Development of luminescent lanthanide-based supramolecular and interlocked architectures : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry at Massey University, (Albany), New Zealand
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Date
2022
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Massey University
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Abstract
The chemistry of mechanically interlocked molecules (MIMs), copper(I)-catalyzed azide-alkyne cycloaddition (click) reactions and lanthanide ions each individually are promising targets for the development of advanced luminescent materials, such as responsive molecular sensors and molecular switches. Herein, the synthesis of a family of dipicolinic acid (DPA) ligands, one containing a propargyl group (L₁) and three containing bulky groups (i.e. a 1,8-naphthalimide (L₂), a tert-butylbenzyl (L₃) and a 9-anthracene (L₄) group) appended to their 4-pyridyl position through CuAAC click chemistry are presented. These groups were chosen based on their ability to sensitize Ln³⁺ emission as well as their potential to act as stopper groups for small macrocycles for the development of quasi-[4]-rotaxanes. L₁ – L₃ formed highly luminescent complexes with Eu³⁺ and Tb³⁺. A CuAAC reaction was successfully carried out on a tris-alkyne appended DPA lanthanide complex, [La(L₁)₃]³ˉ, however synthetic difficulties were faced whilst carrying out the ATCuAAC derivative for the synthesis of quasi-[4]-rotaxanes. Due to this, slightly different DPA chelating systems were investigated such that they inherited both chelating and stoppering abilities. Thus, a series of methyl-protected DPA rotaxane ligands R₂ – R₄ were synthesized and R₃ was proven through photophysical titrations to form Ln³⁺ self-assemblies. UV/Vis titrations supported the formation of 2:1 R₃:Ln³⁺ species whereas fluorescence titrations supported the formation of 3:1 R₃:Ln³⁺ species (i.e. quasi-[4]-rotaxanes), thus further studies are ongoing to confirm this binding ratio. Lastly, preliminary findings regarding the synthesis of amide-protected DPA rotaxane ligands are also presented. The research herein integrates three highly valuable fields of chemistry and provides foundational results for the development of a range of advanced luminescent materials, such as Ln³⁺-containing interlocked molecules.