Dissertations / Theses on the topic 'Platinum-zinc'

Bioinorganic chemistry strives to understand the roles of metals in biological systems, whether in the form of naturally occurring or addition of non-essential metals to natural systems. Metal ions play vital roles in many cellular functions such as gene expression/regulation and DNA transcription and repair. The study of metal-protein-DNA/RNA interactions has been relatively unexplored. It is important to understand the role of metalloprotein interactions with DNA/RNA as this enhanced knowledge may lead to better understanding of diseases and therefore more effective treatments. A major milestone in the development of this field was the discovery of the cytotoxic properties of cisplatin in 1965 and its FDA approval in 1978. Since then, two other chemotherapeutic drugs containing platinum, carboplatin and oxaliplatin, have been used in the clinic. These three compounds are all bifunctional with the ligands surrounding platinum In the cis conformation and rearrangement of the ligands to the trans orientation results in a loss of cytotoxic properties due to rapid deactivation through binding to S-containing proteins. This enhanced reactivity yields new opportunities to study the reactions between proteins and DNA. One of the first crosslinking experiments used transplatin to crosslink NCp7 to viral RNA in order to understand how/where the protein bound to RNA. We have studied the interaction between cis and trans dinuclear platinum complexes and the C-terminal zinc finger (ZF). The trans complex reacts at a faster rate than the cis isomer and causes N- terminal specific cleavage of the ZF. The dinuclear structure plays a critical role in the peptide cleavage as studies with transplatin (the mononuclear derivative) does not result in cleavage. Monofunctional trans platinum-nucleobase complexes (MPNs) serve as a model for the binding of transplatin to DNA. This provides an interesting opportunity to study their reactions with S-containing proteins, such as HIV1 NCp7. MPNs have been shown to bind to the C-terminal ZF of HIV1 NCp7, resulting in zinc ejection. This occurs through a two-step process where the nucleobase π-stacks with Trp37 on the ZF, followed by covalent binding at the labile Cl site to Cys. MPNs have also shown antiviral activity in vitro. The labile Cl on MPNs reduces specificity of these compounds, as it leaves an available coordination site on the platinum center for binding to other S-proteins or DNA. Therefore, we have moved to an inert PtN4 coordination sphere, [Pt(dien)L]2+ (dien= diethylenetri- amine). Due to the strong bond between platinum and nitrogen, covalent reactions are highly unlikely to occur at rapid rates. The strength of the pi-stacking interaction between nucleobases (free and platinated) and the aromatic amino acid, tryptophan (Trp), showed an enhanced binding constant for platinated nucleobases. This was confirmed by density functional theory (DFT) calculations as the difference in energy between the HOMO of Trp and the LUMO of the nucleobase was smaller for the platinum complex. The studies were extended to the Trp-containing C-terminal ZF of HIV1 NCp7 and an increase in association constant was seen compared to free Trp. Reaction of PtN4 nucleobases compounds with a short amino acid sequence con- taining either Ala (no pi-stacking capabilities) or Trp (pi-stacking interactions) revealed an enhanced rate of reactivity for the Trp-containing peptide. This result supports the theory of a two-step reaction mechanism where the platinum-nucleobase complex recognizes the pep- tide through a pi-stacking interaction with Trp followed by covalent binding to the platinum center. The [Pt(dien)L]2+ motif allows for systematic modification of the structural elements surrounding platinum in a search for the most effective compound. Methylation of the dien ligand should, in theory, increase lipophilicity of the compounds, however, due to 2+ charge of the compounds, this simple association does not hold true. Analysis of the cellular accumulation profiles showed little change in the uptake with the addition of methyl groups to the dien ligand, in agreement with the non-linear change in lipophilicity. Modification of L using different nucleobases allows for the tuning of the strength of the π-stacking interaction between Trp and the platinum complex. The addition of inosine (which lacks a H-bonding donor/acceptor at the C2 position) resulted in a lower association constant with both N-AcTrp and the C-terminal zinc finger of HIV1 NCp7. Interestingly, the addition of xanthosine resulted in an ehanced pi-stacking interaction with the C-terminal zinc finger of HIV1 NCp7; likely as a results of the addition of a H-bonding donor (double-bonded O) at the C2 position. The ability of PtN4 nucleobase complexes to inhibit formation of the NCp7 complexation with viral RNA was studied by mass spectrometry and gel electrophoresis. Dissociation of the NCp7-RNA complex was seen upon addition of PtN4 compounds. These compounds were also able to retard formation of the NCp7-RNA complex when pre-incubated with the protein. These results have important implications as inhibition of complex formation between NCp7 and viral RNA has negative implications for viral replication. Despite the success of platinum-nucleobase compounds, it is important to evaluate all potential pi-stacking ligands. A series of pyridine- and thiazole-based compounds were evaluated for the strength of the pi-stacking interaction with N-AcTrp and the C-terminal ZF of HIV1 NCp7. There was notable increase in association constant for the platinum- DMAP (4-dimethylaminopyridine) complex compared to other ligands studied. This result highlights the importance of exploring multiple avenues for the design of specifically targeted inhibitors and further confirms the viability of the medicinal chemistry dual approach of target recognition (non-covalent) followed by target fixation (covalent).

Zinc is an essential cofactor of several proteins. The roles of zinc in these proteins are classified as catalytic, structural or regulatory. Zinc present in structural sites is considered to be a chemically inert, static structural element. On the contrary, previous studies on a C2H2 type zinc finger model compound and the C3H type HIV-1 NCp7 C-terminal zinc knuckle have shown that zinc at these sites can undergo coordination sphere expansion under the influence of a Pt based electrophile. The pentacoordination observed around zinc in these experiments raises an important question: are the structural zinc motifs found in the proteins susceptible to coordination sphere expansion? Through DFT modeling, the existence and nature of the five coordinate zinc species was investigated. mPW1PW91 was chosen as the DFT method by benchmarking against the experimental parameters of a molecule that closely resembles those to be modeled. The results suggest that the observed coordination sphere expansion is due to the flexible nature of thiolate and chloride ligands that are part of the structure. However, if certain conditions are not met, the same flexibility can lead to the destabilization of these rather fragile structures. Unlike the stable three or four coordinate catalytic and structural zinc sites, at regulatory sites, zinc is typically bound to one or two protein ligands. Zinc inhibition of caspases which are central to the process of apoptosis is one such scenario. Several of the caspases are inhibited by zinc at low micromolar range. Regulation of caspases is a strategy for drug development toward apoptosis related diseases; thus it is important to know the molecular details of zinc inhibition of caspases. Currently, it is speculated that zinc binds to the active site His and Cys residues of caspases thus competing with the substrate. However our studies on caspase-3, using enzyme kinetics and biophysical methods, imply more than one zinc binding sites. Contrary to current beliefs, more than 50% of the inhibition is achieved by zinc without affecting substrate binding. Using DFT models, an alternative inhibitory zinc binding site, which better fits our experimental observations, is predicted.

Ternary systems comprising DNA/RNA, proteins and one (or more) metal ion are generating increased interest due to its biological relevance. The knowledge gained from the study of these systems could provide important clues regarding the precise mechanism for transcription factors, repair proteins and metal complexes with anti-tumoral/anti-viral activities.The interactions occurring among the components of these ternary systems can be broadly grouped into covalent and non-covalent. The first kind of interactions can lead to the irreversible transformation of the components in the system, while the second is thought to be reversible leading to transient states and fluxionality. Both kinds of interaction are generally present in living systems, complementing the function of each other.Monofunetional Platinum-nucleobase complexes (MPNs) are synthesized via substitution of a chloride ligand by a nucleobase in platinum complexes with trans geometry. MPNs are particularly interesting for the study of ternary systems since they mimic the first step in the formation of a platinum-DNA adduct and their interaction with aminoacids/proteins provide a good first approach for more complex systems.The presence of the nucleobase as a ligand, significantly modifies the biological activity of these complexes by reducing its cytotoxicity and generating a promising anti-viral activity, especially against HIV-1 virus. The specific role of the nucleobase ligand on these complexes as a non-covalent motif, important for protein recognition, was explored in models involving tryptophan/N-acetyl tryptophan and a small protein domain called zinc finger, containing also a tryptophan residue.The coordination of the nucleobase to a metal ion such as Pt(II) or Pd(II) was found to increase its π-stacking interaction towards aromatic residues in proteins, specifically tryptophan. The enhancing effect was found to depend on the nature of the metal ion, nature of nucleobase and size/complexity of the protein model. Furthermore, DFT studies revealed an important change in the energy for the lowest unoccupied molecular orbital (LUMO) in the coordinated nucleobases, which could place this orbital in an favored position to interact with the highest occupied molecular orbital (HOMO) in the tryptophan residue. Results from calculations showed a good correlation with experimental evidence and could indicate an important role for the frontier molecular orbitals (HOMO/LUMO) of the species involved in the π-stacking interaction.This study was extended to a zinc finger domain from an essential protein in HIV-1 virus, i.e. nucleocapsid protein NCp7. Findings showed that the nucleobase ligand in addition to modulate hydrolysis and reaction rates for MPNs can also be responsible for an initial non-covalent recognition towards a specific protein. This initial recognition has been proposed as the first stage in a two-step mechanism of action for these platinum complexes that ultimately can lead to zinc ejection from the zinc finger domain in the viral NCp7. The significance of the data presented show that is possible to modulate the ligand coordination sphere in metal complexes to can result in great differences in terms of biological effects.The novel chemistry derived from DNA adducts with platinum complexes with a trans geometry was also explored in silico. The molecular dynamics of two free DNA 20-mer is compared with the corresponding metallated-adducts, namely monofunctional, 1,2-bifunctional interstrand and 1,3-bifunctional intrastrand. The differences in terms of structure and energy are compared for these systems, in general the monofunctional adduct exhibited the most interesting feature in terms of structural change in the DNA double strand causing the destacking of the metallated nucleobase. Bifunctional adducts exhibited loss of Watson-crick bonds and localized change in sugar puckering. These results showed that important differences can be found for platinated DNA even at short simulation times < 1 ns.

Le but de cette thèse était d'explorer la chimie de surface des systèmes bimétalliques platine-zinc et leur activité catalytique dans la réaction d'oxydation du CO. La recherche sur ce système bimétallique a été menée sur deux fronts: une étude de surface du système modèle , une couche unique de ZnO discontinue épitaxiée sur du Pt (111), utilisant la microscopie à effet tunnel et le rayonnement synchrotron à proximité de la photoémission par rayons X à pression ambiante, et une étude davantage axée sur la «nanomatériau» du même système bimétallique, en utilisant la chimie complexe de la synthèse colloïdale , microscopie électronique à transmission et à balayage, et enfin XPS de laboratoire.Tout d'abord, une surface modèle constituée d'un film monocouche de ZnO supporté sur du Pt (111) a été fabriquée dans des conditions de vide très poussé. Sa chimie de surface a été explorée par STM puis par rayonnement synchrotron NAP-XPS dans des conditions opératoires. Nous avons pu prouver que ce système était bien un cas typique de catalyse inverse. Les effets synergiques dus à la présence des deux matériaux ont été bien observés, mais uniquement à basse température (jusqu'à 410 K). Au-delà de cette température, les effets de transport de masse empêchent la comparaison de la réactivité des surfaces de ZnO / Pt (111) et de Pt (111). Nous avons montré que des intermédiaires de réaction doivent être formés dans la zone frontière entre le ZnO et le platine, lorsque le film de ZnO est discontinu. Nous avons mis en évidence le rôle clé joué par les hydroxyles présents dans les plaques de ZnO, qui sont dus à la dissociation de H2 ou de H2O de l’atmosphère résiduelle des plaques de platine. En particulier, nous avons détecté par NAP-XPS la présence d'une espèce carboxyle (due à l'association de OH avec CO), qui précède la désorption du CO2. Au-dessus de 410 K, un formiate apparaît et cette dernière espèce est probablement spectatrice du processus d'oxydation du CO. Le transfert des connaissances accumulées dans les précédentes études de la science des surfaces et des catalyseurs modèles au cas plus réaliste des nanocristaux de l’alliage PtZn, tout en aidant à identifier certains phénomènes courants, il montre également ses limites. En fait, les nanocristaux revêtus de leurs ligands oléylamine ont des caractéristiques que les surfaces des modèles UHV ne possèdent pas, en raison du processus de fabrication de la CN lui-même: nous avons trouvé des indices spectroscopiques de la présence d’eau (éventuellement un sous-produit de la réaction, résultant d’une entre la cétone et l'amine); de plus, un recouvrement de la surface du platine par des atomes d'hydrogène est actuellement une explication de nombreux phénomènes observés. Trouver les conditions expérimentales pour produire des nano-alliages bimétalliques à partir de deux précurseurs métal-acac2 était une tâche ardue, bien plus que celle de déposer physiquement un film mince sur un monocristal d’UHV. Nos efforts ont été récompensés car nous avons pu produire des CN en alliage PtZn. C'est l'un des principaux points de la présente étude. La présence de Pt(acac)2 empêche le zinc (dont l'oxydation complète en ZnO, comme c'est le cas lorsque le Zn(acac)2 seul est présent dans l'oléylamine. L'XPS monochromatisé montre que le zinc fabrique un alliage avec le platine, où il reste métallique alors qu’une autre fraction est sous la forme de ZnO, il n’est pas clair si deux canaux de réaction sont en concurrence (alliage PtZn versus oxydation de Zn par l’eau), ou Zn est oxydé par la suite, c’est-à-dire après exposition à l’air. Les CN alliés ont été étudiés en détail par des méthodes avancées de microscopie électronique (y compris dans des conditions opératoires), de diffraction et d’EDS [...]
The purpose of this thesis was to explore the surface chemistry of platinum-zinc bimetallic systems, and their catalytic activity in the oxidation reaction of CO. The research on this bimetallic system was carried out on two fronts: a surface science study of the model system, a discontinuous ZnO single layer epitaxied on Pt(111), using scanning tunneling microscopy and synchrotron radiation near ambien pressure x-ray photoemission, and a more “nanomaterial science” oriented study of the same bi-metallic system, using complex colloidal synthesis chemistry, transmission and scanning electron microscopy, and finally laboratory XPS. First, a model surface consisting of a ZnO monolayer film supported on Pt(111) was fabricated under ultra-high vacuum conditions. Its surface chemistry was explored by STM and then by synchrotron radiation NAP-XPS under operando conditions. We were able to prove that this system was indeed a typical case of inverse catalysis. Synergetic effects due to the presence of both materials were well seen, but only at low temperatures (up to 410 K). Beyond that temperature, mass transport effects prevent the reactivity of the ZnO/Pt(111) and Pt(111) surfaces from being compared. We have shown that reaction intermediates must be formed in the border area between ZnO and platinum, when the ZnO film is discontinuous. We have highlighted the key role played by the hydroxyls present only ion the ZnO patches, which are due to the dissociation of H2 or H2O from the residual atmosphere on the platinum patches. In particular, we have detected by NAP-XPS the presence of a carboxyl species (due to the association of OH with CO), which precedes the desorption of CO2. Above 410 K, a formate appears, and the latter species is likely a spectator in the CO oxidation process. The transfer of the knowledge accumulated in the preceding surface science and model catalysts studies, to the more realistic case of nanocrystals of the PtZn alloy, while it helped identify some common phenomena, it also shows its limitations. In fact the NC coated with their oleylamine ligands have characteristics that UHV model surfaces do not possess, due to the NC fabrication process itself: we have found spectroscopic hints of the presence of water (possibly a byproduct of the reaction, arising from a condensation reaction between the ketone and the amine); in addition, a capping of the platinum surface by H atoms, is, at present, explanatory of many observed phenomena. Finding the experimental conditions to produce bimetallic nano-alloys from two metal-acac2 precursors was a daunting task, much more than that of physically depositing a thin film on a UHV monocrystal. Our efforts were rewarded as we were able to produce PtZn alloy NCs. This one of the main points of the present study. The presence of Pt(acac)2 prevents zinc (whose from being fully oxidized to ZnO, which is the case when Zn(acac)2 alone is present in oleylamine. Monochromatized XPS shows that zinc makes an alloy with platinum, where it remains metallic, while another fraction is under the form of ZnO. It is not completely clear whether two reaction channels are in competion (PtZn alloying versus Zn oxidation by water), or Zn is oxidized afterwards, i.e. after exposure to air. The alloyed NCs have been studied in detail by advanced methods of electron microscopy (including under operando conditions), diffraction and EDS. Unlike the case of the surface model where the STM images were particularly telling, we do not have at this stage of the study an exact model of the interface between the metal alloy and the zinc oxide that surrounds it. On the other hand, we know that the core of the NCs is occupied by the PtZn alloy, and that the outer planes are identical to those of pure platinum. [...]

Etude des proprietes electriques et structurales de deux series de composes a coordinat dmit : composes a etat d'oxydation fractionnaire (m(dmit)::(2))c::(x) et composes donneur-accepteur d(m(dmit)::(2))::(y) (avec m = zn,ni,pt,pd; c = nbu**(+)::(4) et asph**(+)::(4); d = ttf, tmttf, ttmttf, bedt-ttf et tmtsf; n dans (m(dmit)::(2))**(n-) etant egal a 2,1,x,0). Mise en evidence de la nature 2d des composes de la premiere serie et quasi 3d de ceux de la deuxieme; relations structure-conductivite. Mise en evicence de la supraconduction dans le cas du complexe ttf(ni(dmit)::(2))::(2), avec une temperature de transition de 1,62 k sous 7 kbar

碩士
大葉大學
機械工程研究所碩士在職專班
94
Batteries are devices that transform chemical energy into electrical energy. Because of the portability, they are widely applied in various fields. This research focus on analyzing the performance of homemade Zinc-Platinum Batteries by using Arbin full cell test Instruments. During the process of experiments, the proportions and formula of KOH and NH4Cl in the electrolyte solutions are altered to change the distance between the positive electrode and the negative electrode as well as the amount of the current load. By calculating the consuming amount of zinc electrode, we observe the amount of hydrogen produced on the electrode. The results of the experiments indicate that the maximum current a Zinc- Platinum Battery can offer is 1400mA and the current density 166mA/cm2。The concentration of KOH and NH4Cl is in proportion to the battery performance. The best proportion of the electrolyte solutions is when the concentration of KOH reaches 3M, NH4Cl 6M. The distance of between the positive electrode and the negative electrode shows an inverse proportion to the performance. The load of the battery also shows an inverse proportion to the hydrogen amount produced on the electrode. The effectiveness of NH4Cl working to repress zinc corrosion indicates a direction proportion to its concentration. When the concentration of NH4Cl reaches over 5M, it makes poor performance of the battery. The development of a Zinc- Platinum Battery is still at the beginning stage. Its performance is between an Alkaline Battery and Carbon Zinc Battery. It is our hope that with this research, more interests will be aroused and more studies will be conducted to make Zinc-Platinum Batteries meet the highly demanded electricity of 3C products and become popular in the market.

Zinc is produced mainly by electrowinning from acidic zinc sulphate electrolytes. Electrowinning performance is often reported in terms of the specific electrical energy consumption, SEEC, which is a function of cell voltage, U. There is a fundamental relationship between cell voltage and current density. Establishing the parameters governing this relationship, as a function of solution composition and temperature, is critical for the design and optimisation of zinc electrowinning reactors. Zinc is a soft and reactive metal, which makes preparation of an electrode of well-defined and reproducible surface area, on which to conduct electrochemical polarization experiments, difficult. In addition, bulk zinc deposition occurring during cathodic polarization of the electrode causes irreversible morphology changes that alter the real surface are of the electrode. In general, underpotential deposition, UPD, describes the formation of a two-dimensional layer of metal onto a foreign substrate at a potential more positive than that for overpotential deposition, OPD, of the metal. Use of this phenomenon is proposed as a novel technique for generating smooth and reproducible electrode surfaces of reactive metals, using zinc UPD on platinum as a model case. The technique involves polarization of a polished platinum electrode to cause zinc UPD followed by a pulsed polarization step to grow a bulk zinc metal deposit on the electrode. The steady-state zinc deposition rate is recorded as a function of the applied potential. Mass transfer effects are controlled by the use of a rotating disc electrode. After each potential step, the electrode is polarized to a potential near the UPD potential, which dissolves the bulk zinc and regenerates the original smooth electrode. In this manner the voltage - current density relationship for the zinc deposition reaction may be mapped for a particular solution composition. Experiments were conducted to characterize UPD of zinc on platinum in magnesium sulphate and sulphuric acid supporting electrolytes. UPD of zinc on platinum occurs at a voltage approximately 1 V more positive than that of bulk zinc deposition with an estimated charge density of 260 ±30 μC cm⁻², which is in the order of a monolayer of zinc. The UPD layer was determined to evolve into a Pt-Zn alloy which further inhibited hydrogen evolution, relative to the freshly deposited UPD layer. Bulk zinc deposition experiments were carried out in pure zinc sulphate solutions at 25 °C, using the developed technique, and kinetic parameters were evaluated and compared to previously reported values. The Tafel slope for zinc deposition from pH neutral electrolytes was determined to be ca. 60 mV dec⁻¹, while in highly acid electrolytes was ca. 30 mV dec⁻¹, due to the inhibiting effect of hydrogen adsorption. The transition of zinc deposit morphology from a relatively smooth deposit to a dendritic deposit was confirmed to occur at ca. 1000 A m⁻² in 1.0 mol dm⁻³ ZnSO₄. By virtue of the low value of the Tafel slope, the current density for zinc deposition is highly sensitive to overpotential (increasing tenfold for every 30 mV increase). Dendritic growth in industrial zinc electrowinning at a conventional current density of ca. 500 A m⁻² was attributed to the effects on the local current distribution from the vertical distribution of ohmic drop in the electrolyte and screening of the cathode by attached bubbles. The use of forced convection to mitigate these effects is proposed as a means of extending the current density range of zinc electrowinning.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate

碩士
國立中興大學
化學工程學系所
103
In this thesis, the purpose is to study about the photocatalytic activity of titania doped with 3 wt% of zinc oxide and 1 wt% of platinum. The preparation of the photocatalyst is using the sol- gel method and depositing platinum by photoreduction. The parameters of catalyst preparation include amount of water, kinds of solvent, kinds and ratios of disperant, weights of zinc oxide addition, loading of platinum, and sources of UV light for photoreduction of platinum. The photocatalytic activity of the catalyst is tested by photodegradation of methyl orange using quartz glass reactor under UV light illumination. Operating conditions in photocatalytic reaction included initial concentration of methyl orange solution, amounts of catalyst, wavelength of illumination and photodegradation of methylene blue. The results indicated that using the molar ratio 90 of DI water/Titanium isopropoxide with the disperant of sodium dodecylbenzensufonate to prepare titania which doped with 3 wt% zinc oxide and 1 wt% platinum can increase the photocatalytic activity effectively. Under 150 minutes of the UV illumination, the conversion of photodegration of methyl orange solution is about 65.5%. The photodegradation of the methyl orange solution is also performed by the catalyst Pt(1)(ZnO(3)/TiO2(97))(99) under irradiation of UV light (365 nm) and the conversion of degradation is 70.6% in 150 minutea. Using the same catalyst to degradate the methylene blue, the conversion can reach 74.4%. The conversion for the degradation of methyl orange can reach 93.5% when using 1 g of Pt(1)(ZnO(3)/TiO2(97))(99) catalyst.

碩士
長庚大學
化工與材料工程學系
106
In this experiment, the effect of the anode catalyst of direct ammonia fuel cell on the electrochemical oxidation reaction of ammonia was discussed. The metal clusters were deposited on the glassy carbon electrode by means of electric pulse deposition to observe the reaction to ammonia. A direct ammonia fuel cell(DAFC), platinum catalyst for ammonia reaction may be the best, while used as an anode catalyst. There is a poison phenomenon, a nitrogen atom in the process of formation of nitrogen oxide is adsorbed on the catalyst surface, resulting in low current density. The use of electrodeposition of zinc metal on platinum metal, may change the surface of the electronic properties and thus affect the surface - molecular interaction.

碩士
長庚大學
化工與材料工程學系
105
Direct ammonia fuel cell by using ammonia liquid fed in comparison to hydrogen PEM fuel cell and direct methanol fuel cell, DAFC has higher conversion efficiency than PEMFC, with good theoretical capacity (4750A/kg) and OCV (1.17V). DAFC does not produce carbon-containing compounds. Platinum as anode catalyst is the most effective electro-catalyst towards ammonia oxidation for a direct ammonia fuel cell (DAFC), but there is a poison phenomenon. In the oxidation process nitrogen atoms are not easy to desorb the catalyst surface, resulting in retardation of voltage current density. To enhance the catalytic activity of platinum catalyst and reduce the poison phenomenon, platinum catalyst must be modified with catalyst metals, in enhancing the catalytic performance activity. The use of electrodeposition of zinc metal on platinum metal, may change the surface of the electronic properties and thus affect the surface - molecular interaction.

Polypyridine d6 and d8 transition metal complexes have received a great deal of attention because of their wide applications in various areas such as photo-induced energy- and electron-transfer process, artificial photosynthetic centers, electroluminescent displays, dye-sensitized solar cell, and molecular-level machines, etc Compared to 2, 2'-bipyridine-type complexes, 2, 2':6', 2″-terpyridine(tpy)-type complexes have been much less thoroughly examined, because the weak ligand field of tpy-type ligands results in the weak emissive and short-lived excited states of their complexes. However, tpy-type complexes have geometrical advantages, which are achiral and could lead to linear structures upon introduction of substituents at 4'-position of tpy The goal of this work is to overcome the short excited state lifetime drawback of the tpy-type complexes by the development of novel tpy-type ligands, so as to develop long-lived excited state sensitizers potentially for light-harvesting applications Oligo(phenylene-vinylene) (OPV) and derivatives, which are strong luminescent chromophores with semiconducting and electroluminescent properties, were employed to modify the tpy ligand at the 4'-position. Two series of OPV-tpy ligands (mono-tpy and bridging tpy-OPV-tpy ligands) with varying substituents like electron-donating groups (n-C8H17O- and Me2N-) and electron-withdrawing group(-CN) at different positions, were successfully synthesized by means of Wittig-type reactions and the Knoevenagel reaction OPV-tpy and bridging tpy-OPV-tpy ligands show strong luminescence. Their Zn(II) complexes also display strong luminescence with relatively higher quantum yields than the corresponding free ligands. The absorption and luminescent spectra of the free ligands were found to be red-shifted by increasing the length of the phenylene-vinylene or introducing electron donating groups. The Me2N- containing ligand, Me2Npvpt shows strong emission solvatochromism. By varying the solvent polarity, its emission colors were finely tuned to cover the entire visible range from blue (426 nm, Ф = 0.25) in the non polar solvent hexane, to red (626 nm, Ф = 0.52) in the highly polar solvent DMSO. The Zn(II)-induced solvatochromism wase observed in OPV-tpy ligands A series of monometallic Ru(OPV-tpy)22+ complexes and bimetallic [(mpt)Ru(tpy-OPV-tpy)Ru(tpm)]4+ complexes were prepared. All the complexes show very close energy singlet metal-ligand charge transfer (MLCT) transitions and similar electrochemical behaviors. However, progressive changes in the emission, transient absorption and excited state lifetime (tau) were observed. The tau shows a 6000 fold magnitude difference from one vinylene Ru1vRu complex (tau = 14ns, lambdaem max,r,t = 684nm), two vinylene Ru2vRu (tau = 280ns, lambda em max,r,t = 697nm), to four vinylene Ru4vRu complex (tau = 60,000 ns, lambdaem max,r,t = 773nm). Combined spectral data suggest that the energy gap (DeltaE) between triplet MLCT and triplet intraligand (3IL) transitions determines the excited state lifetimes. When DeltaE is large, if 3MLCT is the lowest lying state, tau is very short; if 3IL is the lowest lying state, tau is significantly long. When DeltaE is very small, a long-lived 3MLCT transition might occur, due to reversible energy transfer from 3IL to 3MLCT A series of [Pt(OPV-typ)Cl]+ complexes were synthesized. The long-lived (1 mus - 10mus) phosphorescence with predominant 3pi-pi* in nature was observed in both non-coordinating and coordinating solvents. The transient absorption spectra show ground state bleaching and excited state absorption from visible to far red
acase@tulane.edu

Um mineral é definido com base na sua constituição química e estrutura cristalina, e para se qualificar como tal, deve englobar uma combinação dessas propriedades. É uma substância natural de origem inorgânica. Os minerais são essenciais para a nossa saúde, pois a sua presença é determinante para a atividade celular. No âmbito desta dissertação, percebeu-se que a nível da indústria farmacêutica, os minerais enquadram-se essencialmente como substâncias ativas da fórmula farmacêutica, podendo assim ser usados na prevenção e tratamento de diversas patologias, que podem estar relacionadas ou não com a carência dos mesmos na alimentação diária. O ferro, por exemplo, é utilizado no tratamento da anemia por deficiência deste mineral, o cálcio previne o aparecimento da osteoporose, enquanto a deficiência em magnésio está relacionada com doenças cardiovasculares, diabetes mellitus tipo II, entre outras. Por outro lado, a platina é aplicada no tratamento de diversos cancros, o zinco na terapêutica da doença de Wilson e o lítio na doença bipolar. Na indústria cosmética os minerais são também de grande importância, podendo ser usados como substâncias ativas ou como excipientes, no tratamento ou prevenção de diversas patologias da pele, e em produtos de cuidados pessoais, que são utilizados pelos consumidores como parte das suas atividades diárias de higiene e beleza. A acne e a dermatite seborreica são dois exemplos de patologias que afetam a pele e na qual os minerais são usados como parte do tratamento, respetivamente pelo recurso a composto de zinco e de selénio. Contudo, apesar dos minerais já serem explorados desde a pré-história, ainda hoje em dia são objeto de diversos estudos, com o intuito de estudar novas formas de os aplicar, quer no âmbito da indústria farmacêutica, quer no da cosmética.
A mineral is defined based on its chemical constitution and crystalline structure, and to qualify as such, should encompass a combination of these properties. It is a natural substance of inorganic origin. Minerals are essential for our health because their presence is key to cellular activity. Within the scope of this dissertation, it was noticed that at the level of the pharmaceutical industry, the minerals are essentially as active substances of the pharmaceutical formula, and can thus be used in the prevention and treatment of several pathologies, which may or may not be related to the lack of diets. Iron, for example, is used in the treatment of deficiency anemia in this mineral, calcium prevents the onset of osteoporosis, while magnesium deficiency is related to cardiovascular diseases, diabetes mellitus type II, among others. On the other hand, platinum is applied in the treatment of several cancers, zinc in the therapy of Wilson's disease and lithium in bipolar disease. In the cosmetics industry minerals are also of great importance and can be used as active substances or as excipients in the treatment or prevention of various skin conditions, and personal care products which are used by consumers as part of their daily activities of hygiene and beauty. Acne and seborrheic dermatitis are two examples of conditions that affect the skin and in which the minerals are used as part of the treatment, respectively by the use of zinc and selenium compounds. However, although the minerals have already been exploited since prehistory, they are still the subject of several studies, in order to study new ways of applying them both in the pharmaceutical industry and in cosmetics.