royal Society of Chemistry.
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    Reaction of 1-propanol with Ozone in Aqueous Media
    (Basel : Molecular Diversity Preservation International, 2019) Reisz, Erika; Tekle-Röttering, Agnes; Naumov, Sergej; Schmidt, Winfried; Schmidt, Torsten C.
    The main aim of this work is to substantiate the mechanism of 1-propanol oxidation by ozone in aqueous solution when the substrate is present in large excess. Further goals are assessment of the products, their formation yields as well as the kinetic parameters of the considered reaction. The reaction of ozone with 1-propanol in aqueous solution occurs via hydride transfer, H-abstraction and insertion. Of these three mechanisms, the largest share is for hydride transfer. This implies the extraction of an hydride ion from the activated C-H group by O3 according to reaction: (C2H5)(H)(HO)C-H + O3 ?[(C2H5)(H)(HO)C-H+O3?]cage ?(C2H5)(H)(HO)C+ + HO3 -. The experimentally determined products and their overall formation yields with respect to ozone are: propionaldehyde-(60 ± 3)%, propionic acid-(27.4 ± 1.0)%, acetaldehyde-(4.9 ± 0.3)%, acetic acid-(0.3 ± 0.1)%, formaldehyde-(1.0 ± 0.1)%, formic acid-(4.6 ± 0.3)%, hydrogen peroxide- (11.1 ± 0.3)% and hydroxyl radical-(9.8 ± 0.3)%. The reaction of ozone with 1-propanol in aqueous media follows a second order kinetics with a reaction rate constant of (0.64±0.02)M-1·s-1 atpH = 7 and 23 °C. The dependence of the second order rate constant on temperature is described by the equation: ln kII = (27.17 ± 0.38)-(8180 ± 120) × T-1, which gives the activation energy, Ea = (68 ± 1) kJ mol-1 and pre-exponential factor, A = (6.3 ± 2.4) × 1011 M-1 s-1. The nature of products, their yields and the kinetic data can be used in water treatment. The fact that the hydride transfer is the main pathway in the 1-propanol/ozone system can probably be transferred on other systems in which the substrate is characterized by C-H active sites only. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.
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    Correction: Towards efficient initiators for two-photon induced polymerization: Fine tuning of the donor/acceptor properties (Molecular Systems Design and Engineering (2019) DOI: 10.1039/c8me00101d)
    (Cambridge : Royal Society of Chemistry, 2019) Holzer, Brigitte; Lunzer, Markus; Rosspeintner, Arnulf; Licari, Giuseppe; Tromayer, Maximilian; Naumov, Sergej; Lumpi, Daniel; Horkel, Ernst; Hametner, Christian; Ovsianikov, Aleksandr; Liska, Robert; Vauthey, Eric; Fröhlich, Johannes
    The authors regret that in the published article, affiliations b and c were inadvertently switched. The correct affiliations are shown here. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers. © The Royal Society of Chemistry 2019.