Discovery and analysis of third-generation lanthanide metal-organic frameworks

Abstract

This thesis presents the synthesis and characterisation of related lanthanide coordination polymers, alongside detailed analytical investigations into their structures and induced transformations. Initially, a series of previously unstudied compounds, formed with the (Z)-stilbenedicarboxylic acid isomer, was investigated in the synthesis of ten lanthanide frameworks. Five 2- dimensional layered frameworks were synthesised alongside five 3-dimensional microporous frameworks with a novel net topology. On further investigation it became apparent that the 2-dimensional frameworks are an isolated intermediate of 3-dimensional frameworks and can transform when left for extended periods of time in mother liquor solution. The luminescent properties of these complexes were investigated to reveal strong blue ligand-based luminescence. Work then focussed on generating a library of linker molecules that incorporate alkene functionalities. Seven new lanthanide coordination polymers were synthesised in two structural subsets and investigated under variable pressure conditions. Elevated pressures were utilised in an attempt to drive the alkene functionality closer together in neighbouring ligands for potential [2+2] cyclisation reactions. These investigations revealed a reversible phase transition between the two structurally distinct sets of networks that mimics the lanthanide contraction. Further linker molecules were synthesised to incrementally increase the length of the aromatic backbone, in attempts to create porous frameworks. The previously unreported carboxylic acid linker 3,3'-bis(allyloxy)-[1,1'-biphenyl]-4,4'-dicarboxylic acid was synthesised and characterised in full and included a new lanthanide framework. Finally, to probe internal influences on metal-organic framework structural transformations, guest molecules of ferrocene were introduced to a dysprosium framework synthesised previously in the literature. The framework was selected due to its structural similarities to the well-researched MIL-53 ‘breathing’ framework. Diffraction studies show the inclusion compound alters its structure to accommodate the ferrocene moieties, with magnetic measurements showing the inclusion of ferrocene initiates a slow magnetic relaxation of the framework.