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Voltammetric and spectroelectrochemical results are presented for the one-electron reduction of n-heptyl viologen on clean and silane-modified tin oxide, and on ion-beam modified, indium-tin oxide metallized plastic optically transparent electrodes (ITO MPOTE) surfaces. The use of viologens (dialkyl and diaryl 4,4' bipyridium compounds) in redox chromic displays is well known with a number of papers and patents discussing their use. The ability to vary the coloration rates of the electrochromic reaction of these compounds can be strongly influenced by the state of the electrode surface. Potential-step experiments, where the electrode potential is controlled at low overpotentials, has shown that the viologen reduction occurs through a nucleation process. The work here indicates that an "instantaneous nucleation" model appears to be the favored pathway for the n-heptyl viologen reaction. Chronoabsorptometric analysis of the nucleation process is made possible by monitoring the strongly absorbing viologen cation radical. Chronoabsorptometric data can be used to calculate the nucleation site density on an electrode surface. On silane-modified and ion-beam modified electrode surfaces, a more preferred nucleation site is found for the deposition of the first monolayers of viologen. Through the attachment of a silane or the ion-beam modification of an ITO metallized plastic film (ITO MPOTE), a nonpolar layer is created adjacent to the electrode surface. Prior to electrochemical reduction the n-heptyl viologen dication is partioned and concentrated into this nonpolar layer. The effect is a preconcentration of the viologen next to the electrode surface resulting in a fixed number of nucleation sites and an enhancement of the nucleation rate.

Imidazo[1,5-a]pyridines are an important and versatile class of N-heterocyclic compounds due to their stability, unique biological, and photochemical properties. Due to the conjugation and charged structure, their properties are extended to conducting electricity and also have electronic properties. They can be used for chelating transition metals especially heavy metals that can be harmful to living things (including human). The aim of this research was to develop more useful imidazo[1,5-a]pyridines which are stable in both free and complexed state. A variety of imidazo[1,5-a]pyridyl compounds was synthesized following three useful methods namely (i) The first route includes the isolation of imine intermediates which were then treated with phosphorus oxychloride in one case and hydrochloric acid in another case as catalysts. Both cases resulted in the yield of the same imidazo[1,5-a]pyridyl compounds. (ii) The second route was the development on the first route for those imine intermediates that could not be isolated and only hydrochloric acid catalyst was used. In both the first and second routes, paraformaldehyde was used for the ringclosure step of the reaction. The last route for the formation of imidazo[1,5-a]pyridyl compounds did not involve the use of the paraformaldehyde reagent. The suitable routes were followed depending on the nature of the targeted products and the reaction yields were moderate to excellent. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg,2010.

The study herein described involved the detection of pyridine N-oxide reductase activity in cell-free extracts of E. coli 9723, the determination of co-factors necessary for the enzymatic process, a study of the optimum conditions for enzyme catalysis, and a general characterization of the enzyme.

An attempt is made in the work described in this paper to extend the series started by Hall and Platas by means of a Knoevenagel condensation between 3-hydroxy-1,4-naphtho-quinone-2-(4-methylpyridinium) anhydride and various aromatic aldehydes giving rise to a series of unsaturated substituents on the four position of the pyridine ring.

This dissertation looked at the crystal structure analysis of 2-hydroxymethylpyridine-N-oxide sine this compound could provide data on both substituent effects and hydrogen bonding.

Thesis (MTech (Chemistry))--Cape Peninsula University Of Technology, 2015. / Twelve multicomponent crystals of dicarboxylic acids (succinic, adipic and suberic acid) with derivatives of picoline (4-picoline, 2,4-lutidine, 3,4-lutidine and 3,5-lutidine) were analyzed with the aim of finding correlation between their melting points and crystalline structural features. The solvates of SUC•2,4LUT, SUC•3,4LUT, SUC•3,5LUT and ADP•4PIC are already known structures but were remade for completeness and to obtain their accurate melting temperatures. The acids were selected because of their systematically increasing chain lengths and the selection of the picoline derivatives were based on the systematic variation of the positions of the methyl groups around the pyridine moiety. All the formed multicomponent crystals were analyzed with single crystal X-ray diffraction and parallel to the solution crystallizations, grinding experiments were carried out to prepare the aimed inclusion compounds by using much less of the solvent of crystallization. Thermogravimetry was used to confirm the solvent content of the bulk material and differential scanning calorimetry was applied to obtain information about the melting process, such as the onset and the peak temperature of the melting and the concomitant enthalpy change. The melting temperatures revealed that the inclusion formation significantly decreased the melting points of the staring materials and the melting points of the inclusion compounds for the same acid varied significantly. Hirshfeld surfaces of the base-acid-base moieties and the related fingerprint plots were compared both qualitatively and quantitatively. The melting points of the compounds were plotted against the percentage contribution of the various intermolecular interactions.

Thesis. 1977. Ph.D.--Massachusetts Institute of Technology. Dept. of Chemical Engineering. / M̲i̲c̲ṟo̲f̲i̲c̲ẖe̲ c̲o̲p̲y̲ a̲v̲a̲i̲ḻa̲ḇḻe̲ i̲ṉ A̲ṟc̲ẖi̲v̲e̲s̲ a̲ṉḏ S̲c̲i̲e̲ṉc̲e̲.̲ / Vita. / Bibliography : leaves 378-385. / by John A. Wilkens. / Ph.D.

"January 2002." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Neste trabalho foram realizados as sínteses, caracterização e o estudo da reatividade química dos complexos trans-[RuCl(NO)(py)4](PF6)2½H2O e trans-[RuCl(NO)(py)4]Cl23H2O. Os compostos foram isolados e caracterizados através de técnicas espectroscópicas (UV-vis, infravermelho e 1H RMN), eletroquímicas (voltametria cíclica e polarografia de pulso diferencial) e análise elementar. Os dados espectroscópicos, eletroquímicos e os resultados da análise elementar foram consistentes com as fórmulas dos complexos analisados. Foram utilizados como precursores os compostos [RuCl2(DMSO)4], trans-[RuCl2(py)4] e trans-[Ru(NO2)2(py)4]. O composto com NO foi obtido a partir do complexo trans-[Ru(NO2)2(py)4] em ácido clorídrico concentrado e precipitado como sal de PF6-, formando o complexo trans-[RuCl(NO)(py)4](PF6)2½H2O. O trans-[RuCl(NO)(py)4]Cl23H2O foi obtido a partir de uma solução do complexo trans-[RuCl(NO)(py)4](PF6)2.½H2O, adicionando-se uma solução de cloreto de tetrabutilamônio para precipitar o composto na forma de cloreto. Os espectros na região do UV-vis dos complexos trans-[RuCl(NO)(py)4](PF6)2½H2O e trans-[RuCl(NO)(py)4]Cl23H2O apresentaram três bandas nas regiões ao redor de 230 nm, 260nm e 450 nm. Os espectros de infravermelho apresentaram freqüência de estiramento NO entre 1900 e 1925 cm-1, cujo valor variou dependendo das condições em que foram obtidos os espectros. O ciclovoltamograma do composto trans-[RuCl(NO)(py)4](PF6)2½H2O, obtido em solução de acetonitrila, apresentou um processo redox atribuído ao par NO+/0 e um outro processo com E2c = -0,59 V vs Ag/AgCl atribuído à redução do NO0. A atribuição do processo redox com E½ = +0,30 V vs Ag/AgCl foi confirmada através do experimento de espectro eletroquímica na região do infravermelho, onde a banda atribuída ao NO foi diminuindo à medida que o composto ia sendo reduzido. Na espectroeletroquímica na região de UV-vis em acetonitrila foi possível observar uma reação acoplada à redução do composto trans-[RuCl(NO)(py)4](PF6)2½H2O, podendo ser a substituição do NO0 por uma molécula de solvente. O comportamento eletroquímico do composto trans-[RuCl(NO)(py)4]Cl23H2O foi estudado em solução aquosa. O ciclo voltamograma do composto apresentou um processo redox com E½ =+0,13 V vs Ag/AgCl, que é atribuído ao par NO+/0, um processo em +0,25 V e outro em 0,59 V. Dois processos redox dependentes do processo em +0,25 V foram observados nas faixa entre 0,4-0,7 V e podem ser devidos a produtos formados após uma provável saída do Cl- seguido da liberação do NO, como ocorre com o complexo trans-[RuCl(NO)(cyclam)](PF6)2. No estudo da reatividade do ligante NO no complexo trans-[RuCl(NO)(py)4]2+, observou-se que o NO é pouco reativo ao ataque nucleofílico do OH-, apresentando um pKa do equilíbrio entre as espécies nitro e nitrosilo em 11,5 e um Keq = 6,2.104 L2.mol-2. / In this work, the syntheses, characterization and chemical reactivity of trans-[RuCl(NO)(py)4](PF6)2½H2O and trans-[RuCl(NO)(py)4]Cl23H2O were studied. The complexes were isolated and characterizated by elemental analyses UV-vis, infrared and 1H NMR spectroscopies, cyclic voltammetry and spectroelectrochemistry. [RuCl2(DMSO)4], trans-[RuCl2(py)4] and trans-[Ru(NO2)2(py)4] were used as precursor complexes. The compound with NO ligand was obtained from the reaction of trans-[Ru(NO2)2(py)4] with chloridric acidic, and precipitation with PF6-, resulting in trans-[RuCl(NO)(py)4](PF6)2½H2O. The trans-[RuCl(NO)(py)4]Cl23H2O complex was obtained from a trans-[RuCl(NO)(py)4](PF6)2½H2O acetonitrile solution adding a tetrabutylammonium chloride acetonirile solution. The complex was precipitated as a chloride salt. The UV-vis spectra of trans-[RuCl(NO)(py)4](PF6)2½H2O and trans-[RuCl(NO)(py)4]Cl23H2O displayed three bands around the 230 nm, 260 nm and 450 nm regions. The infrared spectra showed the stretching frequencies NO in the 1900-1925 cm-1 range whose values depend on the conditions with which the spectra were recorded. The cyclic voltammetry of the trans-[RuCl(NO)(py)4](PF6)2½H2O in acetonitrile solutions showed a pair of peaks (E½ = +0.30 V vs Ag/AgCl) corresponding to the NO+/0 redox processes, and other process at E2c = -0.59 V vs Ag/AgCl assigned to NO0 reduction. The assignment of the redox processes was confirmed through infrared spectroelectrochemistry, where the band of NO decreases while the compound was reduced. The UV-vis spectroelectrochemistry in acetonitrile solution, showed a coupled reaction following the trans-[RuCl(NO)(py)4]2+ reduction. This coupled reaction is probably the NO substitution by a solvent molecule. The electrochemical behavior of trans-[RuCl(NO)(py)4]Cl23H2O was studied in aqueous solution. The cyclic voltammetry of this complex displayed a pair of peaks (E½ = +0.13 V vs Ag/AgCl) corresponding to NO+/0 redox processes, a process at -0,25 V and other at 0,59 V. Two other couples dependent on the process at 0.25 V, were observed between +0,4 V and +0,7 V. These may be due to products of the Cl- release followed by the NO release, as occurs in trans-[RuCl(NO)(cyclam)](PF6)2. The trans-[RuCl(NO)(py)4]2+ complex showed a low affinity for OH-, with a pKa of the equilibrium between nitro and nitrosyl species at 11.5 and a Keq = 6.2 x 104 L2.mol-2.