Results
i) Scalable methods for the synthesis of MIM ligands (Chem. Sci. 2016, 7, 3154)
Whilst a number of high-yielding methodologies have been developed for the synthesis of MIMs, these usually focus on the final mechanical bond forming step. However, the synthesis of the precursor units, such as appropriate macrocycles, can often be laborious and low yielding. To rectify this short-coming we developed a more efficient route towards these key precursors. After optimisation the reactions were found to give the desired macrocycle compounds in approximately 70% yield across a range of macrocycle structures, and allowed access to these in gram scale. We are now in talks with a company to make these molecules available to the wider community.
ii) New Methods for the Synthesis of Polynuclear MIM Ligands (J. Am. Chem. Soc. 2016, 138, 16329; Molecules 2017, 22, 89)
It was foreseeable that for our photocatalytic systems we might require two cavities formed by mechanical bonds capable of binding metal ions. Oligomeric [n]rotaxanes, where n = >2, would thus be a desirable target. We developed the first route to oligomeric rotaxanes, where the precise length and macrocycle order could be controlled exactly with precise control of the order of different macrocycles.
iii) Rotaxane Ligands for Early Transition Metals and their Hydrogen Evolving Capabilities (manuscripts in preparation)
We have investigated the electrochemical and spectroscopic properties of first row transition metal complexes of tri-, tetra- and penta-dentate rotaxane ligands. Our results showed that in many instances the ligand environment and coordination behaviour of the rotaxane ligands, including their electrochemical properties, was distinct from their non-interlocked counterparts. A manuscript describing this work is currently in preparation in collaboration with Roessler at QMUL. We also examined our complexes for their ability to act as electrocatalysts in the production of H2 in acidic solutions. Unfortunately, thus far none of our complexes outperform existing HECs.
iv) New Approaches to Catenane Ligands (manuscripts in preparation)
Reports of scalable syntheses of catenanes in the literature are relatively limited compared to rotaxanes and none were suited to our desire to investigate crowded structures. To overcome this we developed a new approach to generate suitable catenanes in quantitative yield. Our method allows access to catenanes using small molecule building blocks that are readily accessible from commercially available materials in a minimal number of steps, including building blocks containing pyridine and other ligands for 1st row transition metal ions.
v) Collaborations and Reviews (Chem. Sci. 2017, 8, 6679; Chem. Commun. 2017, 53, 298. Chem. Soc. Rev. 2017, 46, 2577)
In addition to the results described above I have also contributed to collaborations between my host group and other researchers and contributed to literature reviews in collaboration with Prof Goldup on the subject of metal coordination in MIM synthesis and properties. These reviews have been extremely well received and allowed me to broaden my influence on the field by showcasing my personal views on the opportunities presented by MIM ligands.
Dissemination
Over the course of my fellowship I have produced four research publications and two literature reviews. Three further manuscripts are in preparation. All of these articles were published in open access form and raw data made available through the UoS Repository. In addition to these 9 publications, I have presented my results at national and international meetings including the RSC Macrocyclic and Supramolecular Chemistry annual meeting, the MASC Early Career meeting, the International Symposium on Macrocyclic and Supramolecular Chemistry and the Telluride Workshop on Switches and Motors.
