Small molecule Zn(II) complexes containing N- and S- donor environments may serve as appropriate models for mimicking Zn protein sites, and thus, their reactions with heavy metal ions such as Pt(II) and W(0) may provide insight into possible adduct formation and zinc displacement. To study such possible interactions between zinc finger proteins and platinum-bound DNA, the ZnN2S2 dimeric complex, N,N?-bis(2- mercaptoethyl)-1,4-diazacycloheptane zinc (II), [Zn-1?]2, has been examined for Znbound thiolate reactivity in the presence of Pt(II) nitrogen ? rich compounds. The reactions yielded Zn/Pt di- and tri- nuclear thiolate-bridged adducts and metalexchanged products, which were initially observed via ESI-mass spectrometry (ESI-MS) analysis of reaction solutions, and ultimately verified by comparison to the ESI-MS analysis, 195Pt NMR spectroscopy, and X-ray crystallography of directly synthesized complexes. The isolation of Zn-(?-SR)-Pt-bridged [(Zn(bme-dach)Cl)(Pt(dien))]Cl adduct from these studies is, to our knowledge, the first Zn-Pt bimetallic thiolatebridged model demonstrating the interaction between Zn-bound thiolates and Pt(II). Additional derivatives involving Pd(II) and Au(III) have been explored to parallel the experiments executed with Pt(II). The [Zn-1?]2 was then modified by cleavage with Na+[ICH2CO2]- to produce (N- (3-Thiabutyl)-N?-(3-thiapentaneoate)-1,4-diazacycloheptane) zinc(II), Zn-1?-Ac or ZnN2SS?O, and 1,4-diazacycloheptane-1,4-diylbis(3-thiapentanoato) zinc(II), Zn-1?-Ac2 or ZnN2S?2O2, monomeric complexes (where S = thiolate, S? = thioether). The [Zn-1?]2 di- and Zn-1?-Ac mono-thiolato complexes demonstrated reactivity towards labile-ligand tungsten carbonyl species, (THF)W(CO)5 and (pip)2W(CO)4, to yield, respectively, the [(Zn-1?-Cl)W(CO)4]- complex and the [(Zn-1?-Ac)W(CO)5]x coordination polymer. With the aid of CO ligands for IR spectral monitoring, the products were isolated and characterized spectroscopically, as well as by X-ray diffraction and elemental analysis. To examine the potential for zinc complexes (or zinc-templated ligands) to possibly serve as a toxic metal remediation agents, Zn-1?-Ac and Zn-1?-Ac2 were reacted with Ni(BF4)2. The formation of Zn/Ni exchanged products confirmed the capability of ?free? Ni(II) to displace Zn(II) within the N-, S-, and O- chelate environment. The Zn/Ni exchanged complexes were analyzed by ESI-MS, UV-visible spectroscopy, IR spectroscopy of the acetate regions, and X-ray crystallography. They serve as foundation molecules for more noxious metal exchange / zinc displacement products.

Late transition metal complexes bearing nitrogen-containing ligands have many applications in biotechnology or industrial catalysis. Imidazole is one of the most common biofunctional ligands to play critical roles in meta1loenzymes, since the imidazole moiety of the histidyl residues often constitutes all or part of the binding sites of various transition metal ions. We use the newly synthesized tetradentate ligand containing the imidazolyl and pyridyl functional group to react with zinc, copper, nickel, and iron ions in order to carry out biomimetic studies. We have obtained two crystal structures via different methods of crystallization. One of them is a mononuclear complex while the other is a polymeric structure. The polymeric structure has demonstrated the spontaneous deprotonation on the imidazolyl nitrogen on binding to the metal ion followed by the intermolecular self-assembly process.We believe that the imidazolate -bridged complexes undergo the pH-dependent interconversions between mononuclear (protonated ligand) and self-assembled oligomer (deprotonated ligand). In addition, we have measured the titration curves of the tetradentate ligand and its corresponding metal complexes to determine the preferential binding sites at varying pH. From the titration processes, we got the protonation constant of ligand and stability constants of its corresponding metal complexes.

The impact of a tri-substituted boron moiety on the chelate sensitization of Tb(III) and Eu(III) lanthanide luminescence and their resulting photophysical properties was investigated. Two triarylboron-functionalized carboxylate ligands 1 and 2 and their respective Tb(III) and Eu(III) complexes, 1Tb, 2Tb, 1Eu and 2Eu were synthesized and fully characterized. The photophysical properties of these compounds were studied and it was established that these three-coordinate boron ligands are highly effective in selective activation of Tb(III) and Eu(III) luminescence yielding high efficiency green and red luminescence, respectively. Potential applications of these triarylboron-functionalized chelate Tb(III) and Eu(III) complexes as luminescent sensors for dipicolinic acid (DPA), a biomarker for anthrax spores, as well as small anions such as F- and CN- in organic solution were examined by titration experiments using UV-Vis absorption and fluorescence emission measurements. Further studies were carried out into the application of the lanthanide complexes as solid substrate luminescent sensors for the same analytes. Furthermore a novel zinc-binding compound, composed of both an 8-hydroxyquinoline fluorophore and a dipyridyl metal binding site, was designed for application as a luminescent sensor for Zn(II), due to the recent link between the metal ion and certain high-profile neurological conditions such as Alzheimer’s and epilepsy. The target ligand compound 1-OH was successfully synthesized and characterized using UV-Vis, Fluorescence and NMR spectroscopy. Further studies of the ligand are recorded by studying the effects of the addition of both four-coordinate boron and tris(8-hydroxyquinolinato)aluminum active sites to the 1-OH molecule frame. The four compounds’ abilities in luminescent Zn(II) detection in organic media were examined by titration experiments with Zn(II) using UV-Vis absorption and fluorescence emission measurements. / Thesis (Master, Chemistry) -- Queen's University, 2012-09-11 16:36:17.004

Photocatalytic carbon dioxide reduction transforms CO2 to useful chemicals and fuels, reducing CO2 emissions and making fossil fuels more renewable. Due to a lack of earthabundant sensitizers, we want to design new earth-abundant sensitizers to go with the many known carbon dioxide reduction catalysts. Zn(II) dipyrrin complexes strongly absorb visible light, but their excited state properties have not been widely studied. To investigate their photophysical properties, two Zn dipyrrin complexes, with and without heavy atoms, were synthesized and characterized by NMR and mass spectrometry. The photophysical properties of the two complexes were measured in polar and non-polar solvents, particularly fluorescence quantum yield and extinction coefficient. Also, through transient absorption spectroscopy, the triplet state quantum yield of both complexes was measures to determine the effect of solvent polarity and heavy atoms on the triplet state formation.

De nos jours, un des objectifs importants de la recherche bioinorganique moderne est le développement d'enzymes artificielles. L'étude séquentielle des acides aminés présents dans le centre actif des métalloenzymes peut présenter une voie possible de la stratégie de modélisation enzymatique. Cependant, les peptides linéaires ont leurs limites lors de la reconstitution des centres actifs des métalloenzymes : ils ne possèdent pas la structure tridimensionnelle bien définie, par conséquent leur structure est vulnérable vis-à-vis de la coordination ou de l’hydrolyse des azotes amidiques. La capacité de coordination des métaux par des peptides linéaires peut être améliorée, par exemple, en les attachant à une plateforme tripodale. Les composés tripodaux peuvent assurer une organisation structurale rigide ou moins flexible pour des chaînes latérales des acides aminés, créant ainsi des sites de coordination pré-organisés pour les métaux. Dans cette thèse, la synthèse et la caractérisation des ligands peptidiques tripodaux contenant de l'histidine et la formation des complexes en présence de cuivre(II) et de zinc(II) sont présentées. Les propriétés acido-basiques ont été étudiées par potentiométrie et différentes techniques spectroscopiques ont été utilisées pour la caractérisation structurale (UV-Vis, CD, ESR, RMN et MS). Outre que la caractérisation thermodynamique et structurale, des propriétés catalytiques des complexes en réaction enzymatiques (oxydation du catéchol, dismutation du superoxyde) ont également été étudiées. Nos résultats ont démontré que les ligands peptidiques tripodaux sont capables d'améliorer la stabilité des complexes métalliques et qu'ils peuvent fournir des structures adéquates pour mimer efficacement les fonctions catalytiques des enzymes. Grâce aux études approfondies et systématiques des propriétés acido-basiques et spectroscopiques, nous avons mis en évidence les forces motrices de la coordination des métaux et établi l'impact de la structure tripodale sur la stabilité, la structure et les propriétés catalytiques des complexes formés. Nos résultats confirment l'effet bénéfique des plateformes tripodales durant la complexation des métaux, et soulignent les possibilités qui s’offrent aux peptides tripodaux dans le domaine de la biomimétisme / One of the most important directions of modern bioinorganic research is the development of artificial enzymes. One pathway of enzyme modeling strategy is the study of amino acid sequences present in the active centers of metalloenzymes. Linear peptides, however, have their limitations in reconstituting the active centers of metalloenzymes, since they do not possess the well-defined three dimensional structure, therefore their structure is vulnerable towards amide nitrogen coordination/hydrolysis. Improvement of metal binding capabilities of linear peptides can be obtained by e.g. their functionalization with tripodal ligands. Tripodal compounds may provide a rigid, less flexible platform for the coordinating amino acid side chains, creating pre-organized metal binding sites. In my thesis, I present synthesis and characterization of histidine containing tripodal peptide ligands and their complex formation in presence of copper(II) and zinc(II). Solution equilibrium was studied with pH potentiometric measurements, and several spectroscopic methods were used for structural characterization (UV-Vis, CD, ESR, NMR and MS methods). Beside thermodynamic and structural characterization, enzyme mimicking catalytical properties of the complexes have also been investigated (catechol oxidation, superoxide dismutation). Our results demonstrated that tripodal peptide ligands are capable of enhancing the stability of metal-peptide complexes, and they may provide convenient structures to efficiently mimic the catalytic functions of enzymes. With thorough and systematical solution equilibrium and spectroscopic studies, we uncovered the driving forces of metal coordination, and established the impact of the tripodal structure in stability, structure and catalytic properties of the forming complexes. Our findings confirm the beneficial effect of tripodal scaffolds in peptide-type ligand-metal complexes, and emphasize the possibilities lying within tripodal peptides in the field of enzyme mimicking

Late transition metal complexes bearing nitrogen-containing ligands may act as catalyst in biotechnology or industrial catalysis. Imidazole is one of the most common biofunctional ligands that play critical roles in meta1loenzymes, since the imidazole moiety of the histidyl residues often constitutes all or part of the binding sites of various transition metal centers. In this work, some new zinc(II), copper(II) and nickel(II) complexes containing the imidazolate and pyridyl moieties incorporated in the imine (ImPyI) and amine (ImPyA) ligands were obtained. Different methods of crystallization yield crystals of complexes (2), (6), (8), (9), (10), (17) and (18). Subsequent structural analyses revealed their interesting structures. In zinc(II) and nickel(II) complexes, facial isomers were isolated while none of the meridional isomers were observed. Particularly interesting is the zinc(II) complexes where two facial complexes with different geometries were identified. The mixture of the different nitrogen donor groups in the same ligand provides handy comparison of these structural variations due to the different nature of these donor groups. One tridentate ligand with bromide substitution on the imidazolate and a tetradentate ligand with an additional pyridyl group were synthesized as an extension of this work. One crystal structure of each of the corresponding metal complex bearing these ligands is also discussed here. Most metal complexes are consolidated by extensive weak hydrogen bonds among them in the crystal lattices.

Les substances humiques (SH) sont issues de la dégradation de résidus organiques et représentent la partie la plus importante de la matière organique des systèmes naturels. Les SH sont capables de piéger de nombreux polluants comme les métaux lourds et jouent donc un rôle majeur dans la rétention des ions métalliques. Leurs propriétés complexantes sont dues principalement à certaines fonctions récurrentes : les groupements carboxyliques et phénoliques.<br />Dans une 1ère partie, l'étude de la complexation de molécules modèles possédant des sites similaires à ceux rencontrés dans les biopolymères naturels a permis d'évaluer les capacités complexantes des fonctions les plus répandues (catéchol, hydroxy-carbonyle et acide carboxylique). L'association de techniques spectroscopiques et de calculs de chimie quantique a permis d'établir un classement des pouvoirs chélatants des composés mono-sites vis-à-vis des ions métalliques Al(III), Pb(II) et Zn(II)), et a montré que ce type de classement est conservé lorsque les sites sont en compétition au sein d'une même structure.<br />Dans une 2nde partie, l'examen par fluorescence synchrone de la complexation des 3 métaux polluants par un acide humique standard (AH) a mis en évidence des comportements différents pour chacun d'eux, reflétant des mécanismes de fixation distincts et une spécificité des interactions métallo-humiques. Nous avons ainsi pu établir un classement du pouvoir complexant de AH vis à vis des 3 cations, en accord avec celui obtenu pour les modèles. Enfin, la compétition entre AH et deux molécules organiques de faible poids moléculaires a montré que les pourcentages de polluants extraits de l'acide humique sont faibles et que celui-ci reste un véritable « réservoir toxique » au sein des milieux naturels.

The modern world faces a number of challenges related to energy and the environment. Atmospheric levels of carbon dioxide have now surpassed the 400 ppm mark due to the burning of fossil fuels, yet despite its abundance and potential use as a C1 feedstock for value-added products, there are both thermodynamic and kinetic barriers associated with the strong carbon-oxygen bonds that preclude its widespread deployment in industry. Nuclear energy is an alternative power source that reduces carbon emissions by billions of tonnes each year, but there are widespread concerns regarding the treatment of the radioactive waste that it accrues (of which the main component is uranyl, [UO2]2+). Most of the work presented in this thesis concerns the synthesis of transition-metal complexes, with the aim of directing catalytic reactivity to convert CO2 to useful products. Part of this thesis also concerns the synthesis of uranyl complexes and the study of uranyl reduction chemistry, which is relevant to uranyl remediation and nuclear waste treatment at a fundamental level. Making use of Earth-abundant metals to carry out hydrocarbon oxidation catalysis is a further focus of this work, as the efficient production of oxygenated compounds under mild conditions is of importance to the fine-chemical industry. Chapter 1 reviews important complexes reported in the literature that successfully convert CO2 to useful products through molecular, homogenous electro-catalysis and ring-opening copolymerisation catalysis. Reactions that exemplify a two-electron reduction of uranyl (i.e. uranium(VI) to uranium(IV)) are reviewed, along with uranyl complexes that undergo ligand-centred redox to give ligand-based radicals. The state of the literature on hydrocarbon oxidation catalysis is reviewed in the introduction. The development of multinuclear, macrocyclic complexes and the reactivity of dinuclear Pacman complexes are also presented. Chapter 2 reports the synthesis and characterisation of a new set of Schiff-base macrocycles and acyclic dipyrrin ligands. A number of attempted synthetic routes towards incorporating a dipyrrin coordination compartment in a macro-cyclic setting are discussed. Differences in electronic structures between dipyrromethanes and dipyrromethenes are also examined by theoretical and experimental methods. Chapter 3 introduces the coordination chemistry of these new macrocycles with zinc(II), where the isolation of dinuclear and tetranuclear complexes is demonstrated using different zinc(II) precursors. Tetranuclear zinc-alkyl complexes presented here are shown to be resistant to insertion chemistry with small molecules, but readily form zinc-oxo, -hydroxyl and -alkoxide clusters upon protonolysis with water and alcohols. These molecular clusters display reactivity towards CO2: a zinc-hydroxyl complex precipitates ZnCO3 at high temperature; and zinc-alkoxide complexes have been used to catalyse the copolymerisation reaction between CO2 and cyclohexene oxide to form polycarbonates. Chapter 4 describes the synthesis of late-transition-metal complexes of macrocyclic ligands and dipyrrins, and explores the relationship between macrocycle geometry and electronic structure. Their reactivities towards CO2 are assessed here, using cyclic voltammetry to assess the electro-catalytic activity of a number of the complexes. Chapter 5 reports the oxidation chemistry of hydrocarbon substrates catalysed by copper(II) complexes. High-temperature catalysis occurs with bimetallic copper(II) complexes, and this chapter describes how added FeCl3 acts as a co-catalyst, leading to greater catalyst stability and allowing the catalytic reaction to occur at room temperature. A range of analytical methods have been used to deduce the catalytically active species, and chemical kinetic measurements have been used to deduce a possible reaction mechanism. Chapter 6 reports the synthesis of a uranyl(VI) dipyrrin complex and details characterisation of its electronic structure by theoretical and experimental methods. Theoretical modelling has indicated that the observed two-electron reduction of uranium(VI) to uranium(IV) is facilitated by the dipyrrin ligand, representing a novel uranyl reduction mechanism.

Orientador: Teresa Dib Zambon Atvars / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-27T20:25:11Z (GMT). No. of bitstreams: 1 Germino_JoseCarlos_M.pdf: 14479907 bytes, checksum: c9f86b7bc1995a755d797d3af0c41cfc (MD5) Previous issue date: 2014 / Resumo: Nesta dissertação foram estudadas as propriedades fotoluminescentes de alguns compostos de coordenação de Zn(II) com N,N'-bis(salicilidenos) em soluções de THF e DMSO e em estado sólido: N,N'-bis(salicilideno)-1,2-fenilenodiamino - salofeno (KG-15) e seu composto de coordenação de Zn(II) aquo[N,N'-bis(salicilideno)-1,2- fenilenodimino]zinco(II)([Zn(salofeno)(H2O)]; (KG-15/Zn)); N,N'-bis(salicilideno)-4,5- diaminopirimidina - sal-4,5-pym (KG-17) e seu composto de coordenação de Zn(II) aquo[N,N'-bis(salicilideno)-4,5-diaminopirimidina]zinco(II) ([Zn(sal-4,5-pym)(H2O)]; (KG- 17/Zn). Os N,N'-bis(salicilidenos) e seus compostos de coordenação de Zn(II) foram sintetizados, observando-se aumento de cerca de 30 % dos rendimentos reacionais sob irradiação ultrassônica. Foram caracterizados por FTIR, ressonância magnética nuclear 1D de hidrogênio (1H) e de carbono (13C), caracterização estrutural por CHN, no caso dos ligantes realizou-se a caracterização estrutural por difração de raios-X de monocristal, foram também determinados os potenciais de óxido-redução do [Zn(salofeno)(H2O)] por voltametria cíclica e os valores de energia das bandas foram comparados com dados de espectroscopia eletrônica de absorção. As espectroscopias de fluorescência estacionária e resolvida no tempo em solução diluída de THF e de DMSO (apenas KG-17) e no estado sólido mostraram evidências da ocorrência da transferência de prótons no estado eletrônico excitado nos ligantes livres e coordendados. O composto [Zn(salofeno)(H2O)] apresentou eletroluminescência muito fraca em um dispositivo formado por vidro/ITO/PEDOT:PSS/composto de coordenação/Ca/Al muito baixa. Um diodo montado por vidro/ITO/PEDOT:PSS/PVK:(PFOFPen:[Zn(salofeno)(H2O)])/Ca/Al apresentou luminescência do composto de coordenação de Zn(II) devido à processos de transferência de energia entre o PFOFPen (doador) e o [Zn(salofeno)(H2O)] (receptor), além da eletroluminescência do PFOFPen / Abstract: In this dissertation the photoluminescent properties of some coordination compounds of Zn(II) with N,N'-bis(salicylidenes) in THF and DMSO solutions and solid state were studied: N,N'-bis(salicylidene)-1,2-phenylenediamine - salophen (KG-15) and its Zn(II) coordination compounds aquo[N,N'-bis(salicylidene)-1,2- phenylenediaminate]zinc(II) - [Zn(salophen)(H2O)] (KG-15/Zn) , N,N'-bis(salicylidene)- 4,5-diaminepyrimidine - sal-4,5-pym (KG-17) and its Zn(II) coordination compounds aquo[N,N'-bis(salicylidene)-4,5-diaminate]zinc(II) - [Zn(sal-4,5-pym)(H2O)] (KG-17/Zn). The ligands N,N'-bis(salicylidenes) and their Zn(II) coordination compounds were synthesized, observing an increase of about 30 % of the reaction proceeds under ultrasonic irradiation. The ligands and Zn(II) coordination compounds were characterized by FTIR,1D nuclear magnetic resonance of hydrogen (1H) and carbon (13C), structural characterization by CHN elemental analysis, in the case of the ligands the structural characterization was performed by monocrystal X-ray diffraction. The oxyreduction potential of [Zn(salophen)(H2O)] were determined by cyclic voltammetry and the values of the electrochemical energy band gap were compared with optical data. The stationary and time resolved fluorescence spectroscopy of the compounds in dilute solutions of THF and of DMSO (only KG-17) and in solid state showed proton transfer in the electronic excited state locaded on the ligands. The [Zn(salophen)(H2O)] compound exhibit a very low electroluminescence in a device consisting by glass/ITO/PEDOT:PSS/PVK:[Zn(salophen)(H2O)]/Ca/Al. A diode assembled by glass/ITO/PEDOT:PSS/PVK:(PFOFPen:[Zn(salophen)(H2O)])/Ca/Al showed luminescence of Zn(II) coordination compound due to energy transfer processes between PFOFPen (donor) and [Zn(salophen)(H2O)] (acceptor), beyond the electroluminescence of the PFOFPen / Mestrado / Físico-Química / Mestre em Química

Rotaxanes and porphyrins are two particularly active fields of research in chemistry. However,molecules that combine the interesting properties of these types of structures are not so common. In this thesis we describe new porphyrin-based multi-rotaxanes, whose syntheses constitute interesting challenges.Porphyrins linked to two or four coordinating macrocycles were synthesised. The "gathering-andthreading" effect of copper(I) was used to thread molecular rods through the rings; the subsequent introduction of stoppers led to the formation of rotaxanes. In the case of the porphyrinic bis-macrocycle a [4]rotaxane was obtained. Host/guest complexation studies with rigid nitrogen ligands showed that the rotaxane behaves as a distensible molecular receptor that can adopt an "inflated" or "deflated" conformation and adjust its shape to the size of the guest. In the case of the porphyrinic tetra-macrocycle the formation of a [3]rotaxane of novel architecture was observed.The synthesis of a new, more rigid bis-macrocycle is in progress. This compound will be used for the construction of a [4]rotaxane that could act as a molecular press able to change the conformation of a guest substrate by compression.