| dc.description.abstract | Supramolecular assemblies based on some lanthanide ions (Ln = Nd(III), Sm(III), Eu(III), Tb(III), Dy(III), Er(III), Tm(III), Yb(III)) may have luminescent properties and have shown promise in applications such as sensing, imaging and catalysis. The specific coordination requirements of lanthanide ions determine the resulting supramolecular architecture and therefore careful consideration must be taken when designing ligands for these assemblies. In particular, ditopic terdentate ligands are advantageous in forming assemblies such as helicates, cages, grids, and interlocked molecules due to having two distinct binding sites for Ln(III) coordination. Additionally, the `arms� or `linker� of the ditopic ligands can be readily modified to allow for a wide library of ligands and lanthanide assemblies with various functionalities. The bis-tridentate(1,2,3-triazol-4-yl)-picolinamide (tzpa) motif is a combination of the dipicolinic acid (dpa) and bis(1,2,3-triazol-4-yl)pyridine (btp) motifs, both of which are widely studied in supramolecular chemistry. This thesis, titled `An Investigation of the Self-Assembly of Luminescent Lanthanide Architectures Using Novel Triazole-Pyridine Derivatives� examines the self-assembly of triazole-pyridine derivatives with either lanthanide ions Eu(III) and Tb(III) both in the solution and solid phase with the overall aim of developing responsive and functional luminescent assemblies.
Chapter 1 provides a brief introduction to metallosupramolecular chemistry and lanthanide luminescence. An overview of recent advances in Ln(III)-directed supramolecular self-assemblies is then provided, with particular emphasis on ligands bearing monotonic and ditopic terdentate motifs. It is concluded by highlighting the overall aims of the thesis, which will be discussed in the subsequent chapters.
Chapter 2 describes the synthesis and characterisation of two novel ligands based on the bis- tridentate(1,2,3-triazol-4-yl)-picolinamide (tzpa) motif. The self-assembly of these ligands with Eu(III) and Tb(III) were subsequently explored under both kinetic and thermodynamic conditions in both the solution and solid states. The photophysical properties of the ligands formed under thermodynamic control are investigated using UV-visible absorption, fluorescence and time-gated emission spectroscopy. The quantum yield of these complexes are also determined using a known standard. In addition to this, the self-assembly of these complexes are investigated in situ using UV-visible absorbance, fluorescence and time-gated emission spectroscopy The self-assembly of these ligands are examined and the global stability constants (�) are determined using non-linear regression analysis and indicate multiple species present in solution. The chapter concludes with preliminary photophysical solid state studies of the complexes, as well as a comparison of SEM images of the ligands and complexes. Chapter 3 discusses the expansion of the tzpa motif into chiral systems, by incorporating a chiral napthalene chromophore into the ditopic ligand design. Single crystals of X-ray diffraction quality were obtained for both enantiomers of the ligand, which confirmed the chiral nature of these compounds. Photophysical studies of the complexes formed under thermodynamic and kinetic control were done as previously described for Chapter 2. The chiral nature of these ligands and their resulting complexes allowed for additional photophysical measurements, circular dichroism (CD) and circularly polarised luminescence (CPL) to be undertaken. The chapter concludes with a brief comparison between the photphysical properties of the complexes in Chapter 2 and Chapter 3.
Chapter 4 describes the preliminary studies towards designing a tritopic ligand based on the btp motif, with the intention of forming knot structures. A series of monotopic btp compounds previously reported by the Gunnlaugsson group were synthesised, and attempts to further modify these ligands were carried out. The synthetic pitfalls encountered throughout this project are discussed, as well as potential future synthetic pathways that may prove to be successful are outlined. The chapter aims to serve as a guideline for further future investigations towards the synthesis of tritopic btp ligands.
Chapter 5 outlines the experimental details for the work presented.
Chapter 6 entails the combined references for this Thesis. Additional details to support the preceding chapters are provided in the Appendices. | en |
