Darbe tirtos struktūrinės ir spektroskopinės dviejų šeimų nematinių skystakristalinių dendrimerų ištirpintų chloroforme savybės. Taip pat struktūrinės, spektroskopinės ir magnetooptinės dendrimerų su įterptomis Co nanodalelėmis savybės. Dviejų šeimų skystakristalinių dendrimerų ištirpintų chloroforme optiniai tyrimai parodė, kad pirmos šeimos skystakristalinių dendrimerų vidinę dalį nusakanti sugerties juosta antros ir penktos generacijų atžvilgiu yra paslinkusi per 8nm, tuo tarpu antros šeimos atitinkamai pirmos ir penktos generacijų atžvilgiu per 19nm. Dendrimerų su įterptomis Co nanodalelėmis magnetooptiniai tyrimai parodė, kad Co nanodalelės gali būti valdomos magnetiniais laukais. / Dendritic structure is one of the prevalent topologies on our planet [1]. Dendrimers is generally described as monodispersed low viscosity macromolecules with highly branched, well defined 3D structure, first reported in 1978 by Vögtle. They are always composed of a core molecule and dendritic branches extended from core to terminal groups [26]. The number of functional groups on the dendrimer surface increases exponentially as a function of generation, of that in the higher generations they become much more spherical and amplified highly ordered architectures. Liquid crystalline dendrimers of their unique structural and physical properties have attached considerable attention. Because of their hyper branched spherical structure, interior inside dendrimers have fixed cavities. Strong interaction forces in the terminal mesogenic units determine that in the interior can be incorporated atoms, ions, guest molecules or nanoparticles. They are particularly well suited materials for hosting nanoparticles of the following reasons: nanoparticles are stabilized and don’t agglomerate, dendrimer branches can be use as selective gates to control access of small molecules [19]. As result of their architecture, dendrimers can possess essential physical, chemical and biological properties and whole range of applications in energy, medicine, engineering, information technology and ect. We present optical and structural studies of liquid crystalline poly(propylene imine) (PPI) dendrimers... [to full text]

Verdazyl radicals are a family of multicoloured stable free radicals. Aside from the defining backbone of four nitrogen atoms, these radicals contain multiple highly modifiable sites that grant them a high degree of derivatization. Despite having been discovered more than half a century ago, limited applications have been found for the verdazyl radicals and little is known about their chemistry. This thesis begins with an investigation to determine whether verdazyl radicals have a future as mediating agents in living radical polymerizations and progresses to their application as substrates for organic synthesis, an application that to date has not been pursued either with verdazyl or nitroxide stable radicals. The first part of this thesis describes the successful use of the 1,5-dimethyl-3-phenyl-6-oxoverdazyl radical as a mediating agent for styrene and n-butyl acrylate stable free radical polymerizations. The study of other verdazyl derivatives demonstrated the impact of steric and electronic properties of the verdazyl radicals on their ability to mediate polymerizations. The second part of this thesis outlines the initial discovery and the mechanistic elucidation of the transformation of the 1,5-dimethyl-3-phenyl-6-oxoverdazyl radical into an azomethine imine, which in the presence of dipolarophiles, undergoes a [3+2] 1,3-dipolar cycloaddition reaction to yield unique pyrazolotetrazinone structures. The reactivity of the azomethine imine and the scope of the reaction were also examined. The third part of this thesis describes the discovery and mechanistic determination of a base-induced rearrangement reaction that transforms the verdazyl-derived pyrazolotetrazinone cycloadducts into corresponding pyrazolotriazinones or triazole structures. The nucleophilicity, or the lack thereof, of the base employed leading to various rearrangement products was examined in detail. The final part of this thesis demonstrates the compatibility of the verdazyl-initiated cycloaddition and rearrangement reactions with the philosophy of diversity-oriented synthesis in generating libraries of heterocycles. A library of verdazyl-derived heterocycles was generated in a short amount of time and was tested non-specifically for biological activity against acute myeloid leukemia and multiple myeloma cell lines. One particular compound showed cell-killing activity at the 250 mM range, indicating future potential for this chemistry in the field of drug discovery.

The emergence of verdazyl radicals as starting materials for organic synthesis is providing a unique opportunity to create a variety of distinctive heterocyclic scaffolds. These stable radicals have previously been used as spin probes, polymerization inhibitors, mediators of living radical polymerizations, and as substrates for molecular-based magnets. However, verdazyl radicals have never been employed to fulfill an organic synthetic role until recently. In an effort to pioneer the chemistry behind verdazyl radicals as novel organic substrates, our lab has been inspired to expand and explore the scope of reactions involving their synthetic utility. This thesis assesses the synthetic versatility of verdazyl radicals by constructing a library of structurally complex and diverse verdazyl-derived heterocycles in an approach called diversity-oriented synthesis. The synthetic versatility was further expanded to the preparation of a biphenyl-stacked biphenylophane, which exhibited interesting structural and conformational features as highlighted herein.

<p>In this thesis, I present the electrochemical studies of three dendrimeric polypropylene imine (PPI) nanomaterials and their applications as a platform in the development of a novel label free DNA nanobiosensor based on electrochemical impedance spectroscopy. Cyclic voltammetry (CV), differentia pulse voltammetry (DPV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques were used to study and model the electrochemical reactivities of the nanomaterials on glassy carbon electrode (GCE) as the working electrode.</p>

Verdazyl radicals are a family of multicoloured stable free radicals. Aside from the defining backbone of four nitrogen atoms, these radicals contain multiple highly modifiable sites that grant them a high degree of derivatization. Despite having been discovered more than half a century ago, limited applications have been found for the verdazyl radicals and little is known about their chemistry. This thesis begins with an investigation to determine whether verdazyl radicals have a future as mediating agents in living radical polymerizations and progresses to their application as substrates for organic synthesis, an application that to date has not been pursued either with verdazyl or nitroxide stable radicals. The first part of this thesis describes the successful use of the 1,5-dimethyl-3-phenyl-6-oxoverdazyl radical as a mediating agent for styrene and n-butyl acrylate stable free radical polymerizations. The study of other verdazyl derivatives demonstrated the impact of steric and electronic properties of the verdazyl radicals on their ability to mediate polymerizations. The second part of this thesis outlines the initial discovery and the mechanistic elucidation of the transformation of the 1,5-dimethyl-3-phenyl-6-oxoverdazyl radical into an azomethine imine, which in the presence of dipolarophiles, undergoes a [3+2] 1,3-dipolar cycloaddition reaction to yield unique pyrazolotetrazinone structures. The reactivity of the azomethine imine and the scope of the reaction were also examined. The third part of this thesis describes the discovery and mechanistic determination of a base-induced rearrangement reaction that transforms the verdazyl-derived pyrazolotetrazinone cycloadducts into corresponding pyrazolotriazinones or triazole structures. The nucleophilicity, or the lack thereof, of the base employed leading to various rearrangement products was examined in detail. The final part of this thesis demonstrates the compatibility of the verdazyl-initiated cycloaddition and rearrangement reactions with the philosophy of diversity-oriented synthesis in generating libraries of heterocycles. A library of verdazyl-derived heterocycles was generated in a short amount of time and was tested non-specifically for biological activity against acute myeloid leukemia and multiple myeloma cell lines. One particular compound showed cell-killing activity at the 250 mM range, indicating future potential for this chemistry in the field of drug discovery.

The emergence of verdazyl radicals as starting materials for organic synthesis is providing a unique opportunity to create a variety of distinctive heterocyclic scaffolds. These stable radicals have previously been used as spin probes, polymerization inhibitors, mediators of living radical polymerizations, and as substrates for molecular-based magnets. However, verdazyl radicals have never been employed to fulfill an organic synthetic role until recently. In an effort to pioneer the chemistry behind verdazyl radicals as novel organic substrates, our lab has been inspired to expand and explore the scope of reactions involving their synthetic utility. This thesis assesses the synthetic versatility of verdazyl radicals by constructing a library of structurally complex and diverse verdazyl-derived heterocycles in an approach called diversity-oriented synthesis. The synthetic versatility was further expanded to the preparation of a biphenyl-stacked biphenylophane, which exhibited interesting structural and conformational features as highlighted herein.

Techn. Hochsch., Diss., 2001--Aachen.

Philosophiae Doctor - PhD / In this thesis, I present the electrochemical studies of three dendrimeric polypropylene imine (PPI) nanomaterials and their applications as a platform in the development of a novel label free DNA nanobiosensor based on electrochemical impedance spectroscopy. Cyclic voltammetry (CV), differentia pulse voltammetry (DPV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques were used to study and model the electrochemical reactivities of the nanomaterials on glassy carbon electrode (GCE) as the working electrode. / South Africa

Orientador: Antonio Claudio Herrera Braga / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-12T16:47:01Z (GMT). No. of bitstreams: 1 Rocha_DanieleFernandadeOliveira_M.pdf: 3918609 bytes, checksum: ca79955ba1bba5d8eb4ed332338d0115 (MD5) Previous issue date: 2008 / Resumo: Neste trabalho foi estudado o comportamento de uma série de iminas estruturalmente análogas quando submetidas à biocatálise com fermento de pão e cenoura. Também foi testado NaBH4 em conjunto com alguns aminoálcoois de diferentes tamanhos, como 1-amino-2-propanol, prolinol e 2-a-hidroxibenzil-benzimidazol ou ácido tartárico. A utilização da biocatálise já é consolidada para a redução assimétrica de carbonilas, mas para a ligação C=N há poucos relatos na literatura, devido à facilidade com que esta ligação sofre hidrólise em meios aquosos. Os resultados foram negativos para biocatálise, apresentando hidrólise do substrato em diversas condições e solventes testados, mesmo com a utilização de 18-C-6 como aditivo e com a imobilização do substrato ou do fermento. As causas destes resultados podem ser tanto a falta de afinidade das enzimas com os substratos testados quanto a instabilidade dos mesmos nos meios utilizados. Foi aplicada uma metodologia bastante simples, com mistura manual de ambos em um almofariz. Testadas várias condições e diferentes solventes, nenhuma delas proporcionou um bom excesso enantiomérico. Uma provável causa para estes resultados pode ser a não eficiência da complexação entre o NaBH4 e os reagentes quirais. Testes de EM e RMN de B e H mostram a formação de um boroidreto quiral, mas não em quantidade suficiente para gerar maior assimetria na redução. Uma grande contribuição deste trabalho é a caracterização de um boroidreto quiral formado a partir de NaBH4 e S-(+)-2- a-hidroxibenzil-benzimidazol já reportado na literatura, mas sem um conjunto de dados conciso acerca de sua estrutura. Este composto gerou o maior excesso enantiomérico 27%, para a redução de N-benzil-(1-feniletilideno)amina / Abstract: This project studies the behavior of a series of imines structurally analogues in bioreductions with baker yeast and carrots, and also with NaBH4 using alternative chiral reagents like 1-amine-2-propanol, prolinol and 2-a- hidroxybenzyl-benzimidazole or tartaric acid. For biocatalysis we investigated different temperatures, solvents and proportions of reagents, but all conditions resulted in hydrolysis of the substrate. The instability of the imines or the lack of affinity can be the cause for these results, even using 18-C-6 as additive and immobilized yeast or substrate. By the chemical imine reduction we tried a simple method of induction, mixing manually NaBH4 and the chiral reagent in a mortar, using different solvents and temperatures, but none of them gave a good enantiomeric excess. Probably there was no coupling between NaBH4 and the chiral reagents, and consequently no preference in for one face in the reduction transition state. MS and NMR analysis have shown the formation of a chiral borohydride, but not an enough amount to give asymmetry in the reduction. A great contribution of this project is the characterization of a chiral borohydride obtained from NaBH4 and S-(+)-2-a-hydroxybenzyl-benzimidazole. It was previously reported, but with no confirmation of its structure. This compound reduced Nbenzyl-(1-phenyletilidene)amine with 27% enantiomeric excess / Mestrado / Quimica Organica / Mestre em Química

Quorum sensing (QS) is a population-dependent signaling process bacteria use to control multiple processes including virulence, critical for establishing infection. There are two major pathways of QS systems. Type 1 is species specific or intra-species communication in which N-acylhomoserine lactones (Gram-negative bacteria) or oligopeptides (Gram-positive bacteria) are employed as signaling molecules (autoinducer one). Type 2 is inter-species communication in which S-4,5-dihydroxy-2,3-pentanedione (DPD) or its borate esters are used as signaling molecules. The DPD is biosynthesized by LuxS enzyme from S-ribosylhomocysteine (SRH). Recent increase in prevalence of bacterial strains resistant to antibiotics emphasizes the need for the development of new generation of antibacterial agents. Interruption of QS by small molecules is one of the viable options as it does not affect bacterial growth but only virulence, leading to less incidence of microbial resistance. Thus, in this work, inhibitors of both N-acylhomoserine lactone (AHL) mediated intra-species and LuxS enzyme, involved in inter-species QS are targeted. The γ-lactam and their reduced cyclic azahemiacetal analogs, bearing the additional alkylthiomethyl substituent, were designed and synthesized targeting AHL mediated QS systems in P. aeruginosa and Vibrio harveyi. The γ-lactams with nonylthio or dodecylthio chains acted as inhibitors of las signaling in P. aeruginosa with moderate potency. The cyclic azahemiacetal with shorter propylthio or hexylthio substituent were found to strongly inhibit both las and rhl signaling in P. aeruginosa at higher concentrations. However, lactam and their azahemiacetal analogs were found to be inactive in V. harveyi QS systems. The 4-aza-S-ribosyl-L-homocysteine (4-aza-SRH) analogs and 2-deoxy-2-substituted-S-ribosyl-L-homocysteine analogs were designed and synthesized targeting Bacillus subtilis LuxS enzyme. The 4-aza-SRH analogs in which oxygen in ribose ring is replaced by nitrogen were further modified at anomeric position to produce pyrrolidine, lactam, nitrone, imine and hemiaminal analogs. Pyrrolidine and lactam analogs which lack anomeric hydroxyl, acted as competitive inhibitors of LuxS enzyme with KI value of 49 and 37 µM respectively. The 2,3-dideoxy lactam analogs were devoid of activity. Such findings attested the significance of hydroxyl groups for LuxS binding and activity. Hemiaminal analog of SRH was found to be a time-dependent inhibitor with IC50 value of 60 µM.