Triazole-pyridine derivatives: versatile building blocks for metallosupramolecular assemblies and materials
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HEGARTY, ISABEL, Triazole-pyridine derivatives: versatile building blocks for metallosupramolecular assemblies and materials, Trinity College Dublin.School of Chemistry, 2020Download Item:
Abstract:
This thesis, entitled "Triazole-Pyridine Derivatives: Versatile Building Blocks for Metallosupramolecular Assemblies and Materials", describes the design, synthesis and characterisation of a series of 1,2,3-triazol-4-yl-picolinamide (tzpa) and 2,3-bis(1,2,3-triazol-4-yl)picolinamide (btp) derivatives. The ligands are explored in the context of their coordination chemistry with d-metals Cu(I), Cu(II), and Ag(I), as well as their capacity to coordinate and sensitise the emission of lanthanide (Ln(III)) ions, in particular, Tb(III) and Eu(III). Chapter 1 provides an introduction to symmetrical terdentate ligand motifs, with a particular focus on dipicolinic acid (dpa) and btp. This section will provide a review of the literature, describing recent advances in the coordination chemistry of these ligands with various d- and f-metals both in solution and in soft-materials. This is followed by a review of pyridine-centred, asymmetric ligand motifs and their self-assembly with d- and f-metals as well. The chapter is concluded by highlighting work from the Gunnlaugsson group, which serves as a platform from which the research explored in the following chapters has been based. Chapter 2 describes the design and synthesis of a pair of chiral enantiomeric tzpa ligands, and their self-assembly with Cu(I) and Cu(II) salts in the solid state and in solution is studied. Single crystals of X-ray diffraction quality were grown and the resultant [2 x 2] tetrameric M4L4 grid structures are described. Oxidation of Cu(I) to Cu(II) upon complexation is observed as well as single deprotonation of each ditopic ligand under mild conditions. The effects of both reaction solvent and counterion on the assemblies formed is evident in this chapter. The self-assembly of these ligands with various Cu(I) and Cu(II) salts in solution is investigated through the use of UV-visible absorption and fluorescence spectroscopy, as well as circular dichroism. Speciation and global stability constants (β) related to each species are determined by non-linear regression analysis and indicate the formation of multiple species in solution at various metal:ligand stoichiometries. This chapter concludes by employing cyclic voltammetry (CV) to examine the Cu(I)/(II) redox behaviour of the complexes in order to probe the spontaneous oxidation of Cu(I) observed upon complexation. Chapter 3 describes the design and synthesis of a series of monotopic and ditopic tzpa derivatives, functionalised with coordinating pyridyl groups. These ligands coordination chemistry with Cu(I), Cu(II) and Ag(I) salts is described. A ditopic tzpa ligand functionalised with 3-pyridyl "arms" generates a Ag(I) organogel, while its 2-pyridyl derivative forms a tetrameric [2 x 2] grid structure analogous to that described in Chapter 2. A monotopic tzpa ligand, functionalised with one pyridyl "arm" generates a Ag(I) 1D polymer structure, while a 2D polymer with Cu(II) is formed from a monotopic tzpa derivative with two pyridyl "arms". It will be shown that altering the linker moiety between the terdentate binding sites can significantly affect the solubility of the ligands and thus their coordination chemistry. The self-assembly these ligands with Cu(I) and Cu(II) salts is also investigated through UV-visible absorption and fluorescence spectroscopy and, as in Chapter 2, the speciation and stability constants are determined by non-linear regression analysis. Chapter 4 describes the functionalisation of the tzpa ligand motif with amino acid residues as the first step towards generating Ln(III)-tzpa complexes which would be stable in aqueous media. Firstly, these tzpa ligands are examined in the context of their capacity to sensitise Tb(III) and Eu(III) emission. The self-assembly of an L-phenylalanine functionalised ligand with Tb(III) and Eu(III) is investigated by UV-visible absorption, fluorescence and time-gated emission spectroscopy. The self-assembly of an L-tryptophan functionalised ligand with Tb(III) is also examined, and the fully saturated ML3 assemblies of each of these ligands with Tb(III) are studied in H2O to determine their stability. A monotopic tzpa ligand, not functionalised with an amino acid residue, is also synthesised and its self-assembly with Tb(III) is examined. The self-assembly of chiral ditopic tzpa ligand described in Chapter 2 will also be investigated. Chapter 5 focuses on incorporating the btp coordination motif into a polymer material in order to generate a Tb(III)-sensitised material which is stable in an aqueous environment and responsive to external stimuli. A btp compound, functionalised at the 4-pyridyl position is synthesised and this compound itself forms an organogel in CH3CN. The incorporation of the compound into a p(HEMA-co-MMA-co-EGDMA) polymer matrix is then described and the uptake of Tb(III) and Eu(III) ions into the hard polymer through swelling in aqueous media is investigated. The material is shown to exhibit red/green emission upon Eu(III)/Tb(III) uptake, respectively; however, the system exhibits some limitations that are also discussed. The btp compound will also be utilised to functionalise a polymer backbone, polyethylene-alt-maleic anhydride (p(E-alt-MA)), through covalent attachment, and the introduction of Tb(III)-based supramolecular crosslinks of this polymer is explored. The photophysical properties of this polymer are characterised by UV-visible absorption, fluorescence and time-gated emission spectroscopy, and the self-assembly of the polymer with Tb(III) is also described. Finally, luminescent hydrogels are demonstrated, before concluding this chapter by describing approaches to exploit these preliminary results. Finally, Chapter 6 outlines the experimental and synthetic procedures used for the studies described in this thesis as well as the compound characterisation for the compounds prepared. This is followed by literature references and appendices to support the preceding chapters.
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Science Foundation Ireland (SFI)
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https://tcdlocalportal.tcd.ie/pls/EnterApex/f?p=800:71:0::::P71_USERNAME:HEGARTYIDescription:
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Author: HEGARTY, ISABEL
Advisor:
Gunnlaugsson, ThorfinnuPublisher:
Trinity College Dublin. School of Chemistry. Discipline of ChemistryType of material:
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