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551 results on '"Winter, Rainer F."'

3. Covalently Linked Pigment@TiO2 Hybrid Materials by One‐Pot Solvothermal Synthesis.

Author

Sailer, Frank, Moura, Hipassia M., Purkait, Taniya, Vogelsang, Lars, Sauer, Markus, Foelske, Annette, Winter, Rainer F., Ponrouch, Alexandre, and Unterlass, Miriam M.

Subjects
HYBRID materials, ORGANIC dyes, ORGANIC compounds, THERMAL stability, TITANIUM dioxide
Abstract

Hybrid materials (HMs) combine the high diversity of functionalities of organic compounds with properties typical for inorganic materials, such as high mechanical strength or high thermal stability. Herein, HMs combining organic pigment molecules and TiO2 as inorganic component, with covalently linked components, i.e., so‐called class II HMs, are reported. The synthesis of such HMs is intrinsically challenging, as the apolar organic pigment component and the inorganic polar TiO2 component require different conditions for their respective formation. Herein, we circumvent this issue by employing solvothermal synthesis in superheated isopropanol, which through temperature tunability of the solvent properties allows for both generating and linking both components in one‐pot. First, it is shown that an organic benzimidazole‐based pigment molecule designed for readily binding to Ti can be synthesized solvothermally. Second, new class II titanium‐based HMs are generated from Ti(OiPr)4 and pigment precursors in a solvothermal reaction. The pigment@TiO2 HMs feature significant porosity and are structurally identified as layered structures of lepidocrocite‐like TiO2 linked via pigment molecules. These layered HMs assemble into hierarchical nanoflowers, and depending on the pigment segments, different interlayer spacings in between inorganic layers are observed. Third, the pigment@TiO2 materials are shown to be usable as electrode materials in lithium‐ion batteries. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Fully Reprogrammable 2D Array of Multi‐State Molecular Switching Units

Author

Bauer, Anja, primary, Birk, Tobias, additional, Paschke, Fabian, additional, Fuhrberg, Andreas, additional, Diegel, Josefine, additional, Becherer, Ann‐Kathrin, additional, Vogelsang, Lars, additional, Maier, Markus, additional, Schosser, Werner M., additional, Pauly, Fabian, additional, Zilberberg, Oded, additional, Winter, Rainer F., additional, and Fonin, Mikhail, additional

Published
2024
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9. A Dibenzotetrathiafulvalene-Bridged Bis(alkenylruthenium) Complex and Its One- and Two-Electron-Oxidized Forms

Author

Gogesch, Franciska S., primary, Laininger, Lukas S., additional, Sokov, Nick, additional, Schupp, Stefan M., additional, Senft, Laura, additional, Moura, Hipassia M., additional, Linseis, Michael, additional, Schmidt-Mende, Lukas, additional, Ivanović-Burmazović, Ivana, additional, Unterlass, Miriam M., additional, and Winter, Rainer F., additional

Published
2023
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12. 1,4-Divinylphenylene-bridged diruthenium complexes with 2-hydroxypyridine- and 2- or 8-hydroxyquinoline-olate ligands

Author

Abdel-Rahman, Obadah S., Linseis, Michael, Alowais, Alaa, and Winter, Rainer F.

Subjects
quantum chemistry, ddc:540, General Chemistry, alkenyl complexes, ruthenium, (spectro)electrochemistry
Abstract

Four divinylphenylene-bridged diruthenium complexes [{Ru(CO)(P i Pr3)2(L-κ 2 [N,O] – )}2(μ-CH=CH-C6H4-CH=CH-1,4)] (2a–2d) with N,O-chelating 2-hydroxypyridine and 2-hydroxy- or 8-hydroxyquinoline ligands are presented. They were studied by NMR spectroscopy, electrochemical methods and, in their neutral and oxidized states, by IR, UV/Vis/NIR and, if applicable, by EPR spectroscopy. The experimental studies are complimented by (TD-)DFT calculations. Our results indicate that the pyridine-olate complexes 2a,b exist as three isomers with a ratio of about 78:20:2 that differ with respect to the orientation of the N and O donors relative to the CO and alkenyl ligands in the equatorial coordination plane. Only the isomer with both imine N donors trans to the alkenyl ligand is observed for complexes 2c,d with quinolinato ligands. All complexes undergo two consecutive, chemically and electrochemically reversible one-electron oxidations at low potentials. Our results indicate strong contributions of the divinylphenylene bridge to the redox processes and an even delocalization of the electron hole and the unpaired spin density over the entire π-conjugated divinylphenylene diruthenium backbone with only minor involvement of the peripherally attached κ 2 [N,O] – donor ligands.

Published
2023

15. Pyrene fluorescence in 2,7-di(4-phenylethynyl)pyrene-bridged bis(alkenylruthenium) complexes.

Author

Gogesch, Franciska S., Bauer, Lea, Vollstädt, Florian D., Linseis, Michael, Senft, Laura, Ivanović-Burmazović, Ivana, and Winter, Rainer F.

Subjects
PYRENE, FLUORESCENCE, RADICAL cations, BIG bands, RUTHENIUM
Abstract

Complexes PyrDPE-RuCl and PyrDPE-Ruacac with a π-extended 2,7-di(4-phenylethynyl)pyrene linker undergo simultaneous one-electron oxidations of their {Ru}-styryl entities. The absence of an intervalence charge-transfer (IVCT) band at intermediate stages, where the mixed-valent, singly oxidized radical cation is present, and spin density confinement to the terminal styryl ruthenium site(s) are tokens of a lack of electronic coupling between the {Ru} entities across the π-conjugated linker. The close similarity of the linker-based π → π* bands in the complexes and the free ligand and their insensitivity towards oxidations at the terminal sites indicate that the central pyrenyl fluorophore is electronically decoupled from the electron-rich {Ru}-styryl termini. As a consequence, the complexes offer stable pyrene-based fluorescence emissions at 77 K, which are red-shifted from that of the linker. [ABSTRACT FROM AUTHOR]

Published
2024
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37. Cationic Cycloheptatrienyl Cyclopentadienyl Manganese Sandwich Complexes: Tromancenium Explored with High-Power LED Photosynthesis

Author

Basse, Reinhard, primary, Vanicek, Stefan, additional, Höfer, Thomas, additional, Kopacka, Holger, additional, Wurst, Klaus, additional, Müller, Thomas, additional, Schwartz, Heidi A., additional, Olthof, Selina, additional, Casper, Larissa A., additional, Nau, Moritz, additional, Winter, Rainer F., additional, Podewitz, Maren, additional, and Bildstein, Benno, additional

Published
2021
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39. Cationic Cycloheptatrienyl Cyclopentadienyl Manganese Sandwich Complexes: Tromancenium Explored with High-Power LED Photosynthesis

Author

Basse, Reinhard, Vanicek, Stefan, Hoefer, Thomas, Kopacka, Holger, Wurst, Klaus, Mueller, Thomas, Schwartz, Heidi A., Olthof, Selina, Casper, Larissa A., Nau, Moritz, Winter, Rainer F., Podewitz, Maren, Bildstein, Benno, Basse, Reinhard, Vanicek, Stefan, Hoefer, Thomas, Kopacka, Holger, Wurst, Klaus, Mueller, Thomas, Schwartz, Heidi A., Olthof, Selina, Casper, Larissa A., Nau, Moritz, Winter, Rainer F., Podewitz, Maren, and Bildstein, Benno

Abstract

In this contribution, we revisit the neglected and forgotten cationic, air-stable, 18-valence electron, heteroleptic sandwich complex (cycloheptatrienyl)(cyclopentadienyl)manganese, which was reported independently by Fischer and by Pauson about 50 years ago. Using advanced high-power LED photochemical synthesis, an expedient rapid access to the parent complex and to functionalized derivatives with alkyl, carboxymethyl, bromo, and amino substituents was developed. A thorough study of these tromancenium salts by a range of spectroscopic techniques (H-1/C-13/Mn-55-NMR, IR, UV-vis, HRMS, XRD, XPS, EPR), cyclic voltammetry (CV), and quantum chemical calculations (DFT) shows that these manganese sandwich complexes are unique metallocenes with quite different chemical and physical properties in comparison to those of isoelectronic cobaltocenium salts or (cycloheptatrienyl)(cyclopentadienyl) sandwich complexes of the early transition metals. Electrochemically, all tromancenium ions undergo a chemically partially reversible oxidation and a chemically irreversible reduction at half-wave or peak potentials that respond to the substituents at the Cp deck. As exemplarily shown for the parent tromancenium ion, the product generated during the irreversible reduction process reverts at least partially to the starting material upon reoxidation. Quantum-chemical calculations of the parent tromancenium salt indicate that metal-ligand bonding is distinctly weaker for the cycloheptatrienyl ligand in comparison to that of the cyclopentadienyl ligand. Both the HOMO and the LUMO are metal and cycloheptatrienyl-ligand centered, indicating that chemical reactions will occur either metal-based or at the seven-membered ring, but not on the cyclopentadienyl ligand.

Published
2021

43. Tetraruthenium Macrocycles with Laterally Extended Bis(alkenyl)quinoxaline Ligands and Their F 4 TCNQ •− Salts.

Author

Das, Rajorshi, Linseis, Michael, Senft, Laura, Ivanović-Burmazović, Ivana, and Winter, Rainer F.

Subjects
QUINOXALINES, ELECTRON paramagnetic resonance spectroscopy, NUCLEAR magnetic resonance spectroscopy, MASS spectrometry, OXIDATION states
Abstract

We report on the tetraruthenium macrocycles Ru4-5 and -6 with a π-conjugated pyrene-appended 5,8-divinylquinoxaline ligand and either isophthalate or thiophenyl-2,5-dicarboxylate linkers and their charge-transfer salts formed by oxidation with two equivalents of F4TCNQ. Both macrocyclic complexes were characterized by NMR spectroscopy, mass spectrometry, cyclic and square-wave voltammetry, and by IR, UV–vis–NIR, and EPR spectroscopy in their various oxidation states. [ABSTRACT FROM AUTHOR]

Published
2022
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45. Ruthenium complexes with vinyl, styryl, and vinylpyrenyl ligands: a case of non-innocence in organometallic chemistry

Author

Maurer, Jorg, Linseis, Michael, Sarkar, Biprajit, Schwederski, Brigitte, Niemeyer, Mark, Kaim, Wolfgang, Zalis, Stanislav, Anson, Chris, Zabel, Manfred, and Winter, Rainer F.

Subjects
Ruthenium -- Research, Ruthenium -- Chemical properties, Coordination compounds -- Research, Coordination compounds -- Chemical properties, Ligands -- Research, Ligands -- Chemical properties, Ligands -- Usage, Chemistry
Abstract

Mononuclear ruthenium vinyl complexes L-{Ru}-CH[double bond]CH-R is described where the phosphine ligands, the coordination number at the metal and substituent are varied. The vinyl ligands have contributed to the anodic oxidation processes, rendering them a class of truly 'non-innocent' ligands in organometallic ruthenium chemistry.

Published
2008

46. Aggregation-Induced Improvement of Catalytic Activity by Inner-Aggregate Electronic Communication of Metal-Fullerene-Based Surfactants

Author

Kunkel, Marius, Bitter, Stefan, Sailer, Frank, Winter, Rainer F., and Polarz, Sebastian

Subjects
Dewey Decimal Classification::500 | Naturwissenschaften::540 | Chemie, (homogeneous) catalysis, electrochemistry, oxygen evolution reactions (OER), ddc:540, hydrogen evolution (HER), catalyst
Abstract

A paradigm for active constituents in (homogeneous) catalysis is that optimum performance requires maximum dispersion. Generally, aggregation results in a decline. This is a different case in supramolecular catalysis. A new concept based on surfactants equipped with functional heads is presented, which becomes a more active catalyst itself upon aggregation. The head group of the surfactants is composed of a diethylenetriamine-functionalized fullerene capable of coordinating to catalytically active metals like CoII. The improvement of catalytic properties upon aggregation is demonstrated via electrocatalytic water-splitting reaction as a model system. Detailed electrochemistry studies were performed at concentrations below and above the critical aggregation concentration (cac). While isolated surfactant molecules represent only moderately active catalysts, drastic improvement of efficiency in the hydrogen evolution (HER) as well as in the oxygen evolution reactions (OER) were detected, once vesicular structures have formed. Self-organization of the surfactants leads to an increase in turnover frequencies of up to 1300 % (HER). The strongly beneficial effect of aggregation arises from the favorable alignment of individual molecules, thus, facilitating intermolecular charge transfer processes in the vesicles. © 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Published
2020

47. Ferro-self-assembly: Magnetic and electrochemical adaptation of a multiresponsive zwitterionic metalloamphiphile showing a shape-hysteresis effect

Author

Bitter, Stefan, Schlötter, Moritz, Schilling, Markus, Krumova, Marina, Polarz, Sebastian, Winter, Rainer F., Bitter, Stefan, Schlötter, Moritz, Schilling, Markus, Krumova, Marina, Polarz, Sebastian, and Winter, Rainer F.

Abstract

Metallosurfactants are molecular compounds which combine the unique features of amphiphiles, like their capability of self-organization, with the peculiar properties of metal complexes like magnetism and a rich redox chemistry. Considering the high relevance of surfactants in industry and science, amphiphiles that change their properties on applying an external trigger are highly desirable. A special feature of the surfactant reported here, 1-(Z)-heptenyl-1′-dimethylammonium-methyl-(3-sulfopropyl)ferrocene (6), is that the redox-active ferrocene constituent is in a gemini-position. Oxidation to 6+ induces a drastic change of the surfactant's properties accompanied by the emergence of paramagnetism. The effects of an external magnetic field on vesicles formed by 6+ and the associated dynamics were monitored in situ using a custom-made optical birefringence and dual dynamic light scattering setup. This allowed us to observe the optical anisotropy as well as the anisotropy of the diffusion coefficient and revealed the field-induced formation of oriented string-of-pearls-like aggregates and their delayed disappearance after the field is switched off.

Published
2020

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