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Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1992. / Vita. Abstract. Includes bibliographical references (leaves 156-167). Also available via the Internet.

A grass phytoremediation field study was initiated in July 1997 at the site of a former railroad tie facility that used creosote for tie preservation. The site is contaminated with polycyclic aromatic hydrocarbons (PAHs). A test matrix consisting of 36 planted (clover, fescue and rye grasses) and unplanted cells was established. The focus of the study was to evaluate PAH remediation in fertilized plots that were unplanted or seeded with clover, fescue or rye. Samples were collected from a depth of 15 to 21 cm, and the six most prevalent PAHs, acenaphthene, fluorene, phenanthrene, fluoranthene, pyrene and chrysene were quantified. Data from four sampling periods, t=0, 9, 12 and 17 months is presented. At t=9 months, substantial loss of the five lowest molecular weight (LMW) PAHs had occurred, and the loss was attributed to natural attenuation. During the first 9 months, below average precipitation at the site delayed grass root development. Between t=9 and 12 months, above average precipitation was recorded and this appeared to accelerate chrysene removal rates in both the unplanted and planted cells; however, the rate was higher rate in the planted cells. Similarly, fluoranthene and pyrene degradation seemed to be enhanced in the fescue and rye cells. Over the last 8 months of the study, acenaphthene, fluorene and phenanthrene concentrations approached constant, minimum levels suggesting additional removal will be limited. PAH compounds with higher solubility correlated to decreased constituent soil concentrations. Additional sampling was initiated at t=17 months to compare PAH concentrations with depth. This was done because the observed root mass changed significantly with depth. Samples were taken at two additional depths 10 to 15 and 32 to 38 cm. Increased removal of fluoranthene and pyrene was observed in the uppermost zone, suggesting a role for plants in remediation of these 4 ringed PAHs. / Master of Science

Polyarene dendrimers are composed entirely of aromatic rings and are of interest as they possess rigid and shape-persistent structures, which have potential applications in materials chemistry and as scaffold for functional molecules. This thesis describes the synthesis and characterisation of a number of new polyarene dendrimers containing pentaphenylbenzene-like (pentaaryl dendrimers) and hexaphenylbenzene-like (hexaaryl dendrimers) branching units which are capable of focal and peripheral expansions. These structures are based on terminal and internal 1,3-dialkyne cores, onto which two polyaryl sections were introduced via Diels-Alder reaction. These compounds possess inherent axial chirality as a result of the dialkyne position on the core, and a range of differently substituted polyaryl units which result in further chiral axes. Several crystal structures of pentaryl dendrimers were obtained, with these crystallising either as meso conformers or conformers with C2 symmetry. Introduction of a chiral auxiliary onto the central aromatic ring of these dendrimers provided evidence of the atropisomers in solution. These were studied via VT 13C NMR, revealing fast rotation and an energy barrier of about 66 kJ mol-1. The presence of additional aromatic rings on a hexaaryl dendrimer enabled observation of atropisomerism in solution owing to the greater steric hindrance of rotation of its branching units about the chiral axes. Fluorine-containing analogues of these dendrimers were synthesised and subjected to conformational studies through 19F-19F Exchange Spectroscopy (EXSY). Qualitative and quantitative analysis of the spectra revealed the kinetic and thermodynamic parameters, showing that the energy barrier of rotation of these dendrimers was within the range of 75-80 kJ mol-1, which was sufficient for spectroscopic observation but not for physical separation. Polyaryls with symmetry or lacking symmetry have been synthesised. The lack of symmetry was achieved by stepwise introduction of the polyaryl fragments. This demonstrates a route to polyaryls with sections possessing different structural features and thus potentially engineered properties and future chemical differentiations.

Projects were undertaken investigating the functionalisation of polyaromatic cores (chrysene, pyrene and perylene) for use in organic electronics and aqueous graphene stabilisation. In each case an iridium-catalysed aromatic C-H borylation formed a key synthetic step, allowing access to unique substitution patterns. The development of strategies for the orthogonal and asymmetric functionalisation of polyaromatic hydrocarbons was explored. In a key synthetic step 4,10-dichlorochrysene was regioselectively borylated in high yields at the 2,8-positions though C-H activation chemistry. The subsequent application of sequential palladium-catalysed Suzuki and Kumada coupling reactions to this intermediate enabled the synthesis of a series of chrysene derivatives with a unique orthogonal "A2B2" 2,8- and 4,10-substitution pattern. In addition the application of a trifluoromethylation at the borylated 2,8-positions enabled the synthesis of a donor-acceptor chrysene derivative. The effect of these substitution patterns on the photophysical and electrochemical properties of these derivatives was investigated and their potential use as organic semiconducting materials evaluated. In particular the synthesised chrysene derivatives displayed broadened UV-vis absorption spectra, redshifted fluorescence spectra, increased HOMO levels and decreased band gaps. In an extension of these aromatic substitution methodologies, pyrene and perylene aromatic cores were functionalised to perform as stabilisers for aqueous graphene dispersions, investigating asymmetric motifs that may maximise performance. A series of amphiphilic pyrene- and perylene-based alkylsulfonic acid salts were synthesised via their intermediate hydroxyalkyl derivatives. In addition the application of the previously explored aromatic C-H borylation allowed access to 7- and 5,8,11- asymmetrically substituted pyrene and perylene derivatives. Through collaboration, initial steps have been undertaken to compare and evaluate these novel stabilisers for their ability exfoliate graphite to graphene in aqueous solution.

Photophysical properties of an array of various polyaromatic hydrocarbons were benchmarked with B3LYP, M06 and B97D methods coupled with Pople and CEP-31G(d) basis sets. Results from the benchmark show the importance of diffuse basis sets when modeling the electronic properties of highly conjugated systems and provide qualitative reliable accuracy with certain levels of theory. B97D and M06 are applied to modeling pyrene adducts governed by non-covalent interactions in both gaseous and condensed states to reproduce experimental spectra. DFT calculations with both B97D and M06 functionals show qualitatively and quantitatively that pyrene dimer is a stronger π–base as compared to its monomer. Binding energies coupled with MEP, PCA and Qzz results show that the difference in π-basicity of the monomer and dimer impacts the supramolecular chemistry involved in adducts formed with super π-acidic silver cyclometallic trimer (CTC). Non-covalent interactions between coinage metal CTCs and ammonia/phosphine substrates is reported. Interactions between these substrates and the facial plane of the π-rich gold CTC reveal a novel interaction, where the typical Lewis acid/base roles are reversed for the substrates. Adducts formed through this type of interaction define typical Lewis bases like ammonia and phosphine as Lewis acids, wherein the partially positive hydrogens coordinate to the metallo-aromatic center through dipole-quadrupole interactions. Interactions of ammonia at the side positions is shown to heavily impact the Lewis basicity of the CTC facial plane leading to similar interactions exhibited by the ammonia-gold CTC adducts. Structural and electronic properties of the adducts modeled are examined.

Les composés polyaromatiques polysoufrés représentent une classe de molécules peu étudiées, malgré leurs propriétés intéressantes. La présence du soufre influence les propriétés redox, photophysiques et de complexation. Nous avons préparé une série de ces composés par des réactions de substitution nucléophile aromatique. Ceux-ci peuvent être fonctionnalisés par des unités polyaromatiques, tels que l’anthracène ou le pyrène, ou par des glycosides. Leurs propriétés de luminescence ont été étudiées en particulier sous l’angle de l’émission induite par l’agrégation, où les composés deviennent émissifs lorsqu’ils sont immobilisés en phase solide ou fortement refroidis. Ils permettent également de stabiliser des nanoparticules de fer/platine, où une forte densité d’atomes de soufre divalent joue un rôle important en nanosciences. Les dérivés glycosylés ont été testés chez différentes lectines comme ConA, PAIL, PAIIL et Bc2lA, les trois dernières étant impliquées dans les infections bactériennes chez les patients atteints de mucoviscidose. Les études comprennent les propriétés photophysiques, de réticulation et des mesures d’affinité par des méthodes biophysiques (SPR, ITC et HIA). Ceci a ammené à la production de nouveaux biocapteurs ou sondes luminescentes basés sur des interactions sélectives lectine-sucre dans l’éventualité future de dispositifs de diagnostics et de détection à partir d’expression de lectines (ex. cancer, infections bactériennes, etc.).Une autre classe de composés polyaromatiques a été étudiée, les hélicènes. Ces molécules hélicoïdales chirales sont retrouvées sous deux formes énantiomériques, selon le pas d’hélice. Nous présentons ici une nouvelle méthode de synthèse des hélicènes par une voie organométallique de réactions d’annulation et d’insertions C-H. Une étude poussée des conditions réactionnelles a été réalisée. Nous avons préparé des hélicènes fonctionnalisés. Les dérivés bromés et cyanés du [5]-hélicène ont été déposés sur la surface de Suzuki, afin d’étudier par nc-AFM les propriétés de structuration de ces produits sur une surface isolante. Le [5]-hélicène a aussi été fonctionnalisé par des unités mannosylés, dans les mêmes perspectives que pour les astérisques soufrés glycosylés. Ces hélicènes glycosylés sont les premiers de la sorte décrit dans la littérature. Ils ont présenté des propriétés convenables vers des sondes luminescentes chirales et d’autres biocapteurs, qui sont basés sur les interactions lectine-sucre. / Polysulfurated polyaromatic compounds represent a class of molecules that are not extensively studied, despite their interesting properties. The presence of sulfur affects their redox, photophysical and complexation properties. We prepared a series of these compounds by using some aromatic nucleophilic substitutions. They can be further functionalized by some polyaromatic units, such as anthracene or pyrene, or by some glycosides.Their luminescence properties have been especially studied for their agregation induced emission properties, where the emission of the compounds is turned on when they are immobilized in solid phase or strongly cooled. These compounds can also be used to stabilize iron/platinum nanoparticles, where a high density of divalent sulfur atoms play an important role in nanosciences. Glycosylated derivatives have been tested with different lectins like ConA, PAIL, PAIIL and Bc2lA, the last three being involved in bacterial infections found in patient suffering from cystic fibrosis. Studies include photophysical and reticulation properties, and also affinitiy assays by using biophysical methods (SPR, ITC, and HIA). It provided some novel biosensors or luminescent sensors based on some selective lectin-carbohydrate interactions, in the event of future diagnostic devices and biological detection originating from lectins expressions (ex. cancer, bacterial infection, etc.).Another class of polyaromatic compounds has been studied, the helicenes,. Those chiral helical molecules can be found under two enantiomeric forms, according to the sense of the helical pitch.We herein present a new synthetic method of helicenes based on an organometallic route for some annulation reactions and C-H insertions. An exhaustive study of reaction conditions has been performed. We have prepared some functionnalized helicenes. Brominated and cyanated [5]-helicene derivatives have been deposited on a Suzuki surface, in order to study their structuration properties by nc-AFM on a non conductive surface. [5]-helicene was further functionnalized with some mannosylated units, with the same perspectives as for the glycosylated sulfurated asterisks. Those glycosylated helicenes are the first of their kind described in the literature. They provided some adequate properties toward new chiral and luminescent sensors, as well as other biosensors, which are based on lectin-carbohydrate interactions.

Resumo: O gênero Burkholderia compreende um grupo de bactérias muito diversificado, ocupando vários nichos ecológicos e possui espécies que causam doenças, mas outras espécies apresentam habilidades importantes para os ramos da agricultura, biotecnologia e do ambiente, como a biodegradação. Essas bactérias são morfologicamente semelhantes e o gênero está dividido em dezessete genomovars, onde espécies semelhantes geneticamente são agrupadas, formando o Complexo Burkholderia cepacia (CBC). Por meio de estudos moleculares do gene 16S rRNA e do gene recA foi possível fazer a classificação adequada em espécies dos 450 isolados obtidos da Terra Preta Antropogênica (TPA) e adjacentes, em quatro sítios (TPA Caldeirão Cultivado; TPA Caldeirão Capoeira; TPA Hatahara e TPA Mina-I), foram obtidos 177 isolados do gênero Burkholderia. Desses isolados, pela análise do gene 16S rRNA foi possível classificar 157 isolados ao nível de espécie e pela análise do gene recA somente 105 isolados foram classificados neste mesmo nível. Esses isolados foram utilizados no teste de biodegradação dos hidrocarbonetos. Os hidrocarbonetos poliaromáticos (HPAs) são compostos orgânicos resultantes da combustão incompleta da matéria orgânica e dos derivados de petróleo, são pouco solúveis em água e muito tóxicos para as células, por isso, não são metabolizados por muitos micro-organismos e acabam contaminando e inviabilizando os ambientes. Nos testes de biodegradação os substratos utilizados foram o naftaleno, o fenantreno e o diesel, juntamente com o indicador redox 2,6- diclorofenol-indofenol (DCPIP), que sofre descoloração (de azul para incolor) quando as células utilizam os substratos como fonte de carbono para o crescimento celular, gerando elétrons que vão reduzir o indicador. Pela análise do teste, 19 isolados degradaram o naftaleno, 16 degradaram... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The genus Burkholderia comprises a very diverse group of bacteria occupying various ecological niches and has species that cause disease, but other species have important skills to the branches of agriculture, biotechnology and the environment, as biodegradation. These bacteria are morphologically similar genus and is divided into seventeen genomovars, where genetically similar species are grouped together, forming the Burkholderia cepacia complex (BCC). Through molecular studies of 16S rRNA and recA gene was possible to make the appropriate classification of species in 450 isolates of Terra Preta Antropogênica (TPA) and adjacent at four sites (TPA Caldeirão Cultivado; TPA Caldeirão Capoeira; TPA Hatahara e TPA Mina-I) were obtained 177 isolates of the genus Burkholderia. These isolates by 16S rRNA gene analysis was possible to classify 157 isolates to species level and the recA gene analysis only 105 isolates were classified in the same level. These isolates were used to test the biodegradation of hydrocarbons. Polyaromatic hydrocarbons (PAHs) are organic compounds resulting from incomplete combustion of organic matter and petroleum derivatives, are not very soluble in water and very toxic to cells, therefore, are not metabolized by many microorganisms to contaminate and render environments. In biodegradation tests the substrates used were naphthalene, phenanthrene and the diesel, along with the redox indicator 2,6- dichlorophenol-indophenol (DCPIP), who suffers discoloration (blue to colorless) when cells use the substrates as a source of carbon for cell growth, generating electrons that will reduce the indicator. By analysis of the test, 19 isolates degraded naphthalene, phenanthrene degraded the 16 and 126 degraded diesel, generating a total of 132 isolates of the genus Burkholderia that have the ability to degrade at least... (Complete abstract click eletronic access below) / Orientador: Dejanira de Franceschi de Angelis / Coorientador: Siu Mui Tsai / Banca: Margarete de Fátima Costa / Banca: Eleonora Cano Carmona / Mestre

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Atmospheric aerosols play an important role in various atmospheric issues (effect to the radiation budget of the atmosphere, visibility reduction, smog production, destruction of stratospheric ozone, …). Epidemiological studies proved a correlation between increased mortality and high concentration of ambient particulate matter. Over the past decade, a growing attention has been focused on the organic compounds that are constituents of aerosol particles. Although organic compounds comprise often up to 60% of the total aerosol mass, their composition, concentration and formation mechanisms are not well understood. Diploma thesis will deal with the study of chemical composition of organic compounds bound to atmospheric aerosols with focus on polyaromatic hydrocarbons and sugars. Atmospheric aerosols will be sampled on filters and filter extracts will be analysed for content of studied organic compounds by means of GC, GC-MS or LC, respectively. Development and optimalization of extraction methods (PSE, …) and detection of compounds of interest. Concentration of studied organic compounds in aerosol size fractions PM 10, PM 2.5 and PM 1 will be compared.