Synthesis and characterisation of mononuclear and dinuclear rhenium carbonyl complexes
Brennan, Claire (2007) Synthesis and characterisation of mononuclear and dinuclear rhenium carbonyl complexes. PhD thesis, Dublin City University.
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Chapter One serves as an introduction to the Thesis. Chapter Two describes the synthesis and characterisation of a series of 3-(pyridin-2-yl)-l,2,4-triazole ligands and the corresponding rhenium(I) tricarbonyl. The structure of the complexes have been determined using NMR and IR spectroscopy. The complexes underwent [Re—>7t*(pyridyl-triazole)] transitions in the 295 - 360 nm region of the absorption spectrum. Emission was observed from all the complexes at 298 K and at 77 K. The absorption and emission properties of the pyridyl-triazole complexes were found to be pH dependent. The complexes underwent an irreversible Re(I)/Re(II) oxidation. The a-donor nature of the triazole ligand results in a blue shift of both the absorption and emission spectra when compared to [Re(CO)3(bpy)Cl].
Chapter Three is discusses the synthesis of the rhenium(I) tricarbonyl complexes of 3-(pyrazin-2-yl)-l,2,4-triazoles, analogous to those described in Chapter Two. The complexes were characterised by NMR and IR spectroscopy. The carbonyl bands are observed at higher frequency compared to the corresponding pyridyltriazole complexes. The UV/vis spectra exhibit [Re—mi* (pyrazyl-triazole)] transitions between 390 and 410 nm. The protonated pyrazyl-triazole complexes are weak emitters at 298 K while emission was detected at room temperature from all of the deprotonated pyrazyl-triazole complexes. Emission was detected from all complexes at 77 K. The strongly 7r-accepting pyrazine results in a red shift of both the absorption and emission spectra when compared to the corresponding pyridyl-triazole complexes. Again, spectroscopic and clcctrochemical studies display a strong pH dependency.
Chapter Four describes the synthesis and characterisation of the homo-nuclear rhenium(I) dimer and the hetero-nuclear ruthenium(H)-rhenium(I) dinuclear complexes bridged by the triazole ligand Hbpt (3,5-bis(pyridin-2-yl)-l,2,4- triazole). The complexes have been studied using UV-vis and emission spectroscopy, lifetime studies and electrochemical measurements. For the ruthenium(II)-rhenium(I) complex, the absorption and emission properties indicate intercomponent energy transfer from the rhenium(I) metal centre to the ruthenium(II) metal centre.
Chapter Five discusses the methylation of the ruthenium(II) bipyridyl complex [Ru(bpy)2phpztr]+, (phpztr = 3-(pyrazin-2-yl)-5-phenyl-l,2,4-triazole). Selective deuteriation of the bipyridyl ligands and the triazole ligand was also employed. The photophysical and electrochemical properties of all complexes were also examined. Methylation of the pyrazyl-triazole ligand was found to quench emission from [Ru(bpy)2phpztr]+. Wavelength dependent ground-state resonace Raman measurements were also carried out in order to elucidate the electronic transitions in the absorption spectra. Chapter Six gives an overview of the experimental conditions used. Chapter Seven summaries results of the work undertaken with suggestions on further possible research directions.
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