New Polyoxometalate Photocatalysts for C-H Functionalisation Reactions
Lead Research Organisation:
University of Nottingham
Department Name: Sch of Chemistry
Abstract
Using light to drive chemical reactions via photocatalysis has emerged as a powerful method in the effort to develop greener, more sustainable chemical synthesis. Decatungstate, a photoactive polyoxometalate (POM) compound, has shown great promise as a photocatalyst in organic chemistry as it avoids the use of precious metals common in similar catalysts and is able to mediate a variety of valuable C-H functionalisation reactions. It has also shown applicability in the late-stage functionalisation of complex molecules, which is an emerging strategy for enabling highly efficient derivatization of bioactive molecules.
Despite the interest in and development of decatungstate-mediated H-atom transfer reactions in recent years, there are a number of drawbacks to its use. This photocatalyst is only active in ultraviolet light, which has practical limitations in organic synthesis, and C-H bond selectivities in complex molecules can be limited. These drawbacks need to be mitigated in order to further broaden the scope of this promising catalytic system. Despite the enormous diversity of POM compounds reported in the literature, decatungstate remains the only one in use as a C-H functionalisation photocatalyst in organic chemistry. There is therefore significant scope to further explore the application of POMs as photocatalysts in organic chemistry.
Proposed solution and methodology
The design and synthesis of various 'hybrid' polyoxometalate structures, which have organic ligands attached to the POM cluster, has been investigated extensively by the Newton group. These compounds have similar photochemical characteristics to decatungstate and may therefore be amenable to similar C-H activation chemistry, but with greater tunability due to organic modifications. These organic modifications may allow the energy levels of the POM cluster to be modified to allow for activity in visible light, or allow the addition of supramolecular binding elements that exert greater control over reaction selectivity. These possibilities will investigated in this PhD project.
Previously, tuning of the metal cluster's HOMO / LUMO levels has been demonstrated using phosphonate linkages between the POM and organic ligand. This work will be expanded by designing and synthesizing a range of novel hybrid POM structures that will be fully characterised using a range of techniques including NMR, cyclic voltammetry and UV/Vis spectroscopy. The major goal of the project is to demonstrate the applicability and practicality of hybrid POMs as C-H activation catalysts, and the new catalysts will be therefore be tested in a range of photochemical reactions with the aim over overcoming some of the drawbacks of decatungstate. Alongside this, further novel chemistry using decatungstate will also be explored to expand the scope of this promising photocatalyst.
Despite the interest in and development of decatungstate-mediated H-atom transfer reactions in recent years, there are a number of drawbacks to its use. This photocatalyst is only active in ultraviolet light, which has practical limitations in organic synthesis, and C-H bond selectivities in complex molecules can be limited. These drawbacks need to be mitigated in order to further broaden the scope of this promising catalytic system. Despite the enormous diversity of POM compounds reported in the literature, decatungstate remains the only one in use as a C-H functionalisation photocatalyst in organic chemistry. There is therefore significant scope to further explore the application of POMs as photocatalysts in organic chemistry.
Proposed solution and methodology
The design and synthesis of various 'hybrid' polyoxometalate structures, which have organic ligands attached to the POM cluster, has been investigated extensively by the Newton group. These compounds have similar photochemical characteristics to decatungstate and may therefore be amenable to similar C-H activation chemistry, but with greater tunability due to organic modifications. These organic modifications may allow the energy levels of the POM cluster to be modified to allow for activity in visible light, or allow the addition of supramolecular binding elements that exert greater control over reaction selectivity. These possibilities will investigated in this PhD project.
Previously, tuning of the metal cluster's HOMO / LUMO levels has been demonstrated using phosphonate linkages between the POM and organic ligand. This work will be expanded by designing and synthesizing a range of novel hybrid POM structures that will be fully characterised using a range of techniques including NMR, cyclic voltammetry and UV/Vis spectroscopy. The major goal of the project is to demonstrate the applicability and practicality of hybrid POMs as C-H activation catalysts, and the new catalysts will be therefore be tested in a range of photochemical reactions with the aim over overcoming some of the drawbacks of decatungstate. Alongside this, further novel chemistry using decatungstate will also be explored to expand the scope of this promising photocatalyst.
Planned Impact
This CDT will deliver impact aligned to the following agendas:
People
A2P will provide over 60 PhD graduates with the skill sets required to deliver innovative sustainable products and processes into the UK chemicals manufacturing industry. A2P will inspire and develop leaders who will:
- understand the needs of industrial end-users;
- embed sustainability across a range of sectors; and
- catalyse the transition to a more productive and resilient UK economy.
Economy
A2P will promote a step change towards a circular economy that embraces resilience and efficiency in terms of atoms and energy. The benefits of adopting more sustainable design principles and smarter production are clear. For example, the global production of active pharmaceutical ingredients (APIs) has been estimated at 65,000-100,000 tonnes per annum. The scale of associated waste is > 10 million tonnes per annum with a disposal cost of more than £15 billion. Consequently, even a modest efficiency increase by applying new, more sustainable chemical processes would deliver substantial economic savings and environmental wins. A2P will seek and deliver systematic gains across all sectors of the chemicals manufacturing industry. Our goals of providing cross-scale training in chemical sciences with economic and life- cycle awareness will drive uptake of sustainable best practice in UK industry, leading to improved economic competitiveness.
Knowledge
This CDT will deliver significant new knowledge in the development of more sustainable processes and products. It will integrate the philosophy of sustainability with catalysis, synthetic methodology, process engineering, and scale-up. Critical concepts such as energy/resource efficiency, life cycle analysis, recycling, and sustainability metrics will become seamlessly joined to what is considered a 'normal' approach to new molecular products. This knowledge and experience will be shared through publications, conferences and other engagement activities. A2P partners will provide efficient routes to market ensuring the efficient translation and transferal of new technologies is realised, ensuring impact is achieved.
Society
The chemistry-using industries manufacture a rich portfolio of products that are critical in maintaining a high quality of life in the UK. A2P will provide highly trained people and new knowledge to develop smarter, better products, whilst increasing the efficiency and sustainability of chemicals manufacture.
To amplify the impacts of our CDT, effective public engagement and technology transfer will become crucially important. As a general comment, 'sustainability' styled research is often regarded in a positive light by society, however, the science that underpins its effective implementation is often poorly appreciated. The University of Nottingham has developed an effective communication portfolio (with dedicated outreach staff) to tackle this issue. In addition to more traditional routes of scientific communication and dissemination, A2P will develop a portfolio of engagement and outreach activities including blogs, webpages, public outreach events, and contribution of material to our award-winning YouTube channel, www.periodicvideos.com.
A2P will build on our successful Sustainable Chemicals and Processes Industry Forum (SCIF), which will provide entry to networks with a wide range of chemical science end-users (spanning multinationals through to speciality SMEs), policy makers and regulators. We will share new scientific developments and best practice with leaders in these areas, to help realise the full impact of our CDT. Annual showcase events will provide a forum where knowledge may be disseminated to partners, we will broaden these events to include participants from thematically linked CDTs from across the UK, we will build on our track record of delivering hi-impact inter-CDT events with complementary centres hosted by the Universities of Bath and Bristol.
People
A2P will provide over 60 PhD graduates with the skill sets required to deliver innovative sustainable products and processes into the UK chemicals manufacturing industry. A2P will inspire and develop leaders who will:
- understand the needs of industrial end-users;
- embed sustainability across a range of sectors; and
- catalyse the transition to a more productive and resilient UK economy.
Economy
A2P will promote a step change towards a circular economy that embraces resilience and efficiency in terms of atoms and energy. The benefits of adopting more sustainable design principles and smarter production are clear. For example, the global production of active pharmaceutical ingredients (APIs) has been estimated at 65,000-100,000 tonnes per annum. The scale of associated waste is > 10 million tonnes per annum with a disposal cost of more than £15 billion. Consequently, even a modest efficiency increase by applying new, more sustainable chemical processes would deliver substantial economic savings and environmental wins. A2P will seek and deliver systematic gains across all sectors of the chemicals manufacturing industry. Our goals of providing cross-scale training in chemical sciences with economic and life- cycle awareness will drive uptake of sustainable best practice in UK industry, leading to improved economic competitiveness.
Knowledge
This CDT will deliver significant new knowledge in the development of more sustainable processes and products. It will integrate the philosophy of sustainability with catalysis, synthetic methodology, process engineering, and scale-up. Critical concepts such as energy/resource efficiency, life cycle analysis, recycling, and sustainability metrics will become seamlessly joined to what is considered a 'normal' approach to new molecular products. This knowledge and experience will be shared through publications, conferences and other engagement activities. A2P partners will provide efficient routes to market ensuring the efficient translation and transferal of new technologies is realised, ensuring impact is achieved.
Society
The chemistry-using industries manufacture a rich portfolio of products that are critical in maintaining a high quality of life in the UK. A2P will provide highly trained people and new knowledge to develop smarter, better products, whilst increasing the efficiency and sustainability of chemicals manufacture.
To amplify the impacts of our CDT, effective public engagement and technology transfer will become crucially important. As a general comment, 'sustainability' styled research is often regarded in a positive light by society, however, the science that underpins its effective implementation is often poorly appreciated. The University of Nottingham has developed an effective communication portfolio (with dedicated outreach staff) to tackle this issue. In addition to more traditional routes of scientific communication and dissemination, A2P will develop a portfolio of engagement and outreach activities including blogs, webpages, public outreach events, and contribution of material to our award-winning YouTube channel, www.periodicvideos.com.
A2P will build on our successful Sustainable Chemicals and Processes Industry Forum (SCIF), which will provide entry to networks with a wide range of chemical science end-users (spanning multinationals through to speciality SMEs), policy makers and regulators. We will share new scientific developments and best practice with leaders in these areas, to help realise the full impact of our CDT. Annual showcase events will provide a forum where knowledge may be disseminated to partners, we will broaden these events to include participants from thematically linked CDTs from across the UK, we will build on our track record of delivering hi-impact inter-CDT events with complementary centres hosted by the Universities of Bath and Bristol.
