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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

The Studies of Self-Assembled Pyridyl Alkanethiolate Derivative Monolayer on Gold Clusters

Tu, Chih-hung 07 July 2005 (has links)
The preparation and spectroscopic characterizations of size-controlled Pyridine-functionalized gold clusters formed self-assembled 2D superlattices with hexagonal packing were studied. The characterizations of pyridine-modified Au clusters using TEM, UV-vis, NMR and ESCA techniques are also reported. Pyridine-functionalized monolayer-protected Au clusters (MPCs) were prepared as illustrated in Scheme 1. The gold nanoparticles prepared by the reduction with NaBH4 have 3.2 ¡Ó 0.88 nm average core diameters established by TEM. The ~3 nm particles were used to induce size and shap evolution with heating treatment in toluene or in TOABr (tetraoctylammonium bromide). The pyridine-functionalized MPCs exhibit an identifiable plasmon resonance band at ~515 nm. The confirmation of the functionalization of pyridyl octanethiol in Au MPCs came from the downfield NMR resonances in the region of 120-150 ppm, which were established the resonances of the Py moiety.
2

Catalytic enantioselective synthesis of tertiary propargylic alcohols : Al-catalyzed asymmetric alkylation of pyridyl-ynones with dialkylzinc reagents

Friel, Donna Kay January 2008 (has links)
Thesis advisor: Amir H. Hoveyda / General and efficient methods for catalytic enantioselective synthesis of tertiary alcohols prepared by the addition of C-Metal nucleophiles to ketones. / Thesis (MS) — Boston College, 2008. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.
3

Studies in the Hydantoin Series. II. 5-(3-Pyridyl)hydantoin and Its Derivatives

Banta, Marion Calvin 08 1900 (has links)
It is the purpose of this investigation to study the chemistry of 5-(3-pyridyl)hydantoin and to compare its properties with those of 5-phenylhydantoin.
4

Studies in the Hydantoin Series. I. 5-(4-pyridyl)hydantoin and Its Detrivatives

Crowe, Robert E. 08 1900 (has links)
The work presented in this investigation is concerned with the chemical properties of 5-(4-pyridyl)hydantoin as compared with 5-phenylhydantoin.
5

Monoanionic tin oligomers featuring Sn–Sn or Sn–Pb bonds

Zeckert, Kornelia 19 July 2016 (has links) (PDF)
The reaction of the lithium tris(2-pyridyl)stannate [LiSn(2-py6OtBu)3] (py6OtBu = C5H3N-6-OtBu),1, with the element(II) amides E{N(SiMe3)2}2 (E = Sn, Pb) afforded complexes [LiE{Sn(2 py6OtBu)3}3] for E = Sn (2) and E = Pb (3), which reveal three Sn–E bonds each. Compounds 2 and 3 have been characterized by solution NMR spectroscopy and X-ray crystallographic studies. Large 1J(119Sn–119/117Sn) as well as 1J(207Pb–119/117Sn) coupling constants confirm their structural integrity in solution. However, contrary to 2, complex 3 slowly disintegrates in solution to give elemental lead and the hexaheteroarylditin [Sn(2-py6OtBu)3]2 (4).
6

Biomimetics and Host-Guest Chemistry

Gong, Jiachang 17 December 2004 (has links)
In an effort to produce the tetrahedrally coordinated, catalytically active zinc center, three families of tris(2-pyridyl)methanol derivatives were synthesized and characterized. Zinc binding studies revealed that the binding behaviors of the ligands depended on the steric and electronic properties of the substituents on the pyridyl rings, as well as the functional group on the tertiary alcohol. A novel tris-pyridyl macrocyclic receptor was synthesized. The receptor possesses both hydrogen bond donors and acceptors. NMR titration experiments revealed that the receptor simultaneously bound both ammonium cation and the counter anion. The counter anion significantly influences the association between the receptor and the ammonium cation. Chiral ditopic macrocycles, which enantioselectively bind chiral ammonium cations, have also been synthesized. Their enantioselective binding properties, as well as the ditopic recognition properties were investigated
7

Quantitative Analysis of Tobacco-Specific Nitrosamines and their Precursor Alkaloids in Tobacco Extracts

Wilkinson, Celeste T 01 January 2017 (has links)
Tobacco-specific nitrosamines (TSNA) are carcinogenic constituents derived from alkaloids in tobacco. Researchers are actively exploring several avenues to reduce TSNA levels in tobacco products like moist snuff tobacco. The focus of the research presented within is the quantitative analysis of TSNA in tobacco, specifically N’-nitrosonornicotine (NNN), 4-(methylnitrosamino)-1(3-pyridyl)-1-butanone (NNK), N’-nitrosoanatabine (NAT), and N’-nitrosoanabasine (NAB). Tobacco alkaloids and nitrosamines in tobacco are currently analyzed by different instrumentation due to orders of magnitude difference in their concentrations, chromatographic separation challenges due to structural similarities, and similar mass fragmentation patterns. An analytical column using silica and 1,2-bis(siloxy)ethane hybrid particles of 1.7 µm size is the foundation of a chromatographic separation of NNN, NNK, NAT, NAB, nicotine, nornicotine, anatabine, and anabasine. This is the first rapid and robust quantitative method for the TSNA and their alkaloid precursors using high pH mobile phase conditions with ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The suitability of the method is demonstrated by its application to the analysis of reference tobacco materials for cigarettes and moist snuff. In addition, a novel TSNA analytical method was developed using TSNA-specific molecularly imprinted polymers (MIP) as the selective extraction element from tobacco extract. The affinity mechanisms between MIP and TSNA were found to have extensive cross-reactivity to structurally similar alkaloids present in tobacco extract. TSNA-specific MIP was demonstrated to have stronger retention for the alkaloids than for the TSNA substrate. The MIP-TSNA interaction was optimized to create the first analytical method to quantify underivatized NNN and NNK from tobacco extracts by HPLC-UV.
8

The Synthesis of Molecular Switches Based Upon Ru(II) Polypyridyl Architecture for Electronic Applications

Steen, Robert January 2007 (has links)
<p>According to the famous axiom known as Moore’s Law the number of transistors that can be etched on a given piece of silicon, and therefore the computing power, will double every 18 to 24 months. For the last 40 years Moore’s prediction has held true as computers have grown more and more powerful. However, around 2020 hardware manufac-turers will have reached the physical limits of silicon. A proposed solution to this dilemma is molecular electronics. Within this field researchers are attempting to develop individual organic molecules and metal complexes that can act as molecular equivalents of electronic components such as diodes, transistors and capacitors. By utilizing molecular electronics to construct the next generation of computers processors with 100,000 times as many components on the same surface area could potentially be created.</p><p>We have synthesized a range of new pyridyl thienopyridine ligands and compared the electrochemical and photophysical properties of their corresponding Ru(II) complexes with that with the Ru(II) complexes of a variety of ligands based on 6-thiophen-2-yl-2,2´-bipyridine and 4-thiophen-2-yl-2,2´-bipyridine. While the electrochemistry of the Ru(II) complexes were similar to that of unsubstituted [Ru(bpy)3]2+, substantial differences in luminescence lifetimes were found. Our findings show that, due to steric interactions with the auxiliary bipy-ridyl ligands, luminescence is quenched in Ru(II) complexes that in-corporate the 6-thiophen-2-yl-2,2´-bipyridine motif, while it is on par with the luminescence of [Ru(bpy)3]2+ in the Ru(II) complexes of the pyridyl thienopyridine ligands. The luminescence of the Ru(II) com-plexes based on the 4-thiophen-2-yl-2,2´-bipyridine motif was en-hanced compared to [Ru(bpy)3]2+ which indicates that complexes of this category are the most favourable for energy/electron-transfer sys-tems.</p><p>At the core of molecular electronics are the search for molecular ON/OFF switches. We have synthesized a reversible double cyclome-tallated switch based on the Ru(tpy) complex of 3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline. Upon treatment with acid/base the complex can be switched between the cyclometallated and the S-bonded form. This prototype has potentially three different states which opens the path to systems based on ternary computer logic.</p>
9

Design, Synthesis and Properties of Bipyridine-capped Oligothiophenes for Directed Energy and Electron Transfer in Molecular Electronic Applications

Nurkkala, Lasse January 2007 (has links)
<p>The earliest landmark in computer technology was construction of the Electronic Numerial Integrator and Computer, ENIAC. Computational switching was performed with vacuum tubes and relays, rather large in size, making this computer rather unwieldy. The next milestone came with the integration of transistors into computers as the switching component. Since then, transistors have been miniaturised dramatically, resulting in the amount of components integrated on a computer chip increasing logarithmically with time. The components are nowadays so small and so densely packed that problems with leak currents and cross-talk can arise and the lower limit for transistor size will soon be reached. In order to meet increasing demands on the size and performance of electronics, a new paradigm is due – the molecular electronics approach.</p><p>Oligothiophenes have been shown to possess the physical and chemical characteristics required for electron/energy transport in molecular systems. However oligothiophenes must be electronically coupled to other components within a molecular circuit for them to be functional. In this work, different modes of incorporation of [2,2’]-bipyridinyl functionalities onto the ends of prototypic oligothiophene wires have been examined. The bipyridine connectors allow complexation to metal centres which can then function as a source or sink of electrons in the circuit. Ruthenium tris-bipyridine complexes, in particular, possess interesting electrochemical and photophysical characteristics, making them suitable for use in molecular electronics.</p><p>This thesis reports synthetic strategies to a range of novel ligands based on the [2,2’]-bipyridinyl system, together with a study of the redox and fluorescence properties of their ruthenium tris-bipyridine complexes. The mode of connection between the chelating bipyridine and the first member of the oligothiophene chain was found to have a profound effect upon the fluorescence lifetimes and intensities of the resulting complexes. The discovery of complexes exhibiting long and intense fluorescence (a requirement for directed electron/energy transfer within molecular networks) thus forms an important design element in future prototypes.</p>
10

Molecular Electronic Devices based on Ru(II) Thiophenyl Pyridine and Thienopyridine Architecture

Steen, Robert January 2010 (has links)
According to the famous axiom known as Moore’s Law the number of transistors that can be etched on a given piece of ultra-pure silicon, and therefore the computing power, will double every 18 to 24 months. However, around 2020 hardware manufacturers will have reached the physical limits of silicon. A proposed solution to this dilemma is molecular electronics. Within this field researchers are attempting to develop individual organic molecules and metal complexes that can act as molecular equivalents of electronic components such as wires, diodes, transistors and capacitors. In this work we have synthesized a number of new bi- and terdentate thiophenyl pyridine and pyridyl thienopyridine ligands and compared the electrochemical, structural and photophysical properties of their corresponding Ru(II) complexes with Ru(II) complexes of a variety of ligands based on 6-thiophen-2-yl-2,2'-bipyridine and 4-thiophen-2-yl-2,2'-bipyridine motifs. While the electrochemistry of the Ru(II) complexes were similar to that of unsubstituted [Ru(bpy)3]2+ and [Ru(tpy)2]2+, substantial differences in luminescence lifetimes were found. Our findings show that, due to steric interactions with the auxiliary bipyridyl ligands, luminescence is quenched in Ru(II) complexes that incorporate the 6-thiophen-2-yl-2,2'-bipyridine motif, while it was comparable with the luminescence of [Ru(bpy)3]2+ in the Ru(II) complexes of bidentate pyridyl thienopyridine ligands. The luminescence of the Ru(II) complexes based on the 4-thiophen-2-yl-2,2'-bipyridine motif was enhanced compared to [Ru(bpy)3]2+ which indicates that complexes of this category may be applicable for energy/electron-transfer systems. At the core of molecular electronics is the search for molecular ON/OFF switches. Based on the ability of the ligand 6-thiophen-2-yl-2,2'-bipyridine to switch reversibly between cyclometallated and non-cyclometallated modes when complexed with Ru(tpy) we have synthesized a number of complexes, among them a bis-cyclometallated switch based on the ligand 3,8-bis-(6-thiophen-2-yl-pyridin-2-yl)-[4,7]phenanthroline, and examined their electrochemical properties. Only very weak electronic coupling could be detected, suggesting only little, if any, interaction between the ruthenium cores.

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