Les ligands phosphasalen développés au sein du laboratoire peuvent être considérés comme les analogues phosphorés des ligands salen dont ils diffèrent par la présence de groupements iminophosphorane à la place des imines. L’introduction de ces fonctions a d’importantes conséquences sur les propriétés de ces ligands, qui sont plus électrodonneurs et plus flexibles que les dérivés salen correspondants, capables de stabiliser des métaux à haut degré d’oxydation. Ces ligands ont également un caractère redox non-innocent, une propriété très étudiée de nos jours tant en chimie de coordination qu’en catalyse.Dans la cadre de cette thèse, différents ligands ont été synthétisés en modifiant les différents paramètres au sein du ligand : les substituants du cycle phenolate, MeO vs. tBu (PsalentBu et PsalenOMe); les substituants du phosphore, alkyl vs. aryl (iPrPsalen); et le lien entre les deux azotes, avec l’introduction de différentes o-phenylenediamines à la place d’ethylenediamine, qui donne les ligands Psalophen, PsalophenOMe2, PsalophenMe and PsalophenCF3.Les complexes neutres de cuivre et nickel, ainsi que les produits de mono-oxydation ont été synthétisés et caractérisés. Pour déterminer précisément la structure électronique des complexes différentes techniques ont été utilisés : des spectroscopies UV-visible, RMN et RPE, voltampérométrie cyclique, diffraction de rayons X, mesures magnétiques à l’état solide (SQUID), ainsi que des calculs DFT.De manière générale ces travaux montrent que les phosphasalen sont mieux à même de stabiliser la densité de spin sur le métal, donnant en certains cas des complexes à haute valence (NiIII, CuIII) encore rares dans la littérature. Dans certains cas les observations expérimentales et les calculs pointent vers un état fondamental multiconfigurationel. Contrairement aux ligands salen, les complexes portant un lien aromatique entre les deux azotes dimerisent lors de l’oxydation. Afin de contrôler la densité électronique sur ce cycle, une série des complexes à ligands phosphasalophen ont été également étudies.Une synthèse de complexes phosphasalen de manganèse(II) et (III) a été également réalisée. La stabilisation des complexes oxo ou nitrido, ainsi que la catalyse d’oxydation ont été envisagés avec ces complexes et des résultats prometteurs ont été obtenus. / Phosphasalen ligands developed in our laboratory can be considered as the phosphorous analogues of salen ligands where the imines have been substituted by iminophosphorane functions. The presence of the P-N bond makes these ligands more electro-donating and more flexible than salen analogues. They are able to stabilize high-valent metal complexes, as in the case of a Ni phosphasalen complex, which was characterized as a NiIII complex in solution and in solid state. This was never obtained before with salen-type ligands.Phosphasalen ligands, as the salen ones, can act as redox non-innocent ligands. Therefore, upon oxidation either the ligand or the metal center can be oxidized depending on the relative energy of metal and ligand orbitals. This behavior has been deeply investigated in coordination chemistry and in catalysis.In order to elucidate the factors that influence the oxidation locus different ligands have been synthetized modifiying the phenolate subtituents, MeO vs. tBu (PsalentBu and PsalenOMe); the phosphorous substituents, alkyl vs. aryl (iPrPsalen); and the linker between the two nitrogen atoms, ethylenediamine vs. phenylenediamine (Psalophen, PsalophenOMe2, PsalophenMe and PsalophenCF3).The neutral and one-electron oxidized copper and nickel complexes were synthetized and characterized. In order to determine the electronic structure of the complexes a combination of different characterization techniques were used: UV-vis, EPR and NMR spectroscopies, cyclic voltammetry, X-ray diffraction, magnetic measurements (SQUID), as well as theoretical calculations.In a general manner, phosphasalen ligands favor a metal center oxidation in a higher extent than salen derivatives, leading in some cases to high-valent metal complexes (NiIII, CuIII), remaining rare cases in the literature. For some complexes, experimental observations and theoretical calculations point to the presence of multiconfigurational ground states. Contrary to salen, complexes bearing an aromatic linker between the two nitrogen atoms dimerize upon oxidation. In order to tune the electronic density in the central ring, a series of phosphasalophen complexes displaying different substituents in the aromatic bridge, have been studied.Manganese (II) and (III) phosphasalen complexes has been also studied. The stabilization of oxo and nitride complexes as well as catalytic applications have been targeted for these complexes and encouraging results have been obtained.

Redox reactions are crucial to biological processes that protect organisms against oxidative stress. Metalloenzymes, such as cytochrome c peroxidases which reduce excess hydrogen peroxide into water in the periplasm of multiple bacterial organisms, play a key role in detoxification mechanisms. While accurate computational tools can be used to simulate ground state redox potentials in biomolecules, adapting such approaches to properly describe redox reactions in transition metal complexes, particularly in hemes in heterogeneous protein environments, remains a significant challenge. Here we present the results of polarizable hybrid QM/MM studies of the reduction potentials of two heme sites in the cytochrome c peroxidase of Nitrosomonas europaea. The simulated redox potential of the catalytic site Low Potential (LP) is in good agreement with the experiment, while for the High Potential (HP) heme the computational estimate significantly overestimate the experimental value. We have found that environment polarization shifts the computed value of the redox potential of the catalytic LP heme by 1.3 V, while it does not affect that of the non-catalytic High Potential (HP) heme. We demonstrate that it is necessary to account for mutual polarization of heme site and the protein environment when describing redox processes, particularly those that involve more charged heme sites. We have explored the role of various factors such as heme geometries, axial ligands, propionate side chains, and electrostatic field of the protein in tuning the redox potentials of hemes in NeCcP. The fluctuations in computed vertical ionization and electron attachment energies are predominantly affected by fluctuations in the electrostatic field of the environment but not by fluctuations in heme geometries. We attribute the difference in computed LP and HP heme reduction potentials of 0.05 V and 1.15 V, respectively, to different axial ligands and electrostatic interactions of the hemes with the protein environment. / 2023-06-30T00:00:00Z

INTRODUCTION: Inflammatory bowel disease (IBD) is a complex, chronic, autoimmune disease of the gastrointestinal tract. Reactive oxygen species (ROS), a product of active leukocytes, have been implicated in the pathogenesis of IBD. The ability to reliably measure ROS in blood, urine, and stool samples could represent a new approach to assessing disease activity and response to therapy in pediatric patients with IBD. OBJECTIVES: To assess the relationship between redox measurements and clinical disease activity in pediatric patients with IBD. METHODS: Biological specimens, including stool, urine, blood plasma, and intestinal aspirates, were collected from patients at Boston Children’s Hospital. Each sample’s oxidation-reduction potential was measured by two oxidation-reduction potential probes (an Arrowdox probe and a Mettler Toledo probe). Probes were directly immersed into the sample, returning a millivolt measurement of oxidation-reduction potential. Linear regression was performed to explore the relationship between patient-reported outcome measures (PROMs) and redox measurements of biological specimens. Patients were also stratified by disease severity, and ANOVA testing was performed to test for differences in oxidation-reduction potential observed in patients with remittent, mild, moderate, and severe disease activity. RESULTS: Redox values in stool, urine, plasma, and intestinal aspirate did not significantly correlate with PROMs or differ significantly among groups categorized by disease severity. CONCLUSIONS: Measurements of oxidation-reduction potential from stool, urine, plasma, and intestinal aspirate do not appear to be useful for assessing disease severity in pediatric patients with inflammatory bowel disease.

<p>Thorium complexes primarily exist in the thermodynamically stable (IV) oxidation state with only a few low-valent thorium(III) and thorium(II) complexes having been isolated. As a result, redox chemistry with thorium at the metal center is synthetically challenging without carefully selected ligand systems. This redox-restricted nature of thorium(IV) makes redox-active ligands (RALs) an attractive option to facilitate multi-electron redox chemistry with thorium. In this work, first, a series of thorium(IV) complexes featuring the redox-active iminoquinone ligand and its derivatives, including the iminosemiquinone and amidophenolate species, were synthesized and characterized. Rare thorium oxygen multiple bonds were then accessed by exploiting the RALs on the thorium center and using dioxygen in dry air. Other oxidation chemistry was attempted with the thorium amidophenolate complexes as well. Second, armed with the knowledge of synthesizing multiple bonds with thorium(IV) complexes, similar chemistry was explored with cerium as it is in the same group as thorium. A series of cerium(III) and cerium(IV) complexes featuring the redox-active iminoquinone ligand and its derivatives were synthesized. Oxidation chemistry was explored with the cerium amidophenolate complexes and a rare cerium oxo was isolated. Finally, with interest in expanding and addressing a gap in the literature related to the synthesis, characterization, and utility of thorium alkyls, several tetrabenzylthorium complexes were synthesized, characterized, and some reactivity was explored. A highlight of this work involved the isolation of the first crystal structure of ligand and solvent free tetrabenzylthorium since its first synthesis in 1974. Full spectroscopic and structural characterization of the complexes was performed via ¹H NMR spectroscopy, X-ray crystallography, EPR spectroscopy, electronic absorption spectroscopy, and SQUID magnetometry, which all confirmed the identity and electronic structure of these complexes. </p>

Alkali-ion batteries have revolutionized modern life through enabling the widespread application of portable electronic devices. The call for adapting renewable energy in many applications will also see an increase in the demand of alkali-ion batteries, specially to account for the intermittent nature of the renewable energy sources. However, the advancement of such technologies will require innovation on the forefront of materials development as well as fundamental understanding on the physical and chemical processes from atomic to device length scales. Herein, we focus on advancing energy storage devices such as alkali-ion batteries through cathode materials development and discovery as well as fundamental understanding through multiscale advanced synchrotron spectroscopic and microscopic characterizations. Multiscale electrochemical properties of cathode materials are unraveled through complementary characterizations and design principles are developed for stable cathode materials for alkali-ion batteries. In Chapter 1, we provide a comprehensive background on alkali-ion batteries and cathode materials. The future prospect of Li-ion and beyond Li-ion batteries are summarized. Surface to bulk chemistry of alkali-ion cathode materials is introduced. The prospect of combined cationic and anionic redox processes to enhance the energy density of cathode materials is discussed. Structural and chemical complexities in cathode materials during electrochemical cycling as well as due to anionic redox are summarized. In Chapter 2, we explain an inaugural effort on tuning the 3D nano/mesoscale elemental distribution of cathode materials to positively impact the electrochemical performance of cathode materials. We show that engineering the elemental distribution can take advantage of depth dependent redox reactions and curtail harmful side reactions at cathode-electrolyte interface which can stabilize the electrochemical performance. In Chapter 3, we show that the surface to bulk chemistry of cathode particles is distinct under applied electrochemical potential. We show that the severe surface degradation at the beginning stages of cycling can impact the long-term cycling performance of cathode materials in alkali-ion batteries. In Chapter 4, we utilize the structural and chemical complexities of sodium layered oxide materials to synthesize stable cathode materials for half cell and full cell sodium-ion batteries. Meanwhile, challenges with enabling long term cycling (more than 1000 cycles) are deciphered to be transition metal dissolution and local and global structural transformations. In Chapter 5, we utilize anionic redox in conjunction with conventional cationic redox of cathode materials for alkali-ion batteries to enhance the energy density. We show that the stability of anionic redox is closely related to the local transition metal environment. We also show that a reversible evolution of local transition metal environment during cycling can lead to stable anionic redox. In Chapter 6, we provide design principles for cathode materials for advanced alkali-ion batteries for application under extreme environments (e.g., outer space and nuclear power industries). For the first time, we systematically study the microstructural evolution of cathode materials under extreme irradiation and temperature to unravel the key factors affecting the stability of battery cathodes. Our experimental and computational studies show that a cathode material with smaller cationic antisite defect formation energy than another is more resilient under extreme environments. / Doctor of Philosophy / Alkali-ion batteries are finding many applications in our life, ranging from portable electronic devices, electric vehicles, grid energy storage, space exploration and so on. Cathode materials play a crucial role in the overall performance of alkali-ion batteries. Reliable application of alkali-ion batteries requires stable and high-energy cathode materials. Hence, design principles must be developed for high-performance cathode materials. Such design principles can be benefited from advanced characterizations that can reveal the surface-to-bulk properties of cathode materials. Herein, we focus on formulating design principles for cathode materials for alkali-ion batteries. Aided by advanced synchrotron characterizations, we reveal the surface-to-bulk properties of cathodes and their role on the long-term stability of alkali-ion batteries. We present tuning structural and chemical complexities as a method of designing advanced cathode materials. We show that energy density of cathode materials can be enhanced by taking advantage of a combined cationic and anionic redox. Lastly, we show design principles for stable cathode materials under extreme conditions in outer space and nuclear power industries (under extreme irradiation and temperature). Our study shows that structurally resilient cathode materials under extreme irradiation and temperature can be designed if the size of positively charged cations in cathode materials are almost similar. Our study provides valuable insights on the development of advanced cathode materials for alkali-ion batteries which can aid the future development of energy storage devices.

Continued emission of green house gases has energized research activity worldwide to develop efficient ways to harness renewal energy. The availability of large scale energy storage technologies is essential to make renewal energy a reliable source of energy. Redox flow batteries show potential in this direction. These batteries typically need expensive membranes which need replacement be-cause of fouling. The recently proposed soluble lead redox flow battery (SLRFB), in which lead ions deposit on electrodes in charge cycle and dissolve back in discharge cycle, can potentially cut down the cost of energy storage by eliminating membrane. A number of challenges need to be overcome though. Low cycleability, residue formation, and low efficiencies are foremost among these, all of which require an understanding of the underlying mechanisms. A model of laminar flow-through SLRFB is first developed to understand buildup of residue on electrodes with continued cycling. The model accounts for spatially and temporally growing concentration boundary layers on electrodes in a self consistent manner by permitting local deposition/dissolution rates to be controlled by local ion transport and reaction conditions. The model suggests controlling role for charge transfer reaction on electrodes (anode in particular) and movement of ions in the bulk and concentration boundary layers. The non-uniform current density on electrodes emerges as key to formation of bare patches, steep decrease in voltage marking the end of discharge cycle, and residue buildup with continuing cycles. The model captures the experimental observations very well, and points to improved operational efficiency and decreased residue build up with cylindrical electrodes and alternating flow direction of recirculation. The underlying mechanism for more than an order of magnitude increase in cycle life of a beaker cell battery with increase in stirrer speed is unraveled next. Our experiments show that charging with and without stirring occurs identically, which brings up the hitherto unknown but quite strong role of natural convection in SLRFB. The role of stirring is determined to be dislodgement/disintegration of residue building up on electrodes. The depletion of active material from electrolyte due to residue formation is offset by “internal regeneration mechanism”, unraveled in the present work. When the rate of residue formation, rate of dislodging/disintegration from electrode, and rate of regeneration of active material in bulk of the electrolyte becomes equal, perpetual operation of SLRFB is expected. The identification of strong role of free convection in battery is put to use to demonstrate a battery that requires stirring/mixing only intermittently, during open circuit stages between charge and discharge cycles when no current is drawn. Inspired by our experimental finding that the measured currents for apparently diffusion limited situations (no external flow) are far larger than the maxi-mum possible theoretical value, the earlier model is modified to account for natural convection driven by concentration gradient of lead ions in electrolyte. The model reveals the presence of strong natural convection in battery. The induced flow in the vicinity of the electrodes enhances mass transport rates substantially, to the extent that even in the absence of external flow, normal charge/discharge of battery is predicted. The model predicted electrochemical characteristics are verified quantitatively through voltage-time measurements. The formation of flow circulation loops driven by electrode processes is validated qualitatively through PIV measurements. Natural convection is predicted to play a significant role in the presence of external flow as well. The hitherto unexplained finding in the literature on insensitivity of charge-discharge characteristics to electrolyte flow rate is captured by the model when mixed mode of convection is invoked. Flow reversal and wavy flow are predicted when natural convection and forced convection act in opposite directions in the battery. The effect of the presence of non-conducting material (PbO on anode) on the performance of SLRFB is studied using a simplified approach in the model. The study reveals the presence of charge coup de fouet phenomenon in charge cycle. The phenomenon as well as the predicted effect of depth of discharge on the magnitude of charge coup de fouet are confirmed experimentally.

[ES] Un aumento de la generación de energía a partir de fuentes renovables (solar, eólica) requiere una alta flexibilidad de las redes eléctricas. En este sentido, las baterías de flujo redox de vanadio (BFRV) han demostrado una excelente capacidad para proporcionar dicha flexibilidad, mediante el almacenamiento eficiente de energía eléctrica en el rango de los kWh a los MWh. Sin embargo, sus elevados costes son en la actualidad unos de los mayores inconvenientes que dificultan una amplia penetración en el mercado. En la presente Tesis Doctoral se presenta el desarrollo y evaluación de una celda tubular especialmente diseñada con una membrana de 5.0mm. Las células tubulares así diseñadas deberían alcanzar una mayor densidad de potencia (kWm^(-3)). Del mismo modo, la sustitución de uno de los electrodos por un electrodo bifuncional de aire debería de incrementar la energía específica de dicha celda (Whkg^(-1)) y reducir, por tanto, los costes energéticos asociados (€/kWh). El diseño de la celda desarrollado en la presente Tesis Doctoral facilita la fabricación de los colectores y membranas actuales con el empleo de procesos de extrusión y marca un paso importante hacia la fabricación rentable de semiceldas y celdas completas en el futuro. Para evaluar el comportamiento de la nueva celda diseñada se han llevado a cabo estudios de polarización, de espectroscopia de impedancia, y medidas de ciclos de carga/descarga. Las celdas desarrolladas presentan una corriente de descarga máxima de 89.7mAcm^(-2) y una densidad de potencia de 179.2kW/m^3. Además, los bajos sobrepotenciales residuales obtenidos en los electrodos de la celda resultan prometedores. No obstante, la resistencia del área específica de celda de 3.2 ohm*cm² impone limitaciones significativas en la densidad de corriente. Eficiencias Coulomb del 95 % han sido obtenidas, comparables a los valores alcanzados en celdas planas de referencia. Sin embargo, las pérdidas óhmicas resultan elevadas, reduciendo la eficiencia energética del sistema al 56 %. Las celdas tubulares fabricadas con un electrodo de difusión de gas de una sola capa con Pt/IrO2 como catalizador permiten alcanzar densidades de corriente máximas de 32mAcm^(-2) (Ecell =2.1 V/0.56V Ch/Dch). Los elevados sobrepotenciales de activación y el reducido voltaje en circuito abierto (debido a potenciales mixtos) conducen a una densidad de potencia comparativamente baja de 15.4mW/ cm². El paso de iones de vanadio a través de la membrana se considera uno de los grandes inconvenientes en este tipo de celdas tubulares, lo que lleva a que la densidad de energía real de 23.2Wh l^(-1) caiga por debajo del valor nominal de 63.9Wh l^(-1). / [CAT] Un augment de la generació d'energia a partir de fonts renovables (solar, eòlica) requereix una alta flexibilitat de les xarxes elèctriques. En aquest sentit, les bateries de flux redox de vanadi (VRFB) han demostrat una excel·lent capacitat per a proporcionar aquesta flexibilitat, mitjançant l'emmagatzematge eficient d'energia elèctrica en el rang dels kWh als MWh. En la present Tesi Doctoral es presenta el desenvolupament i avaluació d'una cel·la tubular especialment dissenyada amb una membrana de 5.0mm. Les cèl·lules tubulars així dissenyades haurien assolir una major densitat de potència (kWm^(-3)). De la mateixa manera, la substitució d'un dels elèctrodes per un elèctrode bifuncional d'aire hauria d'incrementar l'energia específica d'aquesta cel·la (Whkg^(-1)) i reduir, per tant, els costos energètics associats (€/kWh). El disseny de la cel·la desenvolupat en la present tesi doctoral facilita la fabricació dels col·lectors i membranes actuals amb l'ocupació de processos d'extrusió i marca un pas important cap a la fabricació rendible de semiceldas i cel·les completes en el futur. Per avaluar el comportament de la nova cel·la dissenyada s'han dut a terme estudis de polarització, d'espectroscòpia d'impedància, i mesures de cicles de càrrega/ descàrrega. Les cel·les desenvolupades presenten un corrent de descàrrega màxima de 89.7mAcm^(-2) i una densitat de potència de 179.2kW/m^3. A més, els baixos sobrepotencials residuals obtinguts en els elèctrodes de la cel·la resulten prometedors. No obstant això, la resistència de l'àrea específica de cel·la de 3.2 ohm*cm² imposa limitacions significatives en la densitat de corrent. Eficiències Coulomb del 95 % han estat obtingudes, comparables als valors assolits en cel·les planes de referència. No obstant això, les pèrdues òhmiques resulten elevades, reduint l'eficiència energètica del sistema al 56 %. Les cel·les tubulars fabricades amb un elèctrode de difusió de gas d'una sola capa amb Pt/IrO2 com a catalitzador permeten assolir densitats de corrent màximes de 32mAcm^(-2) (Ecell =2.1 V/0.56V Ch/Dch). Els elevats sobrepotencials d'activació i el reduït voltatge en circuit obert (a causa de potencials mixtes) condueixen a una densitat de potència comparativament baixa de 15.4mW/ cm². El pas de ions de vanadi a través de la membrana es considera un dels grans inconvenients en aquest tipus de cel·les tubulars, el que porta al fet que la densitat d'energia real de23.2Wh l^(-1) caigui per sota del valor nominal de 63.9Wh l^(-1). / [EN] An increase of the power generation from volatile renewable sources (solar, wind) requires a high flexibility in power grids. All Vanadium Redox Flow Batteries (VRFBs) have demonstrated their ability to provide flexibility by storing electrical energy on a kWh to MWh scale. High power and energy specific costs do, however prevent a wide market penetration. In this dissertation a tubular cell design with a membrane diameter of 5.0mm is developed and evaluated. Tubular VRFB cells shall lead to an enhanced power den- sity (kWm^(-3)). Replacement of an electrode with a bifunctional air electrode (Vanadium/ Air Redox Flow Battery) shall allow to increase the specific energy (Whkg^(-1)) and reduce energy specific costs (€/kWh). The developed design facilitates a fabrication of the current collectors and membrane by an extrusion process and marks an important step towards the cost-efficient ex- trusion of entire half cells and cells in the future. To evaluate the cell performance and investigate loss mechanisms, polarization curve, electrochemical impedance spectroscopy and charge/discharge cycling measurements are conducted. Tubular VRFB cells with flow-by electrodes reveal a maximum dis- charge current and power density of 89.7mAcm^(-2) and 179.2kW/m^3, respectively. Low residual overpotentials at the cell's electrodes are encouraging, but the area spe- cific cell resistance of 3.2 ohm*cm² imposes limitations on the current density. Coulomb efficiencies of 95% are comparable to values of planar reference cells, but high ohmic losses reduce the system energy efficiency to 56 %. Tubular VARFB cells with a mono-layered gas diffusion electrode and a Pt/IrO2 catalyst allow for a maximum current density of 32mAcm^(-2) (Ecell =2.1 V/0.56V Ch/Dch). High activation overpotentials and a reduced open-circuit voltage (due to mixed potentials) lead to a comparably low power density of 15.4mW/ cm². Cross- over of vanadium ions through the membrane are considered as a major drawback for tubular VARFB cells and the actual energy density of 23.2Wh l^(-1) falls below the nominal value of Wh l^(-1). / Financial support of my research activities was provided by the BMBF through the common research project tubulAir±. / Ressel, SP. (2019). Tubular All Vanadium and Vanadium/Air Redox Flow Cells [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/131203 / TESIS

No description available.

The evolution of the present work began with the syntheses of novel bis(alkylimino)acenaphthene (BIAN) ligands. At the outset of this research, despite the presence of dozens of aryl-BIAN ligands in the literature, there were as of yet no reported BIAN ligands bearing alkyl substituents. Given the nearly ubiquitous use of transition metal complexes of alkyl diazabutadiene (DAB) ligands for e.g. catalysis and as ligands for carbene chemistry, interest was generated in developing this emerging field of synthetic chemistry. Initial studies focused on the synthesis of alkyl-BIAN ligands since the traditional synthetic approaches that had been developed for aryl-BIAN ligands were unsuccessful for the alkyl analogues. As an alternate synthetic route, it was decided to employ amino- and imino-alane transfer reagents which had previously proved successful for the conversion of C=O into C=N-R functionalities. While this transfer route had proved successful to synthesize moderate yields of highly fluorinated DAB ligands, it was unknown how or whether this methodology would apply in the case of alkylated BIAN systems. Over the past decade, there has been a surge of interest regarding lanthanide complexes that are capable of undergoing spontaneous electron transfer processes. There are several reports in the literature that describe the ability of Ln(II) ions to undergo spontaneous oxidation, thereby causing one-electron reduction of the coordinated ligand and generally resulting in the corresponding Ln(III) complex. The present work focused on an enhanced understanding of the electronic communication between the lanthanide and the attached ligand. Particular emphasis was placed on defining the resulting oxidation states and the manner in which delocalized electrons of the radical anion species travel over a conjugated system. This fundamental information was gleaned from single-crystal X-ray diffraction studies and magnetic moment measurements that were obtained using the Evans method. Additional insights stemmed from the use of more classical techniques such as IR and NMR spectroscopy. In favorable cases, the presence or absence of spectral peaks can permit assignment of the lanthanide oxidation state. Accordingly, the research plan was to synthesize a series of BIAN-supported decamethyllanthanocene complexes with the goal of learning how to control the spontaneous charge transfer that had been reported in the literature. A longer term goal was to develop a bifunctional ligand of the BIAN type that was capable of accommodating two lanthanide or main group element moieties. Systems with tunable electronic interactions between lanthanide or main group elements are of interest because they offer the prospect of extended delocalization of electron density. Systems of this type have potential applications as e.g. molecular wires and single-molecule magnets. Indeed, such systems have been investigated by using bis(bipyridyl) and bis(terpyridyl) ligands to support two redox-active moieties. However, in the present work, it was recognized that a bifunctional BIAN-type ligand might be of considerable interest as the supporting structure for studying the communication between lanthanide or main group element moieties. A synthesis of variously substituted tetrakis(imino)pyracene (TIP) ligands was therefore undertaken. The flat, rigid nature of the TIP ligands rendered them ideal scaffolds for studying the redox behavior and electronic communication between lanthanide or main group element centers. The new TIP ligand class also proved to be useful for the assembly of the first example of a metallopolymer based on a BIAN-type ligand. / text

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by neurofibrillary tangles, senile plaques and loss of synapses. Many studies support the notion that oxidative stress plays an important role in AD pathogenesis. Previous studies from our laboratory employed redox proteomics to identify oxidatively modified proteins in the AD inferior parietal lobule (IPL). The proteins were consistent with AD pathology and have been central to further investigations of the disease. The present study was focused on the identification of specific targets of protein S-glutathionylation in AD, early AD (EAD), and mild cognative impairment (MCI) using a redox proteomics approach. In AD IPL we identified deoxyhemoglobin, α-crystallin B, glyceraldehyde phosphate dehydrogenase (GAPDH), and α-enolase as significantly S-glutathionylated relative to these brain proteins in control IPL. Both, GAPDH and α-enolase were also shown to have reduced activity in the AD IPL. With further investigation gammaenolase, dimethylarginine dimethylaminohyrdolase (DDAH), Cathepsin D, and 14-3-3 gamma were identified as significantly S-glutathionylated in the EAD IPL. Alpha enolase was also identified as significantly S-glutathionylated in MCI IPL. These results provide a correlation in proteins S-glutathionylated in the progression of AD even in the reversible conditions of amnestic MCI. Amyloid beta-peptide (1-42) [Aβ(1-42)], one of the main component of senile plaque, can induce in vitro and in vivo oxidative damage to neuronal cells through its ability to produce free-radicals. The aim of this study was to investigate the protective effect of the xanthate, D609, on Aβ(1-42)-induced protein oxidation using a redox proteomics approach. D609 was recently found to be a free radical scavenger and antioxidant. In the present study, rat primary neuronal cells were pretreated with 50 μM of D609 followed by incubation with 10 μM Aβ(1-42) for 24 hours. In the cells treated with Aβ(1-42) alone four proteins that were significantly oxidized were identified: Glyceraldehyde 3-phosphate dehydrogenase, pyruvate kinase, malate dehydrogenase, and 14-3-3 zeta. Pretreatment of neuronal cultures with D609 prior to Aβ (1-42) protects all the identified oxidized proteins in the present study against Abeta(1- 42)-mediated protein oxidation. Therefore, D609 may ameliorate the Aβ(1-42)-induced oxidative modification.