| 1. |
- Howe, Andrew, 1995-
(författare)
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Immobilisation of Ru-Based Molecular Catalysts for Electrochemical Water Oxidation
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Artificial photosynthesis requires catalysts for efficient and selective conversions of small molecules. Molecular catalysts are advantageous to use in these instances as they offer precise control over chemical reactivity. They are synthetically tuneable, and their catalytic mechanisms are often well documented and more readily understood than those of solid-state catalysts. In this thesis, the synthetic incorporation of molecular catalysts into heterogenised molecular anodes for water oxidation are evaluated. The catalysts are incorporated as structural linkers into porous metal-organic framework (MOF) structures, and as coordination oligomers stacked onto graphitic surfaces. The preparation of MOF/molecular catalyst hybrid materials of two topologies, UiO (UiO = Universitet i Oslo) and NU-1000 (NU = Northwestern University), were investigated. Multiple synthetic methods for the incorporation of molecular ruthenium-based catalysts into MOFs were examined in papers I and II. In paper III of this thesis, a Ru-bda type molecular complex was successfully used in the solvothermal synthesis of a new MOF. The resulting material is the first of its kind that is built exclusively from molecular water oxidation catalyst linkers. It is shown that MOF incorporation greatly enhances the structural stability of the catalyst linker in chemical water oxidation experiments, giving rise to higher turnover numbers compared to that of a homogenous reference system. Finally, paper IV describes a stable and inert molecular ruthenium complex, which possesses a flexible adaptative multidentate equatorial (FAME) type equatorial ligand with a carbanion on the equatorial ligand that forms a C-Ru bond. This molecular complex is studied in homogeneous phase, and subsequently incorporated into a coordination oligomer, which can be activated for water oxidation catalysis. This finding broadens the field of molecular catalysis significantly, and proves that supramolecular interactions can be used to promote electrocatalysis in complexes which are otherwise too inert and stable to engage in electrocatalytic reactions.
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| 2. |
- Bagnall, Andrew J.
(författare)
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Novel electrode and photoelectrode materials for hydrogen production based on molecular catalysts
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The PhD project focussed on the application of a cobalt tetraazamacrocyclic complex, in the literature commonly referred to as [Co(CR)Cl2]+ as a molecular catalyst for the hydrogen evolution reaction (HER). This was within the broader scope of the EU MSCA H2020 ITN ‘eSCALED’ project, which primarily aimed to create artificial leaf devices for the storage of solar energy in chemical fuels and, as part of this, sought the development of novel bio-inspired and scalable materials. This included researching molecular catalysts without platinum group metals (PGMs) currently relied upon in commercial technology.Three main projects were pursued: firstly, studies of the mechanism of the catalyst itself under organic electrocatalytic conditions. Catalytic intermediates were generated and identified using spectroscopy (UV-vis, NMR, EPR) and the catalytic behaviour was followed with electrochemical techniques. An ECEC mechanism with a rate-determining second protonation step associated with the release of H2 was identified, noting in particular an initial protonation step on the macrocycle at the Co(II) state that was hypothesised to involve the macrocycle amine group acting as a proton relay under the investigated conditions.Secondly, a new synthetic strategy towards novel derivatives of [Co(CR)Cl2]+ was developed to prepare a derivative for anchoring onto sp2-carbon surfaces by pi-stacking interactions. The immobilised catalyst was studied by electrochemical methods and compared with another derivative from collaborators at ICIQ, showing that both derivatives work as heterogenised electrocatalysts for the HER with high faradaic efficiencies and good stability over one hour at pH 2 and especially pH 7, but one derivative displays higher current densities and stability, invoking some consideration of rational design principles for modifying molecular catalysts.Thirdly, studies of a photocatalytic system made up of copper indium sulfide quantum dots (CuInS2 QDs) as a photosensitiser with either [Co(CR)Cl2]+ or its benzoic acid-functionalised derivative were carried out in ascorbate buffer, focussing on the photocatalytic performance and electron transfer (ET) processes between the CuInS2 QDs and the catalyst to explain the remarkable activity and robustness reported for closely related systems. CuInS2 QDs modified to have a ‘hybrid-passivation’ ligand system for compatibility with NiO films were used. Rapid QD-catalyst ET processes were noted for both catalysts. A static binding model with a strong binding equilibrium was adapted for the system, applying a Poisson distribution. This prompts a reconsideration of the importance of anchoring groups for QD-catalyst ET efficiency in solution.
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| 3. |
- Howe, Andrew, 1995-, et al.
(författare)
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Synthesis of a Metal-Organic Framework Made Entirely of the Molecular Ruthenium Water Oxidation Complex
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A new type of metal-organic framework (MOF) is described, with the linker moeities made entirely from Ru water oxidation catalyst with the formula [(RuII(bda)(py(PhCOOH)2)], 1, (bda = [2,2′-bipyridine]-6,6′-dicarboxylate and; py(PhCOOH)2 = (4,4'-(pyridine-3,5-diyl)dibenzoic acid), that is based on the Ru-bda family of water oxidation catalysts has been prepared and characterised. Due to its fixed equatorial ligand, with no features that can negatively influence the solvothermal synthesis, A MOF was preapred using 1 as the sole linker, producing a Zr-based framework, 2, that can be prepared in bulk or on a thin-film and characterised. The MOF formation was confirmed by powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM), and Ru linker incorporation was shown by energy-dispersive X-ray (EDX) spectroscopies, X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectroscopy (ICP-OES) analyses. Clear redox couples associated with 1 can be observed upon electrochemical characterisation using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). This provides an interesting study of the electrochemical behaviour of a molecular water oxidation catalysts when it is an integral, structural component of a framework, which has found certain supramolecular, non-covalent, anionic and steric conditions need to be met in order to obtain effective catalysis when using Ru-bda type of catalyst.
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| 4. |
- Parada, Giovanny A.
(författare)
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Synthesis of Biomimetic Systems for Proton and Electron Transfer Reactions in the Ground and Excited State
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A detailed understanding of natural photosynthesis provides inspiration for the development of sustainable and renewable energy sources, i.e. a technology that is capable of converting solar energy directly into chemical fuels. This concept is called artificial photosynthesis. The work described in this thesis contains contributions to the development of artificial photosynthesis in two separate areas.The first one relates to light harvesting with a focus on the question of how electronic properties of photosensitizers can be tuned to allow for efficient photo-induced electron transfer processes. The study is based on a series of bis(tridentate)ruthenium(II) polypyridyl complexes, the geometric properties of which make them highly appealing for the construction of linear donor-photosensitizer-acceptor arrangements for efficient vectorial photo-induced electron transfer reactions. The chromophores possess remarkably long lived 3MLCT excited states and it is shown that their excited-state oxidation strength can be altered by variations of the ligand scaffold over a remarkably large range of 900 mV.The second area of relevance to natural and artificial photosynthesis that is discussed in this thesis relates to the coupled movement of protons and electrons. The delicate interplay between these two charged particles regulates thermodynamic and kinetic aspects in many key elementary steps of natural photosynthesis, and further studies are needed to fully understand this concept. The studies are based on redox active phenols with intramolecular hydrogen bonds to quinolines. The compounds thus bear a strong resemblance to the tyrosine/histidine couple in photosystem II, i.e. the water-plastoquinone oxidoreductase enzyme in photosynthesis. The design of the biomimetic models is such that the distance between the proton donor and acceptor is varied, enabling studies on the effect the proton transfer distance has on the rate of proton-coupled electron transfer reactions. The results of the studies have implications for the development of artificial photosynthesis, in particular in connection with redox leveling, charge accumulation, as well as electron and proton transfer.In addition to these two contributions, the excited-state dynamics of the intramolecular hydrogen-bonded phenols was investigated, thereby revealing design principles for technological applications based on excited-state intramolecular proton transfer and photoinduced tautomerization.
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| 5. |
- Singh, Pradyumna S., et al.
(författare)
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(I,0) Mixed-Valence State of a Diiron Complex with Pertinence to the [FeFe]-Hydrogenase Active Site : An IR, EPR, and Computational Study
- 2009
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 48:23, s. 10883-10885
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Tidskriftsartikel (refereegranskat)abstract
- Biphenyl-2,2'-dithiolate (bpdt) bridged Fe-2(bpdt)(CO)(6) (1) undergoes two sequential electrochemically quasi-reversible reductions. The one-electron reduction product 1(-) is unusually stable against irreversible structural changes and could be characterized by IR and EPR spectroscopy supported by computational methods. Reduction to the (I,0) state does not trigger bridging coordination of CO but partial deligation of the dithiolate in 1(-) that ultimately forms a diamagnetic dimerization product.
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| 6. |
- Öberg, Elisabet, et al.
(författare)
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C, C-Diacetylenic Phosphaalkenes as Heavy Diethynylethene Analogues
- 2009
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 74:24, s. 9265-9273
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Tidskriftsartikel (refereegranskat)abstract
- A series of C,C-diacetylenic phosphaalkenes 1b−e has been prepared from 1-chloropenta-1,2-dien-4-ynes 6b−e in a reaction with Mes*PCl2 (Mes* = 2,4,6-(tBu)3Ph) in the presence of LDA. Under identical conditions, isomeric butadiyne-substituted phosphaalkenes 2c−f can be obtained from 3-chloropenta-1,4-diynes 5c−f. The title compounds represent rare examples of diethynylethenes in which a constituting methylene has been replaced by a phosphorus center. The formation of both isomers can be rationalized by a common pathway that involves isomeric allenyllithium species. Spectroscopic, electrochemical, and theoretical investigations show that the phosphorus heteroatoms are an intrinsic part of the compounds’ π−systems and lead to decreased HOMO−LUMO gaps compared to those in all-carbon-based reference compounds.
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| 7. |
- Andersson, Claes-Henrik, et al.
(författare)
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Synthesis and IR Spectroelectrochemical Studies of a [60]Fulleropyrrolidine-(tricarbonyl)chromium Complex : Probing C-60 Redox States by IR Spectroscopy
- 2011
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Ingår i: European Journal of Inorganic Chemistry. - : John Wiley & Sons. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :11, s. 1744-1749
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis of a new fulleropyrrolidine-(tricarbonyl)chromium complex: 1-methyl-2-(4-methoxyphenyl)-3,4-[60]fulleropyrrolidine-(tricarbonyl)chromium is described together with its characterization by IR, NMR and cyclic voltammetry. IR spectro-electrochemistry has been used to probe the redox level of the fullerene derivative via the relative position of the vibrational bands of the CO ligands, which are sensitive to the electronic state of the complex. Other strategies to incorporate a tricarbonylchromium moiety to fullerene C60 are also briefly discussed and evaluated.
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| 8. |
- Bedin, Michele, 1984-, et al.
(författare)
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Dinuclear iron and manganese complex with an asymmetric ligand
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Three complexes using the same asymmetric and dinucleating ligand DPCPMP (2-(N-(3-((bis((pyridin-2-yl)methyl)amino)methyl)-2-hydroxy-5-methylbenzyl)-N-((pyridin-2-yl)methyl)amino acetic acid) have been synthesised. The ligand contains one pocket with three nitrogen donors and another pocket with two nitrogen donors and one oxygen donor. The complexes were containing two iron ions ([Fe2(DPCPMP)(CH3COO)2]), two manganese ions ([Mn2(DPCPMP)(CH3COO)2]) or one iron and one manganese ion ([FeMn(DPCPMP)(CH3COO)2]) mimicing the metal content in the three different subclasses of class I ribonucleotide reductases. The asymmetric ligand was chosen in order to investigate if a small alteration of the coordiantion environment (pyridine versus carboxylate donor) could steer the metal ions in the heterobimetallic complex into a specific pocket of the ligand or not. The complexes have been characterized and investigated with mass spectrometry, electrochemistry, IR, UV-vis, EPR and Mössbauer spectroscopy. From CV and Mössbauer spectroscopy of the heterobimetallic complex it is proposed that the asymmetry is not able to steer the metals into different pockets and instead a mixture of two different isomers is created in the synthesis.
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| 9. |
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| 10. |
- Arkhypchuk, Anna, 1984-
(författare)
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Novel Approaches to Phosphorus-containing Heterocycles and Cumulenes
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Fast development in all areas of life and science over the last 50 years demands versatile, energy efficient and cheap materials with specific but easily tuneable properties which can be used for example in organic light emitting diodes (OLEDs), thin-film transistors, photovoltaic cells, etc. This thesis is devoted to the development of novel synthetic approaches to molecules with potential applications in the field of molecular electronics. The acquisition of a detailed mechanistic understanding of the newly developed reactions is central to the work presented in this thesis.The first chapter is dedicated to the development of a new procedure for the preparation of phospha-Wittig-Horner (pWH) reagents, i.e. a reagents that has been known to convert carbonyl compounds into compounds with P=C double bonds. Each step of the synthetic sequence, i.e. preparation of the starting P,P-dichlorophosphines, their phosphorylation using the Michaelis-Arbuzov protocol, coordination to the metal centre and final hydrolysis, are presented in detail. A possible route to uncoordinated pWH reagents is also discussed.The second chapter focuses on the reactivity of the pWH reagents with acetone under different reaction conditions. The results show how changes in the ratio of starting material vs. base as well as reaction time or structure of the pWH reagent can influence the reaction outcome and the stability of the obtained products. The possibility to prepare unusual phosphaalkenes with unsaturated P-substituents is presented.The third chapter of the thesis is dedicated to the reactivity of pWH reagents towards symmetric and asymmetric ketones which contain one or two acetylene units. The proposed mechanisms of the reactions are studied by means of in situ FTIR spectroscopy as well as theoretical calculations. Physical-chemical properties of oxaphospholes, cumulenes and bisphospholes are presented.The last chapter is dedicated to reactivity studies of pWH reagents towards ketenes, and the exploration of a reliable route to 1-phosphaallenes. Detailed mechanistic studies of the pWH reaction that are based on the isolation and crystallographic characterization of unique reaction intermediates are presented. The reactivity of phosphaallenes towards nucleophiles such as water and methanol are examined.In summary, this thesis presents synthetic routes to novel phosphorus-containing molecules, together with detailed studies of the reaction mechanisms of the observed transformations.
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