Development of a molecular toolbox for multifunctional lanthanide-based supramolecular materials : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University, Albany, New Zealand

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Using simple building blocks to develop functional supramolecular materials is an active area of research. To this extent the use of lanthanide ions (Ln³⁺ to direct supramolecular self-assembly with organic ligands has become a popularised method whereby the interesting photophysical properties of Ln³⁺ can be manipulated by simple modification of the organic architecture. Applications of such systems vary from solar waveguides, OLEDS, molecular sensors, contrast agents, bio-probes, security inks and barcodes. Herein, a synthetic strategy has been developed and investigated to readily functionalise the organic scaffolds 2,6-pyridinedicarboxamide (PDA) and 6-carbamoylpyridine-2-carboxcylic acid (PDC), using 1,2,3-triazole “click” chemistry. Using this approach, we have synthesised and assessed the f-directed self-assembly ability of some novel PDA-based and PDC-based assemblies. Initial studies focused on symmetrical incorporation of the 1,2,3-triazole linker into the PDA motif via side carbonyls. This resulted in the development of four ligand architectures (1-4), which in the presence of Eu³⁺ and Tb³⁺ self-assemble into Ln(L)₃ (CF₃SO₃)₃ (where L = 1-3) luminescent assemblies. While results of the PDA systems were promising, the systems were relatively unstable in competitive solvents, and as a result subsequent systems focused on the unsymmetrical modification of the PDC motif. Incorporation of our synthetic strategy into the PDC motif was straightforward and additionally improved both Ln³⁺ complex stability and emission intensity. Using this approach, amphiphilic ligand 5 and visibly emissive amphiphilic complexes Ln(5)₃ (where Ln = Eu³⁺, Tb³⁺, Sm³⁺ and Dy³⁺) were synthesised. The incorporation of a long alkane chain via the 1,2,3-triazole in ligand 5 allowed for the fabrication of ultra-thin luminescent films by Langmuir-Blodgett (LB) technique resulting in bright visibly emissive monolayer films. Furthermore, mixing of the emissive Ln(5)₃ complexes resulted in tunable emission dependent on the composition in both solution and monolayer film. Following this, single component dual emissive systems Ln(6)₃, [Ln(7)₃](CF₃SO₃)₃ and Ln(8)₃ were developed. This entailed the incorporation of blue emissive 1,8-naphthalimide (6 & 7) and pyrene (8) via the 1,2,3-triazole linker. When complexed with Eu³⁺ it resulted in dual emissive systems which were colour-tunable, changing colour dependent on the excitation wavelength, and in the case of Eu(6)₃ and Eu(8)₃ it results in white emissive solids and solutions. These properties were transferable to thin films, by spin coating techniques. Finally, the synthetic strategy was used in the initial development of multi-nuclear assemblies forming three multitopic ligands (9-11) and initial complexation studies were undertaken.
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Listed in 2022 Dean's List of Exceptional Theses
Supramolecular chemistry, Functional organic materials, Rare earth metals, Metal-organic frameworks, Dean's List of Exceptional Theses