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- Ergun Dönmez, Merve, 1986-, et al.
(author)
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Analytical and preparative separation and isolation of functionalized fullerenes by conventional HPLC stationary phases : method development and column screening
- 2020
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In: RSC Advances. - : ROYAL SOC CHEMISTRY. - 2046-2069. ; 10:33, s. 19211-19218
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Journal article (peer-reviewed)abstract
- Isolation and purification of functionalized fullerenes from often complex reaction mixtures is challenging due to the hydrophobic nature and low solubility in regular organic solvents. We have developed an HPLC method that efficiently, employing regular reversed phase stationary phases, separates not only C-60 from C-70 in a model mixture, but also C-60 monoadducts from polyadducts and unreacted C-60 from fulleropyrrolidine and hydroarylation example reaction mixtures. Six HPLC columns with regular reversed phase stationary phases were evaluated using varying proportions of acetonitrile in toluene as eluent; with C18 and C12 stationary phases with high surface area (450-400 m(2) g(-1)) being the most efficient regarding separation efficiency and analysis time for all mixtures. The analytical method is effectively transferrable to a preparative scale to isolate the monoaddition products from complex fullerene reaction mixtures.
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| 2. |
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| 3. |
- Ergun Dönmez, Merve, 1986-, et al.
(author)
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Playing with Protic Additives to Improve the Outcome of Rhodium‐Catalyzed Hydroarylation of Fullerene C60 with Arylboronic Acids
- 2024
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In: Helvetica Chimica Acta. - : John Wiley & Sons. - 0018-019X .- 1522-2675. ; 107
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Journal article (peer-reviewed)abstract
- A new one-phase process for hydroarylation of C60 fullerene using arylboronic acids and a rhodium catalyst in an aromatic solvent containing soluble protic additives is described. Yields of monohydroarylated product with tert-butanol and water as the protic additive range from 14 to 50% depending on which arylboronic acid is used after reaction times of 4 hours or less which is a significant improvement from the outcome of reactions carried out using conditions from the literature. Accurate monitoring of reaction outcomes was achieved by a combination of UV-Vis spectroscopy and 1H-NMR spectroscopy: C60 conversion was determined using an analytical HPLC-UV-vis method employing commonly available columns for the separation, while product formation was quantified by 1H-NMR spectroscopy with an internal standard. Moreover, two new arylboronic acids carrying 4-alkynyl aryl substituents, synthesized using Sonogashira couplings, are reported, as well as the use of these in the hydroarylation of C60.
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| 4. |
- Ergun Dönmez, Merve, 1986-
(author)
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Rhodium Catalyzed Fullerene C60 Hydroarylation with Arylboronic Acids : Development and Mechanistic Study Using HPLC Analysis and NMR Spectroscopy
- 2024
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Doctoral thesis (other academic/artistic)abstract
- The unique spherical carbon molecule fullerene C60 holds potential across several application areas, particularly after modification and fine-tuning to achieve desired properties. Due to its accessibility and broad scope, the functionalization of fullerene C60 via rhodium-catalyzed hydroarylation using organoboron compounds has significant potential for being an efficient tool for fullerene and alkene/alkyne cross-coupling. Here, we explored this reaction in an attempt to understand and take advantage of its possibilities fully. A straightforward and simple analytical method was developed employing HPLC using commonly available stationary phases to separate and isolate reaction components of hydroarylation of C60 using arylboronic acids. This method was validated for quantifying unreacted C60 in a hydroarylation reaction and used to determine its conversion. Combining this methodology with 1H and 19F NMR quantification methods using internal standards provided fast and simple screening of the reaction components. Using these tools, the hydroarylation reaction conditions were improved by probing changes in the rhodium catalyst load, time, reaction temperature, and the effect of different protic additives. The arylboronic acid scope for hydroarylation of fullerene C60 was investigated using these optimized conditions. This was followed by a screening of hydroarylation reactions for selected alkenes and alkynes using fluorinated arylboronic acid with analysis via 19F NMR spectroscopy. The formation rate of products and consumption rate for arylboronic acids in the hydroarylation reaction of C60 were compared when different protic solvents were added or when protected arylboronic acids were used. A deeper investigation of the possible reaction mechanism required individual assessment of the components. Depending on the nature of the protic solvent added to the reaction mixture, arylboronic acids were found to exhibit various forms in different ratios. A deuterium labeling study was conducted to provide evidence of the source of the proton in the hydroarylation product. It was concluded that the 1,4-rhodium shift might take place when electron-poor arylboronic acids were used in hydroarylation. Lastly, a stable intermediate arene η6 Rh complex forms when electron-rich arylboronic acids are used in the hydroarylation of fullerene C60. The formation of such a complex was proved by the significant change in 1H and 13C NMR chemical shifts of aryl signals, which showed specific arene 103Rh-13C couplings in the 13C NMR spectrum.
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| 6. |
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| 7. |
- Gogoll, Adolf, et al.
(author)
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Chemical shift assignment of geminal protons in 3,7-diazabicyclo [3.3.1]nonanes : An unexpected deviation from the axial/equatorial chemical shift order
- 1997
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In: Magnetic Resonance in Chemistry. - : John Wiley & Sons. - 0749-1581 .- 1097-458X. ; 35:1, s. 13-20
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Journal article (peer-reviewed)abstract
- The chemical shift order of axial and equatorial methylene protons in 1,5-disubstituted 3,7-diazabicyclo[3.3.1]nonan-9-ones may be altered by substituents in the 1,5-positions, but the corresponding alcohols behave differently. Unambiguous signal assignments for a series of the title compounds are provided, based on 3JCH coupling constants and on {1H} 13C heteronuclear Overhauser effects. Substituent anisotropy effects as a source of the chemical shift changes are discussed.
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| 8. |
- Karlsson, Anton, et al.
(author)
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Graphene oxide microstructure control of electrosprayed thin films
- 2023
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In: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 13:2, s. 781-789
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Journal article (peer-reviewed)abstract
- The graphene oxide (GO) microstructure, in terms of flake distribution, folding, and crumpling, in thin films affects properties such as electrical conductivity and optical transparency after GO reduction. A thin film can be tailored to the user's application if the microstructure resulting from different deposition methods can be controlled. In this work, we compare the microstructures of GO coatings created through electrospray deposition (ESD) with random deposition processes. The comparisons include both MATLAB simulations and a dip coating process. The microstructure of ESD GO thin films can be altered by changing the distance between the nozzle and the substrate. We developed a semi-automatic image analysis script that analyzes scanning electron microscopy images to find effects of GO stacking or agglomeration, without the risk of human bias. A low nozzle to substrate distance creates structures of flat GO flakes, but solvent flooding the samples causes drying patterns. A high nozzle to substrate distance causes folding and crumpling of the GO flakes due to solvent evaporation, resulting in agglomerated GO on the substrate. For our ESD setup, a nozzle to substrate distance of 2-4 mm produced GO coatings with the lowest combined influence of drying effects and GO flake folding or crumpling.
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| 9. |
- Karlsson, Anton, et al.
(author)
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Microstructure control of electrosprayed graphene oxide thin films
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Other publication (other academic/artistic)abstract
- The graphene oxide (GO) microstructure, in terms of flake distribution, folding, and crumpling, in thin films affects properties such as electrical conductivity and optical transparency after GO reduction. A thin film can be tailored to the application if the microstructure of different deposition methods can be controlled. In this work, we compare the microstructures of GO coatings created through electrospray deposition (ESD) to randomly places flakes. The microstructure of ESD GO thin films can be altered through changes of the distance between the nozzle and the substrate. We developed a semi-automatic image analysis script that analyzes scanning electron microscopy images to find effects of GO stacking or agglomeration, without the risk of human bias. A low nozzle to substrate distance creates structures of flat GO flakes, but solvent flooding the samples cause drying patterns. A high nozzle to substrate distance folds and crumples GO flakes due to solvent evaporation, resulting in agglomerated GO on the substrate. Simulations are in agreement with a randomized placement of GO flakes for the dip coating process. For our setup, an ESD nozzle to sample distance of 2-4 mm produced coatings fairly close to a random distribution out of the ESD samples.
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| 10. |
- Karlsson, Susanne, et al.
(author)
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How Close Can You Get? : Studies of Ultrafast Light-Induced Processes in Ruthenium-[60] Fullerene Dyads with Short Pyrazolino and Pyrrolidino Links
- 2008
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In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 47:16, s. 7286-7294
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Journal article (peer-reviewed)abstract
- Two pyrazoline- and one pyrrolidine-bridged Ru(II)bipyridine-[60]fullerene dyads have been prepared and studied by ultrafast time-resolved spectroscopy. A silver-assisted synthesis route, in which Ag(I) removes the chlorides from the precursor complex Ru(bpy)(2)Cl-2 facilitates successful coordination of the [60]fullerene-substituted third ligand. Upon light excitation of the ruthenium moiety, the emission was strongly quenched by the fullerene. The main quenching mechanism is an exceptionally fast direct energy transfer (k(obs) > , 1 x 10(12) s(-1) in the pyrazoline-bridged dyads), resulting in population of the lowest excited triplet state of fullerene. No evidence for electron transfer was found, despite the extraordinarily short donor-acceptor distance that could kinetically favor that process. The observations have implications on the ongoing development of devices built from Ru-polypyridyl complexes and nanostructured carbon, such as C-60 or nanotubes.
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