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| 2. |
- Johansson, Adam Johannes, 1976-
(författare)
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Biomimetic Transition Metal Catalysts : Insights from Theoretical Modeling
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The scientific interest in the chemistry of synthetic transition metal complexes is motivated by at least two arguments:1.These can be regarded as models of biological transition metal complexes, e.g. metalloenzymes, whose functions can be difficult to reveal in detail due to their complexity.2.Transition metal complexes are used for catalytic purposes in the industrial synthesis of chemicals. There is a large potential for further development of this technology, which can be motivated both by economic and environmental arguments.In the present thesis, density functional theory (a quantum mechanical method) has been applied to model reactions involving synthetic iron and copper complexes in solution. The complexity of the solvent environment is a challenging problem for theoretical investigations and a significant part of the theses has been to investigate the mechanistic effects of metal-coordinating solvent molecules, Lewis bases and counter ions. For example, it is explained why the cleavage of the O-O bond in heme-diiron-peroxides is faster in the presence of a coordinating Lewis base. Furthermore, the experimentally observed structure-activity relationship between the Fe(III)(µ-O)2Fe(IV) and (H2O)Fe(III)(µ-O)Fe(IV)O motifs is given an explanation. In addition, the present thesis presents a systematic investigation of how the self-interaction error in density functional theory (DFT) affects the modeling of transition metal catalysis.
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| 3. |
- Olsson, Christian, et al.
(författare)
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Heparin-coated cardiopulmonary bypass circuits reduce circulating complement factors and interleukin-6 in paediatric heart surgery
- 2000
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Ingår i: Scandinavian Cardiovascular Journal. - 1401-7431 .- 1651-2006. ; 34:1, s. 33-40
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Tidskriftsartikel (refereegranskat)abstract
- Children are sensitive to the inflammatory side effects of cardiopulmonary bypass (CPB). Our intention was to investigate if the biocompatibility benefits of heparin-coated CPB circuits apply to children. In 20 operations, 19 children were randomized to heparin-coated (group HC, n = 10) or standard (group C, n = 10) bypass circuits. Plasma levels of acute phase reactants, interleukins, granulocytic proteins and complement factors were measured. All were significantly elevated after CPB. Levels of complement factor C3a (851 (791-959)ng/ml [median with quartiles] in group C, 497 (476-573)ng/ml in group HC, p < 0.001), Terminal Complement Complex (114 (71-130) AU/ml in group C, 35.5 (28.9-51.4) AU/ml in group HC, p < 0.001), and interleukin-6 (570 (203-743) pg/ml in group C, 168 (111-206)pg/ml in group HC, p = 0.005), were significantly reduced in group HC. Heparin-coated CPB circuits improve the biocompatibility of CPB during heart surgery in the paediatric patient population, as reflected by significantly reduced levels of circulating complement factors and interleukin-6.
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| 4. |
- Abdel-Magied, Ahmed F., et al.
(författare)
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Chemical and Photochemical Water Oxidation Mediated by an Efficient Single-Site Ruthenium Catalyst
- 2016
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631 .- 1864-564X. ; 9:24, s. 3448-3456
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Tidskriftsartikel (refereegranskat)abstract
- Water oxidation is a fundamental step in artificial photosynthesis for solar fuels production. In this study, we report a single-site Ru-based water oxidation catalyst, housing a dicarboxylate-benzimidazole ligand, that mediates both chemical and light-driven oxidation of water efficiently under neutral conditions. The importance of the incorporation of the negatively charged ligand framework is manifested in the low redox potentials of the developed complex, which allows water oxidation to be driven by the mild one-electron oxidant [Ru(bpy)(3)](3+) (bpy = 2,2'-bipyridine). Furthermore, combined experimental and DFT studies provide insight into the mechanistic details of the catalytic cycle.
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| 5. |
- Antonsson, H, et al.
(författare)
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VIBRATIONAL MOTION AND GEOMETRICAL STRUCTURE IN ADSORBED CO STUDIED BY CORE LEVEL PHOTOELECTRON-SPECTROSCOPY
- 1990
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048. ; 54, s. 601-613
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Tidskriftsartikel (refereegranskat)abstract
- High resolution core level spectra from CO adsorbed on clean and hydrogen precovered Ni(100) and CO adsorbed on Cu(100) are presented. The core level binding energy is shown to be sensitive to the adsorption site. Cluster calculations reproduce the general trend of the binding energy shifts between the on top and hollow sites of CO/Ni(100). In the coadsorption system CO/H/Ni(100) three different adsorption sites have been observed with a maximum binding energy shift of 2.6 eV for the Ols level. The temperature dependence of the Cls and Ols line profiles in CO/Ni(100) has been carefully investigated. The temperature dependent broadening is due to thermal excitations of frustrated translations parallel to the surface. The spectra from CO on Cu(100) show no temperature dependence below 200K.
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| 6. |
- Arafa, Wael A. A., et al.
(författare)
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Dinuclear manganese complexes for water oxidation : evaluation of electronic effects and catalytic activity
- 2014
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 16:24, s. 11950-11964
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Tidskriftsartikel (refereegranskat)abstract
- During recent years significant progress has been made towards the realization of a sustainable and carbon-neutral energy economy. One promising approach is photochemical splitting of H2O into O-2 and solar fuels, such as H-2. However, the bottleneck in such artificial photosynthetic schemes is the H2O oxidation half reaction where more efficient catalysts are required that lower the kinetic barrier for this process. In particular catalysts based on earth-abundant metals are highly attractive compared to catalysts comprised of noble metals. We have now synthesized a library of dinuclear Mn-2 (II,III) catalysts for H2O oxidation and studied how the incorporation of different substituents affected the electronics and catalytic efficiency. It was found that the incorporation of a distal carboxyl group into the ligand scaffold resulted in a catalyst with increased catalytic activity, most likely because of the fact that the distal group is able to promote proton-coupled electron transfer (PCET) from the high-valent Mn species, thus facilitating O-O bond formation.
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| 7. |
- Bassan, Arianna, et al.
(författare)
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A Density Functional Study of a Biomimetic Non-Heme Iron Catalyst : Insights into Alkane Hydroxylation and Olefin Oxidation by a Formally HO-Fe(V)=O Oxidant
- 2004
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 11:2, s. 692-705
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Tidskriftsartikel (refereegranskat)abstract
- The reactivity of [HO(tpa)FeVO] (TPA=tris(2-pyridylmethyl)amine), derived from OO bond heterolysis of its [H2O(tpa)FeIIIOOH] precursor, was explored by means of hybrid density functional theory. The mechanism for alkane hydroxylation by the high-valent iron–oxo species invoked as an intermediate in Fe(tpa)/H2O2 catalysis was investigated. Hydroxylation of methane and propane by HOFeVO was studied by following the rebound mechanism associated with the heme center of cytochrome P450, and it is demonstrated that this species is capable of stereospecific alkane hydroxylation. The mechanism proposed for alkane hydroxylation by HOFeVO accounts for the experimentally observed incorporation of solvent water into the products. An investigation of the possible hydroxylation of acetonitrile (i.e., the solvent used in the experiments) shows that the activation energy for hydrogen-atom abstraction by HOFeVO is rather high and, in fact, rather similar to that of methane, despite the similarity of the HCH2CN bond strength to that of the secondary CH bond in propane. This result indicates that the kinetics of hydrogen-atom abstraction are strongly affected by the cyano group and rationalizes the lack of experimental evidence for solvent hydroxylation in competition with that of substrates such as cyclohexane.
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| 9. |
- Bassan, Arianna, et al.
(författare)
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A Theoretical Study of the Cis-Dihydroxylation Mechanism in Naphthalene 1,2-dioxygenase
- 2004
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Ingår i: Journal of Biological Inorganic Chemistry. - : Springer Science and Business Media LLC. - 0949-8257 .- 1432-1327. ; 9:4, s. 439-452
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic mechanism of naphthalene 1,2-dioxygenase has been investigated by means of hybrid density functional theory. This Rieske-type enzyme, which contains an active site hosting a mononuclear non-heme iron(II) complex, uses dioxygen and two electrons provided by NADH to carry out the cis-dihydroxylation of naphthalene. Since a (hydro)peroxo-iron(III) moiety has been proposed to be involved in the catalytic cycle, it was probed whether and how this species is capable of cis-dihydroxylation of the aromatic substrate. Different oxidation and protonation states of the Fe–O2 complex were studied on the basis of the crystal structure of the enzyme with oxygen bound side-on to iron. It was found that feasible reaction pathways require a protonated peroxo ligand, FeIII–OOH; the deprotonated species, the peroxo-iron(III) complex, was found to be inert toward naphthalene. Among the different chemical patterns which have been explored, the most accessible one involves an epoxide intermediate, which may subsequently evolve toward an arene cation, and finally to the cis-diol. The possibility that an iron(V)-oxo species is formed prior to substrate hydroxylation was also examined, but found to implicate a rather high energy barrier. In contrast, a reasonably low barrier might lead to a high-valent iron-oxo species [i.e. iron(IV)-oxo] if a second external electron is supplied to the mononuclear iron center before dioxygenation.
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