Interlocked fullerene and endohedral metallofullerene hosts for molecular machine-like sensing

Mechanically interlocked molecules such as rotaxanes, which resemble a molecular abacus with rod-like molecules passing through one or more rings and catenanes, which are two or more interpenetrating rings, are firmly established entities in the field of nanoscale molecular machines because of their ability to undergo controlled and reversible molecular motion through changes in the relative positions of their constituent parts. The inherent dynamics of such molecules can be controlled by light, electrochemical and chemical-based stimuli. This proposal aims to exploit their unique topological interlocked host cavities to recognize guest molecules as a means of causing the ring component of a rotaxane or catenane to move from one position to another along an rod-like axle or larger ring component as a sophisticated means of sensing negatively charged species of biological, medical and environmental importance.
Through the attachment of nanoscale 'light bulbs' including luminescent metal 'filaments' inside an all carbon sphere-like football, to specific positions on the ring and axle components, the switching on or off of the light bulb is designed to occur when a target negatively charged species is recognised and causes ring components to slide or shuttle from one station position to another. Such materials can be thought of as "molecular machine-like sensors".
Coating these materials on to conducting and optically transparent surfaces will produce devices that will change colour and/or emit light and undergo electrochemical perturbation in response to the addition of a specific negatively charged substrate. Fundamentally, the project will add considerable volume to our understanding of how complex molecular architectures, designed to exhibit dynamic motion, respond when confined to the sorts of surfaces that will, ultimately, underpin their application.

Through the construction of higher-order interlocked rotaxane and catenane host systems that contain integrated redox- and photo-active fullerenes and erbium-endohedral metallofullerene motifs, the aim of this project is to exploit the underdeveloped field of dynamic molecular recognition and transduction mechanisms as a means of sensing specific biological and pollutant dicarboxylate analytes.
The research theme of mechanically bonded interlocked host molecule assembly for targeted molecular recognition and sensing applications relates directly to one of the physical sciences Grand Challenges, 'Directed Assembly of Extended Structures and Targeted Properties' and also fits with the EPSRC priority themes of 'Synthetic Coordination Chemistry and Synthetic Supramolecular Chemistry'. It also contributes to 'manufacturing in the future' high value chemical sector. The proposed work will make a significant and fundamental advance to the state-of-the-art in the field where the development of new dynamic mechanically interlocked molecule sensory materials will strengthen the UK's scientific knowledge base in areas of economic and societal benefit, most notably in healthcare personalized diagnostics and the monitoring of environmental pollutants.
Being fundamental research it is inherently difficult to predict long term benefit beyond the scientific community. In the shorter term, achieving an understanding of the fundamental processes that underpin the development of a new approach to 'molecular machine-like sensors' will lead to prototype sensors and probes for biological and environmental analytes within five years. In the longer term, in particular the chiral sensory systems developed during the course of this programme will have potential impact in healthcare and diagnostic medicine.