The interaction behavior of humic acids with uranium(VI) and the influence of humic substances on the migration behavior of uranium was investigated. A main focus of this work was the synthesis of four different humic acid model substances and their characterization and comparison to the natural humic acid from Aldrich. A radiometric method for the determination of humic acid functional groups was applied in addition to conventional methods for the determination of the functionality of humic acids. The humic acid model substances show functional and structural properties comparable to natural humic acids. Modified humic acids with blocked phenolic OH were synthesized to determine the influence of phenolic OH groups on the complexation behavior of humic acids. A synthesis method for 14C-labeled humic acids with high specific activity was developed. The complexation behavior of synthetic and natural humic acids with uranium(VI) was investigated by X-ray absorption spectroscopy, laser-induced fluorescence spectroscopy and FTIR spectroscopy. The synthetic model substances show an interaction behavior with uranium(VI) that is comparable to natural humic acids. This points to the fact that the synthetic humic acids simulate the functionality of their natural analogues very well. For the first time the influence of phenolic OH groups on the complexation behavior of humic acids was investigated by applying a modified humic acid with blocked phenolic OH groups. The formation of a uranyl hydroxy humate complex was identified by laserspectroscopic investigations of the complexation of Aldrich humic acid with uranium(VI)at pH 7. The migration behavior of uranium in a sandy aquifer system rich in humic substances was investigated in column experiments. A part of uranium migrates non-retarded through the sediment, bound to humic colloids. The uranium migration behavior is strongly influenced by the kinetically controlled interaction processes of uranium with the humic colloids. The influence of humic acids on the sorption of uranium(VI) onto phyllite was investigated in batch experiments using two different humic acids. The uranium(VI) sorption onto the rock phyllite is influenced by the pH-dependent sorption behavior of the humic acids.

The objective of the work described in this thesis was to understand sorption reactions of uranium occurring at the water-clay mineral interfaces in the presence and absence of arsenic and other inorganic ligands. Uranium(VI) removal by clay minerals is influenced by a large number of factors including: type of clay mineral, pH, ionic strength, partial pressure of CO2, load of the sorbent, total amount of U present, and the presence of arsenate and other inorganic ligands such as sulfate, carbonate, and phosphate. Both sulfate and carbonate reduced uranium sorption onto IBECO bentonite due to the competition between SO42- or CO32- ions and the uranyl ion for sorption sites, or the formation of uranyl-sulfate or uranyl-carbonate complexes. Phosphate is a successful ligand to promote U(VI) removal from the aqueous solution through formation of ternary surface complexes with a surface site of bentonite. In terms of the type of clay mineral used, KGa-1b and KGa-2 kaolinites showed much greater uranium sorption than the other clay minerals (STx-1b, SWy-2, and IBECO montmorillonites) due to more aluminol sites available, which have higher affinity toward uranium than silanol sites. Sorption of uranium on montmorillonites showed a distinct dependency on sodium concentrations because of the effective competition between uranyl and sodium ions, whereas less significant differences in sorption were found for kaolinite. A multisite layer surface complexation model was able to account for U uptake on different clay minerals under a wide range of experimental conditions. The model involved eight surface reactions binding to aluminol and silanol edge sites of montmorillonite and to aluminol and titanol surface sites of kaolinite, respectively. The sorption constants were determined from the experimental data by using the parameter estimation code PEST together with PHREEQC. The PEST- PHREEQC approach indicated an extremely powerful tool compared to FITEQL. In column experiments, U(VI) was also significantly retarded due to adsorptive interaction with the porous media, requiring hundreds of pore volumes to achieve breakthrough. Concerning the U(VI) desorption, columns packed with STx-1b and SWy-2 exhibited irreversible sorption, whereas columns packed with KGa-1b and KGa-2 demonstrated slow, but complete desorption. Furthermore, most phenomena observed in batch experiments were recognized in the column experiments, too. The affinity of uranium to clay minerals was higher than that of arsenate. In systems containing uranium and arsenate, the period required to achieve the breakthrough in all columns was significantly longer when the solution was adjusted to pH 6, due to the formation of the uranyl-arsenate complex. In contrast, when pH was adjusted to 3, competitive sorption for U(VI) and As(V) accelerated the breakthrough for both elements. Finally, experiments without sorbing material conducted for higher concentrations of uranium and arsenic showed no loss of total arsenic and uranium in non-filtered samples. In contrast, significant loss was observed after filtration probably indicating the precipitation of a U/As 1:1 phase.

Um das Verhalten von Actiniden im Menschen (Stoffwechsel), in geologischen und in biologischen Systemen vorherzusagen, ist es erforderlich deren Speziation genau zu kennen. Zur Bestimmung dieser wird das chemische Verhalten des Urans hinsichtlich Komplexbildungsreaktionen und Redoxreaktionen in Modellsystemen untersucht. Anhand der gewonnenen thermodynamischen Konstanten und dem Redoxverhalten können Risikoabschätzungen für das jeweilige untersuchte System getroffen werden. Das umweltrelevante Uran(IV)-Uran(VI)-Redoxsystem besitzt mit der metastabilen fünfwertigen Oxidationsstufe einen zumeist kurzlebigen Zwischenzustand. Innerhalb dieser Arbeit gelang es erstmalig die Uran(V)-Fluoreszenz mittels laserspektroskopischer Methoden nach zu weisen. Beispielsweise konnte das Bandenmaximum von aquatischem Uranyl(V) im perchlorhaltigem Medium (λex = 255 nm) mit 440 nm, bei einer Fluoreszenzlebensdauer von 1,10 ± 0,02 µs bestimmt werden. Die fluoreszenzspektroskopische Untersuchung eines aquatischen [U(V)O2(CO3)3]5--Komplexes (λex= 255 nm und 408 nm) zeigte bei Raumtemperatur keine Fluoreszenz. Durch Anwendung der Tieftemperaturtechnik wurden bekannte Quencheffekte des Carbonats unterdrückt, so dass bei beiden Anregungswellenlängen ein für Uran(V) typisches Fluoreszenzspektrum im Bereich von 375 nm bis 450 nm, mit Bandenmaxima bei 401,5 nm (λex = 255 nm) und 413,0 nm (λex = 408 nm) detektiert werden konnte. Darüber hinaus konnte bei 153 K (λex = 255 nm) eine Fluoreszenzlebensdauer von 120 ± 0,1 µs bestimmt werden. Untersetzt wurden diese fluoreszenzspektroskopischen Nachweise durch mikroskopische Studien verschiedener Uran(IV)-Festphasen (Uraninit…UO2, Uran(IV) Tetrachlorid…UCl4) und einer sulfathaltigen Uran(IV)-Lösung (UIVSO4). Diese wurden durch kontinuierliche Sauerstoffzufuhr zu Uran(VI) oxidiert. Die ablaufende Oxidation wurde mit dem konfokalen Laser Scanning Mikroskop (CLSM) verfolgt, wobei die Proben mit einer Wellenlänge von 408 nm zur Fluoreszenz angeregt wurden. Die auftretenden Bandenmaxima bei 445,5 nm (UO2), bei 445,5 nm (UCl4) und bei 440,0 nm (UIVSO4) konnten eindeutig der Uran(V)-Fluoreszenz zugeordnet werden. Zur Bestimmung thermodynamischer Konstanten mit Hilfe der Tieftemperaturfluoreszenz wurde zunächst der Einfluss der Temperatur auf das Fluoreszenzverhalten des freien Uranyl(VI)-Ions näher betrachtet. Es zeigte sich, dass mit Erwärmung der Probe (T>298 K) die Fluoreszenzlebensdauer von 1,88 µs (298 K) deutlich absinkt. Die Fluoreszenzintensität verringerte sich dabei um 2,3 % pro 1 K zwischen 273 K und 313 K. Im Gegensatz dazu, steigt die Fluoreszenzlebensdauer um das 150-fache auf 257,9 µs bei einer Verminderung der Temperatur (T <298 K) auf 153 K. Das weitere Absenken der Temperatur (T <153 K) zeigte keinen Einfluss auf die Fluoreszenzlebensdauer. Die Lage der Hauptemissionsbanden des freien Uranyl(VI)-Ions (488,0 nm, 509,4 nm, 532,4 nm, 558,0 nm, 586,0 nm) zeigte bei diesen Untersuchungen keine temperaturabhängige Verschiebung. Die Validierung der Tieftemperaturtechnik zur Bestimmung thermodynamischer Konstanten mittels zeitaufgelöster laserinduzierten Fluoreszenzspektroskopie erfolgte anhand des Uran(VI)-Citrat-Systems. Im Gegensatz zu bisherigen fluoreszenzspektroskopischen Betrachtungen bei Raumtemperatur wurde das Fluoreszenzsignal bei tiefen Temperaturen mit einsetzender Komplexierung nicht gequencht, woraus die Ausprägung einer gut interpretierbaren Fluoreszenz resultierte. Die Analyse der spektralen Daten mit SPECFIT ergaben mit log β101 = 7,24 ± 0,16 für den [UO2(Cit)]--Komplex und log β202 = 18,90 ± 0,26 für den [(UO2)2(Cit)2]2 -Komplex exakt die in der Literatur angegebenen Stabilitätskonstanten. Zudem konnten Einzelkomponentenspektren mit Bandenmaxima bei 475,3 nm, 591,8 nm, 513,5 nm, 537,0 nm und 561,9 nm für den 1:0:1-Komplex und 483,6 nm, 502,7 nm, 524,5 nm, 548,1 nm und 574,0 nm für den 2:0:2-Komplex und Fluoreszenzlebensdauern von 79 ± 15 µs (1:0:1) und 10 ± 3 µs (2:0:2) bestimmt werden. Zur Modellkomplexierung des Uran-Citrat-Systems wurde in dieser Arbeit auch das Komplexbildungsverhalten von U(IV) in Gegenwart von Citronensäure untersucht. Hierbei wurden über den gesamten pH-Wertbereich gelöste Uran-Citrat-Spezies spektroskopisch nachgewiesen und die Stabilitätskonstanten sowie die Einzelkomponentenspektren für die neu gebildeten Uran(IV) und (VI)-Spezies bestimmt. Für die neu gebildeten Citrat-Komplexe des sechswertigen Urans wurden Komplexbildungskonstanten von log β203 = 22,67 ± 0,34 ([(UO2)2(Cit)3]5-) und log β103 = 12,35 ± 0,22 ([UO2(Cit)3]7-) und für die Komplexe des vierwertigen Urans von log β1-21 = -9,74 ± 0,23 ([U(OH)2Cit]-) und log β1 31 = -20,36 ± 0,22 ([U(OH)3Cit]2-) bestimmt. Untersuchungen zum Redoxverhalten von Uran in Gegenwart von Citronensäure zeigten unter aeroben und anaeroben Versuchsbedingungen eine photochemische Reduktion vom U(VI) zu U(IV), welche spektroskopisch nachgewiesen werden konnte. Dabei zeigt speziell die Reaktion unter oxidierenden Bedingungen, welchen großen Einfluss vor allem organischen Liganden auf das chemische Verhalten des Urans haben können. Sowohl die Reduktion unter O2- als auch die unter N2-Atmosphäre, weisen ein Maximum bei einem pH Wert von 3,5 bis 4 auf. Unter anaeroben Bedingungen reduziert die Citronensäure mit ca. 66 %, 14 % mehr Uran(VI) zu Uran(IV) als unter anaeroben Bedingungen mit ca. 52 %. Ab einem pH-Wert von 7 konnte eine Reduktion nur unter sauerstofffreien Bedingungen festgestellt werden. Die Wechselwirkung von U(VI) in Gegenwart von Glucose wurde hinsichtlich Reduktion und Komplexierung des Uran(VI) betrachtet. Mit Hilfe der zeitaufgelösten laserinduzierten Fluoreszenzspektroskopie bei tiefen Temperaturen wurde dabei ein Uranyl(VI)-Glucose-Komplex nachgewiesen. Die Komplexierung wurde lediglich bei pH 5 beobachtet und weist eine Komplexbildungskonstante von log βI=0,1 M = 15,25 ± 0,96 für den [UO2(C6H12O6)]2+-Komplex auf. Mit einer Fluoreszenzlebensdauer von 20,9 ± 2,9 µs und den Hauptemissionsbanden bei 499,0nm, 512,1 nm, 525,2 nm, 541,7 nm und 559,3 nm konnte der Uranyl(VI)-Glucose-Komplex fluoreszenzspektroskopisch charakterisiert werden. Unter reduzierenden Bedingungen wurde, ab pH-Wert 4 eine auftretende Umwandlung vom sechswertigen zum vierwertigen Uran durch Glucose in Gegenwart von Licht beobachtet. Der Anteil an gebildetem Uran(IV) steigt asymptotischen bis zu einem pH-Wert von 9, wo das Maximum mit 16 % bestimmt wurde. Als Reaktionsprodukt der Redoxreaktion wurde eine Uran(VI)-Uran(IV)-Mischphase mit der Summenformel [UIV(UVIO2)5(OH)2]12+ identifiziert. Mit Hilfe der cryo-TRLFS wurde, durch Verminderung von Quencheffekten die Uranspeziation in natürlichen Medien (Urin, Mineralwasser) direkt bestimmt. Proben mit Uran Konzentrationen von < 0,1 µg/L konnten dadurch analysiert werden. In handelsüblichen Mineralwässern wurde die zu erwartende Komplexierung durch Carbonat nachgewiesen. Im Urin zeigte sich in Abhängigkeit vom pH-Wert eine unterschiedliche Uranspeziation. Die fluoreszenzspektroskopische Untersuchung wies bei niedrigerem pH Wert (pH<6) eine Mischung aus Citrat- und Phosphat-Komplexierung des U(VI) und bei höheren pH-Wert (pH>6) eine deutliche Beteilung von Carbonat an der Komplexierung auf. Diese Ergebnisse stehen in sehr guter Übereinstimmung mit theoretischen Modellrechnungen zur Uranspeziation im Urin. Die in dieser Arbeit gewonnenen Ergebnisse zeigen, dass für eine zuverlässigere Prognose des Urantransportes in Geo- und Biosphäre in Zukunft nicht nur Betrachtungen zur Komplexchemie, sondern auch zum Redoxverhalten des Urans nötig sind, um die Mobilität in der Natur richtig abschätzen zu können.

Diffuse Layer Modeling was used to describe single and multi-solute adsorption of Pb(II), Cu(II), Zn(II) and Cd(II) to ferrihydrite and As(V), V(V) Si and Ca(II) on granular ferric hydroxide, a commercially available iron oxide. Macroscopic data were used in conjunction with x-ray adsorption spectroscopy (XAS) data to evaluate the diffuse layer surface complexation model (DLM) for predicting sorption over a range of conditions. A self-consistent database was created for each of the adsorbents. The DLM provided excellent fits to the single solute data for the ferrihydrite system with the incorporation of spectroscopic evidence. Little competition was seen in the bisolute systems, except under very high coverages. While the DLM captured the lack of competition under low and medium coverages, competitive effects were not adequately modeled by the updated DLM for high coverages. Challenges remain in adequately describing metal removal when sorption may not be the primary mechanism of removal. The capabilities of the DLM were then evaluated for describing and predicting multisolute sorption to granular ferric hydroxide (GFH). The model can adequately describe anion competition, but the electrostatic effects due to outer sphere sorption were overpredicted, leading to an inadequate model fit for As(V) and Ca²⁺ systems. Despite the limitations of the DLM, it may be an appropriate compromise between goodness of fit and number of parameters for future integration into dynamic transport models and thermodynamic databases. / text

Ce mémoire est essentiellement consacré à la synthèse électrochimique et à la caractérisation structurale de matériaux composites d'électrode nanostructurés du type polymère fonctionnalisé contenant une dispersion homogène de nanoparticules d'oxydes de ruthénium ou d'iridium, ainsi qu'à l'étude de leurs propriétés électrocatalytiques vis-à-vis de l'oxydation en milieu aqueux de l'arsenic(III) en arsenic(V). La combinaison de l'oxydation électrocatalytique de l'arsenic(III) avec la technique d'ultrafiltration LPR (Liquid phase Polymer-assisted Retention) nous a permis de confirmer tout l'intérêt de cette approche combinée pour éliminer l'arsenic. Dans ce processus, les matériaux nanocomposites à base d'oxyde d'iridium ont montré les propriétés les plus intéressantes, car ils sont capables de catalyser l'oxydation de l'arsénite en milieu neutre et à des potentiels peu positifs. Enfin, les matériaux d'électrode nanostructurés à base d'oxyde d'iridium sont également efficaces pour l'oxydation catalytique à 4 électrons de l'eau en dioxygène et présentent donc un fort intérêt potentiel dans le contexte de la réaction de dissociation de l'eau. Mots clés : oxyde de ruthénium, oxyde d'iridium, nanocomposite, électrocatalyse, arsenic, ultrafiltration, oxydation de l'eau

Les polyazamacrocycles trouvent de nombreuses applications dans le domaine de la complexation de cations métalliques ou d'anions. Le laboratoire à longtemps étudié la fonctionnalisation des dérivés tétraazamacrocycliques et leurs propriétés de complexation. Afin d'accroître le savoir-faire du laboratoire et d'explorer de nouvelles propriétés de complexation des polyamines cycliques, nous nous sommes intéressé à transposer ce savoir à la fonctionnalisation d'un macrocycle plus petit : le tacn. Ce travail repose sur la mise au point d'une nouvelle stratégie de fonctionnalisation sélective du tacn et la synthèse de nouveaux dérivés. Les composés obtenus ont permis l'étude de leurs propriétés de complexation vis-à-vis de différents métaux de transition. Les propriétés de complexes de cuivre (II) ont été étudiées pour des applications en imagerie TEP ou en radioimmunothérapie. La détection de zinc (II) basée sur une détection IRM par de nouvelles sondes ditopiques tacn-do3a a été étudiée. La complexation de fer (II) pour des applications en transition de spin ont également permis de déterminer les propriétés de complexation de dérivés du tacn.

O presente trabalho procurou investigar influência da presença de proteínas do soro do leite na atividade antioxidante da vanilina e ácido vanílico frente ao radical DPPH&bull; e a espécie de ferro hipervalente ferrilmioglobina MbFe(IV)=O em meio simulando o trato gastrointestinal. A constante de associação (KA) entre a vanilina e a &beta;-lactoglobulina (BLG) foi determinada utilizando-se as técnicas de espectroscopia de emissão molecular (KA = 400 &plusmn; 12&middot;102 L&middot;mol-1) e microcalorimétria (KA = 5,6&plusmn;0,3&middot;102 L&middot;mol-1) ambas em tampão fosfato com CH+ = 10-7,4 mol&middot;L-1 e força iônica 0,32 (NaCl). Para a interação entre a vanilina e albumina de soro bovino (BSA) encontrou-se o valor de 340 &plusmn; 13&middot;102 L&middot;mol-1 em meio de tampão fosfato com CH+ = 10-6,4 mol&middot;L-1 e força iônica 0,32 (NaCl), obtido por espectroscopia de emissão molecular. Constatou-se pela técnica de microcalorimetria que a complexação possui caráter exotérmico e as contribuições de interações hidrofóbicas para a complexação são fracas. A reatividade da vanilina e ácido vanílico com o radical DPPH&bull; foi investigada em meio de emulsão aquosa Tween-20&reg; com CH+ = 10-2,0 mol&middot;L-1. Os resultados obtidos demonstraram que a vanilina não pode ser considerada um bom antioxidante frente ao DPPH&bull; (k298 = 1,42&plusmn;0,04&middot;10-1 L&middot;mol-1&middot;s-1), no entanto, o ácido vanílico apresentou maior reatividade frente ao radical DPPH&bull; (k298 = 17,1&plusmn;0,3 &middot;10-1 L&middot;mol-1&middot;s-1). A presença das proteínas BLG e BSA nas reações de redução do radical DPPH&bull; pela vanilina e ácido vanílico conduziu a um efeito antagônico na constante de velocidade de reação. Os parâmetros termodinâmicos do estado de transição da reação com DPPH&bull; apresentaram valores relativamente altos de entalpia de ativação e moderados valores de entropia de ativação: &Delta;H&Dagger;298 = 34,0 &plusmn; 0,3 kJmol-1 para a vanilina e 46,2 &plusmn; 0,1 kJmol-1 no complexo com BSA e 51,0 &plusmn; 0,6 kJ&middot;mol-1 no complexo com BLG, valores negativos de entropia &Delta;S&Dagger;298 = -147,4 &plusmn; 0,9 J&middot;mol-1&middot;K-1, -105,3 &plusmn; 0,5 J&middot;mol-1&middot;K-1 e -90 &plusmn; 2 J&middot;mol-1&middot;K-1 respectivamente. Os valores de entalpia e entropia de ativação encontrados para o ácido vanílico foram: &Delta;H&Dagger;298= 19,6 &plusmn; 0,2 kJ&middot;mol-1, 10,2 &plusmn; 0,03 kJ&middot;mol-1 e 37,6 &plusmn; 0,3 kJ&middot;mol-1 para os complexos com BSA e BLG respectivamente e valores negativos de entropia &Delta;S&Dagger;298=-174 &plusmn; 0,5 J&middot;mol-1&middot;K-1, -206,0 &plusmn; 0,1 J&middot;mol-1&middot;K-1 e -116 &plusmn; 1 J&middot;mol-1&middot;K-1. A partir destes valores de entalpia e entropia de ativação o mecanismo de redução do radical DPPH&bull; foi atribuído a um processo de abstração de átomo de hidrogênio (HAT/PCET). A reação de desativação da espécie MbFe(IV)=O pela vanilina apresentou constante de velocidade de k298 = 57&plusmn;1 L&middot;mol-1&middot;s-1 sendo superior quando comparada ao ácido vanílico k298 = 15&plusmn;1 L&middot;mol-1&middot;s-1, fato este atribuído as cargas totais, negativa, do redutor e da proteína nas presentes condições experimentais. Observa-se um efeito antagônico da complexão da vanilina pelas proteínas na atividade antioxidante frente à ferrilmioglobina, onde o efeito reduziu, mas não impediu a reação de transferência de elétrons por esfera-externa à longa distância. Em contrapartida, a presença das proteínas BLG e BSA não influenciaram a reatividade do ácido vanílico frente à espécie MbFe(IV)=O. Os parâmetros de ativação encontrados para a reação de redução da MbFe(IV)=O com a vanilina apresentaram valores de &Delta;H&Dagger;298 = 58,8 &plusmn; 0,3 kJmol-1 e &Delta;S&Dagger;298 = -14 &plusmn; 1 J&middot;mol-1&middot;K-1, &Delta;H&Dagger;298 = 45,5 &plusmn; 0,3 kJ&middot;mol-1 e &Delta;S&Dagger;298 = -60 &plusmn; 1 J &middot;mol-1&middot;K-1, &Delta;H&Dagger;298 = 68,6 &plusmn; 0,4 kJ&middot;mol-1 e &Delta;S&Dagger;298 = 17 &plusmn; 1 J &middot;mol-1&middot;K-1 para vanilina \"livre\", complexo com BSA, e complexo com BLG respectivamente. Para a redução com ácido vanílico foram determinados os seguintes valores de entalpia e entropia de ativação: &Delta;H&Dagger;298 = 41,8 &plusmn; 0,2 kJ&middot;mol-1 e &Delta;S&Dagger;298 = -82,4 &plusmn; 0,7 J&middot;mol-1&middot;K-1, &Delta;H&Dagger;298 = 37,7 &plusmn; 0,3 kJ&middot;mol-1 e &Delta;S&Dagger;298 = -96 &plusmn; 1,0 J&middot;mol-1&middot;K-1, &Delta;H&Dagger;298 = 53,5 &plusmn; 0,2 kJ&middot;mol-1 e &Delta;S&Dagger;298 = -44 &plusmn; 1,0 J&middot;mol-1&middot;K-1 para vanilina \"livre\", complexo com BSA, e complexo com BLG respectivamente. / The present study evaluate the influence of the presence of whey proteins in the antioxidant activity of vanillin and vanillic acid towards the DPPH&bull; radical species and the hypervalent iron species ferrylmyoglobin, MbFe(IV)=O under conditions simulating the gastrointestinal tract. The association constant (KA) between vanillin and &beta;- lactoglobulin (BLG) was obtained using molecular emission spectroscopy (KA = 400 &plusmn; 12&middot;102 L&middot;mol-1) and microcalorimetric titration (KA = 5.6&plusmn;0.3&middot;102 L&middot;mol-1) both in phosphate buffer CH + = 10-7.4 mol&middot;L -1 and ionic strength 0.32 (NaCl). For the interaction between vanillin and bovine serum albumin (BSA) it was founded value of 340 &plusmn; 13&middot;102 L&middot;mol-1 in phosphate buffer with CH+ = 10-6,4 mol&middot;L-1 and ionic strength 0.32 (NaCl), as obtained by molecular emission spectroscopy. It was founded by microcalorimetry tritation that the complexation has a exothermic character and the contributions of hydrophobic interactions for complexation are weak. The reactivity of vanillin and vanillic acid toward DPPH&bull; radical was studied in aqueous emulsion using Tween-20&reg; with CH + = 10-2.0 mol&middot;L-1. The results show that vanillin can not be considered a good antioxidant (k298 = 1.42&plusmn;0.04&middot;10-1 L&middot;mol-1&middot;s-1), however vanillic acid show higher reactivity than vanillin towards the radical DPPH&bull; (k298 = 17.1&plusmn;0.3&middot;10-1 L&middot;mol-1&middot;s-1). The presence of the proteins BLG and BSA in the reduction reactions of the DPPH&bull; radical by vanillin and vanillic acid led to an antagonic effect in the reaction rate constant. The thermodynamic parameters for the transition state of the reaction with DPPH&bull; showed relatively high values of enthalpy of activation and moderately negative entropy of activation: &Delta;H&Dagger;298= 34.0 &plusmn; 0.3 kJmol-1 for vanillin and 46.2 &plusmn; 0.1 kJmol-1 for complex with BSA and 51.0 &plusmn; 0.6 kJ&middot;mol-1 for complex with BLG, negatives values of entropy &Delta;S&Dagger;298 = -147.4 &plusmn; 0.9 J&middot;mol-1&middot;K-1, -105.3 &plusmn; 0.5 J&middot;mol-1&middot;K-1 and -90 &plusmn; 2 J&middot;mol-1&middot;K-1 respectively. The values of enthalpy and entropy of activation found for vanillic acid were: &Delta;H&Dagger;298 = 19.6 &plusmn; 0.2 kJ&middot;mol-1, 10.2 &plusmn; 0.03 kJ&middot;mol-1 and 37.6 &plusmn; 0.3 kJ&middot;mol-1 for BSA and BLG respectively and negative values of entropy &Delta;S&Dagger;298 = -174 &plusmn; 0.5 J&middot;mol-1&middot;K-1, -206.0 &plusmn; 0.1 J&middot;mol-1&middot;K-1 and -116 &plusmn; 1 J&middot;mol-1&middot;K-1. From these values of enthalpy and entropy of activation the mechanism of radical DPPH&bull; reduction was assigned to a process of hydrogen atom transfer (HAT/PCET). The deactivation reaction of the MbFe(IV)=O species by vanillin shown rate constant of k298 = 57&plusmn;1 L&middot;mol-1&middot;s-1, which it is higher than vanillic acid k298 = 15&plusmn;1 L&middot;mol-1&middot;s-1. This fact is assigned to the total negative charges of the reductor and the protein under the experimental conditions. It is observed an antagonistic effect of the complexation of vanillin by proteins in the antioxidant activity, in which the effect diminish, but not avoid the long range electron transfer by out-sphere reaction. On the other hand, the presence of BLG and BSA do not affect the reactivity of vanillic acid towards the MbFe(IV)=O species. The activation parameters found for the reduction of MbFe(IV)=O by vanillin revealed values of &Delta;H&Dagger;298 = 58.8 &plusmn; 0.3 kJmol-1 and &Delta;S&Dagger;298 = -14 &plusmn; 1 J&middot;mol-1&middot;K-1, &Delta;H&Dagger;298 = 45.5 &plusmn; 0.3 kJ&middot;mol-1 e &Delta;S&Dagger;298 = -60 &plusmn; 1 J &middot;mol-1&middot;K-1, &Delta;H&Dagger;298 = 68.6 &plusmn; 0.4 kJ&middot;mol-1 and &Delta;S&Dagger;298 = 17 &plusmn; 1 J &middot;mol-1&middot;K-1 for free vanillin, complex with BSA and complex with BLG respectively. For the reduction by vanillic acid it were with the following values of enthalpy and entropy of activation: &Delta;H&Dagger;298 = 41.8 &plusmn; 0.2 kJ&middot;mol-1 and &Delta;S&Dagger;298 = -82.4 &plusmn; 0.7 J&middot;mol-1&middot;K-1, &Delta;H&Dagger;298 = 37.7 &plusmn; 0.3 kJ&middot;mol-1 and &Delta;S&Dagger;298 = -96 &plusmn; 1.0 J&middot;mol-1&middot;K-1, &Delta;H&Dagger;298 = 53.5 &plusmn; 0.2 kJ&middot;mol-1 and &Delta;S&Dagger;298 = -44 &plusmn; 1.0 J&middot;mol-1&middot;K-1 for free vanillin, complex with BSA and complex with BLG respectively.

Ce travail porte sur la synthèse chimique d’analogues simples d’anthocyanes, une classe majeure de pigments naturels solubles dans l’eau. Onze ions flavylium substitués par des groupements hydroxyl,méthoxyl et beta-D-glucopyranosyloxyl en positions 4’, 5 et 7 ont été préparés en utilisant des procédures simples. De plus, les deux principales 3-désoxyanthocyanidines du sorgho rouge, l’apigéninidine (APN) et la lutéolinidine (LTN), ont été synthétisées en une seule étape. Les propriétés physico-chimiques ainsi que l’activité antioxydante ont été étudiées pour le chlorure de 3’,4’,7-trihydroxyflavylium (P1), son 7-O-beta-D-glucoside (P2) et le chlorure de 3’,4’,5,7-tétrahydroxyflavylium (LTN). Grâce à leur noyau catéchol, ces pigments complexent rapidement FeIII, AlIII and CuI et ne se lient que faiblement à FeII tout en stimulant son autoxydation en FeIII. Suite à la complexation de CuII, les pigments subissent une oxydation. Les aglycones P1 et LTN sont des ligands modérés de l’albumine de sérum humain (HSA) et leurs chalcones ont montré une plus grande affinité pour la HSA que leurs formes colorées. Leur capacité antioxydante a été démontrée par le test de réduction du radical stable DPPH et par l’inhibition de la peroxydation lipidique induite par le fer héminique, un modèle de stress oxydant postprandial dans l’estomac. Les aglycones P1 et LTN (particulièrement, dans leur forme incolore chalcone) sont plus efficaces que le glucoside P2. / This work deals with the chemical synthesis of simple analogs of anthocyanins, the main class of watersolublenatural pigments. Eleven flavylium ions with hydroxyl, methoxyl and beta-D-glucopyranosyloxylsubstituents at positions 4’, 5 and 7 have been prepared by straightforward chemical procedures.Moreover, the two main 3-deoxyanthocyanidins of red sorghum, apigeninidin (APN) and luteolinidin(LTN), have been synthesized in a one-step protocol. The physicochemical properties and antioxidantactivity are investigated for 3’,4’,7-trihydroxyflavylium chloride (P1), its 7-O-beta-D-glucoside (P2) and3’,4’,5,7-tetrahydroxyflavylium chloride (LTN). Owing to their catechol B-ring, they rapidly bind FeIII,AlIII and CuI, more weakly interact with FeII while promoting its autoxidation to FeIII. Following CuIIbinding, the pigments undergo oxidation. Aglycones P1 and LTN are moderate ligands of human serumalbumin (HSA) with chalcones having a higher affinity for HSA than the corresponding colored forms.The antioxidant activity of P1, P2 and LTN is investigated via two tests: reduction of the stable DPPHradical and inhibition of heme-induced lipid peroxidation (a model of postprandial oxidative stress inthe stomach). Aglycones P1 and LTN (especially in their colorless chalcone form) are more potent thanglucoside P2.

Organic ligand complexation reactions at the mineral-water interface play an important role in several environmental and geochemical processes such as adsorption, dissolution, precipitation, pollutant transport, nutrient cycling, and colloidal stability. Although organic ligand surface complexation reactions have been extensively studied, a molecular level understanding regarding the mechanisms underlying the adsorption of such compounds is still limited. The purpose of the current study was to investigate the interactions between some common naturally occurring organic ligands and a common aluminosilicate clay mineral, kaolinite, using a combination of macroscopic and microscopic experimental methods. Molecular level information regarding the structure and binding mode of adsorbed species was obtained using in situ MIR-FTIR spectroscopy. Other experimental techniques including adsorption experiments, surface titrations, and surface complexation modelling were also employed in order to quantify and describe the macroscopic adsorption properties of the organic ligands examined. Three low molecular weight organic acids (oxalic, salicylic, and phthalic acid) and humic acid were chosen as representative organic ligands. Spectroscopic evidence revealed that low molecular weight organic acids are able to form both inner and outer sphere complexes on kaolinite, and the relative concentrations of these surface complexes varies with solution chemistry. Inner sphere coordination modes inferred are a mononuclear bidentate for oxalate (five-membered chelate ring) and phthalate (seven-membered chelate ring); and a mononuclear monodenate (six-membered pseudochelate ring) for salicylic acid. Similar coordination modes were shown to form on simpler mineral (hyrd)oxides. Elucidation of the coordination chemistry of these ligands can provide insights into the dissolution mechanisms of silicate minerals In contrast to low molecular weight organic acids, there was no evidence of inner sphere complexation by humic acid acids on kaolinite or gibbsite. The combined spectroscopic and macroscopic adsorption results suggest that cation bridging and van der Waals interactions are the two most probable mechanisms for the adsorption of humic acid by these mineral substrates. This finding casts doubts over the use of low molecular weight organic acids as humic acid analogs.

The present PhD thesis entitled “Design, Synthesis and Evaluation of Chromofluorogenic Probes for Contaminating Species” is focused on the development of new chromo-fluorogenic sensors based on the principles of molecular recognition. The first part of this thesis is focused on the design and synthesis of suitable organic compounds as sensors for metal cations. The selected sensing paradigm was the binding site-signalling subunit approach. The synthetized receptors employs a chromophore (fluorescein or BODIPY) skeleton as signalling subunit and it is functionalized with aminoethoxy moieties as binging site; the metal coordination reduces the electron-donating ability of the nitrogen atom conjugated to the chromophore resulting in optical changes noticeable to the naked-eye. The sensing behavior is highly selective to trivalent cations (Fe3+, Al3+ and Cr3+) with remarkable limits of detection. The receptors based on BODIPYdyes retain the sensing abilities in mixed aqueous solutions. The remaining chapters of the thesis are centered in the detection and removal of nerve agents surrogates. The design, synthesis, characterization and application of new BODIPY chemosensors were studied. These chemosensors were designed containing different reactive sites in order to avoid interferences produced by acids or hydrolysis products, and also be able to distinguish between the different G-nerve agent mimics (DCNP and DFP). The BODIPY-probes allows screening of nerve agent surrogates with remarkable limits of detection and optical changes noticeable to the naked-eye. The sensing abilities are retained in solid support, allowing practical application in real-time monitoring by simple colorimetric tests. The displacement assay approach has been used to develop a selective sensor for V-nerve agent surrogates versus G-type. For this purpose, two Eu3+ and Au3+ BODIPY-complexes were prepared. In this case, V-surrogate is capable of coordinate the metallic center, releasing the BODIPY ligand. This causes a change in the optical properties visible to the naked-eye. Finally, the use of supramolecular-based organocatalyst for destruction of OP nerve agent surrogates was studied. Hydrolysis studies were performed in presence of 1,3-diindolylureas and thioureas, amines, aminoalcohol and glycols. Addition of catalyst enhances the electrophilic character of the P atom, and the final nucleophilic attack of water that results in the formation of the corresponding less toxic organophosphate derivatives, thus higher hydrolysis rates are obtained. / Barba Bon, A. (2014). Design, Synthesis and Evaluation of Chromo-fluorogenic Probes for Contaminating Species [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48521 / TESIS