| 1. |
- Ahlgren, Joakim, et al.
(författare)
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Release of Organic P Forms from Lake Sediments
- 2011
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 45:2, s. 565-572
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Tidskriftsartikel (refereegranskat)abstract
- The effects of different physical and chemical conditions on the decomposition and release of organic and inorganic P compound groups from the sediment of Lake Erken were investigated in a series of laboratory experiments. Conditions investigated were temperature, oxygen level, and the effects of additions of carbon substrate (glucose) and poison (formalin). The effects on the P compound groups were determined by measurements with 31P NMR before and after the experiments, as well as analysis of P in effluent water throughout the experiment. Phosphate analysis of the effluent water showed that oxygen level was the most influential in terms of release rates, with the sediments under anoxic conditions generally releasing more phosphate than the other treatments. 31P NMR showed that the various treatments did influence the P compound group composition of the sediment. In particular, the addition of glucose led to a decrease in orthophosphate and polyphosphate while the addition of formalin led to a decrease in phosphorus lipids, DNAphosphate and polyphosphate. Oxic conditions resulted in an increase in polyphosphates, and anoxic conditions in a decrease in these. Temperature did not seem to affect the composition significantly.
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| 2. |
- Bergman, Jan, et al.
(författare)
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Synthesis of cyclopent[b]indolones
- 1990
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Ingår i: Tetrahedron. - 0040-4020 .- 1464-5416. ; 46:17, s. 6067-6084
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Tidskriftsartikel (refereegranskat)abstract
- A number of cyclopent[b]indol-1-ones as well as -3-ones have been synthesized, using a new methodology involving intramolecular ring closure of α,β-unsaturated acylindoles. In some cases 1,2,3,4-tetrahydrocarbazol-4-ones were obtained. This methodology was used in the syntheses of the indole alkaloid yuehchukene and the carbazole alkaloid analogue demethoxycarbazomycin B.
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| 3. |
- Blom, Magnus, et al.
(författare)
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Photomodulable bis-porphyrin molecular tweezers as dynamic host systems for diamine guests
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Bisporphyrin molecular tweezers with an enediyne (1) or a stiff stilbene (2) photoswitchable spacer are proposed as systems for modulation of bitopic binding to diamine guests via E/Z photoisomerization. The photoisomerization has been monitored by UV-Vis and 1H NMR spectroscopy and occurs without side reactions such as Bergman cyclization. Possible applications are rationalized in terms of competitive binding involving monoamine/diamine mixtures, and are supported by conformational analysis of the envisioned host-guest complexes. Binding dynamics for conformationally flexible guests show significantly different performance of aliphatic 1,w-diamine guests with varying N-N distance.
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| 4. |
- Blom, Magnus, et al.
(författare)
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Photoswitchable peptidomimetics with a stiff-stilbene chromophore for inhibition of Mycobacterium tuberculosis RNR
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Peptidomimetics incorporating two amino acids 1 and 2 with a stiff stilbene chromophore have been screened by a computational study and compared to a previously investigated analog 3 with stilbene chromophore. The effect of E-Z isomerization of the chromophores on the conformational properties of the petidomimetics was assessed via the frequency of hydrogen bonding between the two peptide strands attached to either side of the chromophore. Substantial differences between the three amino acids were thus indicated, in line with the anticipated effect of chromophore rigidity variation.
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| 5. |
- Blom, Magnus, 1984-, et al.
(författare)
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Synthesis and characterization of photoswitchable stiff-stilbene based amino acid derivatives
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Synthetic routes towards the Boc-protected amino acids 1 and 2 incorporating the stiff stilbene chromophore via the corresponding indanone carboxylic acids have been devised. Crucial steps are a reductive McMurry coupling of the indanone carboxylic acids, yielding stiff stilbene dicarboxylic acid esters. Hydrolysis to the monoester and conversion to the azides, followed by a Curtius rearrangement afforded the Boc-protected amino acid ester 1.
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| 6. |
- Blom, Magnus, 1984-, et al.
(författare)
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Synthesis and Properties of Bis-Porphyrin Molecular Tweezers : Effects of Spacer Flexibility on Binding and Supramolecular Chirogenesis
- 2016
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Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Ditopic binding of various dinitrogen compounds to three bisporphyrin molecular tweezers with spacers of varying conformational rigidity, incorporating the planar ene-diyne (1), the helical stiff stilbene (2), or the semirigid glycoluril motif fused to the porphyrins (3) are compared. Binding constants Ka = 10^4 to 10^6 M^-1 reveal subtle differences between these tweezers, that are discussed in terms of porphyrin dislocation modes. Exciton coupled circular dichroism (ECCD) of complexes with chiral dinitrogen guests provides experimental evidence for the conformational properties of the tweezers. The results are further supported and rationalized by conformational analysis.
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| 7. |
- Bäckvall, Jan-Erling, et al.
(författare)
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Evidence for (π-allyl)palladium(II)(quinone) complexes in the palladium-catalyzed 1,4-diacetoxylation of conjugated dienes
- 1988
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Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 29:18, s. 2243-2246
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Tidskriftsartikel (refereegranskat)abstract
- Evidence for a coordination of p-benzoquinone to palladium in [4-acetoxy-η3-(1,2,3)-cyclohexenyl]-palladium(II) complexes was provided by changes of the 1H NMR chemical shift values of the π-allyl protons and a decrease of the spin-lattice relaxation time constant for the p-benzoquinone protons. The intermediate (π-allyl)palladium(benzoquinone) complexes previously postulated in palladium-catalyzed 1,4-oxidations of 1,3-dienes were detected by NMR spectroscopy.
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| 8. |
- Bäckvall, Jan-Erling, et al.
(författare)
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Palladium‑Hydroquinone Catalysed Electrochemical 1,4‑Oxidation of Conjugated Dienes
- 1987
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Ingår i: Journal of the Chemical Society. Chemical communications. - 0022-4936. ; 16, s. 1236-1238
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Tidskriftsartikel (refereegranskat)abstract
- The mediator system palladium(II)–hydroquinone was shown to catalyse the anodic oxidation of cyclohexa-1,3-diene in acetic acid to produce selectively either trans- or cis-1,4-diacetoxycyclohex-2-ene (1) depending on the conditions.
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| 9. |
- Engdahl, Carin, et al.
(författare)
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Long‑Range Deuterium Isotope Effects on 13C NMR Shifts of Intramolecularly Hydrogen‑Bonded 9‑Hydroxyphenalen‑1‑ones
- 1991
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 29:1, s. 54-62
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Tidskriftsartikel (refereegranskat)abstract
- The 1H and 13C NMR spectra of 9-hydroxyphenalenone (1) and 9-hydroxy-2-methylphenalenone (2) have been completely assigned. Primary and secondary deuterium isotope effects were determined in three solvents (chloroform, acetone and dimethyl sulphoxide), including the effect of temperature on the secondary isotope effects. Both negative and large long-range secondary isotope effects were found for both 1 and 2. The average secondary isotope effects for corresponding carbons follow the same sign and magnitude pattern in both compounds.
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| 10. |
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| 11. |
- Gogoll, Adolf, 1957-, et al.
(författare)
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Complete 1H and 13C NMR spectral assignment of venturicidin A by 2D NMR spectroscopy
- 1989
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Ingår i: Magnetic Resonance in Chemistry. - : Wiley. - 0749-1581 .- 1097-458X. ; 27:9, s. 863-871
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Tidskriftsartikel (refereegranskat)abstract
- After correlation of the majority of signals by COSY and one-bond heteronuclear correlation, the complete assignment of the 1H and 13C NMR spectra of the macrolide antibiotic venturicidin A required the application of long-range CH coupling information. This was accessible by the COLOC-S and selective INEPT experiments, and the sensitivity of these experiments is discussed. Steric information was obtained from a NOESY spectrum, and the solution structure compared with that in the crystal.
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| 12. |
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Guo, Xiaohu, et al.
(författare)
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Structure and mechanism of a phage-encoded SAM lyase revises catalytic function of enzyme family
- 2021
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Ingår i: eLIFE. - : eLife Sciences Publications Ltd. - 2050-084X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- The first S-adenosyl methionine (SAM) degrading enzyme (SAMase) was discovered in bacteriophage T3, as a counter-defense against the bacterial restriction-modification system, and annotated as a SAM hydrolase forming 5’-methyl-thioadenosine (MTA) and L-homoserine. From environmental phages, we recently discovered three SAMases with barely detectable sequence similarity to T3 SAMase and without homology to proteins of known structure. Here, we present the very first phage SAMase structures, in complex with a substrate analogue and the product MTA. The structure shows a trimer of alpha–beta sandwiches similar to the GlnB-like superfamily, with active sites formed at the trimer interfaces. Quantum-mechanical calculations, thin-layer chromatography, and nuclear magnetic resonance spectroscopy demonstrate that this family of enzymes are not hydrolases but lyases forming MTA and L-homoserine lactone in a unimolecular reaction mechanism. Sequence analysis and in vitro and in vivo mutagenesis support that T3 SAMase belongs to the same structural family and utilizes the same reaction mechanism.
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| 17. |
- Huang, Hao, et al.
(författare)
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Hydroquinone–pyrrole dyads with varied linkers
- 2016
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 12, s. 89-96
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Tidskriftsartikel (refereegranskat)abstract
- A series of pyrroles functionalized in the 3-position with p-dimethoxybenzene via various linkers (CH2, CH2CH2, CH=CH, C≡C) has been synthesized. Their electronic properties have been deduced from 1H NMR, 13C NMR, and UV–vis spectra to detect possible interactions between the two aromatic subunits. The extent of conjugation between the subunits is largely controlled by the nature of the linker, with the largest conjugation found with the trans-ethene linker and the weakest with the aliphatic linkers. DFT calculations revealed substantial changes in the HOMO–LUMO gap that correlated with the extent of conjugation found experimentally. The results of this work are expected to open up for use of the investigated compounds as components of redox-active materials in sustainable, organic electrical energy storage devices.
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| 18. |
- Huang, Hao, 1988-, et al.
(författare)
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Synthesis and Characterization of Poly-3-((2,5-hydroquinone)vinyl)-1H-pyrrole : investigation on Backbone/Pendant Interactions in a Conducting Redox Polymer
- 2017
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 19:16, s. 10427-10435
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Tidskriftsartikel (refereegranskat)abstract
- We herein report the synthesis and electrochemical characterization of poly-3-((2,5-hydroquinone)vinyl)-1H-pyrrole, consisting of a polypyrrole backbone derivatized at the beta position by a vinyl-hydroquinone pendant group. The structure of the polymer was characterized by solid state NMR spectroscopy. The interactions between the polypyrrole backbone and the oxidized quinone or reduced hydroquinone pendant groups are probed by several in situ methods. In situ attenuated total reflectance-Fourier transform infrared spectroscopy shows spectroscopic response from both the doping of the polymer backbone and the redox activity of the pendant groups. Using an in situ Electrochemical Quartz Crystal Microbalance we reveal that the polymer doping is unaffected by the pendant group redox chemistry, as opposed to previous reports. Despite the continuous doping the electrochemical conversion from the hydroquinone state to the quinone state results in a significant conductance drop, as observed by in situ conductivity measurements using an InterDigitated Array electrode set-up. Twisting of the conducting polymer backbone as a result of a decreased separation between pendant groups due to π-π stacking in the oxidized state is suggested as the cause of this conductance drop.
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| 19. |
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| 20. |
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| 21. |
- Nájera, Carmen, et al.
(författare)
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Nitroselenation of conjugated dienes : Preparation of 3,4-epoxy-3-nitro-1-alkenes
- 1990
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Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 31:29, s. 4199-4202
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Tidskriftsartikel (refereegranskat)abstract
- Conjugated dienes were transformed to synthetically useful 3,4-epoxy-3-nitro-1-alkenes via a nitroselenation-oxidation sequence. Conjugated dienes were transformed to synthetically useful 3,4-epoxy-3-nitroalkenes via a nitroselenation-oxidation sequence.
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| 22. |
- Olsson, Sandra, 1987-
(författare)
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Host-Guest Interactions for Structural Analysis of Organic Molecules : Development of new Tools for Stereochemical Characterization
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The focus of this thesis is on the development of molecular tweezers as host-guest systems for stereochemical characterization of small organic molecules.There are two central problems to stereochemical characterization of small molecules. The first is that there are few methods for the determination of absolute stereochemistry and the complexity of the task increases with the number of chiral centres in the molecule. The second is the flexibility of small molecules. The data received from NMR spectroscopy, the standard method for structural characterization is an average of all conformers present in solution, making exact determination of the structure challenging if stereocenters are involved.This research group has previously developed two bis-porphyrin molecular tweezers that can be used as hosts for relative stereochemical determination by NMR (NAMFIS) by limiting the flexibility of the guest molecules and for absolute stereochemical determination Exciton-Coupled Circular Dichroism (ECCD) by providing suitable chromophores. However, the use of these tweezers was limited to diamine molecules.To extend the application of both tweezer host systems, a range of metalloporphyrins have been investigated both computationally and experimentally to identify candidates binding strongly to oxygen containing functional groups (Paper I). One of the porphyrins identified has been used to synthesise a new system with the potential to be used for relative stereochemical determination by NMR (NAMFIS) of molecules with a wide variety of functional groups (Paper IV).To further develop the systems, the photo-isomerization properties of the stiff stilbene linker of one of the tweezers has been investigated. Macrocyclic diether model compounds, incorporating the stiff stilbene linker have been used to show that the photo-isomerizability strongly is affected by molecular strain (Paper II). The results suggest that if paired with a suitable porphyrin (with no UV/Vis absorption overlap) a photo-switchable tweezer might be constructed.To map the guest range of the stiff stilbene linked tweezer it was found that this tweezer gives strong to moderate signals for monoamines with a rigid structure (Paper III). As ditopic binding is usually a requirement for an ECCD signal when using bis-porphyrin molecular tweezers, this is a discovery that should be of general interest.
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| 23. |
- Olsson, Sandra K., 1987-, et al.
(författare)
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Design of oxophilic metalloporphyrins : an experimental and DFT study of methanol binding
- 2018
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry. - 1477-9226 .- 1477-9234. ; 47:33, s. 11572-11585
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Tidskriftsartikel (refereegranskat)abstract
- By systematic measurements we have evaluated a series of tetraphenyl metalloporphyrins and halogenated tetraphenyl metalloporphyrin derivatives for binding to ligands with oxygen containing functional groups, using methanol, acetic acid and acetone as examples. Experimental binding constants identified three metalloporphyrins with good binding to all three ligands: MgTPFPP, MgTPPBr8 and ZnTPPBr8 as well as a range of porphyrins binding to select ligands. Based on these results the optimal porphyrins can be selected for the desired binding interactions. We also show how to use DFT calculations to evaluate the potential binding between a metalloporphyrin and a ligand, which is deduced from free energies of binding ΔG, charge transfer ΔQ, and change of metal spin state. Computations on unsubstituted porphyrins in lieu of tetraphenyl porphyrin systems yield reliable predictions of binding interactions with good correlation to the corresponding experimental data. The calculations have also yielded interesting insights into the effect of halogenation in the β-position on the binding to ligands with oxygen containing functional groups.
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| 24. |
- Olsson, Sandra K., 1987-, et al.
(författare)
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Effect of Ring Size on Photoisomerization Properties of Stiff Stilbene macrocycles
- 2019
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Ingår i: Beilstein Journal of Organic Chemistry. - : Beilstein Institut. - 2195-951X .- 1860-5397. ; 15, s. 2408-2418
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Tidskriftsartikel (refereegranskat)abstract
- A series of stiff stilbene macrocycles have been studied to investigate the possible impact of the macrocycle ring size on their photodynamic properties. The results show that reducing the ring size counteracts the photoisomerization ability of the macrocycles. However, even the smallest macrocycle studied (stiff stilbene subunits linked by a six carbon chain) showed some degree of isomerization when irradiated. DFT calculations of the energy differences between the E- and Z-isomers show the same trend as the experimental results. Interestingly the DFT study highlights that the energy difference between the E- and Z-isomers of even the largest macrocycle (linked by a twelve carbon chain) is significantly higher than that of the stiff stilbene unit itself. In general, it is indicated that addition of even a flexible chain to the stiff stilbene unit may significantly affect its photochemical properties and increase the photostability of the resulting macrocycle.
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| 25. |
- Olsson, Sandra K., 1987-, et al.
(författare)
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Exciton-Coupled Circular Dichroism Characterization of Monotopically Binding Guests in Host-Guest Complexes with a Bis(zinc porphyrin) Tweezer
- 2018
-
Ingår i: ChemPlusChem. - Weinheim : Wiley-VCH Verlagsgesellschaft. - 2192-6506. ; 83, s. 1169-1178
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Tidskriftsartikel (refereegranskat)abstract
- A stiff-stilbene-linked bisporphyrin tweezer with inherent helicity was used for exciton-coupled circular dichroism (ECCD) characterization of a series of monotopically binding amine guest molecules. CD signals were observed for a variety of monoamines at relatively low tweezer/amine (host/guest) ratios between 1 :10 to 1: 70. For the amines producing the most intense CD signals, a binding stoichiometry of 1:2 was found. A likely explanation is the presence of guest-guest interactions in the complexes. This is supported by the correlation observed between CD signal intensity and magnitude of possible noncovalent binding between the guests, which can be divided into three groups showing no, moderate and strong response, respectively. Further support for this rationalization comes from molecular modelling.
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| 26. |
- Olsson, Sandra K., 1987-, et al.
(författare)
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Synthesis of a novel bis-Mg-porphyrin tweezer
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We have synthesised a novel semi-rigid bis-(magnesium-porphyrin) tweezer with a glycoluril backbone. meso-Tetrakis(pentafluorophenyl)porphyrin constitutes the two porphyrin units, each holding a magnesium(II) ion, and being connected to the glycoluril backbone via two -positions. This connection prevents any porphyrin rotation, leaving changes in gap size as sole conformational variation. Magnesium(II) tetrakis(pentafluorophenyl)porphyrin has in previous studies shown to bind well to both nitrogen-containing and oxygen-containing functional groups. The tweezer has the potential to retain this binding ability, which would be useful in the stereochemical characterization of small flexible molecules with multiple stereocentra and a wide variety of functional groups.
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| 27. |
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| 28. |
- Sterby, Mia, 1989-, et al.
(författare)
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Characterization of PEDOT-Quinone Conducting Redox Polymers for Water Based Secondary Batteries
- 2017
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 235, s. 356-364
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Tidskriftsartikel (refereegranskat)abstract
- Lithium-ion technologies show great promise to meet the demands that the transition towards renewable energy sources and the electrification of the transport sector put forward. However, concerns regarding lithium-ion batteries, including limited material resources, high energy consumption during production, and flammable electrolytes, necessitate research on alternative technologies for electrochemical energy storage. Organic materials derived from abundant building blocks and with tunable properties, together with water based electrolytes, could provide safe, inexpensive and sustainable alternatives. In this study, two conducting redox polymers based on poly(3,4-ethylenedioxythiophene) (PEDOT) and a hydroquinone pendant group have been synthesized and characterized in an acidic aqueous electrolyte. The polymers were characterized with regards to kinetics, pH dependence, and mass changes during oxidation and reduction, as well as their conductance. Both polymers show redox matching, i.e. the quinone redox reaction occurs within the potential region where the polymer is conducting, and fast redox conversion that involves proton cycling during pendant group redox conversion. These properties make the presented materials promising candidates as electrode materials for water based all-organic batteries.
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| 29. |
- Sterby, Mia, 1989-
(författare)
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Electrochemical Characterizations of Conducting Redox Polymers : Electron Transport in PEDOT/Quinone Systems
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organic electrode materials for rechargeable batteries have caught increasing attention since they can be used in new innovative applications such as flexible electronics and smart fabrics. They can provide safer and more environmentally friendly devices than traditional batteries made from metals. Conducting polymers constitute an interesting class of organic electrode materials that have been thoroughly studied for battery applications. They have high conductivity but are heavy relative to their energy storage ability and will hence form batteries with low weight capacity. Quinones, on the other hand, are low weight molecules that participate in electron transport in both animals and plants. They could provide batteries with high capacity but are easily dissolved in the electrolyte and have low conductivity. These two constituents can be combined into a conducting redox polymer that has both high conductivity and high capacity. In the present work, the conducting polymer PEDOT and the simplest quinone, benzoquinone, are covalently attached and form the conducting redox polymer used for most studies in this thesis. The charge transport mechanism is investigated by in situ conductivity measurements and is found to mainly be governed by band transport. Other properties such as packing, kinetics, mass changes, and spectral changes are also studied. A polymerization technique is also analyzed, that allows for polymerization from a deposited layer. Lastly, two different types of batteries using conducting redox polymers are constructed. The thesis gives insight into the fundamental properties of conducting redox polymers and paves the way for the future of organic electronics.
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| 30. |
- Umereweneza, Daniel, et al.
(författare)
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Antibacterial and cytotoxic prenylated dihydrochalcones from Eriosema montanum
- 2021
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Ingår i: Fitoterapia (Milano). - : Elsevier BV. - 0367-326X .- 1873-6971. ; 149
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Tidskriftsartikel (refereegranskat)abstract
- Two new prenylated dihydrochalcones (1,2) and eighteen known secondary metabolites (3−20) were isolated from the CH2Cl2-MeOH (1:1) extracts of the roots, the stem bark and the leaves of Eriosema montanum Baker f. (Leguminosae). The structures of the isolated compounds were characterized by NMR, IR, and UV spectroscopic and mass spectrometric analyses. The structures of compounds 5, 10, 11 and 13 were confirmed by single crystal X-ray diffraction. The antibacterial activity of the crude extracts and the isolated constituents were established against Gram-positive and Gram-negative bacteria. Among the tested compounds, 1–4 and 10 showed strong activity against the Gram-positive bacterium Bacillus subtilis with minimum inhibitory concentration (MIC) ranging from 3.1 to 8.9 μM, as did the leaf crude extract with an MIC of 3.0 μg/mL. None of the crude extracts nor the isolated compounds were active against Escherichia coli. Compounds 1, 3 and 4 showed higher cytotoxicity, evaluated against the human breast cancer cell line MCF-7, with EC50 of 7.0, 18.0 and 18.0 μM, respectively. These findings contribute to the phytochemical understanding of the genus Eriosema, and highlight the pharmaceutical potential of prenylated dihydrochalcones.
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| 31. |
- Umereweneza, Daniel, et al.
(författare)
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Antiviral iridoid glycosides from Clerodendrum myricoides
- 2021
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Ingår i: Fitoterapia. - : Elsevier BV. - 0367-326X .- 1873-6971. ; 155
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Tidskriftsartikel (refereegranskat)abstract
- The methanol root extract of Clerodendrum myricoides (Hochst.) Vatke afforded two new (1, 2) and two known (3, 4) iridoid glycosides. The structures of the isolated compounds were established based on NMR, IR, UV and MS data analyses. The crude extract and the isolated constituents were assayed for antiviral activity against the human respiratory syncytial virus (RSV) in human laryngeal epidermoid carcinoma (HEp-2) cells. The crude extract inhibited RSV infectivity at EC50 = 0.21 mu g/ml, while it showed cytotoxicity against HEp-2 cells with CC50 = 9 mu g/ml. Compound 2 showed 43.2% virus inhibition at 100 mu M, while compounds 1 as well as 3 and 4 had only weak antiviral and cytotoxic activities.
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| 32. |
- Umereweneza, Daniel, et al.
(författare)
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Macrocyclic Pyrrolizidine Alkaloids and Silphiperfolanol Angelate Esters from Solanecio mannii
- 2023
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; 26:8
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Tidskriftsartikel (refereegranskat)abstract
- Three new compounds, the silphiperfolanol angelate ester umutagarananol (1), the macrocyclic pyrrolizidine alkaloids umutagarinine A and B (2-3), and five known secondary metabolites (4-8) were isolated from the CH2Cl2-MeOH (1 : 1) extract of the roots and the stem bark of Solanecio mannii (Hook. f.) (Asteraceae). The isolated compounds were characterized by NMR and IR spectroscopic, and mass spectrometric analyses, whereas the relative stereochemistry of 4 was established by NAMFIS-based combined computational and solution NMR analysis. Synthetic modification of 5 provided two new compounds, 2-angeloyloxy-4,8-epoxypresilphiperfolane (9) and 2-angeloyloxy-4,8-epoxypresilphi-perfolane (10). The crude extracts and the isolated constituents showed weak antibacterial activities (EC50 0.7-13.3 mM) against the Gram-negative Escherichia coli and the Gram-positive Bacillus subtilis. Compounds 2, 3 and 4 exhibited strong cytotoxicity against MCF-7 human breast cancer cells, with EC50 values of 35.6, 21.7 and 12.5 mu M, respectively.
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| 33. |
- Wallner, Andreas, et al.
(författare)
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Formation and NMR Spectroscopy of ω-Thiol Protected α,ω-Alkanedithiol Coated Gold Nanoparticles and Their Usage in Molecular Charge Transport Junctions
- 2011
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 27:14, s. 9057-9067
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Tidskriftsartikel (refereegranskat)abstract
- Gold nanoparticles (AuNPs) coated with stabilizing molecular monolayers are utilized in areas ranging from life sciences to nanoelectronics. Here we present a novel and facile one-pot single phase procedure for the preparation of stable AuNPs with good dispersity, which are coated with α,ω-alkanedithiols whose outer ω-thiol is protected by a triphenylmethyl group. Using dielectrophoresis we were able to trap these AuNPs, coated with ω-thiol protecting groups, in a 20 nm gold electrode nanogap. The ω-thiol group was then deprotected under acidic conditions in situ once the AuNPs were correctly positioned in the device. The subsequent deprotection resulted in an increase of conductance by three orders of magnitude, indicating that the isolated dithiol coated AuNPs were fused into a covalently bonded network with AuNP-molecule-AuNP as well as electrode-molecule-AuNP linkages. Furthermore, complete characterization of the AuNP surface-bonded alkanedithiols was achieved using a series of one- and two-dimensional NMR spectroscopy techniques. Our spectra of the molecule-coated AuNPs show well resolved signals, only slightly broader than for free molecules in solution, in contrast to many earlier reported NMR spectral data of molecules attached to AuNPs. Complementary diffusion NMR spectroscopic experiments were performed to prove that the observed alkanedithiols are definitely surface bonded species and do not exist in free and unattached form.
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| 34. |
- Yang, Dong, et al.
(författare)
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Air- and Light-Stable P-4 and As-4 within an Anion-Coordination-Based Tetrahedral Cage
- 2017
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Ingår i: Journal of the American Chemical Society. - : AMER CHEMICAL SOC. - 0002-7863 .- 1520-5126. ; 139:16, s. 5946-5951
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Tidskriftsartikel (refereegranskat)abstract
- In contrast to the stable dinitrogen molecule, white phosphorus (P-4) and yellow arsenic (As-4) are very reactive allotropic modifications of these two heavier pnictogen elements, which has greatly hampered the study of their properties and applications. Thus, the safe storage and transport of them is imperative. Supramolecular caged structures are one of the most efficient approaches for the encapsulation and stabilization of reactive species; however, their use in the P-4 and As-4 chemistry is very rare. In the current work, we demonstrate a new design strategy for constructing finite cages and including guests based on anion coordination chemistry. The phosphate-coordination-based tetrahedral cages can readily accommodate the tetrahedral guests P-4 and As-4, which is facilitated by the shape and size complementarity as well as favorable sigma-pi and lone-pair-pi interactions. Moreover, the latter case represents the first example of As-4 inclusion in a well-defined tetrahedral cage.
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| 35. |
- Yang, Li, 1987-, et al.
(författare)
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Conducting redox polymers with non-activated charge transport properties
- 2017
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 19:36, s. 25052-25058
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Tidskriftsartikel (refereegranskat)abstract
- Non-activated charge transport has been demonstrated in terephthalate-functionalized conducting redox polymers. The transition from a temperature-activated conduction mechanism to a residual scattering mechanism was dependent on the doping level. The latter mechanism is associated with apparent negative activation barriers to charge transport and is generally found in polymer materials with a high degree of order. Crystallographic data, however, suggested a low degree of order in this polymer, indicating the existence of interconnected crystal domains in the predominantly amorphous polymer matrix through which the charge was transported. We have thus shown that the addition of bulky pendant groups to conducting polymers does not prevent efficient charge transport via the residual scattering mechanism with low barriers to charge transport.
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| 36. |
- Åkerlund, Lisa, 1986-
(författare)
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Electrochemical characterizations of conducting redox polymers with proton traps : Enabling proton cycling in aprotic systems for high potential energy storage
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Floods, droughts and unpredictable weather could be the new reality for millions of people in a near future, unless we drastically decrease our greenhouse gas emissions to prevent the global average temperature from increasing even further. Material innovations will most certainly be essential for many of the technical solutions needed in order to tackle environmental issues. One major challenge is how to deal with the massive energy demand, following the average lifestyle of today, in a way that is both reliable and sustainable. Renewable energy sources have a varying output over time, hence cannot meet the demand for electricity by themselves. To buffer between demand and production, new ways to store the renewably produced energy are crucial. From a life cycle aspect conventional battery types are far from sustainable, and, with the increasing number of electronic devices for numerous applications, we need new options.This thesis explores conducting redox polymers (CRPs), which can be utilized as organic cathode materials in high potential energy storage. Hydroquinone (HQ) was applied as the capacity carrying pendant group, and by the introduction of a proton trap functionality the high reduction potential of quinone-proton cycling was achieved also in aprotic electrolytes. The high reduction potential allows for redox matching with the polymer backbone, crucial for CRPs to work as energy storage materials without any additives, and this was studied by in situ conductance with IDA. In situ EQCM was applied in order to examine the cycling chemistry, and the constant mass uptake during the full oxidation cycle (and reverse during the reduction cycle) indicated uptake of charge compensating ions. Further, the proton trap functionality and its effectiveness were investigated by compositional variation, FTIR and variation of electrolyte. In situ UV/Vis was applied in order to study the electronic transitions of the bandgap, the charge carriers and the pendant group redox conversion.The results presented introduce a new route for utilizing protonated forms of quinones as capacity carriers in aprotic media, by incorporating a proton trap in the material. The battery prototypes point to the versatility of the proton trap materials, having reversible proton cycling also when the electrolyte contains metal salts. With dual-ion type batteries the cycling chemistry of the anode is disconnected from the cathode, which allows for free choice of anode material.
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