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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Luminescent lanthanide-containing materials : from small molecules to conducting metallopolymers

Wilkerson, Julie Marie 14 November 2013 (has links)
Luminescent lanthanide complexes have been widely studied for various biotechnology and materials science uses, however, the application of these luminescent systems in metallopolymers has been relatively limited, especially when compared to those incorporating transition metal complexes. The unique and interesting photophysical properties of lanthanide complexes (i.e., high color purity and long radiative lifetimes) make these systems ideal for the development of luminescent metallopolymers, which are a unique class of hybrid materials that synthetically incorporate metal centers into organic polymers, thereby taking advantage of the beneficial properties of both traditional inorganic (i.e., catalysis, optics, electronics) and organic (i.e., easy to process, flexible, low weight) materials. A new class of lanthanide complexes exhibiting metal-based visible and near-IR photoluminescence has been designed, synthesized and fully characterized by melting point, ESI-MS, elemental analysis and single crystal and powder X-ray diffraction (when possible). The photophysical properties of these luminescent monomer complexes were studied in solution and the solid state, with the emission spectra displaying the characteristic line-like emission peaks of the trivalent lanthanide ions. This indicates efficient energy transfer from ligand centered excited states to the emissive excited states of the lanthanides. The monomer complexes have been electropolymerized, resulting in conducting metallopolymers that display metal-based photoluminescence. Because these hybrid materials retain the desirable properties of both inorganic semiconductors and organic polymers, such as near metallic electrical conductivity, ease of processing, flexibility and light weight, they are promising for applications in solid-state lighting. / text
2

Oligothiophenes and conducting metallopolymers : fundamental studies and development of functional materials

Lytwak, Lauren Ashley 17 July 2014 (has links)
Diimine rhenium(I) tricarbonyl complexes are known as phosphorescent emitters and electro- and photocatalysts for the reduction of CO₂ to CO. Conducting metallopolymers containing this rhenium(I) moiety should not only retain the photoluminescent and catalytic properties of the complex but also gain the conductivity, processability, and mechanical flexibility typical of [pi]-conjugated polymers. A series of tricarbonyl rhenium(I) diimine-type monomers and metallopolymers have been prepared. Appended to the ligands are thiophene and 3,4-ethylenedioxythiophene (EDOT) groups for electropolymerization of the metal complexes. UV-Vis absorption and emission spectroscopy studies of the monomers indicate that light emission originates from triplet ligand-centered (³LC) [pi] [right arrow] [pi]* and triplet metal-to-ligand charge transfer (³MLCT) excited states. Additionally, both the monomers and metallopolymers show electrocatalytic activity towards the reduction of CO₂ to CO. Furthermore, the EDOT-functionalized diimine-type ligand (EDOT₂-BPP) also serves as a good sensitizing ligand for luminescent lanthanide emission. A series of lanthanide complexes that utilize tris([beta]-diketonates) and EDOT₂-BPP ligands have been synthesized and studied using X-ray crystallography and photophysical techniques. Large quantum yields and microsecond lifetimes were found for the EuIII and SmIII complexes. Complexes of TbIII were found to have weak luminescent emission due to the less-than-optimal energy gap between the sensitizing ligands and the excited state of the TbIII ion. Oligothiophenes are models for polymeric systems because of solution processability, controlled chain length, and a well-defined structure. We have synthesized a library of alkyl and polyfluoroalkyl-substituted oligothiophenes to study how molecular structure, long-range order, spatial orientation, and varying degree of electronic coupling between molecules influences charge separation in photovoltaics. These oligoalkylthiophenes have been characterized by X-ray diffraction, photophysical methods, electrochemistry, and UV-Vis and EPR spectroscopies. Although the electronic properties of these oligoalkylthiophenes do not vary with alkyl group, aggregates of oligooctylthiophene, made through solution processing, have distinct morphologies with varying amounts of electronic disorder. The extent of electronic disorder within the aggregate is determined by comparing the suppression of the 0-0 vibronic band in the fluorescence spectra to that of the non-aggregated parent molecule. This extent of electronic disorder was correlated with the local contact potential of individual aggregates through Kelvin probe force microscopy (KPFM) measurements. / text
3

Conducting polymers for n-type semiconductors, molecular actuators, and organic photovoltaics

Dinser, Jordan Alyssa 02 December 2013 (has links)
The majority of conjugated polymers are more stable as p-doped materials than n-doped materials. Stable n-doped polymers are still desirable and for all polymer OPVs, pLEDS, n-channel FETs, and other polymeric electronic devices. The use of donor-acceptor architectures has led to improvements in n-type polymer performance. The approach taken here has been to include a metal-coordination site within a donor-acceptor polymer backbone in order to explore the effect of redox matching between the conjugated polymer backbone and the transition metal center. Conducting polymers have shown promise as polymeric actuators for prosthetics, robotics, and dynamic braille displays. For the majority of conducting polymers, the actuation mechanism is a bulk phenomenon related to the uptake and expulsion of counterions. This performance may be improved by incorporating monomers which display geometry changes as a function of oxidation state into the polymer backbone. The molecular-level actuation should additively yield a macroscopic actuation that would surpass as well as compliment the bulk mechanism discussed above. We have synthesized a conjugated polymer which incorporates the sym-dibenzocyclooctatetraene moiety, which is known to undergo a change in geometry from a tub-shaped neutral structure to a planar radical anion, into the polymer backbone. The solution processability of conjugated polymers promises large-scale roll-to-roll processing for organic photovoltaics. However, the use of thin active layers in the majority of high efficiency devices reported to date prohibits this. The recently reported donor-acceptor copolymer KP115 shows high efficiencies in polymer-fullerene blend bulk heterojunction devices even with very thick active layers. This has been reported to be unrelated to the morphology of the blends. By further characterizing this material and preparing derivatives of this polymer, we aim to relate the unique performance of these devices to a structural feature of the polymer. It is proposed that the low recombination rates observed for these blends may be due to the presence of discrete donor and acceptor units in the polymer backbone. In order to further explore this idea, we have a prepared a derivative of KP115 in which a conjugation-breaking meta-phenyl linkage has been introduced between the silolodithiophene unit and the dithienylthiazolo[5,4-d]thiazole unit. / text
4

Synthesis of Metallocene Derivatives: Precursors for the Preparation of [1]Metallocenophanes

2015 February 1900 (has links)
The planar-chiral C2-symmetrical dibromoferrocene derivatives, (S,S,Sp,Sp)-1,1'-dibromo-2,2'-di(2-butyl)ferrocene (88) and (S,S,Sp,Sp)-1,1'-dibromo-2,2'-bis{2-[1-(trimethylsilyl)propyl]} ferrocene (92), were synthesized using the well-established “Ugi’s amine” chemistry. The steric influences of the alkyl groups on ferrocenes 88 and 92 in salt-metathesis reactions were investigated. The reaction of 88 and 92 with iPr2NBCl2 yielded mixtures of bora[1]ferrocenophanes (bora[1]FCPs) 94 and 99 and 1,1'-bis(boryl)ferrocenes 95 and 100 respectively. Ferrocene 92 was expected to yield the highest product ratio of bora[1]FCPs to 1,1' bis(boryl)ferrocenes due to the significant amount of steric bulk on ferrocene from the alkyl groups; however, the product ratio was less than the product ratio obtained for the less bulky ferrocene 88. The product ratios for 88 and 92 were compared to the known product ratios for (Sp,Sp)-1,1'-dibromo-2,2'-di(isopropyl)ferrocene (78) and (Sp,Sp)-1,1'-dibromo-2,2'-di(3-pentyl)ferrocene (79) to determine the effects of the alkyl groups in salt-metathesis reactions. To gain more insight into the effects of the alkyl groups on ferrocenes 88 and 92, a series of conformational analyses of 78, 88, and 92 were performed using density functional theory (DFT) calculations. The DFT calculations aided in the explanation for the unexpectedly low product ratio obtained for ferrocene 92. In efforts to obtain new [1]ruthenocenophanes ([1]RCPs), the synthesis of the ruthenium analog of 78, (Sp,Sp)-1,1'-dibromo-2,2'-di(isopropyl)ruthenocene (105), was attempted. To accomplish this, (R,R)-1,1'-bis(α-N,N-dimethylaminoethyl)ruthenocene (109) was prepared using the same chemistry that was used to prepare its ferrocene analog. However, the synthesis of (R,R,Sp,Sp)-1,1'-dibromo-2,2'-bis(α-N,N-dimethylaminoethyl)ruthenocene (110) via the dilithiation of 109 was unsuccessful. The synthesis of dibromoferrocene derivatives using “Ugi’s amine” chemistry is a long and inflexible process. Therefore, a method to prepare dibromoferrocene derivatives through an alternative synthetic pathway was investigated. The synthesis of (Ss,Ss)-1,1'-bis(p-tolylsulfinyl) ferrocene (118) was accomplished by reacting dilithioferrocene•tmeda with (1R,2S,5R)-(-)-menthyl (SS)-p-tolylsulfinate (117). The diastereoselective dilithiation and subsequent silylation of 118 to obtain (Ss,Ss,Sp,Sp)-2,2'-bis(trimethylsilyl)-1,1'-bis(p-tolylsulfinyl)ferrocene (120) proved to be problematic.
5

Conducting metallopolymers with tridentate ligands and coordination chemistry with corresponding model compounds

Keskin, Şeyma 22 July 2014 (has links)
Conducting polymers that contain metals are remarkable materials, because they have the properties of both organic backbones and metals. Depending on the position of the metal relative to the conjugated backbone, i.e. attached to or directly in the backbone, these two can couple resulting in advancement of the functionality and therefore potential applications of these types of materials. Complexes of tridentate ligands with donor atoms such as phosphorus, nitrogen, and sulfur also have a wide variety of applications. In addition, complexes of tridentate ligands have advantages of stability and control of electron density by variation of donor atoms. Therefore, conjugated polymers with tridentate ligand units will have promise for various applications and advantages in their designs. Complexes of PNP ligand with molybdenum and carbonyl ancillary ligands were synthesized and characterized. Isomerization and conversion reactions between them were investigated as well as the coordination modes. Many types of PNP ligands have been studied in the literature because the hemilabile property of the nitrogen atom promotes some catalytic reactions and gives different coordination geometries. Conducting polymers can be used as redox-active ligands and they can be used to control electron density on the metal attached to them. Synthesis and characterization of a novel polymerizable ligand 3,5-bis-EDOT-N,N-bis[2-diphenylphosphinoethyl]aniline was achieved. Related molybdenum complexes with ancillary ligands as carbonyls were also synthesized and characterized. Monomer complexes and the free ligand were electropolymerized and studied. Tris(bipyridine)ruthenium(II) chloride and analogous complexes have been studied extensively in the literature due to their luminescent and photochemical properties, and excited state lifetimes. Conducting polymers with similar ruthenium groups have been investigated for various applications. Synthesis of four ruthenium complexes with the polymerizable ligand 2,6-Bis[4-[2-(3,4-diethylenedioxy)thiophene]pyrazol-1-yl]pyridine and four different bidentate ligands were reproduced; electropolymerizations of the complexes were achieved; electrochemical, UV-Vis and luminescence studies were performed and discussed. Various complexes of copper, silver, platinum, and palladium with nitrogen and phosphorus donors have been reported for their luminescence behavior as well as their interesting structures. Model complexes of these metals with N,N-bis[2-(diphenylphosphino)ethyl]phenyl-amine (a PNP ligand) have been synthesized and characterized. Absorption and luminescence behaviors as well as the coordination modes were investigated. / text
6

Métallopolymères des éléments f : nouveaux matériaux hybrides semi-conducteurs phosphorescents pour les diodes électroluminescentes organiques / Lanthanide-containing metallopolymers : New semi-conducting hybrid materials for organic electroluminescent diodes

Sergent, Alessandra 08 February 2013 (has links)
Ce travail de thèse porte sur la synthèse et la caractérisation physico-chimique de métallopolymères conjugués des éléments f en but d’utiliser ces matériaux comme composants actifs de diodes électroluminescentes. En effet, les ions lanthanides possèdent des propriétés d’émission intéressantes dans le cadre de nos applications. La chaine polymère permet quant à elle l’introduction de groupements transporteurs de charges. Ces matériaux devraient donc réunir les caractéristiques requises (transport des charges et émission) pour être utilisés dans des PLEDs (Polymer Light-Emitting Diodes), lesquelles emploient pour leur fabrication des techniques de dépôts en solution. Les PLEDs présentent l’intérêt d’avoir une structure simplifiée par rapport aux OLEDs (Organic Light-Emitting Diodes) qui sont construites par juxtaposition de couches successives de petites molécules évaporées sous vide.La synthèse de trois séries de polymères conjugués a été réalisée. La réaction de polymérisation utilisée s’effectue selon un couplage de Suzuki-Miyaura entre des motifs fluorènes et des monomères porteurs de groupements carbazoles et/ou benzimidazoles permettant de coordiner l’ion lanthanide. Plusieurs métallopolymères ont également été isolés. Les composés synthétisés ont été caractérisés par analyse élémentaire, RMN et chromatographie par exclusion stérique. Des études de photoluminescence sur ces composés en présence ou non d’ions lanthanides luminescents ont été effectuées. Enfin, les polymères et métallopolymères ont été utilisés dans la conception de diodes électroluminescentes. / This work deals with the synthesis and physico-chemical characterization of lanthanide-containing metallopolymers to use them as active components in electroluminescent diodes. The emission properties of trivalent lanthanides are particularly interesting in the case of our application. The conjugated chain polymer built up with charge-transport groups. These materials should provide all the properties (conduction and emission) to be used as active layer in PLEDs (Polymer Light-Emitting Diodes) which are devices made by solution deposition techniques. The PLEDs offer the advantage to have a simplified structure in comparison with OLEDs (Organic Light-Emitting Diodes) which are built by juxtaposition of layers constituted by small organic molecules.The syntheses of three series of conjugated polymers have been achieved. The polymerization reaction has been carried out by a Pd-catalyzed Suzuki-Miyaura coupling between fluorenes moieties and monomers bearing carbazole and/or benzimidazole groups acting as a coordinating site for the lanthanide ion. Several metallopolymers were also synthesized. The isolated compounds were characterized by NMR, elemental analyses, and GPC. Photophysical studies have been performed on all the polymers and metallopolymers. Finally, these compounds have been used for the design of electroluminescent devices.
7

Creating more effective functional materials: altering the electronics of conducting metallopolymers for different applications.

Raiford, Matthew Thomas 26 August 2015 (has links)
Conducting metallopolymers possess attractive electronic properties for use in sensors, photoelectronic devices, catalysts, and other applications. Modification of the conducting polymer backbone, through chemical or electrochemical methods, enables control of catalytic, electronic, and optical properties of the metal via inductive modulation of the electron density. Understanding in detail the relationship between the metal and polymer backbone could lead to more effective metallopolymer materials. We hope to study this relationship by probing the band gaps, excited state energy levels, catalytic activity, and sensor function in four metallopolymer systems. Devices with sub-stochiometric ratios of Cu2ZnSnS4 NPs (CZTS: (Cu2Sn)1-xZn1/xS)(0≥x≥0.75)) grown in Cu(II) conducting metallopolymers were produced to study band gap tuning in hybrid materials. The valence and conductance bands of CZTS (x = 0.60) aligned with the HOMO/LUMO of the Cu(II) metallopolymer. Changing the alignment facilitated charge transfer in the hybrid material, leading to photovoltaic materials with efficiencies of ~0.1%. Chemoresistive ionophore sensors were developed by incorporating selective binding groups, such as thiourea, into conducting polymer backbones. Thiourea monomers and polymers showed high selectivity for Pb(II) ions over many competitive ions. XPS experiments demonstrated that reversible chelation of Pb(II) ions could be achieved through a simple uptake/rinse process. The conductivity of the thiourea polymer increased fifty-fold, from 7.75×10−2 S/cm2 to 3.5 S/cm2, after Pb(II) exposure. Sensitivity measurements indicated the sensors have limits of detection near 10−10 M. Highly conjugated ligands were synthesized to explore effective sensitization of visible and near-IR emitting lanthanides. (3,4-ethylenedioxy)thiophene was appended to dipyridophenazine and dipyridoquinoxaline to introduce a group that could be easily electropolymerized. These bi-functional ligands emitted from π-π* and an inter-ligand charge transfer excited states, and therefore, two distinct triplet states were observed. These separate energy pathways allowed for efficient sensitization of both visible (Tb(III), Eu(III), Dy(III)) and near-IR emitting (Nd(III), Yb(III), Er(III)) ions. Finally, we explored the oxidation of a rhodium-containing conducting metallopolymer and the subsequent effect on the activity of the metal center. Oxidation of the backbone led to ancillary ligand attenuation, allowing for control of the catalytically active species in the conducting metallopolymer. Rh(I,III) monomer and metallopolymer catalytic studies showed potential for new heterogenous/homogeneous hybrid catalysts. / text
8

Copper and iron complexes of linear and crosslinked polymers as catalysts for phosphoester hydrolysis and oxidative transformation of phenolic and catecholic substrates

Lykourinou, Vasiliki 01 June 2006 (has links)
The goal of this study is to utilize polymers as macromolecular ligands for the construction of catalysts by formation of coordination complexes with transition metals with the main focus on complexes of Cu(II) and Fe(III) and further determine (a) their catalytic efficiency (b) mechanism of action (c) similarities to enzymatic systems and synthetic metal complexes. The reactions of interest are (1) hydrolytic cleavage of a series of phosphoesters(2) oxidation of catechol type of substrates (3) hydroxylation of phenolic substrates and chlorinated phenols (4) activation of molecular oxygen and/ or hydrogen peroxide (5)oxidative cleavage of DNA plasmid. The major premise of the study is that by mimicking the macromolecular nature and some structural features of enzymes, polymers can in principle, catalyze chemical transformations with similar efficiencies and specificities and can offer alternatives to peptide based catalysts or simple metal complexes with the advantage of a wider range of building blocks, increased stability and the potential of reusability. The crosslinked resins used contained the functional groups iminodiacetate (chelex resin), diethylenetriamine and tris(2-aminomethylamine) and were based on styrene-divinylbenzene backbone. The catalytic proficiencies of the Fe(III) and the Cu(II) complexes of chelex resin and diethylenetriamine approached 100 and 1000 respectively towards the model phosphodiester BNPP at pH 8.0 and 25°C. Moreover, the Fe(III) complexes of linear copolymers with repeating unit of three vinylpyridines to one acrylamide (P1) showed selectivity towards phosphodiester hydrolysis over monoesters and phosphonate esters and exhibited catalytic proficiencies approaching 50,000 towards BNPP hydrolysis. Further exploration of the catalytic capabilities of copolymer P1 revealed that Cu(II) complexes of this macromolecular ligand are potentially capable of assembling to active dicopper intermediates found in the catalytic pathways of copper oxygenases like tyrosinase and catechol oxidase and thus were able to accelerate catechol oxidation to ortho-quinones with rate accelerations approaching 10,000 and hydroxylate phenols with rate accelerations close to one million. The results suggest that these Cu(II)-polymer systems can potentially be used as model systems to further understand metal centered reactive oxygen species (ROS) generated in vivo and can be very promising remediation agents for the dechlorination of persistant chlorine containing pollutants.

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