| 1. |
- Abrahamsson, Maria, et al.
(författare)
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Steric influence on the excited-state lifetimes of ruthenium complexes with bipyridyl-alkanylene-pyridyl ligands.
- 2008
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Ingår i: Inorganic Chemistry. - : ACS. - 0020-1669 .- 1520-510X. ; 47:9, s. 3540-3548
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Tidskriftsartikel (refereegranskat)abstract
- The structural effect on the metal-to-ligand charge transfer (MLCT) excited-state lifetime has been investigated in bis-tridentate Ru(II)-polypyridyl complexes based on the terpyridine-like ligands [6-(2,2'-bipyridyl)](2-pyridyl)methane (1) and 2-[6-(2,2'-bipyridyl)]-2-(2-pyridyl)propane (2). A homoleptic ([Ru(2)(2)](2+)) and a heteroleptic complex ([Ru(ttpy)(2)](2+)) based on the new ligand 2 have been prepared and their photophysical and structural properties studied experimentally and theoretically and compared to the results for the previously reported [Ru(1)(2)](2+). The excited-state lifetime of the homoleptic Ru-II complex with the isopropylene-bridged ligand 2 was found to be 50 times shorter than that of the corresponding homoleptic Ru-II complex of ligand 1, containing a methylene bridge. A comparison of the ground-state geometries of the two homoleptic complexes shows that steric interactions involving the isopropylene bridges make the coordination to the central Ru-II ion less octahedral in [Ru(2)(2)](2+) than in [Ru(1)(2))(2+). Calculations indicate that the structural differences in these complexes influence their ligand field splittings as well as the relative stabilities of the triplet metal-to-ligand charge transfer ((MLCT)-M-3) and metal-centered ((MC)-M-3) excited states. The large difference in measured excited-state lifetimes for the two homoleptic Ru-II complexes is attributed to a strong influence of steric interactions on the ligand field strength, which in turn affects the activation barriers for thermal conversion from (MLCT)-M-3 states to short-lived (MC)-M-3 states.
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| 2. |
- Galkin, Maxim V., et al.
(författare)
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Hydrogen-free catalytic fractionation of woody biomass
- 2016
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 9:23, s. 3280-3287
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Tidskriftsartikel (refereegranskat)abstract
- The pulping industry could become a biorefinery if the lignin and hemicellulose components of the lignocellulose are valorized. Conversion of lignin into well-defined aromatic chemicals is still a major challenge. Lignin depolymerization reactions often occur in parallel with irreversible condensation reactions of the formed fragments. Here, we describe a strategy that markedly suppresses the undesired condensation pathways and allows to selectively transform lignin into a few aromatic compounds. Notably, applying this strategy to woody biomass at organosolv pulping conditions, the hemicellulose, cellulose, and lignin were separated and in parallel the lignin was transformed into aromatic monomers. In addition, we were able to utilize a part of the lignocellulose as an internal source of hydrogen for the reductive lignin transformations. We hope that the presented methodology will inspire researchers in the field of lignin valorization as well as pulp producers to develop more efficient biomass fractionation processes in the future.
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| 3. |
- Eriksson, Anna, et al.
(författare)
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On-target titanium dioxide-based enrichment for characterization of phosphorylations in the Adenovirus pIIIa protein
- 2013
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Ingår i: Journal of Chromatography A. - : Elsevier BV. - 0021-9673 .- 1873-3778. ; 1317:SI, s. 105-109
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Tidskriftsartikel (refereegranskat)abstract
- A recently developed titanium dioxide (TiO2) based on-target method for phosphopeptide enrichment and matrix assisted laser desorption-ionization mass spectrometry (MALDI MS) analysis was used to investigate phosphorylations in the Adenovirus type 2 structural protein pIIIa. Lysates of purified virus particles were separated on 1-D SDS-PAGE and the band for the pIIIa protein was excised for tryptic digestion into peptides that were enriched with the on-target method. The enrichment provided by the method clearly improved the detectability of phosphorylated peptides and the results show for the first time evidence for multi-phosphorylated peptides in pIIIa. Moreover, three novel phosphorylations were identified in the protein sequence, even though the precise positions could not be determined. These results illustrate the potential of the method for the characterization of novel phosphoproteomes in biological samples of medical relevance.
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| 4. |
- Kaukoranta, Päivi, et al.
(författare)
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Iridium Catalysts with Chiral Imidazole-Phosphine Ligands for Asymmetric Hydrogenation of Vinyl Fluorides and other Olefins
- 2008
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Ingår i: Advanced Synthesis and Catalysis. - : Wiley. - 1615-4150 .- 1615-4169. ; 350:7-8, s. 1168-1176
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Tidskriftsartikel (refereegranskat)abstract
- New chiral bidentate imidazole-phosphine ligands have been prepared and evaluated for the iridium-catalysed asymmetric hydrogenation of olefins. The imidazole-phosphine-ligated iridium catalysts hydrogenated trisubstituted olefins with the same sense of enantiodiscrimination as known iridium catalysts possessing oxazole and thiazole as N-donors. The imidazole-based catalysts were shown to hydrogenate vinyl fluorides, in some cases with the highest ee values published to date.
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| 5. |
- Pettersson Dahlin, Andreas, et al.
(författare)
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Capillary electrophoresis coupled to mass spectrometry from a polymer modified poly(dimethylsiloxane) microchip with an integrated graphite electrospray tip
- 2005
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 130:2, s. 193-199
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Tidskriftsartikel (refereegranskat)abstract
- Hybrid capillary-poly(dimethysiloxane) (PDMS) microchips with integrated electrospray ionization (ESI) tips were directly fabricated by casting PDMS in a mould. The shapes of the emitter tips were drilled into the mould, which produced highly reproducible three-dimensional tips. Due to the fabrication method of the microfluidic devices, no sealing was necessary and it was possible to produce a perfect channel modified by PolyE-323, an aliphatic polyamine coating agent. A variety of different coating procedures were also evaluated for the outside of the emitter tip. Dusting graphite on a thin unpolymerised PDMS layer followed by polymerisation was proven to be the most suitable procedure. The emitter tips showed excellent electrochemical properties and durabilities. The coating of the emitter was eventually passivated, but not lost, and could be regenerated by electrochemical means. The excellent electrochemical stability was further confirmed in long term electrospray experiments, in which the emitter sprayed continuously for more than 180 h. The PolyE-323 was found suitable for systems that integrate rigid fused silica and soft PDMS technology, since it simply could be applied successfully to both materials. The spray stability was confirmed from the recording of a total ion chromatogram in which the electrospray current exhibited a relative standard deviation of 3.9% for a 30 min run. CE-ESI-MS separations of peptides were carried out within 2 min using the hybrid PDMS chip resulting in similar efficiencies as for fused silica capillaries of the same length and thus with no measurable band broadening effects, originating from the PDMS emitter.
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| 6. |
- Zhang, Jinbao, et al.
(författare)
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Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric Analysis of Poly(3,4-ethylenedioxythiophene) in Solid-State Dye-Sensitized Solar Cells : Comparison of In Situ Photoelectrochemical Polymerization in Aqueous Micellar and Organic Media
- 2015
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 87:7, s. 3942-3948
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Tidskriftsartikel (refereegranskat)abstract
- Solid-state dye-sensitized solar cells (sDSCs) are devoid of such issues as electrolyte evaporation or leakage and electrode corrosion, which are typical for traditional liquid electrolyte-based DSCs. Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the most popular and efficient p-type conducting polymers that are used in sDSCs as a solid-state hole-transporting material. The most convenient way to deposit this insoluble polymer into the dye-sensitized mesoporous working electrode is in situ photoelectrochemical polymerization. Apparently, the structure and the physicochemical properties of the generated conducting polymer, which determine the photovoltaic performance of the corresponding solar cell, can be significantly affected by the preparation conditions. Therefore, a simple and fast analytical method that can reveal information on polymer chain length, possible chemical modifications, and impurities is strongly required for the rapid development of efficient solar energy-converting devices. In this contribution, we applied matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) for the analysis of PEDOT directly on sDSCs. It was found that the PEDOT generated in aqueous micellar medium possesses relatively shorter polymeric chains than the PEDOT deposited from an organic medium. Furthermore, the micellar electrolyte promotes a transformation of one of the thiophene terminal units to thiophenone. The introduction of a carbonyl group into the PEDOT molecule impedes the growth of the polymer chain and reduces the conductivity of the final polymer film. Both the simplicity of sample preparation (only application of the organic matrix onto the solar cell is needed) and the rapidity of analysis hold the promise of making MALDI MS an essential tool for the physicochemical characterization of conducting polymer-based sDSCs.
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| 7. |
- Abrahamsson, Maria, et al.
(författare)
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A new strategy for the improvement of photophysical properties in ruthenium(II) polypyridyl complexes. Synthesis and photophysical and electrochemical characterization of six mononuclear ruthenium(II) bisterpyridine-type complexes
- 2005
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 44:9, s. 3215-3225
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of six ruthenium(II) bistridentate polypyridyl complexes is described. These were designed on the basis of a new approach to increase the excited-state lifetime of ruthenium(II) bisterpyridine-type complexes. By the use of a bipyridylpyridyl methane ligand in place of terpyridine, the coordination environment of the metal ion becomes nearly octahedral and the rate of deactivation via ligand-field (i.e., metal-centered) states was reduced as shown by temperature-dependent emission lifetime studies. Still, the possibility to make quasi-linear donor-ruthenium-acceptor triads is maintained in the complexes. The most promising complex shows an excited-state lifet me of tau = 15 ns in alcohol solutions at room temperature, which should be compared to a lifetime of tau = 0.25 ns for [Ru(tpy)(2)](2+). The X-ray structure of the new complex indeed shows a more octahedral geometry than that of [Ru(tpy)(2)](2+). Most importantly, the high excited-state energy was retained, and thus, so was the potential high reactivity of the excited complex, which has not been the case with previously published strategies based on bistridentate complexes.
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| 8. |
- Carlsson, Anna-Carin, 1976, et al.
(författare)
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Symmetric Halogen Bonding is Preferred in Solution
- 2012
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 134, s. 5706-5715
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Tidskriftsartikel (refereegranskat)abstract
- Halogen bonding is a recently rediscovered secondary interaction that shows potential to become a complementary molecular tool to hydrogen bonding in rational drug design and in material sciences. Whereas hydrogen bond symmetry has been the subject of systematic studies for decades, the understanding of the analogous three-center halogen bonds is yet in its infancy. The isotopic perturbation of equilibrium (IPE) technique with 13C NMR detection was applied to regioselectively deuterated pyridine complexes to investigate the symmetry of [N−I−N]+ and [N−Br−N]+ halogen bonding in solution. Preference for a symmetric arrangement was observed for both a freely adjustable and for a conformationally restricted [N−X−N]+ model system, as also confirmed by computation on the DFT level. A closely attached counterion is shown to be compatible with the preferred symmetric arrangement. The experimental observations and computational predictions reveal a high energetic gain upon formation of symmetric, three-center four-electron halogen bonding. Whereas hydrogen bonds are generally asymmetric in solution and symmetric in the crystalline state, the analogous bromine and iodine centered halogen bonds prefer symmetric arrangement in solution.
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| 9. |
- Carlsson, Anna-Carin, 1976, et al.
(författare)
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Symmetry of [N-X-N]+ Halogen Bonds in Solution
- 2012
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Ingår i: Chemical Communications. - 1364-548X .- 1359-7345. ; 48:10, s. 1458-1460
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Tidskriftsartikel (refereegranskat)abstract
- The first investigation of halogen bond symmetry is presented. In contrast to related hydrogen bonds, the iodous halogen bond is symmetric in solution and in the crystal. The bromous analogue is symmetric in solution, but shows asymmetry in the solid state. NMR results are in agreement with DFT predictions.
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| 10. |
- Edström, Lena, 1978-
(författare)
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Adsorption Studies with Liquid Chromatography : Experimental Preparations for Thorough Determination of Adsorption Data
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Analytical chemistry is a field with a vast variety of applications. A robust companion in the field is liquid chromatography, the method used in this thesis, which is an established workhorse and a versatile tool in many different disciplines. It can be used for identification and quantification of interesting compounds generally present in low concentrations, called analytical scale chromatography. It can also be used for isolation and purification of high value compounds, called preparative chromatography. The latter is usually conducted in large scale with high concentrations. With high concentrations it is also possible to determine something called adsorption isotherms.Determination of adsorption isotherms is a useful tool for quite a wide variety of reasons. It can be used for characterisation of chromatographic separation systems, and then gives information on the retention mechanism as well as provides the possibility to study column-column and batch-batch reproducibility. If a protein is immobilised on a solid support, adsorption isotherms can be used for pharmacological characterisation of drug-protein interactions. Moreover, they can be used for the study of unexpected chromatographic phenomena.If the adsorption isotherm is known it is also possible to simulate chromatograms, and subsequently optimise the separation process numerically. The gain of a numerically optimised separation process is higher purity or yield of valuable compounds such as pharmaceuticals or antioxidants, as well as reducing the solvent usage. Taken all together, it saves time, money and the environment.However, the process of the adsorption isotherm determination requires a number of careful experimental considerations and preparations, and these are the main focus of the thesis. Important steps along the way include the choice of separation system and of suitable analytes, preparation of mobile phases and sample solutions, calibration, determination of injection profiles and column void, and of course the adsorption isotherm determination method itself. It is also important to keep track of parameters such as temperature and pH. These issues are discussed in this thesis.At the end, a description of useful methods for processing of the raw adsorption isotherm data is presented, as well as a brief passage on methods for numerical optimisation.
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