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Molecular Robotics for Synthesis and Catalysis

Periodic Reporting for period 1 - RoboCat (Molecular Robotics for Synthesis and Catalysis)

Reporting period: 2017-07-01 to 2019-06-30

The aim of this project was to design, synthesize and investigate the operation of synthetic molecular machines capable of performing sophisticated tasks in chemical synthesis. The molecular machines are inspired by biological systems such as enzymes, and a key goal was to use them to regulate catalytic operations with regards to chemoselectivity and stereoselectivity. Another goal was to achieve temporal control of reactions with the help of a molecular robot, i.e. to develop chemically fuelled systems for dissipative catalysis.
The project also aimed to optimize structures of molecular machines for use as a synthetic platforms. Here, a fundamentally new type of dynamic system was developed with unique properties – the use of dynamic entanglements in the form of molecular knots. This type of system had previously not been considered for molecular machines and I have now developed many applications for these knot-machines. For example, dynamic knotting can be used as a gripping component in molecular robotics.
I have thus developed fundamentally new approaches for controlling entangled architectures on the supramolecular level, as well as novel molecular robotic systems that can perform chemoselective and temporally controlled catalytic operations. These results are of great fundamental importance and will be integral in developing the molecular robotics of the future. The concept of robotic catalysis may well mark the beginning of a fundamentally new approach for the construction of molecules, as unprecedented levels of control is possible with such devices. Furthermore, the development of advanced entangled structures such as the ones created through this project is extremely important for the next generation of advanced responsive materials.
"Following the inception of the project, I synthesized and evaluated components that can participate in robotic and switchable catalysts. After initial experimentation, I started to explore alternative switching and gripping mechanisms for robotic catalysts. Eventually, I designed the catalysts to incorporate so called topological switches (T1.1 and 1.2) which can also be used to retain molecular cargo (T1.3). In practice, I used an open axle that could be tied into a molecular knot upon addition of metal stimuli. Interestingly, this knot could be used to retain an object (a crown ether macrocycle) on the thread mechanically, making it the first ever example of a molecular knot performing a mechanical function. This project was published in the top journal Angewandte Chemie, and the paper was selected as a Very Important Paper.
Furthermore, this exploration of molecular knots made me think of knotting as programmable entanglements for use as components for molecular robotics. The first of these projects to be completed was the use of open molecular knots as building blocks to create larger knotted chiral assemblies. We combined molecular knots of defined handedness to create double knots, the so-called granny and square knots. The results from this study were published in Journal of the American Chemical Society, one of the most prestigious peer-reviewed journals in chemistry.

At the commencement of the project, an evaluation of the state-of-the-art of molecular robotics indicated that a viable approach was to embark on a redesign of the molecular robotic catalysts. The goal was to be able to ""fuel"" the catalysts at the core of this project with a chemical fuel to achieve temporal and spatial control of catalysis. This is similar to how enzymes catalyze reactions with chemical energy carriers as fuel. A full molecular robot was synthesized (T2.1 and T3.1) and characterized in all available switching states. Its fuelled switching with the use of decarboxylative fuels was then confirmed over several cycles and the use of the machine in dissipative catalysis was evaluated (T2.2 and T3.2). The robotic catalyst regulates a biomimetic reduction reaction, and can be fuelled with many pulses of a chemical fuel to achieve chemoreductions in an efficient manner. This project marks the first successful application of dissipative catalysis with a molecular robot and a successful completion of the project objectives. The project will be highly important for creating molecular assembly lines with controlled connectivity between different machines, a key requirement for next generation molecular robotics. This work has just been accepted for publication in the prestigious journal Angewandte Chemie, where it has been selected as the front cover.

The project has thus been highly successful in terms of exploitable results. Three papers have already been published, and another further five papers are written up or being written up for publication. For a detailed summary of training, career development activities, transfer-of-knowledge, as well as the project methodology, output and conclusions for each project, see the technical report.

Transfer-of-knowledge activitites
I have participated in a wide variety of transfer-of-knowledge activities. More details are available in the Technical report, but specific activities include:
• Attended five national and three international conferences all across Europe and presented my results.
• Demonstrated our research on molecular machines and molecular knots at the European Researcher’s Night on 28 Sep 2018 at the Manchester Museum.
• Presented a popular science version of my research to high school students.
• Mentored six PhD students, and supervised a full master thesis project.

Career development activitites
I have also participated in a wide range of professional development activitites:
• I have acted as one of four project manager for the group as a whole, being responsible for projects related to chemical topology and catalysis. This role also includes management of the group’s satellite lab at ECNU Shanghai.
• I have been very active in initiating collaborations, both national and international.
• Co-authored a successful grant application.
• Acted as safety supervisor for the group.
• Responsible for procurement and maintenance of laboratory equipment (dishwasher).
• Organized the regular sub-group meetings of the topology section of the group."
The research outlined in the previous section has so far resulted in three published article and five manuscripts (the Leigh group uses alphabetical order of authors on manuscripts):
1. C. Biagini, S. D. P. Fielden, D. A. Leigh, F. Schaufelberger, S. Di Stefano and D. Thomas, “Dissipative Catalysis with a Molecular Machine”, Angew. Chem. Int. Ed. 2019, DOI: 10.1002/anie.201905250
2. D. A. Leigh, L. Pirvu and F. Schaufelberger, “Stereoselective Synthesis of Molecular Square and Granny Knots”, J. Am. Chem. Soc. 2019, 141, 6054-6059.
3. D. A. Leigh, L. Pirvu, F. Schaufelberger, D. J. Tetlow and L. Zhang, “Reversibly Securing a Supramolecular Architecture with a Stopper Knot”, Angew. Chem. Int. Ed. 2018, 57, 10484-10488

For information on the five manuscript that are being written up, see the technical report.

The impact of this research is fundamental, as it entails completely new ways to think about catalysis and synthesis at the nanoscale. With the exciting addition of switchable molecular knotting, we are also creating a new tool for chemists and material scientists all over the world that has the potential to completely change the way we think about molecular knots and links, their properties and how we describe them.