Developing novel 2,6-pyridinedicarboxamide-1,2,3 triazole ligands for luminescent lanthanide materials : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry, School of Natural and Computational Sciences, Massey University, Albany, New Zealand
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2020
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Massey University
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Abstract
Lanthanide complexes possess unique photophysical properties leading to a vast number of applications in a wide range of areas. Emission of lanthanides, however, show much lower absorption coefficients with slow emissive rates and longer lifetimes. Therefore, lanthanides are usually excited through organic ligands. Research reveals that ligands rich in oxygen and nitrogen atoms are more favourable for developing metallosupramolecular lanthanide systems. Recent studies have shown that PDC (2,6-pyridyldicarboxamide) based ligand systems are excellent candidates because of their predictable coordination number and structural advantage towards complexing with Lanthanides. In addition to that PDC-based ligands are easy to functionalize with various substituents to enhance coordination and sensitize emission of lanthanides. Therefore, this project is focused on developing new 1,2,3-triazole containing PDC-derived ligands for the subsequent preparation of luminescent complexes with europium and terbium. Six ligand systems; (four of them were symmetrical systems [L1-L4] while [L5, L6] were asymmetrical ligand systems) have been successfully synthesized using the CuAAC reaction. All ligands were characterized by UV-Vis, FTIR, ¹H NMR and ¹³C NMR spectroscopy. Europium and terbium complexes were synthesized using L1, L2, L4 and L5 ligands and photophysical studies were carried out in acetonitrile solution. The presence of characteristic europium and terbium emission bands demonstrate the successful coordination of lanthanides to the ligands. Complexation and self-assembly studies of L5 ligands with Eu³⁺ using UV-Vis and fluorescence spectroscopic titrations show that the expected 3:1 ligand:lanthanide ratio is observed and the bulky triazole substituents do not affect complex formation. This is important as it will allow us to move on to more complex and larger ligands that incorporate amino acids/peptides. This will allow for more favourable/stronger self-assembly and potentially self-assembly in water – giving access to biological (imaging) and sensing applications.
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The following Figures were removed for copyright reasons: 1 (=Bünzli, 2017 Fig 1); 3 (=Petoud et al., 2003 Fig 2 (Left); 13 (=Bünzli, 2017 Fig 3), & 14 (=Zhu et al., 2017 Abstract). Other possibly copyrighted Figures remain for clarity's sake.