| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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| 6. |
- 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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| 7. |
- 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
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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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| 8. |
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| 9. |
- 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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| 10. |
- 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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| 11. |
- 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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| 12. |
- 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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