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Synthesis of 1, 2,4-triazoles and their ruthenium bis-bipyridyl complexes

Hughes, Donal (1999) Synthesis of 1, 2,4-triazoles and their ruthenium bis-bipyridyl complexes. PhD thesis, Dublin City University.

Abstract
On foot of the success of the ruthenium tris-bipyridine complex as a complex capable of catalysing reactions which can convert solar energy into electrical energy, much work has been done to synthesize alternative ligands for use with ruthenium in an effort to increase stability. 1 ,2,4-triazoles have, for a number of years, been synthesised with a view to acting as ligands in these ruthenium complexes. These complexes are vital pieces in the puzzle that will ultimately result in the development of successful artificial photosynthetic systems. While previous work has concentrated on investigation of electrochemical and photophysical properties of ruthenium complexes, this work concerns the synthesis of new 1,2,4-triazole ligands and their complexes. These triazoles have been carefully pre-designed with the aim of being successful ligands in the search for the more efficient electrochemical devices. The thesis follows the logical thought process of the organic experimentalist. The initial challenge was not only to synthesise a heretofore-unknown ligand, but to also develop a synthetic procedure, which can be routinely followed, enabling the facile production of high yields of analogous ligands. The first chapter introduces the problem, which must be investigated. The reader is then introduced to the people and the research behind 1,2,4-triazole synthesis aswell as the synthetic methods used. The next logical step in the process was to produce model compounds. This has the practical advantage of giving the researcher experience in the reactions required in the synthesis. It allows reaction methods to be compared and the possible pitfalls established at an early stage. During model synthesis, one of the stages of triazole synthesis, namely amidrazone formation, produced a bipyridyl dihydrazide molecule from which we obtained a never before reported crystal structure. Along with successful model compound synthesis, a thorough spectroscopic investigation of the 1,2,4-triazoles by 1H-NMR is described. Chapter two describes the synthesis of larger 1,2,4-triazole containing molecules most of which comprise two 1 ,2,4-traizole moieties encased in a heteroaromatic system. Research carried out into these ligands is discussed and the synthetic methods used evaluated. The experimental section of chapter two describes the synthesis of a number of new 1 ,2,4-triazole ligands, termed the “target ligands” of the research. Extensive 1H-NMR and microanalytical data is provided to confirm the punty of the ligands X-ray crystal structures of all but one of the ligands have been obtained, all of which are new and the publication of which is keenly awaited. Chapter three takes the research a stage further by incorporating the “target ligands” into ruthenium complexes. The issue of the removal of methyl ether protecting groups is discussed and solved. All of the target ligands were successfully complexed Detailed 1H-NMR analysis is provided for all the complexes and a deuterated bis-bipyridyl version of each of the complexes prepared and spectroscopically compared. The X-ray crystal structure of one complex gives a superb illustration of the spatial make-up of these rarely reported molecules. Chapter three also contains an organic experimentalist’s introduction to the electrochemistry involved and a cursory investigation of each complex is provided. Ground and excited state absorption and emission results are presented, among others. Chapter four aims to put the thesis into perspective from a practical point of view. For all the experimental work, descriptions of solvent and chemical preparation, equipment and instrumentation used is provided. The aim of the thesis is to have, in this work, a bench-top manual of triazole production to serve as a clear and simple guide to aid researchers in furthering 1 ,2 ,4- triazole synthesis toward the goal of the ultimate “target molecule”.
Metadata
Item Type:Thesis (PhD)
Date of Award:1999
Refereed:No
Supervisor(s):James, Paraic and Vos, Johannes G.
Uncontrolled Keywords:Ligands Synthesis; Solar energy; Electrical energy generation;
Subjects:Physical Sciences > Chemistry
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Science and Health > School of Chemical Sciences
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 3.0 License. View License
ID Code:18858
Deposited On:20 Aug 2013 14:51 by Celine Campbell . Last Modified 08 Dec 2023 13:17
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