Derivate des Ionentransporters Valinomycin

In der vorliegenden Arbeit wurden Derivate des Ionentransporters Valinomycin synthetisiert und als Sensorelemente in Modellmembransysteme inkorporiert. Als Modellmembranen wurden festkörpergestützte Lipiddoppelschichten (tBLMs, tethered bilayer lipid membranes) verwendet. rnValinomycin transportiert selektiv Kalium-Ionen durch Membranen, was durch einen Rückgang des Widerstandes über elektrochemische Messmethoden nachgewiesen werden kann. Es ist ein zyklisches Dodecadepsipeptid, das aus zwei verschiedenen Aminosäuren (L- und D-Valin) und  Hydroxysäuren (L Milchsäure und D Hydroxyisovaleriansäure) besteht. In dieser Arbeit wurde ein L Valin durch ein L-Lysin ausgetauscht, um eine freie Aminogruppe zum Anbinden verschiedenster Liganden zu erhalten. rnDie Synthese erfolgte in Lösung über einen linearen Decadepsipeptid-Precursor, hierbei wurde hauptsächlich mit Benzyl- und Boc-Schutzgruppen gearbeitet. An den Precursor wurden dann unterschiedlich modifizierte Lysin-Didepside gebunden und das daraus erhaltene lineare Dodecadepsipeptid zyklisiert.rnInsgesamt wurden sechs verschiedene Derivate synthetisiert, deren Ionentransportfähigkeit mit Hilfe eines angebundenen Liganden blockiert wurde. Diese Blockade kann entweder mechanisch durch Festhalten des Ionencarriers an der Oberfläche der Membran oder chemisch durch Einbringen einer Ladung erfolgen, da geladene Moleküle eine Membran nicht überwinden können. rnAcetyl-Lysin-Valinomycin wurde als Testsystem hergestellt, um zu zeigen, dass die Synthese einen funktionsfähigen Ionencarrier ergeben hatte. Im nächsten Schritt wurde Lysin-Valinomycin mit freier Aminogruppe synthetisiert, um es als pH-Sensor zu nutzen und damit zu überprüfen, ob das chemische Einbringen einer Ladung möglich ist. Es konnte ein pH abhängiger Kalium-Transport nachgewiesen werden, die Blockade der Ionentransportfähigkeit über eine eingebrachte Ladung ist somit möglich. rnAuf dem gleichen Konzept beruht Ferrocen-Valinomycin. Wird der Ferrocen-Ligand oxidiert, liegt eine positive Ladung vor und der Ionencarrier kann die Membran nicht mehr überwinden. Eine Reduktion macht diesen Prozess reversibel. Ferrocen-Valinomycin konnte innerhalb einer tBLM chemisch oxidiert und reduziert werden, dieses System kann somit als chemischer Redox-Sensor eingesetzt werden.rnEine mechanische Blockade liegt dem Biotin- und dem Sulfonamid-Valinomycin zugrunde. Dabei soll die Zugabe von Streptavidin bzw. BCA II (bovine Carboanhydrase) den Ionentransport durch die Membran stoppen. Beide Valinomycin-Derivate zeigten aber keine Ionentransportfähigkeit, eine Inkorporation in tBLMs konnte jedoch über SPR gezeigt werden. rnDie Synthese eines fluoreszenz-markierten (FITC) Valinomycins ergab zwar auch keinen transportfähigen Ionencarrier, aber mit diesem Derivat konnte der Diffusionskoeffizient von Valinomycin in sBLMs mit Hilfe von Fluorescence Recovery after photobleaching (FRAP) bestimmt werden.rn

Advanced lithium battery chemistries for sustainable transportation

The specific energy of lithium-ion batteries (LIBs) is today 200 Wh/kg, a value not sufficient to power fully electric vehicles with a driving range of 400 km which requires a battery pack of 90 kWh. To deliver such energy the battery weight should be higher than 400 kg and the corresponding increase of vehicle mass would narrow the driving range to 280 km. Two main strategies are pursued to improve the energy of the rechargeable lithium batteries up to the transportation targets. The first is the increase of LIBs working voltage by using high-voltage cathode materials. The second is the increase of battery capacity by the development of a cell chemistry where oxygen redox reaction (ORR) occurs at the cathode and metal lithium is the anode (Li/O2 battery). This PhD work is focused on the development of high-voltage safe cathodes for LIBs, and on the investigation of the feasibility of Li/O2 battery operating with ionic liquid(IL)-based electrolytes. The use of LiMn1-xFexPO4 as high-voltage cathode material is discussed. Synthesis and electrochemical tests of three different phosphates, more safe cathode materials than transition metal oxides, are reported. The feasibility of Li/O2 battery operating in IL-based electrolytes is also discussed. Three aspects have been investigated: basic aspects of ORR, synthesis and characterization of porous carbons as positive electrode materials and study of limiting factors to the electrode capacity and cycle-life. Regarding LIBs, the findings on LiMnPO4 prepared by soluble precursors demonstrate that a good performing Mn-based olivine is viable without the coexistence of iron. Regarding Li/O2 battery, the oxygen diffusion coefficient and concentration values in different ILs were obtained. This work highlighted that the O2 mass transport limits the Li/O2 capacity at high currents; it gave indications on how to increase battery capacity by using a flow-cell and a porous carbon as cathode.

Nano-fabrication of complex functional structures using non- conventional lithography

In Chapter 1 I will present a brief introduction on the state of art of nanotechnologies, nanofabrication techniques and unconventional lithography as a technique to fabricate the novel electronic device as resistive switch so-called memristor is shown. In Chapter 2 a detailed description of the main fabrication and characterization techniques employed in this work is reported. Chapter 3 parallel local oxidation lithography (pLOx) describes as a main technique to obtain accurate patterning process. All the effective parameters has been studied and the optimized condition observed to highly reproducible with excellent patterned nanostructures. The effect of negative bias, calls local reduction (LR) studied. Moreover, the use of AC bias shows faster patterning process respect to DC bias. In Chapter 4 (metal/ e-SiO2/ Si nanojunction) it is shown how the electrochemical oxide nanostructures by using pLOx can be used in the fabrication of novel devices call memristor. We demonstrate a new concept, based on conventional materials, where the lifetime problem is resolved by introducing a “regeneration” step, which restores the nano-memristor to its pristine condition by applying an appropriate voltage cycle. In Chapter 5 (Graphene/ e-SiO2/ Si), Graphene as a building block material is used as an electrode to selectively oxidize the silicon substrate by pLOx set up for the fabrication of novel resistive switch device. In Chapter 6 (surface architecture) I will show another application of pLOx in biotechnology is shown. So the surface functionalization combine with nano-patterning by pLOx used to design a new surface to accurately bind biomolecules with the possibility of studying those properties and more application in nano-bio device fabrication. So, in order to obtain biochips, electronic and optical/photonics devices Nano patterning of DNA used as scaffolds to fabricate small functional nano-components.

The synthesis of maleic anhydride: study of a new process and improvement of the industrial catalyst

Maleic anhydride is an important chemical intermediate mainly produced by the selective oxidation of n-butane, an industrial process catalyzed by vanadyl pyrophosphate-based materials, (VO)2P2O7. The first topic was investigated in collaboration with a company specialized in the production of organic anhydrides (Polynt SpA), with the aim of improving the performance of the process for the selective oxidation of n-butane to maleic anhydride, comparing the behavior of an industrial vanadyl pyrophosphate catalysts when utilized either in the industrial plant or in lab-scale reactor. The study was focused on how the catalyst characteristics and reactivity are affected by the reaction conditions and how the addition of a dopant can enhance the catalytic performance. Moreover, the ageing of the catalyst was studied, in order to correlate the deactivation process with the modifications occurring in the catalyst. The second topic was produced within the Seventh Framework (FP7) European Project “EuroBioRef”. The study was focused on a new route for the synthesis of maleic anhydride starting from an alternative reactant produced by fermentation of biomass:“bio-1-butanol”. In this field, the different possible catalytic configurations were investigated: the process was divided into two main reactions, the dehydration of 1-butanol to butenes and the selective oxidation of butenes to maleic anhydride. The features needed to catalyze the two steps were analyzed and different materials were proposed as catalysts, namely Keggin-type polyoxometalates, VOPO4∙2H2O and (VO)2P2O7. The reactivity of 1-butanol was tested under different conditions, in order to optimize the performance and understand the nature of the interaction between the alcohol and the catalyst surface. Then, the key intermediates in the mechanism of 1-butanol oxidehydration to MA were studied, with the aim of understanding the possible reaction mechanism. Lastly, the reactivity of the chemically sourced 1-butanol was compared with that one of different types of bio-butanols produced by biomass fermentation.

Organic/inorganic polyoxometalate-based hybrids for oxidation catalysis and energy conversion

This thesis work has been carried out during the Erasmus exchange period at the “Université Paris 6 – Pierre et Marie Curie”, in the “Edifices PolyMétalliques – EPOM” team, leaded by Prof. Anna Proust, belonging to the “Institut Parisien de Chimie Moléculaire”, under the supervision of Dr. Guillaume Izzet and Dr. Geoffroy Guillemot. The redox properties of functionalized Keggin and Dawson POMs have been exploited in photochemical, catalytic and reactivity tests. For the photochemical purposes, the selected POMs have been functionalized with different photoactive FGs, and the resulting products have been characterized by CV analyses, luminescence tests and UV-Vis analyses. In future, these materials will be tested for hydrogen photoproduction and polymerization of photoactive films. For the catalytic purposes, POMs have been firstly functionalized with silanol moieties, to obtain original coordination sites, and then post-functionalized with TMs such as V, Ti and Zr in their highest oxidation states. In this way, the catalytic properties of TMs were coupled to the redox properties of POM frameworks. The redox behavior of some of these hybrids has been studied by spectro-electrochemical and EPR methods. Catalytic epoxidation tests have been carried out on allylic alcohols and n-olefins, employing different catalysts and variable amounts of them. The performances of POM-V hybrids have been compared to those of VO(iPrO)3. Finally, reactivity of POM-VIII hybrids has been studied, using styrene oxide and ethyl-2-diazoacetate as substrates. All the obtained products have been analyzed via NMR techniques. Cyclovoltammetric analyses have been carried out in order to determine the redox behavior of selected hybrids.

Complex colloids by the emulsion solvent evaporation process

In this thesis, different complex colloids were prepared by the process of solvent evaporation from emulsion droplets (SEED). The term “complex” is used to include both an addressable functionality as well as the heterogeneous nature of the colloids.Firstly, as the SEED process was used throughout the thesis, its mechanism especially in regard to coalescence was investigated,. A wide variety of different techniques was employed to study the coalescence of nanodroplets during the evaporation of the solvent. Techniques such as DLS or FCS turned out not to be suitable methods to determine droplet coalescence because of their dependence on dilution. Thus, other methods were developed. TEM measurements were conducted on mixed polymeric emulsions with the results pointing to an absence of coalescence. However, these results were not quantifiable. FRET measurements on mixed polymeric emulsions also indicated an absence of coalescence. Again the results were not quantifiable. The amount of coalescence taking place was then quantified by the application of DC-FCCS. This method also allowed for measuring coalescence in other processes such as the miniemulsion polymerization or the polycondensation reaction on the interface of the droplets. By simulations it was shown that coalescence is not responsible for the usually observed broad size distribution of the produced particles. Therefore, the process itself, especially the emulsification step, needs to be improved to generate monodisperse colloids.rnThe Janus morphology is probably the best known among the different complex morphologies of nanoparticles. With the help of functional polymers, it was possible to marry click-chemistry to Janus particles. A large library of functional polymers was prepared by copolymerization and subsequent post-functionalization or by ATRP. The polymers were then used to generate Janus particles by the SEED process. Both dually functionalized Janus particles and particles with one functionalized face could be obtained. The latter were used for the quantification of functional groups on the surface of the Janus particles. For this, clickable fluorescent dyes were synthesized. The degree of functionality of the polymers was found to be closely mirrored in the degree of functionality of the surface. Thus, the marriage of click-chemistry to Janus particles was successful.Another complex morphology besides Janus particles are nanocapsules. Stimulus-responsive nanocapsules that show triggered release are a highly demanding and interesting system, as nanocapsules have promising applications in drug delivery and in self-healing materials. To achieve heterogeneity in the polymer shell, the stimulus-responsive block copolymer PVFc-b-PMMA was employed for the preparation of the capsules. The phase separation of the two blocks in the shell of the capsules led to a patchy morphology. These patches could then be oxidized resulting in morphology changes. In addition, swelling occurred because of the hydrophobic to hydrophilic transition of the patches induced by the oxidation. Due to the swelling, an encapsulated payload could diffuse out of the capsules, hence release was achieved.The concept of using block copolymers responsive to one stimulus for the preparation of stimulus-responsive capsules was extended to block copolymers responsive to more than one stimulus. Here, a block copolymer responsive to oxidation and a pH change as well as a block copolymer responsive to a pH change and temperature were studied in detail. The release from the nanocapsules could be regulated by tuning the different stimuli. In addition, by encapsulating stimuli-responsive payloads it was possible to selectively release a payload upon one stimulus but not upon the other one.In conclusion, the approaches taken in the course of this thesis demonstrate the broad applicability and usefulness of the SEED process to generate complex colloids. In addition, the experimental techniques established such as DC-FCCS will provide further insight into other research areas as well.

The oxidation capacity of the atmosphere - OH and HO 2 radical measurements in a boreal forest environment using laser induced fluorescence spectroscopy

Das wichtigste Oxidationsmittel für den Abbau flüchtiger Kohlenwasserstoffverbindungen (VOC, engl.: volatile organic compounds) in der Atmosphäre ist das Hydroxylradikal (OH), welches sich in einem schnellen chemischen Gleichgewicht mit dem Hydroperoxylradical (HO2) befindet. Bisherige Messungen und Modellvergleiche dieser Radikalspezies in Waldgebieten haben signifikante Lücken im Verständnis der zugrundeliegenden Prozesse aufgezeigt.rnIm Rahmen dieser Doktorarbeit wurden Messungen von OH- und HO2-Radikalen mittelsrnlaserinduzierten Fluoreszensmesstechnik (LIF, engl.: laser-induced fluorescence) in einem Nadelwald in Süd-Finnland während der Messkampagne HUMPPA–COPEC–2010 (Hyytiälä United Measurements of Photochemistry and Particles in Air – Comprehensive Organic Precursor Emission and Concentration study) im Sommer 2010 durchgeführt. Unterschiedliche Komponenten des LIF-Instruments wurden verbessert. Eine modifizierte Methode zur Bestimmung des Hintergrundsignals (engl.: InletPreInjector technique) wurde in den Messaufbaurnintegriert und erstmals zur Messung von atmosphärischem OH verwendet. Vergleichsmessungen zweier Instrumente basierend auf unterschiedlichen Methoden zur Messung von OH-Radikalen, chemische Ionisationsmassenspektrometrie (CIMS - engl.: chemical ionization mass spectrometry) und LIF-Technik, zeigten eine gute Übereinstimmung. Die Vergleichsmessungen belegen das Vermögen und die Leistungsfähigkeit des modifizierten LIF-Instruments atmosphärische OH Konzentrationen akkurat zu messen. Nachfolgend wurde das LIF-Instrument auf der obersten Plattform eines 20m hohen Turmes positioniert, um knapp oberhalb der Baumkronen die Radikal-Chemie an der Schnittstelle zwischen Ökosystem und Atmosphäre zu untersuchen. Umfangreiche Messungen - dies beinhaltet Messungen der totalen OH-Reaktivität - wurden durchgeführt und unter Verwendung von Gleichgewichtszustandsberechnungen und einem Boxmodell, in welches die gemessenen Daten als Randbedingungen eingehen, analysiert. Wenn moderate OH-Reaktivitäten(k′(OH)≤ 15 s−1) vorlagen, sind OH-Produktionsraten, die aus gemessenen Konzentrationen von OH-Vorläuferspezies berechnet wurden, konsistent mit Produktionsraten, die unter der Gleichgewichtsannahme von Messungen des totalen OH Verlustes abgeleitet wurden. Die primären photolytischen OH-Quellen tragen mit einem Anteil von bis zu einem Drittel zur Gesamt-OH-Produktion bei. Es wurde gezeigt, dass OH-Rezyklierung unter Bedingungen moderater OH-Reaktivität hauptsächlich durch die Reaktionen von HO2 mit NO oder O3 bestimmt ist. Während Zeiten hoher OH-Reaktivität (k′(OH) > 15 s−1) wurden zusätzliche Rezyklierungspfade, die nicht über die Reaktionen von HO2 mit NO oder O3, sondern direkt OH bilden, aufgezeigt.rnFür Hydroxylradikale stimmen Boxmodell-Simulationen und Messungen gut übereinrn(OHmod/OHobs=1.04±0.16), während HO2-Mischungsverhältnisse in der Simulation signifikant unterschätzt werden (HO2mod/HO2obs=0.3±0.2) und die simulierte OH-Reaktivität nicht mit der gemessenen OH-Reaktivität übereinstimmt. Die gleichzeitige Unterschätzung der HO2-Mischungsverhältnisse und der OH-Reaktivität, während OH-Konzentrationen von der Simulation gut beschrieben werden, legt nahe, dass die fehlende OH-Reaktivität in der Simulation eine noch unberücksichtigte HO2-Quelle darstellt. Zusätzliche, OH-unabhängigernRO2/HO2-Quellen, wie z.B. der thermische Zerfall von herantransportiertem peroxyacetylnitrat (PAN) und die Photolyse von Glyoxal sind indiziert.

The sensitivity of the photostationary state of NOx and its implication for the oxidation capacity in a semi-rural and boreal forest region

Für das Vermögen der Atmosphäre sich selbst zu reinigen spielen Stickstoffmonoxid (NO) und Stickstoffdioxid (NO2) eine bedeutende Rolle. Diese Spurengase bestimmen die photochemische Produktion von Ozon (O3) und beeinflussen das Vorkommen von Hydroxyl- (OH) und Nitrat-Radikalen (NO3). Wenn tagsüber ausreichend Solarstrahlung und Ozon vorherrschen, stehen NO und NO2 in einem schnellen photochemischen Gleichgewicht, dem „Photostationären Gleichgewichtszustand“ (engl.: photostationary state). Die Summe von NO und NO2 wird deshalb als NOx zusammengefasst. Vorhergehende Studien zum photostationären Gleichgewichtszustand von NOx umfassen Messungen an unterschiedlichsten Orten, angefangen bei Städten (geprägt von starken Luftverschmutzungen), bis hin zu abgeschiedenen Regionen (geprägt von geringeren Luftverschmutzungen). Während der photochemische Kreislauf von NO und NO2 unter Bedingungen erhöhter NOx-Konzentrationen grundlegend verstanden ist, gibt es in ländlicheren und entlegenen Regionen, welche geprägt sind von niedrigeren NOx-Konzetrationen, signifikante Lücken im Verständnis der zugrundeliegenden Zyklierungsprozesse. Diese Lücken könnten durch messtechnische NO2-Interferenzen bedingt sein - insbesondere bei indirekten Nachweismethoden, welche von Artefakten beeinflusst sein können. Bei sehr niedrigen NOx-Konzentrationen und wenn messtechnische NO2-Interferenzen ausgeschlossen werden können, wird häufig geschlussfolgert, dass diese Verständnislücken mit der Existenz eines „unbekannten Oxidationsmittels“ (engl.: unknown oxidant) verknüpft ist. Im Rahmen dieser Arbeit wird der photostationäre Gleichgewichtszustand von NOx analysiert, mit dem Ziel die potenzielle Existenz bislang unbekannter Prozesse zu untersuchen. Ein Gasanalysator für die direkte Messung von atmosphärischem NO¬2 mittels laserinduzierter Fluoreszenzmesstechnik (engl. LIF – laser induced fluorescence), GANDALF, wurde neu entwickelt und während der Messkampagne PARADE 2011 erstmals für Feldmessungen eingesetzt. Die Messungen im Rahmen von PARADE wurden im Sommer 2011 in einem ländlich geprägten Gebiet in Deutschland durchgeführt. Umfangreiche NO2-Messungen unter Verwendung unterschiedlicher Messtechniken (DOAS, CLD und CRD) ermöglichten einen ausführlichen und erfolgreichen Vergleich von GANDALF mit den übrigen NO2-Messtechniken. Weitere relevante Spurengase und meteorologische Parameter wurden gemessen, um den photostationären Zustand von NOx, basierend auf den NO2-Messungen mit GANDALF in dieser Umgebung zu untersuchen. Während PARADE wurden moderate NOx Mischungsverhältnisse an der Messstelle beobachtet (10^2 - 10^4 pptv). Mischungsverhältnisse biogener flüchtige Kohlenwasserstoffverbindungen (BVOC, engl.: biogenic volatile organic compounds) aus dem umgebenden Wald (hauptsächlich Nadelwald) lagen in der Größenordnung 10^2 pptv vor. Die Charakteristiken des photostationären Gleichgewichtszustandes von NOx bei niedrigen NOx-Mischungsverhältnissen (10 - 10^3 pptv) wurde für eine weitere Messstelle in einem borealen Waldgebiet während der Messkampagne HUMPPA-COPEC 2010 untersucht. HUMPPA–COPEC–2010 wurde im Sommer 2010 in der SMEARII-Station in Hyytiälä, Süd-Finnland, durchgeführt. Die charakteristischen Eigenschaften des photostationären Gleichgewichtszustandes von NOx in den beiden Waldgebieten werden in dieser Arbeit verglichen. Des Weiteren ermöglicht der umfangreiche Datensatz - dieser beinhaltet Messungen von relevanten Spurengasen für die Radikalchemie (OH, HO2), sowie der totalen OH-Reaktivität – das aktuelle Verständnis bezüglich der NOx-Photochemie unter Verwendung von einem Boxmodell, in welches die gemessenen Daten als Randbedingungen eingehen, zu überprüfen und zu verbessern. Während NOx-Konzentrationen in HUMPPA-COPEC 2010 niedriger sind, im Vergleich zu PARADE 2011 und BVOC-Konzentrationen höher, sind die Zyklierungsprozesse von NO und NO2 in beiden Fällen grundlegend verstanden. Die Analyse des photostationären Gleichgewichtszustandes von NOx für die beiden stark unterschiedlichen Messstandorte zeigt auf, dass potenziell unbekannte Prozesse in keinem der beiden Fälle vorhanden sind. Die aktuelle Darstellung der NOx-Chemie wurde für HUMPPA-COPEC 2010 unter Verwendung des chemischen Mechanismus MIM3* simuliert. Die Ergebnisse der Simulation sind konsistent mit den Berechnungen basierend auf dem photostationären Gleichgewichtszustand von NOx.

Solar thermal decoupled water electrolysis process I: Proof of concept

A new concept for a solar thermal electrolytic process was developed for the production of H-2 from water. A metal oxide is reduced to a lower oxidation state in air with concentrated solar energy. The reduced oxide is then used either as an anode or solute for the electrolytic production of H-2 in either an aqueous acid or base solution. The presence of the reduced metal oxide as part of the electrolytic cell decreases the potential required for water electrolysis below the ideal 1.23 V required when H-2 and O-2 evolve at 1 bar and 298 K. During electrolysis, H-2 evolves at the cathode at 1 bar while the reduced metal oxide is returned to its original oxidation state, thus completing the H-2 production cycle. Ideal sunlight-to-hydrogen thermal efficiencies were established for three oxide systems: Fe2O3-Fe3O4, Co3O4-CoO, and Mn2O3-Mn3O4. The ideal efficiencies that include radiation heat loss are as high or higher than corresponding ideal values reported in the solar thermal chemistry literature. An exploratory experimental study for the iron oxide system confirmed that the electrolytic and thermal reduction steps occur in a laboratory scale environment.

Adsorption behavior of redox-active suppressor additives: Combined electrochemical and STM studies

The redox chemistry and the related surface phase behavior of Safranine (SAF) and Janus Green B (JGB) have been studied by means of cyclic voltammetry in combination with in situ Scanning Tunneling Microscopy using HOPG (Highly Oriented Pyrolytic Graphite) and single crystalline Cu(1 0 0) as model substrates, both revealing different widths of the accessible potential windows. JGB and SAF serve as prototypical heterocyclic suppressor/leveler additives that are used for the metallization of 3D-TSVs (3D Through Silicon Vias) following a classical "leveling" concept. SAF can be considered as the reductive decomposition product of JGB that is formed at the copper/electrolyte interface upon electroplating. Both additives reveal a pronounced pH-dependent redox-chemistry with redox-transitions lying close to or even beyond the anodic limit of the copper potential window. Affected by these redox-processes are in particular the aromatic cores of those heterocycles that can be (quasi)reversibly reduced by a two electron transfer process within the potential window of copper. Therefore we identify the reduced form of those dyes as the active components for the suppressing/leveling effect in copper plating. STM data clearly shows a dye surface phase behavior that is crucially determined by its potential-dependent redox-chemistry. This will be exemplarily discussed for the SAF dye. On chloride-modified Cu(1 0 0) mono-reduced SAF forms a structurally well-defined monolayer of cationic stacking polymers. However, this coupled anion/cation layer reveals only minor suppressing capabilities with respect to the copper dissolution and deposition processes. Complete reduction of the aromatic heterocycle finally leads to the 3D precipitation of hydrophobic reaction products. 3D clusters of this SAF precipitate are discussed as the active structural motif for the suppressing effect of these dyes. (C) 2011 Elsevier Ltd. All rights reserved.

Conformationally Controlled Electron Delocalization in n-Type Rods: Synthesis, Structure, and Optical, Electrochemical, and Spectroelectrochemical Properties of Dicyanocyclophanes

A series of dicyanobiphenyl-cyclophanes 1-6 with various pi-backbone conformations and characteristic n-type semiconductor properties is presented. Their synthesis, optical, structural, electrochemical, spectroelectrochemical, and packing properties are investigated. The X-ray crystal structures of all n-type rods allow the systematic correlation of structural features with physical properties. In addition, the results are supported by quantum mechanical calculations based on density functional theory. A two-step reduction process is observed for all n-type rods, in which the first step is reversible. The potential gap between the reduction processes depends linearly on the cos(2) value of the torsion angle phi between the pi-systems. Similarly, optical absorption spectroscopy shows that the vertical excitation energy of the conjugation band correlates with the cos(2) value of the torsion angle phi. These correlations demonstrate that the fixed intramolecular torsion angle phi is the dominant factor determining the extent of electron delocalization in these model compounds, and that the angle phi measured in the solid-state structure is a good proxy for the molecular conformation in solution. Spectroelectrochemical investigations demonstrate that conformational rigidity is maintained even in the radical anion form. In particular, the absorption bands corresponding to the SOMO-LUMO+i transitions are shifted bathochromically, whereas the absorption bands corresponding to the HOMO-SOMO transition are shifted hypsochromically with increasing torsion angle phi.

Targeting p-Conjugated Multiple Donor-Acceptor Motifs Exemplified by Tetrathiafulvalene-Linked Quinoxalines and Tetrabenz bc,ef,hi,uv ovalenes: Synthesis, Spectroscopic, Electrochemical, and Theoretical Characterization

An efficient synthetic approach to a symmetrically functionalized tetrathiafulvalene (TTF) derivative with two diamine moieties, 2-[5,6-diamino-4,7-bis(4-pentylphenoxy)-1,3-benzodithiol-2-ylidene]-4,7- bis(4-pentylphenoxy)-1,3-benzodithiole-5,6-diamine (2), is reported. The subsequent Schiff-base reactions of 2 afford large p-conjugated multiple donoracceptor (DA) arrays, for example, the triad 2-[4,9-bis(4-pentylphenoxy)-1,3-dithiolo[4,5-g]quinoxalin-2-ylidene]-4,9 -bis(4-pentylphenoxy)-1,3-dithiolo[4,5-g]quinoxaline (8) and the corresponding tetrabenz[bc,ef,hi,uv]ovalene-fused pentad 1, in good yields and high purity. The novel redox-active nanographene 1 is so far the largest known TTF-functionalized polycyclic aromatic hydrocarbon (PAH) with a well-resolved 1H NMR spectrum. The electrochemically highly amphoteric pentad 1 and triad 8 exhibit various electronically excited charge-transfer states in different oxidation states, thus leading to intense optical intramolecular charge-transfer (ICT) absorbances over a wide spectral range. The chemical and electrochemical oxidations of 1 result in an unprecedented TTF+ radical cation dimerization, thereby leading to the formation of [1+]2 at room temperature in solution due to the stabilizing effect, which arises from strong pp interactions. Moreover, ICT fluorescence is observed with large solvent-dependent Stokes shifts and quantum efficiencies of 0.05 for 1 and 0.035 for 8 in dichloromethane.

A tetrathiafulvalene-functionalized naphthalene diimide: synthesis, electrochemical and photophysical properties

A tetrathiafulvalene donor has been attached to the naphthalene diimide core via a rigid bridge affording a new planar molecular dyad. Its electronic properties have been studied experimentally by the combination of electrochemistry and UV-vis-NIR spectroscopy. Various electronic excited charge-transfer states are generated in different oxidation states, leading to almost full absorption in the visible to near-IR region with high extinction coefficients. The observed electronic properties are explained on the basis of density-functional-theory. In particular, the oxidized radical species show a strong tendency to undergo aggregation, in which the long-distance attractive interactions overcome the electrostatic repulsions. (C) 2011 Elsevier Ltd. All rights reserved.

Central Europe in the Process of European Integration. A Comparative Study of the Strategies of the Czech Republic, Hungary, Poland and Slovakia towards the Deepening and Widening of the European Union

Membership of the European Union U is usually seen as a strategic goal of the associated states of central and eastern Europe. At the beginning of the 1990s central European countries, where the economic and political transformation was relatively advanced, received preferential treatment from the European Community, which was starting to evolve a policy of differentiation. Podraza studied the strategies of four central European countries towards changes under way in the European Union, analysing several aspects for each case: (1) the process of political transformation (2) decision-making structures in the field of foreign policy and European integration (3) integration strategies: (a) main foreign policy priorities (b) application for membership of the European Union (c) the Commission option on each country (d) accession partnership, including a National Programme for the Adoption of the Acquis (NPAA) (e) regular Commission reports (f) accession negotiations

Simultaneous determination of 3-hydroxyanthranilic and cinnabarinic acid by high-performance liquid chromatography with photometric or electrochemical detection

A convenient and rapid method for the simultaneous determination by HPLC of 3-hydroxyanthranilic acid and the dimer derived by its oxidation, cinnabarinic acid, is described. Buffers or biological samples containing these two Trp metabolites were acidified to pH 2.0 and extracted with ethyl acetate with recoveries of 96.5 +/- 0.5 and 93.4 +/- 3.7% for 3-hydroxyanthranilic and cinnabarinic acid, respectively. The two compounds were separated on a reversed-phase (C18) column combined with ion-pair chromatography and detected photometrically or electrochemically. The method was applied successfully to biological systems in which formation of either 3-hydroxyanthranilic or cinnabarinic acid had been described previously. Thus, interferon-gamma-treated human peripheral blood mononuclear cells formed and released significant amounts of 3-hydroxyanthranilic acid into the culture medium and mouse liver nuclear fraction possessed high "cinnabarinic acid synthase" activity. In contrast, addition of 3-hydroxyanthranilic acid to human erythrocytes resulted in only marginal formation of cinnabarinic acid. We conclude that the method described is specific, sensitive, and suitable for the detection of the two Trp metabolites in biological systems.