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Structural and Photochemical Properties of Fe(III) Complexes with Mixed Donor a-Hydroxy Acid ChelatesGrabo, Jennifer January 2015 (has links)
No description available.
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Collisional and photoexcitation of transition metal clustersParry, Imogen Sophie January 2014 (has links)
The properties of transition metal clusters differ from those of both atomic and bulk size regimes. Such clusters are incompletely understood and potentially useful, making them attractive targets for further study. The very smallest clusters studied in this thesis (CuO, Cu<sub>2</sub> and Cu<sub>3</sub>) have been investigated with velocity map imaging. 1+1' photodissociation of CuO X <sup>2</sup>Π<sub>3/2</sub> was observed, via the C, D, E, F and H states of CuO. CuO* was photodissociated to form Cu(<sup>2</sup>D<sub>3/2</sub>) + O(<sup>1</sup>D<sub>2</sub>). D<sub>0</sub>(CuO) was determined to be 3.041±0.030 cm<sup>-1</sup>. Non-resonant three-photon Cu<sub>2</sub> photodissociation occurred throughout the energy range studied to produce one ground-state and one highly-excited copper atom,Cu*. Cu* was ionised by a single additional visible photon. Nearly all Cu* atoms with internal energies between 41000 and 53000 cm<sup>-1</sup> were observed. D<sub>0</sub>(Cu<sub>2</sub>) has been calculated to be 1.992±0.037 eV. Features arising from photodissociation of Cu<sub>3</sub> were observed in the Cu<sup>+</sup> and Cu<sub>2</sub><sup>+</sup> ion yield spectra and images. Their structure was ill-resolved due to uncertainties in the internal energy of both parent Cu<sub>3</sub> and product Cu<sub>2</sub>. These features correspond to single-photon dissociation of Cu<sub>3</sub> to produce metastable D-states of the copper atom and vibrationally excited Cu<sub>2</sub>. One series of features implies a previously-unobserved state of either Cu<sub>2</sub> or Cu<sub>3</sub>. Rh<sub>n</sub>N<sub>2</sub>O<sup>+</sup> and Rh<sub>n</sub>ON<sub>2</sub>O<sup>+</sup> (n=5, 6) were collisionally activated in collision-induced dissociation (CID) experiments with Ar and <sup>13</sup>CO. These experiments were carried out in a Fourier Transform Ion Cyclotron Resonance(FT-ICR)spectrometer. Argon collisions induced both N<sub>2</sub>O desorption and N<sub>2</sub>O reduction. The branching ratios observed reproduced those seen in prior IR-MPD experiments. <sup>13</sup>CO was observed to chemisorb to the cluster upon collision, activating not only N<sub>2</sub>O desorption and reduction but also CO oxidation. Formation of CO2 was noted to be particularly rapid on the n=5 cluster compared to the n=6 cluster. Reactions of Rh<sub>n</sub>N<sub>2</sub>O<sup>+</sup> (n=4-6) clusters were also activated by black body radiation. This technique is known as BIRD - black-body induced infrared radiative dissociation. These studies revealed that the N<sub>2</sub>O desorption barrier exceeds the N<sub>2</sub>O reduction barrier on all clusters studied, but that the entropic favourability of desorption increases its rate relative to reduction with increasing cluster internal energy. The BIRD rate was much reduced upon cooling the ICR cell to 100 K. A further test of the BIRD mechanism increased the number of N<sub>2</sub>O ligands and hence the absorption rate. An approximately linear increase in the dissociation rate of Rh<sub>n</sub>(N<sub>2</sub>O)<sub>m</sub><sup>+</sup> was observed with index m. Deviations from linearity were caused by variations in the N<sub>2</sub>O desorption rate. In the case of Rh<sub>5</sub>(N<sub>2</sub>O)<sub>m</sub><sup>+</sup>, desorption rates corresponded closely to N<sub>2</sub>O binding energies calculated by density functional theory. The system was modelled using a master equation approach.
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Subvalent Cluster Compounds and Synthesis in Alternative Reaction MediaÅkerstedt, Josefin January 2012 (has links)
With the aim of finding alternative reaction media for the synthesis of subvalent main group and transition metal cluster compounds, traditionally made through solid state reactions or in superacidic media, different alternative reaction media have been explored in this work. Room-temperature ionic liquids are amongst the more unconventional reaction media used. The syntheses performed have been aimed at both anionic and cationic cluster and the main tools used for characterization have been different X-ray diffraction and spectroscopic techniques. Selected ionic liquids have along with dichloromethane been shown to work as alternative reaction media for room temperature synthesis of the Bi5[GaCl4]3 salt. The salt containing the subvalent naked bismuth polycation Bi5 3+ was isolated from reduction reactions of BiCl3 in Ga/GaCl3-dichloromethane respectively Ga/GaCl3-ioinc liquid media. Three different classes of ionic liquids based on phosphonium-, imidazolium- and pyrrolidinium- salts have been used in synthesis. Homopolyatomic clusters from the lighter Group 15 element arsenic have also been studied. Solutions from the oxidative and reductive reaction routes of arsenic and AsCl3 in Lewis acidic toluene media were studied by EXAFS spectroscopy. The results were evaluated using molecular dynamics simulations of arsenic clusters. A discussion on how the calculated As4 cluster model relates to the experimental data resulted from this study. In terms of homopolyatomic anionic clusters the [K+(2,2,2-crypt)]2Ge9 2- compound containing the naked Ge9 2- anionic cluster has been isolated. The crystallographic investigation of [K+(2,2,2-crypt)]2Ge9 2- shows Zintl cluster anion Ge9 2- to be tricapped trigonal-prismatic with a symmetry very close to D3h. A chemical bonding analysis reveals two local minima of D3h symmetry and the cluster interaction scheme to be based on highly delocalised bonding. Ligand supported transition metal clusters from tungsten and palladium have also been prepared. Reduction of WCl6 in a reaction mixture of ionic liquid and co-solvent toluene resulted in tritungsten decachloride; W3Cl10(MeCN)3, being formed. Furthermore, palladium sandwich compounds; [Pd2(Ga2Cl7)(C7H8)2], [Pd2(GaCl4)(C9H12)2]∙C9H12 and [Pd2(Ga2Cl7)(C6H5Cl)2] have been prepared using GaCl3-arene reaction media. / <p>QC 20121212</p>
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Threshold photo-ionisation and density functional theory studies of metal-carbide clusters.Dryza, Viktoras January 2008 (has links)
Neutral gas-phase metal-carbide clusters are generated by laser ablation and are detected in the constructed time-of-flight mass-spectrometer by laser ionisation. Photo-ionisation efficiency (PIE) experiments are performed on the metal-carbide clusters to determine their ionisation potentials (IPs). Complimentary density functional theory (DFT) calculations are performed on the energetically favorable structural isomers of the metalcarbide clusters. Comparison between the calculated IPs of the isomers and the experimental IP allows the carrier of the observed ionisation onset for a metal-carbide cluster to be assigned. The niobium-carbide clusters Nb₃Cy (y = 0–4), Nb₄Cy (y = 0–6) and Nb₅Cy (y = 0–6) are examined by PIE experiments and DFT calculations. The IPs of the niobium-carbide clusters are found to be either left reasonably unchanged from the IPs of the bare metal clusters or moderately reduced. The clusters Nb₃C₂, Nb₄C₄, Nb₅C₂ and Nb₅C₃ display the largest IP reductions for their corresponding cluster series. The structures assigned to the IPs of the Nb₃Cy (y = 1–3) clusters are based on the carbon atoms attaching to the niobium faces and/or niobium-niobium edges of the triangular Nb₃ cluster. However, for Nb₃C₄ the ionisation onset is assigned to a low-lying isomer, which contains a molecular C₂ unit, rather than the lowest energy isomer, a niobium atom deficient 2×2×2 face-centred cubic (fcc) nanocrystal structure. The structures assigned to the IPs of the Nb₄Cy (y = 1–4) clusters are based on the carbon atoms attaching in turn to the niobium faces of the tetrahedral Nb₄ cluster, developing a 2×2×2 fcc nanocrystal structure for Nb₄C₄. For Nb₄C₃ two ionisation onsets are observed; one weak onset at low energy and another more intense onset at high energy. It is proposed that the two onsets are due to ionisation from both a metastable ³A₁ state and the ground ¹A₁ state of the lowest energy isomer. The ionisation onsets of Nb₄C₅ and Nb₄C₆ are also proposed to originate from metastable triplet states of the lowest energy isomers, with the transitions from the ground singlet states calculated to be greater than the highest achievable photon energy in the laboratory. The structures of Nb₄C₅ and Nb₄C₆ have one and two carbon atoms in a 2×2×2 fcc nanocrystal substituted with molecular C₂ units, respectively. The structures assigned to the IPs of the Nb₅Cy (y = 1–6) clusters are based on the underlying Nb₅ cluster being in either a “prolate” or “oblate” trigonal bipyramid geometry; the former has six niobium faces available for carbon addition, while the latter has two niobium butterfly motifs and two niobium faces available for carbon addition. Both the structures of Nb₅C₅ and Nb₅C₆ have the underlying Nb₅ cluster in the oblate trigonal bipyramid geometry and contain one and two molecular C₂ units, respectively. The tantalum-carbide clusters Ta₃Cy (y = 0–3), Ta₄Cy (y = 0–4) and Ta₅Cy (y = 0–6) are examined by PIE experiments and DFT calculations. The IPs of the tantalum-carbide clusters in each series show trends that are very similar to the corresponding iso-valent niobium-carbide cluster series, although the IP reductions upon carbon addition are smaller for the former. For the vast majority of tantalum-carbide clusters, the same structural isomer is assigned to the ionisation onset as that assigned for the corresponding niobium-carbide cluster. Bimetallic tantalum-zirconium-carbide clusters are generated using a constructed double ablation cluster source. The Ta₃ZrCy (y = 0–4) clusters are examined by PIE experiments and DFT calculations. The IP trend for the Ta₃ZrCy cluster series is reasonably similar to that of the Ta₄Cy cluster series, although the IP reductions upon carbon addition are greater for the former. The structures assigned to the IPs of the Ta₃ZrCy (y = 1–4) clusters are based on the carbon atoms attaching in turn to the metal faces of the tetrahedral Ta₃Zr cluster. In summary, the work presented in this thesis demonstrates that the structures of metalcarbide clusters can be inferred by the determination of their IPs through PIE experiments in combination with DFT calculations on candidate structural isomers. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1347219 / Thesis (Ph.D.) - University of Adelaide, School of Chemistry and Physics, 2008
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Threshold photo-ionisation and density functional theory studies of metal-carbide clusters.Dryza, Viktoras January 2008 (has links)
Neutral gas-phase metal-carbide clusters are generated by laser ablation and are detected in the constructed time-of-flight mass-spectrometer by laser ionisation. Photo-ionisation efficiency (PIE) experiments are performed on the metal-carbide clusters to determine their ionisation potentials (IPs). Complimentary density functional theory (DFT) calculations are performed on the energetically favorable structural isomers of the metalcarbide clusters. Comparison between the calculated IPs of the isomers and the experimental IP allows the carrier of the observed ionisation onset for a metal-carbide cluster to be assigned. The niobium-carbide clusters Nb₃Cy (y = 0–4), Nb₄Cy (y = 0–6) and Nb₅Cy (y = 0–6) are examined by PIE experiments and DFT calculations. The IPs of the niobium-carbide clusters are found to be either left reasonably unchanged from the IPs of the bare metal clusters or moderately reduced. The clusters Nb₃C₂, Nb₄C₄, Nb₅C₂ and Nb₅C₃ display the largest IP reductions for their corresponding cluster series. The structures assigned to the IPs of the Nb₃Cy (y = 1–3) clusters are based on the carbon atoms attaching to the niobium faces and/or niobium-niobium edges of the triangular Nb₃ cluster. However, for Nb₃C₄ the ionisation onset is assigned to a low-lying isomer, which contains a molecular C₂ unit, rather than the lowest energy isomer, a niobium atom deficient 2×2×2 face-centred cubic (fcc) nanocrystal structure. The structures assigned to the IPs of the Nb₄Cy (y = 1–4) clusters are based on the carbon atoms attaching in turn to the niobium faces of the tetrahedral Nb₄ cluster, developing a 2×2×2 fcc nanocrystal structure for Nb₄C₄. For Nb₄C₃ two ionisation onsets are observed; one weak onset at low energy and another more intense onset at high energy. It is proposed that the two onsets are due to ionisation from both a metastable ³A₁ state and the ground ¹A₁ state of the lowest energy isomer. The ionisation onsets of Nb₄C₅ and Nb₄C₆ are also proposed to originate from metastable triplet states of the lowest energy isomers, with the transitions from the ground singlet states calculated to be greater than the highest achievable photon energy in the laboratory. The structures of Nb₄C₅ and Nb₄C₆ have one and two carbon atoms in a 2×2×2 fcc nanocrystal substituted with molecular C₂ units, respectively. The structures assigned to the IPs of the Nb₅Cy (y = 1–6) clusters are based on the underlying Nb₅ cluster being in either a “prolate” or “oblate” trigonal bipyramid geometry; the former has six niobium faces available for carbon addition, while the latter has two niobium butterfly motifs and two niobium faces available for carbon addition. Both the structures of Nb₅C₅ and Nb₅C₆ have the underlying Nb₅ cluster in the oblate trigonal bipyramid geometry and contain one and two molecular C₂ units, respectively. The tantalum-carbide clusters Ta₃Cy (y = 0–3), Ta₄Cy (y = 0–4) and Ta₅Cy (y = 0–6) are examined by PIE experiments and DFT calculations. The IPs of the tantalum-carbide clusters in each series show trends that are very similar to the corresponding iso-valent niobium-carbide cluster series, although the IP reductions upon carbon addition are smaller for the former. For the vast majority of tantalum-carbide clusters, the same structural isomer is assigned to the ionisation onset as that assigned for the corresponding niobium-carbide cluster. Bimetallic tantalum-zirconium-carbide clusters are generated using a constructed double ablation cluster source. The Ta₃ZrCy (y = 0–4) clusters are examined by PIE experiments and DFT calculations. The IP trend for the Ta₃ZrCy cluster series is reasonably similar to that of the Ta₄Cy cluster series, although the IP reductions upon carbon addition are greater for the former. The structures assigned to the IPs of the Ta₃ZrCy (y = 1–4) clusters are based on the carbon atoms attaching in turn to the metal faces of the tetrahedral Ta₃Zr cluster. In summary, the work presented in this thesis demonstrates that the structures of metalcarbide clusters can be inferred by the determination of their IPs through PIE experiments in combination with DFT calculations on candidate structural isomers. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1347219 / Thesis (Ph.D.) - University of Adelaide, School of Chemistry and Physics, 2008
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First-principles calculations of solid-state transition metal NMR parameters in functional inorganic materials / Calculs de paramètres RMN de métaux de transition des composés inorganiques de l'état solideNguyen, Thui Thuong 09 April 2015 (has links)
Ce manuscrit de thèse est dédié aux calculs quantiques de paramètres de spectroscopie de résonance magnétique nucléaire (RMN) de métaux de transition dans des composés inorganiques de l’état solide. Le manuscrit est divisé en cinq parties. La première partie présente les atouts de la spectroscopie RMN en tant que technique d’investigation de composés inorganiques de l’état solide. Dès lors que le noyau sondé est un métal de transition, l’expérience doit être complétée par des calculs quantiques afin d’interpréter au mieux les données expérimentales. La seconde partie du manuscrit est dédiée à la description de la RMN et des outils méthodologiques utilisés dans ce travail. Le troisième chapitre est dédié au calcul du déplacement chimique de l’isotope 95 du molybdène dans des clusters halogénés de formule [Mo6X14]2- (X = Cl, Br, I). Une attention particulière est donnée à l’influence des effets de solvatation sur le calcul. Le quatrième chapitre est dédié à l’étude des composés A6Re3Mo3S8(CN)5 (A = K, Cs) dont la structure cristallographique est basée sur un motif octaédrique hétéronucléaire Re3Mo3S8(CN)6. La résolution structurale par diffraction des rayons X sur monocristal n’ayant pas permis de résoudre le problème de la distribution des métaux de transition dans l’octaèdre, une étude spectroscopique in silico sur la base de calculs DFT moléculaires et périodiques a été entreprise. Dans le dernier chapitre, des composés hétéronucléaires de formule [Ln6-6xLn6xO(OH)8(NO3)6(H2O)12]2+ (Ln = Pr-Lu, Y) ont été étudiés du point de vue théorique afin de mieux comprendre les données spectroscopiques collectées. / This work is devoted to the calculations of nuclear magnetic resonance (NMR) parameters of transition metal nuclei in inorganic solid-state materials using first-principles calculations. The manuscript is divided in five chapters. The first one shows that NMR is an interesting spectroscopic method to gain some information on the properties of inorganic materials. As far as the probed nucleus is a transition metal, experiments must be completed with quantum chemical calculations in order to better interpret the spectroscopic data. The second chapter is devoted to the quantum chemical tools that are necessary to the understanding of this work are presented. The third chapter deals with the computations of 95Mo NMR parameters of [Mo6X14]2- (X = Cl, Br, I) octahedral clusters. A special attention is paid to the influence of solvation effects on the computed NMR parameters. The fourth chapter is devoted to the study of A6Re3Mo3S8(CN)5 (A = K, Cs) compounds. Their crystal structures are based on a heteronuclear octahedral motif Re3Mo3S8(CN)6. Since X-ray diffraction refinements did not solve the colouring problem in the octahedron, an in silico spectroscopic study has been carried out using molecular and periodic DFT calculations. The last chapter of this report deals with heteronuclear polyoxolanthanides that have been studied using first-principles calculations in order to better understand their 89Y NMR spectra.
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TETRANUCLEAR CU(I) CLUSTERS WITH TUNABLE EMISSIONS BASED ON REMOTE STERIC CONTROLBenjamin M Washer (14213087) 05 December 2022 (has links)
<p>Solid-state (SS) luminescent materials are an important class of materials in a myriad of technological applications including light-emitting devices (LEDs) and displays, SS lasers, sensors, imaging agents, etc. Unfortunately, the design of efficient SS emitters is often plagued by sensitivity to environment/matrix (e.g. aggregation-induced quenching, AIQ), competing non-radiative relaxation pathways, and complicated emission mechanisms that are difficult to systematically study and tune. Copper-based systems have been proven to be good candidates for SS emissive materials due to their low-cost, high synthetic variation and well-defined features. Examples of copper-cluster systems, specifically, have been shown to be highly stable, exhibit high photoluminescent quantum yields (ΦPL), and are often relatively insensitive to environmental changes. However, many of these systems are complicated in nature, and often evoke additional relaxation pathways. To mitigate these issues, tetranuclear Cu(I)-pyrazolate complexes have been made which exhibit high ΦPL, matrix insensitivity and proceed through one major radiative emission pathway: cluster-centered based phosphorescence (3CC). The pyrazoles are highly tunable, and by increasing the size of the ligand substituents (H, F, Cl/Me/Br), a rigidochromic effect is observed, causing a significant blue-shift in their photoluminescence, making these viable materials for organic LEDs (OLEDs), especially in the deep-blue region. Furthermore, by increasing the chain length of the ligand substituent (e.g., Me → Et), another material which exhibits stimuli-responsive luminochromism in response to solvent vapor or heat can be achieved. This material exhibits blue ↔ green rigidochromic luminescence in response to stimuli via isomerization of the ethyl units from exo ↔ endo resulting in additional steric effects that effectively prevent rigidification of the Cu4 cluster. This additional phenomenon opens the door for further exploration of Cu(I)-pyrazolate complexes for stimuli-responsive luminescent materials (SRLMs) applications.</p>
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SPECTROSCOPY AND FORMATION OF LANTHANUM-HYDROCARBON COMPLEXESCao, Wenjin 01 January 2018 (has links)
Lanthanum-mediated bond activation reactions of small hydrocarbon molecules, including alkenes, alkynes, and alkadienes, were carried out in a laser vaporization metal cluster beam source. Time-of-flight mass spectrometry and mass-analyzed threshold ionization (MATI) spectroscopy, in combination with quantum chemical and multi-dimensional Franck-Condon factor calculations, were utilized to identify the reaction products and investigate their geometries, electronic structures, and formation mechanisms.
La-hydrocarbon association was only observed in the reaction of La with isoprene. C-H bond activation was observed in all reactions, hydrogen elimination was observed as the prominent reaction for the alkenes (2-butene, isobutene, 1-pentene, and 2-pentene), alkynes (1-butyne, 2-butyne, and 1-pentyne), and 1,4-pentadiene, and C-C bond activation was observed for the five-membered hydrocarbons (1-pentene, 2-pentene, 1-pentyne, isoprene, and 1,4-pentadiene).
The La-hydrocarbon radicals formed in these reactions had lanthanacyclic structures in various sizes, and each of the La-hydrocarbon complexes had a doublet ground state with a 6s1 La-based electron configuration. Ionization removed the 6s electron, and the resultant ion was in a singlet state. Formations of dehydrogenated products were either through a concerted hydrogen elimination process or the dehydrogenation after ligand isomerization. The C-C bond activation proceeded through La-assisted hydrogen migration, followed by C-C bond cleavage, or vice versa.
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Mechanistic insights into carbon monoxide and CoA binding at the Ni,Ni-[4Fe-4S] active site of the acetyl-CoA synthase from Carboxydothermus hydrogenoformansKreibich, Julian 23 August 2021 (has links)
Die Acetyl-CoA Synthase (ACS) beinhaltet ein einzigartiges Metallcluster (Cluster A) in seinem aktiven Zentrum, welches wichtig für ein autotrophes Wachstum von Bakterien und Archaeen ist, die den reduktiven Acetyl-CoA-Weg nutzen. Der letzte Schritt dieses Syntheseweges wird von der ACS am proximal zum [4Fe-4S] Cluster liegenden Ni ion katalysiert (Nip). In meiner Arbeit wurde die ACS von Carboxydothermus hydrogenoformans (ACSCh) auf seine Ligandenbindung untersucht und in verschiedenen Konformationen kristallisiert.
Zuerst wurde die ACSCh in einer neuen Konformation (ACSCh-closed) kristallisiert und deren Struktur mit einer Auflösung von 2.1 Å bestimmt. Diese wies einen geringeren Kontakt zur Solventumgebung auf als die vorher bekannte Struktur der ACSCh (ACSCh-open, PDB-ID: 1RU3). Das Cluster A der ACSCh-closed unterscheidet sich von der ACSCh-open in der Koordination des Nip, welches verzerrt tetraedrisch koordiniert in ACSCh-closed vorliegt und quadratisch planar in ACSCh-open. Eine Analyse des Modells wies einen molekularen Tunnel auf, der nur in ACSCh-closed vorhanden ist, welcher als CO-Kanal zur Substratversorgung dienen könnte.
Zweitens wurde die Kristallstruktur einer CO gebunden ACSCh-closed mit einer Auflösung von 2.0 Å gelöst. Darin wurde eine Elektronendichte am Nip identifiziert, die als CO überzeugend modelliert werden konnte. CO bindet am ebenfalls verzerrt tetraedrisch koordinierten Nip. Die Konformationsänderung von ACSCh-open zu ACSCh-closed scheint der entscheidende Schritt zu sein, um CO zur Bindungsstelle zu leiten.
Die dritte Struktur zeigt eine CoA gebundene ACSCh Struktur mit einer Auflösung von 2.3 Å. CoA bindet am Nip, wobei Nip quadratisch planar koordiniert wird. Die Gegenwart von CoA wurde mit Berechnungen verschiedener Elektronendichte-Karten für CoA validiert.
Die Bindung von CO und CoA an ACSCh wurde zudem mittels isothermaler Titrationskalorimetrie weiter charakterisiert. Dabei bindet CoA enthalpisch getrieben mit einem KD von 3.1 µM und CO entropisch getrieben mit einem KD von 9.4 µM an ACSCh. / The acetyl-CoA synthase (ACS) harbors a unique metal cluster (cluster A) in its active site, which is important for bacteria and archaea to survive in autotrophic growth using the reductive acetyl-CoA. The last step of this pathway is catalyzed by ACS at the Nip, the Ni ion proximal to the [4Fe-4S] cluster. In my study, the monomeric ACS of Carboxydothermus hydrogenoformans (ACSCh) was studied in its ligand binding and crystallized in different forms.
At first, an ACSCh structure was solved in a new conformation at dmin of 2.1 Å and less solvent exposed (called ACSCh-closed) than the known structure of ACSCh (called ACSCh-open, PDB-ID:1RU3). The cluster A of ACSCh-closed differs to that of ACSCh-open in the coordination of the proximal Ni, which is distorted tetrahedrally coordinated in ACSCh-closed and square planar coordinated in ACSCh-open. Analysis of the model revealed a molecular tunnel that is only present in ACSCh-closed, which might act as CO channel for substrate delivery.
Secondly, a CO-bound ACSCh-closed crystal was obtained and solved at a resolution of 2.0 Å. An electron density fitting with a diatomic ligand at the Nip site was clearly identified and modeled as a CO molecule. CO binds at the Nip site completing the tetrahedral coordination geometry of Nip. The conformational switch between open and closed is responsible for CO migration and binding to the catalytic site.
A third crystal structure depicts a CoA bound ACSCh structure at 2.3 Å resolution. CoA binds at the Nip which shows a square planar geometry. This was further supported by calculating different electron density maps for CoA.
The binding of CO and CoA to ACSCh has been characterized by isothermal calorimetry experiments. While CoA binding is enthalpically driven with a KD of 3.1 µM, CO binds to ACSCh by entropic contribution with a KD of 9.4 µM.
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THE ROLE OF ION TRANSFER IN NANODROPLET-MEDIATED ELECTRODEPOSITIONJoshua Reyes Morales (16925016) 05 September 2023 (has links)
<p dir="ltr">Nanoparticles have seen immense development in the past several decades due to their intriguing physicochemical properties. The modern chemist is interested not only in methods of synthesizing nanoparticles with tunable properties but also in the chemistry that nanoparticles can drive. While several methods exist to synthesize nanoparticles, it is often advantageous to put nanoparticles on a variety of conductive substrates for multiple applications (such as energy storage and conversion). Despite enjoying over 200 years of development, the electrodeposition of nanoparticles suffers from a lack of control over nanoparticle size and morphology. Understanding that structure-function studies are imperative to understand the chemistry of nanoparticles, new methods are necessary to electrodeposit a variety of nanoparticles with control over macro-morphology but also microstructure. When a nanodroplet full of a metal salt precursor is incident on the electrode biased sufficiently negative to drive electroplating, nanoparticles form at a shocking rate (on the order of microseconds to milliseconds). We start with the general nuts-and-bolts of the experiment (nanodroplet formation and methods for electrodeposition). The deposition of new nanomaterials often requires one to develop new methods of measurement, and we detail new measurement tools for quantifying nanoparticle porosity and nanopore tortuosity within single nanodroplets. Owing to the small size of the nanodroplets and fast mass transfer, the use of nanodroplets also allows the electrodeposition of high entropy alloy nanoparticles at room temperature. Electrodeposition in aqueous nanodroplets can also be combined with stochastic electrochemistry for a variety of interesting studies. We detail the quantification of the growth kinetics of single nanoparticles in single aqueous nanodroplets. Nanodroplets can also be used as tiny reactors to trap only a few molecules, and the reactivity of those molecules can be electrochemically probed and evaluated with time. Overall, this burgeoning synthetic tool is providing unexpected avenues of tunability of metal nanoparticles on conductive substrates. Moreover, there is little understanding of how ion transfer can affect the fundamental of nanoparticle synthesis with nanodroplet-mediated electrodeposition. This thesis details different experiments performed to study the role of ion transfer during the nucleation and growth of nanoparticles.</p>
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