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Neste trabalho, o corante 9-aminoacridina foi derivatizado com compostos vinílicos que possuem grupos retiradores de elétrons. A incorporação destes leva à mudanças nas propriedades fotofísicas dos derivados, tais como deslocamentos para regiões de menor energia nos espectros de absorção e emissão, sugerindo a presença de transferência de carga intramolecular (ICT). Os estudos de fluorescência resolvida no tempo confirmam este processo para os derivados. Este estado ICT possui um tempo formação na faixa de 150 – 300 ps e um tempo de vida entre 1 – 3 ns, que depende do solvente. Os derivados que apresentam pelo menos um grupo carbonila como retirador de elétron, possuem um tempo de vida longo na faixa de 8 –10 ns, atribuído à emissão do enol, formado a partir da conjugação estendida por ponte de hidrogênio. A polimerização destes derivados com o ácido metacrílico promoveram mudanças em suas propriedades fotofísicas estacionárias e resolvidas no tempo devido à quebra da conjugação  estendida. Este fato é ilustrado pelos espectros de absorção e emissão que mostram bandas estruturadas, deslocadas para a região de maior energia e um decaimento monoexponencial, semelhante ao observado com 9-aminoacridina. Anisotropia de fluorescência resolvida no tempo mostra que nos copolímeros o tempo de relaxação rotacional do corante é muito sensível à mudança conformacional do poli (ácido metacrílico) com o pH, possibilitando assim o estudo da dinâmica deste polímero em solução aquosa. / In this work, the dye 9-aminoacridine was derivatized with vinylic compounds containing electron withdrawing groups. The incorporation of these groups leads to changes in the photophysical properties of the dye, such a red shift in the absorption and emission spectra, suggesting the presence of intramolecular charge transfer (ICT) effect. Time-resolved studies have confirmed such process in all derivatives. This ICT state has a risetime in the range 150 – 300 ps and a fluorescence lifetime between 1 – 3 ns, that depends of the solvent. The derivatives with at least one carbonyl group as electron withdrawing, have an additional lifetime in the range of 8 –10 ns, attributed to the enol emission formed by the extended conjugation. The polimerization of these derivatives with methacrylic acid induces changes in the stationary and time-resolved properties of the dye due to the breaking of the extended conjugation. This fact is illustrated by the absorption and emission spectra that show structured bands with a blue shift, and a monoexponencial decay, similar to the behavior of 9- aminoacridine. Time-resolved fluorescence anisotropy of the bound dye shows that the copolymers have a segment relaxation of the chain is very sensitive to the change in the conformational shape of poly (methacrylic acid) with pH, and such a process is well indicated by following the rotational relaxation of the dye.

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This dissertation describes the development of a novel ring fragmentation reaction in which cyclic γ-silyloxy-β-hydroxy-α-diazoesters undergo efficient rupture of the Cβ−Cγ bond when treated with tin tetrachloride to provide tethered aldehyde ynoate products with varying tether length, in high yield. Tethered aldehyde ynoates are versatile intermediates and this functional group combination is unique to this fragmentation. The synthetic utility of tethered aldehyde ynoates is highlighted by their predisposition to undergo facile intramolecular [1,3]- dipolar cycloaddition reactions in presence of bistrimethylsylil-α-amino acids to provide 2,5-dihydropyroles. The ability to quickly assemble such structural motifs encouraged studies on the synthesis of steroidal alkaloid solanidine. A new method for the N-amination of oxazolidiones with NH2Cl was investigated and provides efficient access to acyl hydrazines. However, the full scope of the reaction has not been yet fully explored. The study of isopropyl radical additions to N-acylhydrazones and comparison of several stereocontrol elements on the oxazolidinone moiety revealed that all are effective.

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Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Triplet; rigidly linked polychromophores; intramolecular energy transfer. Includes bibliographical references (p. 83-87).

The effect of hydrogen bonding on the conformation of organic moleculesunifies two projects in this thesis. In one project, the stability of the intramolecularhydrogen bond in derivatives of 2-guanidinobenzimidazole was studied bydynamic 1H NMR spectrometry. The impact that this intramolecular hydrogenbond had on the bond order of the neutral guanidino group and on the dynamicconformation of these aromatic structures was related to the concept of hydrogenbond-assisted resonance. In another project, an oligomer possessing repetitiveconformation and capable of much inter- and intramolecular hydrogen bondingwas designed and synthesized. The sensitivity of this oligomer to changes inanion concentration, as well as its own propensity to self-aggregate weremeasured.Hydrogen bonds found in many biological oligomers are connected thougha system of conjugated bonds. Guanidinobenzimidazole is a conjugated systemof carbon and nitrogen, connected by an intramolecular hydrogen bond. Severalderivatives of guanidinobenzimidazole were synthesized, and the effect ofseveral simple alkyl for hydrogen substitutions were studied.Guanidinobenzimidazole was used as a model to study what effect theconjugation and the intramolecular hydrogen bond have on each other.The formation of redundant low energy hydrogen bonds is universal inbiological oligomers. In DNA and RNA multiple hydrogen bonds are formed witha typical energy contribution of only 1-2 kcal/mol. Individually, these interactionsdo not give the biological oligomers their conformational stability, but togetherthey are very stable. The urea and amide based oligomers designed in the workand discussed in the thesis should form multiple hydrogen bonds withthemselves and/or with anionic guests. Chiral oligoureas were designed topossess this characteristic of cooperative conformation that so many biologicaloligomers and polymers share.