Development and Exploration of Mechanically Interlocking Molecules for Their Use as Imaging and Electronic Devices

The world of mechanically interlocking molecules (MIMs) has gained providence since the 2016 Nobel Prize Awards, for which Stoddart and Sauvage received the prize for their pioneering work on molecular machines. The world of interlocking molecules has continued to be investigated and developed due to their versatility and flexibility. . In particular, this project will look at rotaxanes and their potential uses within ever-growing imaging, electronic and magnetic industries. Rotaxanes are becoming more and more prominent in the world of mechanostereochemistry as their potentials are neverending. These types of MIMs possess a mechanical bond, but what element is intriguing is that in order to break apart these units, one must break a chemical bond. Rotaxanes comprise a ring and a dumbbell component; interestingly, these components are noncovalently bonded, but to break the components apart, a covalent bond must be broken. This project aims to synthesise rotaxanes with click chemistry through the btp [2,6-bis(1,2,3-triazole-4-yl)pyridine] binding motif. This btp motif offers versatility due to the triazoles and pyridine units present, offering the unique opportunity to template out MIM through hydrogen bonding. Including this, the btp motif has the ability to bind the trivalent compounds; in particular, we look at lanthanide (III) ion, including Eu(III), Tb(III), Ln(III) and Gd(III). This enhances the motif possibility within imaging Technologies due to the phosphorescent and fluoresces capabilities of Ln(III) ions. The aim of this project was to thread a btp macrocycle with a btp thread (ligand) and then incorporate cyclen complexes as the stoppers to prevent the dethreading of the macrocycle from the thread. This project harnesses the copper azide-alkyne cycloaddition (click chemistry) to build our components whilst also employing various other organic chemistry reactions to yield the desired targets.
Our project has made significant strides, having successfully built pseudorotaxane units along with a rotaxane unit, which could potentially be developed into a switchable rotaxane. We have conducted in-depth ultra-violet spectroscopy, Nuclear magnetic resonance spectroscopy, and Mass spectrometry on all samples and components. A key area of interest for us is how building these MIMs can impact their yield and versatility, leading us to explore alternative approaches and methodologies to evaluate which route best suits the system we are trying to build. These MIMs have shown promising magnetic properties, including ferromagnetic and paramagnetic potentials, with the use of Ln(III) ions. We have investigated this with AFM measurements and Scanning Transmission Microscopy to observe the surface and internal structure when the magnetism is exploited. Further characterization and analysis of the produced rotaxanes and self-assemble behaviour was conducted using various microscopy techniques, such as SEM, AFM, and TEM, with crystallization also being noted. With the emerging outlook on the world of nanomaterials and the technologies encompassing them, our project is at the forefront of this exciting field with these self-assembling Ln(III) MIMs.