Publikationen

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Erstellt: Mon, 06 Feb 2023 18:15:28 +0100 in 0.2774 sec


Schuett, Timo; Anufriev, Ilya; Endres, Patrick; Stumpf, Steffi; Nischang, Ivo; Hoeppener, Stephanie; Bode, Stefan; Schubert, Ulrich Sigmar; Geitner, Robert
A user-guide for polymer purification using dialysis. - In: Polymer chemistry, ISSN 1759-9962, Bd. 14 (2023), 1, S. 92-101

Dialysis diffusion kinetics are investigated via in situ NMR spectroscopy for numerous different raw polymeric solutions to result in a general guideline for polymer purification using dialysis. In several approaches, a polymer was on purpose contaminated with its respective monomer, regenerated conducting conventional dialysis and monitored online utilizing in situ NMR spectroscopy. Consequently, polymer type and molar mass, monomer type, molar mass cut-off of the dialysis tubing and type of solvent were varied resulting in 29 different purification approaches and over 40 000 NMR-spectra. As a result, several major parameters were identified affecting the purification process significantly such as the chosen solvent, viscosity and alpha value. On the contrary, parameters such as dialysis tubing molar mass cut-off and molar mass of the polymer did not affect the purification in a significant manner. Furthermore, physical properties such as density, viscosity, alpha value, and dipole moment of the ingredients were combined in a principal component analysis in order to identify the most important parameters.



https://doi.org/10.1039/D2PY00972B
Geitner, Robert;
Physikalische Chemie : Trendbericht. - In: Nachrichten aus der Chemie, ISSN 1868-0054, Bd. 70 (2022), 5, S. 64-67

Die Aufklärung von Reaktionsmechanismen ist in der Katalyse wichtig, um die geschwindigkeitsbegrenzende Schritte zu verstehen und zu beschleunigen. Mit maschinellem Lernen lassen dann sich auf Basis der Mechanismen neue Katalysatoren entwickeln. Photochemische Umsetzungen in weichen Membranen folgen einer anderen Kinetik als Reaktionen in Lösung. Mikroschwimmer, Mikromotoren oder Phototaxis zählen zu aktiver Materie. Sie wandeln kontinuierlich Energie aus ihrer Umgebung um und bewegen sich autonom.



https://doi.org/10.1002/nadc.20224122539
Huang, Tianbai; Kupfer, Stephan; Richter, Martin; Gräfe, Stefanie; Geitner, Robert
Bidentate Rh(I)-phosphine complexes for the C-H activation of alkanes: computational modelling and mechanistic insight. - In: ChemCatChem, ISSN 1867-3899, Bd. 14 (2022), 18, e202200854, S. 1-9

The C-H activation and subsequent carbonylation mediated by metal complexes, i. e., Rh(I) complexes, has drawn considerable attention in the past. To extend the mechanistic insight from Rh complexes featuring monodentate ligands like P(Me)3 towards more active bisphosphines (PLP), a computationally derived fully conclusive mechanistic picture of the Rh(I)-catalyzed C-H activation and carbonylation is presented here. Depending on the nature of the bisphosphine ligand, the highest lying transition state (TS) is associated either to the initial C-H activation in [Rh(PLP)(CO)(Cl)] or to the rearrangement of the chloride in [Rh(PLP)(H)(R)(Cl)]. The chloride rearrangement was found to play a key role in the subsequent carbonylation. A set of 20 complexes of different architectures was studied, in order to fine tune the C-H activation in a knowledge-driven approach. The computational analysis suggests that a flexible ligand architecture with aromatic rings can potentially increase the performance of Rh-based catalysts for the C-H activation.



https://doi.org/10.1002/cctc.202200854
Nolte, Oliver; Geitner, Robert; Volodin, Ivan A.; Rohland, Philip; Hager, Martin; Schubert, Ulrich Sigmar
State of charge and state of health assessment of viologens in aqueous-organic redox-flow electrolytes using in situ IR spectroscopy and multivariate curve resolution. - In: Advanced science, ISSN 2198-3844, Bd. 9 (2022), 17, 2200535, S. 1-10

Aqueous-organic redox flow batteries (RFBs) have gained considerable interest in recent years, given their potential for an economically viable energy storage at large scale. This, however, strongly depends on both the robustness of the underlying electrolyte chemistry against molecular decomposition reactions as well as the device's operation. With regard to this, the presented study focuses on the use of in situ IR spectroscopy in combination with a multivariate curve resolution approach to gain insight into both the molecular structures of the active materials present within the electrolyte as well as crucial electrolyte state parameters, represented by the electrolyte's state of charge (SOC) and state of health (SOH). To demonstrate the general applicability of the approach, methyl viologen (MV) and bis(3-trimethylammonium)propyl viologen (BTMAPV) are chosen, as viologens are frequently used as negolytes in aqueous-organic RFBs. The study's findings highlight the impact of in situ spectroscopy and spectral deconvolution tools on the precision of the obtainable SOC and SOH values. Furthermore, the study indicates the occurrence of multiple viologen dimers, which possibly influence the electrolyte lifetime and charging characteristics.



https://doi.org/10.1002/advs.202200535
Schütt, Timo; Geitner, Robert; Bode, Stefan; Schubert, Ulrich Sigmar
Dialysis diffusion kinetics in polymer purification. - In: Macromolecules, ISSN 1520-5835, Bd. 54 (2021), 20, S. 9410-9417

Diffusion kinetics of a prior developed automated dialysis system are investigated via in situ NMR spectroscopy for an optimization of conventional and advanced polymer purification. Using a polymeric solution, mixed with the respective monomer, several parameters like starting concentration, solvent volume, and solvent exchange by flow or complete one-time exchange are varied, resulting in a significant decrease of purification time for the automated setup. With an increased solvent flow (from 0.9 to 5.5 mL/min), 5.4 h and 2000 mL of solvent are required to decrease the monomer concentration to the detection limit. Without solvent flow, which corresponds to conventional dialysis, only 9 h and 250 mL of solvent are required for the same result, which is a time- and solvent-saving development for common purification of polymers.



https://doi.org/10.1021/acs.macromol.1c01241