Phosphorus-containing interlocked molecules as frustrated Lewis pairs for small molecule activation

Interlocked molecules are supramolecular architectures where two or more discrete molecules are bound together by a mechanical bond. This unique type of bond does not involve a direct bond between atoms of the molecules, and can only be broken by breaking a chemical bond within one of the molecules. For example, the mechanical bond in catenanes is analogous to how links on a chain are bound together. Another example of an interlocked molecule is a rotaxane, which consists of a dumbbell-shaped molecule threaded through a large cyclic structure, known as a macrocycle. The two components at the end of the "dumbbell" are larger than the internal diameter of the macrocyclic structure, creating a mechanical bond between the two molecules. These supramolecular species have found applications as molecular machines in which the molecular components respond to external stimuli. The 2016 Nobel Prize in Chemistry was awarded jointly to Jean-Pierre Sauvage, Fraser Stoddart and Bernard Feringa "for the design and synthesis of molecular machines". In addition, interlocked molecules have found applications as catalysts, dyes and molecular sensors.
The majority of interlocked structures are made up of organic molecules (containing C, H, N, O atoms only), so the incorporation of inorganic atoms such as phosphorus into these architectures poses an interesting challenge. The incorporation of phosphorus into organic molecules has become an area of research in its own right, and has led to the discovery of many novel phosphorus-containing heterocycles. This has been achieved by the use of simple and reactive phosphorus species in well-known organic cyclisation reactions. It is these organic reactions that are often used to make up the components that form the interlocked molecules.
The aim of this project is to close an obvious gap in the chemical literature, and to use simple and reactive phosphorus species in well-known organic cyclisation reactions to synthesise interlocked molecules. Ultimately, this will give rise to the incorporation of phosphorus-containing heterocycles into the interlocked molecules. Phosphorus chemistry is ubiquitous in catalysis, and we envisage that phosphorus-containing interlocked molecules could find applications in this field through the activation of covalent bonds in small molecules, such as H2, CO2 or NH3.

This project falls into the "Manufacturing the Future" ESPRC theme and the following research areas:

- Synthetic Supramolecular Chemistry
- Synthetic Coordination Chemistry
- Synthetic Organic Chemistry
- Catalysis

The primary impact of the OxICFM CDT will be the highly-trained world-class scientists that it delivers. This impact will encompass both the short term (during their doctoral studies), the medium term (subsequent employment) and ultimately the longer timescale defined by their future careers and consequent impact on science, engineering and policy in the UK.

The impact of OxICFM students during their doctoral studies will be measured by the culture change in graduate training that the Centre brings about - in working at the interface between inorganic synthesis and manufacturing, and fostering cross-sector industry/academia working practices. By embedding not only from larger companies, but also SMEs, we have developed a training regime that has broader relevance across the sector, and the potential for building bridges by fostering new collaborations spanning enormous diversity in scientific focus and scale. Moreover, at a broader level, OxICFM offers to play a unique role as a major focus (and advocate) for manufacturing engagement with academic inorganic synthetic science in the UK.

From a scientific perspective, OxICFM will be uniquely able to offer a broad training programme incorporating innovative and challenging collaborative projects spanning all aspects of fundamental and applied inorganic synthesis, both molecular and materials based (40+ faculty). These will address key challenges in areas such as energy provision/storage, catalysis, and resource provision/renewal necessary to enhance the capability and durability of UK plc in the medium term. To give some idea of perspective, the output from previous CDTs in Oxford's MPLS Division include two start-up companies and in excess of 30 patents.

It is not only in the industrial and scientific realms that students will have impact during their timeframe of their doctorate. Part of the training programme will be in public engagement: team-based challenges in resource development/training and outreach exercises/implementation will form part of the annual summer school. These in turn will constitute a key part of the impact derived from the CDT by its engagement with the public - both face-to-face and through electronic/web-based media. As the centre matures, our aspiration is that our students - from diverse backgrounds - will act as ambassadors for the programme and promote even higher levels of inclusion from all parts of society.

For our partners, and businesses both large and small in the manufacturing sector, it will be our students who are considered the ultimate output of the OxICFM CDT. Our programme has been shaped by the need of such companies (frequently expressed in preliminary discussions) to recruit doctoral graduates who can apply themselves to a broad spectrum of multi-disciplinary challenges in manufacturing-related synthesis. OxICFM's cohort-based training programme integrates significant industry-led training components and has been designed to deliver a much broader skill set than standard PhD schemes. The current lack of CDT training at the interface of inorganic chemistry and manufacturing (and the relevance of inorganic molecules/materials to numerous industrial sectors) heightens the need for - and the potential impact of - the OxICFM CDT. Our students will represent a tangible and valuable asset to meet the long-term skills demand for scientists to develop new materials and nanotechnology identified in the UK Government's 2013 Foresight report.

In the longer term, the broad and relevant training delivered by OxICFM, and the uniquely wide perspective of the manufacturing sector it will deliver, will allow our graduates to obtain (and thrive in) positions of significant responsibility in industry and in research facilities/institutes. Ultimately we believe that many will go on to be future research leaders, driving innovation and changing research culture, and thereby making a lasting contribution to the UK economy.