High Resolution ESR Spectroscopy for Catalysis Research
Lead Research Organisation:
CARDIFF UNIVERSITY
Department Name: Chemistry
Abstract
Electron Spin Resonance (ESR) spectroscopy is a magnetic resonance technique used in the analysis of any system containing unpaired electrons. It is therefore an extremely powerful, advanced and versatile tool for the study of paramagnetic compounds and free radicals. However, one drawback of ESR that is often encountered at the common microwave frequency (9.5 GHz) adopted by most commercial instruments, is the overlapping signals observed for radicals with low g-anisotropy, particularly in disordered systems, or the complex spectra arising from paramagnetic systems containing more than one unpaired electron. As a result, a significant amount of information on the identity of the radical can be lost and the spectra themselves can be very difficult to interpret. This information can be more readily extracted, and the ease of spectral analysis considerably simplified, by performing the ESR measurements at higher frequencies (94 GHz, referred to as W-band ESR). W-band ESR is regarded as a powerful complimentary spectroscopic technique with unique capabilities for providing information on the structure and dynamics of paramagnetic systems, by offering higher resolution and electronic insights into systems bearing unpaired electrons. High resolution ESR is thus an essential compliment to the traditional ESR tool-box in providing a more complete description of the spin Hamiltonian and the detailed characterization of reactive free radicals in the liquid phase and paramagnetic complexes in the solid state and frozen solution.
In this project, we will install a continuous wave (CW) W-band ESR spectrometer in Cardiff University, which will be specifically set-up for projects in catalysis research. The CW instrument will enable us to perform more advanced ESR measurements of paramagnetic metal centres, surface and bulk defects, localised electrons, dopants, spin labels/probes and free radicals (of relevance to homogeneous or heterogeneous catalytic systems), primarily in solids & liquids, at the gas-solid and liquid-solid interface, at high and low temperatures and under photolysis conditions. Catalysis represents the ultimate challenge for any technique, with reactions occurring at specific atomic sites, at fast times scales and often in complex media. This requires the utilization of advanced spectroscopic methodologies that can probe not only the changes in electronic structure, symmetry, spin states and coordination numbers, but also that can reveal insights into the dynamics and nature of the reactive intermediates involved in the catalytic cycle. The W-band ESR instrument can access all of this key information for catalytic systems bearing unpaired electrons, and thus will provide an important additional capability for catalysis research in the UK.
The instrument will provide the catalysis community access to an ESR instrument dedicated for research projects in homogeneous and heterogeneous catalysis, namely in the detection of reactive oxygen species in heterogeneous catalysis, understanding the involvement of surface bound radicals and defects in catalysis and photocatalysis, investigating the role of redox active centres in catalysis & the characterization of homogeneous organometallic catalysis, and characterising the transition metal ions doped into microporous materials and confined environments. These project work-packages will be undertaken through collaborations with key stakeholders and project partners in the Cardiff Catalysis Institute (CCI), the UK Catalysis Hub, the GW4 Alliance of Universities and other UK catalysis groups and industrial partners. The instrument will be managed by the PI and CoI, is supported by Cardiff University and Bruker UK Limited, and will add an essential additional capacity to the UK scientific equipment infrastructure. The insights gained in this project will ultimately be used to develop the next generation of improved, cheaper and more efficient catalysts.
In this project, we will install a continuous wave (CW) W-band ESR spectrometer in Cardiff University, which will be specifically set-up for projects in catalysis research. The CW instrument will enable us to perform more advanced ESR measurements of paramagnetic metal centres, surface and bulk defects, localised electrons, dopants, spin labels/probes and free radicals (of relevance to homogeneous or heterogeneous catalytic systems), primarily in solids & liquids, at the gas-solid and liquid-solid interface, at high and low temperatures and under photolysis conditions. Catalysis represents the ultimate challenge for any technique, with reactions occurring at specific atomic sites, at fast times scales and often in complex media. This requires the utilization of advanced spectroscopic methodologies that can probe not only the changes in electronic structure, symmetry, spin states and coordination numbers, but also that can reveal insights into the dynamics and nature of the reactive intermediates involved in the catalytic cycle. The W-band ESR instrument can access all of this key information for catalytic systems bearing unpaired electrons, and thus will provide an important additional capability for catalysis research in the UK.
The instrument will provide the catalysis community access to an ESR instrument dedicated for research projects in homogeneous and heterogeneous catalysis, namely in the detection of reactive oxygen species in heterogeneous catalysis, understanding the involvement of surface bound radicals and defects in catalysis and photocatalysis, investigating the role of redox active centres in catalysis & the characterization of homogeneous organometallic catalysis, and characterising the transition metal ions doped into microporous materials and confined environments. These project work-packages will be undertaken through collaborations with key stakeholders and project partners in the Cardiff Catalysis Institute (CCI), the UK Catalysis Hub, the GW4 Alliance of Universities and other UK catalysis groups and industrial partners. The instrument will be managed by the PI and CoI, is supported by Cardiff University and Bruker UK Limited, and will add an essential additional capacity to the UK scientific equipment infrastructure. The insights gained in this project will ultimately be used to develop the next generation of improved, cheaper and more efficient catalysts.
Planned Impact
Who will benefit from this research?
Free radicals and redox reactions are common in nature. Many radicals are present in the air around us, in the foods we consume, and in the many products we use on a daily basis. Most foods contain chemical additives ('anti-oxidants') whose role is to minimize the adverse effects of these free radicals. There is even evidence to suggest that several degenerative diseases may involve deleterious free radical processes. However, it is wrong to think that all free radicals or paramagnetic species produce adverse effects. Indeed many essential redox reactions occurring in the body actually rely on the participation of free radicals, while the hydroxyl radical acts as the primary 'cleaning agent' in the atmosphere. In chemistry and biology, numerous chemical transformations are dependent on the participation of paramagnetic species and radicals, particularly in catalysis. Despite their importance, the role of these radicals is exceedingly complex and still not fully understood. The importance of catalysis itself cannot be underestimated as a subject and for its contributions to the UK economy, since it will play an essential role for solutions to major problems in society (energy, environment, quality of life). To develop better catalysts and to understand their mode of action, one needs better tools to characterize the intrinsic mechanisms at faster time scales, the intermediates at higher resolution or the catalyst structure under relevant conditions. All these insights can be achieved using advanced ESR techniques. In this Strategic Equipment bid, the high resolution ESR instrument will provide an important enabling tool for revealing a molecular basis for understanding catalytic reactions. This instrument and the associated expertise at Cardiff will provide an important tool for the wider UK catalysis community, particularly the numerous catalysis research groups at the local, regional and national level. Furthermore, owing to the importance of free radicals and paramagnetic species in many systems, the wider academic and industrial community conducting research in free radicals, may also benefit from the new spectrometer.
How will they benefit?
The primary mode by which the key users of this Strategic Equipment bid will benefit, is through the creation of academic (and industrial) networks around the thematic area of paramagnetism in catalysis, whereby users can access state-of-the-art ESR facilities and expertise covering all aspects of radicals, defects or paramagnetic centres involved in catalytic reactions. These networks will be developed with key stakeholders through engagement with the CCI, UK Catalysis Hub and GW4 Alliance of Universities. The instrument will be installed in a dedicated refurbished laboratory to facilitate ease of user access and operation (i.e. sample preparation and treatment on site) and secondment of PhD/PDRA personnel will be encouraged. In this way, we will provide our key beneficiaries not only with important spectroscopic data on their samples (collaboration & coproduction), which will contribute to improvements in catalysts design and function that may be subsequently exploited for economic gain, but also provide them with direct 'hands-on' experience and training on the instrument, thereby improving their skills (capacity & involvement). Understanding the nature and behaviour of a modern catalyst (operating at extreme conditions, in complex phases and with mixed components) is exceedingly challenging, and requires access not only to advanced instrumentation but also to specialist practitioners capable of operating the spectrometers and analysing the result data, in order to understand the catalytic mechanism and thus make better catalysts. This instrument will serve the UK catalysis community in this endeavour and thus help to deliver improved catalysts (exploitation & application).
Free radicals and redox reactions are common in nature. Many radicals are present in the air around us, in the foods we consume, and in the many products we use on a daily basis. Most foods contain chemical additives ('anti-oxidants') whose role is to minimize the adverse effects of these free radicals. There is even evidence to suggest that several degenerative diseases may involve deleterious free radical processes. However, it is wrong to think that all free radicals or paramagnetic species produce adverse effects. Indeed many essential redox reactions occurring in the body actually rely on the participation of free radicals, while the hydroxyl radical acts as the primary 'cleaning agent' in the atmosphere. In chemistry and biology, numerous chemical transformations are dependent on the participation of paramagnetic species and radicals, particularly in catalysis. Despite their importance, the role of these radicals is exceedingly complex and still not fully understood. The importance of catalysis itself cannot be underestimated as a subject and for its contributions to the UK economy, since it will play an essential role for solutions to major problems in society (energy, environment, quality of life). To develop better catalysts and to understand their mode of action, one needs better tools to characterize the intrinsic mechanisms at faster time scales, the intermediates at higher resolution or the catalyst structure under relevant conditions. All these insights can be achieved using advanced ESR techniques. In this Strategic Equipment bid, the high resolution ESR instrument will provide an important enabling tool for revealing a molecular basis for understanding catalytic reactions. This instrument and the associated expertise at Cardiff will provide an important tool for the wider UK catalysis community, particularly the numerous catalysis research groups at the local, regional and national level. Furthermore, owing to the importance of free radicals and paramagnetic species in many systems, the wider academic and industrial community conducting research in free radicals, may also benefit from the new spectrometer.
How will they benefit?
The primary mode by which the key users of this Strategic Equipment bid will benefit, is through the creation of academic (and industrial) networks around the thematic area of paramagnetism in catalysis, whereby users can access state-of-the-art ESR facilities and expertise covering all aspects of radicals, defects or paramagnetic centres involved in catalytic reactions. These networks will be developed with key stakeholders through engagement with the CCI, UK Catalysis Hub and GW4 Alliance of Universities. The instrument will be installed in a dedicated refurbished laboratory to facilitate ease of user access and operation (i.e. sample preparation and treatment on site) and secondment of PhD/PDRA personnel will be encouraged. In this way, we will provide our key beneficiaries not only with important spectroscopic data on their samples (collaboration & coproduction), which will contribute to improvements in catalysts design and function that may be subsequently exploited for economic gain, but also provide them with direct 'hands-on' experience and training on the instrument, thereby improving their skills (capacity & involvement). Understanding the nature and behaviour of a modern catalyst (operating at extreme conditions, in complex phases and with mixed components) is exceedingly challenging, and requires access not only to advanced instrumentation but also to specialist practitioners capable of operating the spectrometers and analysing the result data, in order to understand the catalytic mechanism and thus make better catalysts. This instrument will serve the UK catalysis community in this endeavour and thus help to deliver improved catalysts (exploitation & application).
Publications
Blackaby WJM
(2018)
Mono- and dinuclear Ni(i) products formed upon bromide abstraction from the Ni(i) ring-expanded NHC complex [Ni(6-Mes)(PPh3)Br].
in Dalton transactions (Cambridge, England : 2003)
Buckingham M
(2018)
Electrochemically Driven C-H Hydrogen Abstraction Processes with the Tetrachloro-Phthalimido-N-Oxyl (Cl 4 PINO) Catalyst
in Electroanalysis
Crombie C
(2021)
Enhanced Selective Oxidation of Benzyl Alcohol via In Situ H 2 O 2 Production over Supported Pd-Based Catalysts
in ACS Catalysis
Folli A
(2021)
Probing the structure of Copper(II)-Casiopeina type coordination complexes [Cu(O-O)(N-N)]+ by EPR and ENDOR spectroscopy
in Journal of Catalysis
Liu Z
(2018)
Tuning the reactivity of nitriles using Cu(ii) catalysis - potentially prebiotic activation of nucleotides.
in Chemical science
Luckham SLJ
(2019)
Unravelling the Photochemical Transformations of Chromium(I) 1,3 Bis(diphenylphosphino), [Cr(CO)4(dppp)]+, by EPR Spectroscopy.
in Organometallics
Richards E
(2019)
An EPR characterisation of stable and transient reactive oxygen species formed under radiative and non-radiative conditions
in Research on Chemical Intermediates
Ritterskamp N
(2017)
Understanding the Coordination Modes of [Cu(acac)2(imidazole)n=1,2] Adducts by EPR, ENDOR, HYSCORE, and DFT Analysis.
in Inorganic chemistry
Sampford KR
(2019)
Twisting the arm: structural constraints in bicyclic expanded-ring N-heterocyclic carbenes.
in Dalton transactions (Cambridge, England : 2003)
Description | Catalysis is extremely important for the chemical industry and vital to our modern economy. The importance of catalytic reactions should not be underestimated since they play an essential role for solutions to major problems in society (e.g. energy, environment, sustainability). To develop improved catalysts, one requires better tools to characterize the intrinsic mechanisms at faster time scales, the intermediates at higher resolution and the catalyst structures under relevant conditions. One important technique offering considerable insights into the structure and mechanisms of catalytic reactions is high resolution ESR. This important spectroscopic tool is incredibly powerful for the detection and characterization of paramagnetic reaction intermediates and exploring their role in reaction mechanisms; therefore, it provides an experimental molecular basis for improved understanding of catalytic reactions. A wide range of research projects requiring access to a dedicated high resolution ESR spectrometer, included detection of catalytic intermediates, identifying the role of paramagnetic transition metal ions in reactions, studying the nature of the Reactive Oxygen Species (ROS) involved in oxidation pathways and exploring magnetic behaviour in semiconductor based supported nanoparticles or ferromagnetic supports in catalysis. Projects involving all these areas of research were indeed studied since the project started. Highlights include studying the photochemical transformations of Cr(I) tetracarbonyl complexes, tuning the reactivity of nitriles using Cu(II) complexes, investigating the binding environments of Cu(II) by N-donor chelating resins on exchange supports, and improving the selectivity of photocatalytic NOx abatement using doped TiO2 semiconductor nanaoparticles. This work demonstrates the wide variety of research projects that the instrument has enabled, and more broadly the role and importance of paramagnetic and radical species in chemistry and materials science. |
Exploitation Route | Most of the research to date has been very collaborative. We have provided our collaborators access to a highly advanced EPR spectrometer, enabling them to study their systems in greater details. hence most of the outcomes associated with their research activities are specific to their individual programmes of research. However, simultaneously, we are also widening the access of this advanced spectrometer to the catalysis community so we believe going forward other scientists will use the instrument more regularly. At the same time, we are also developing in house improved design capabilities to improve the ease of utilising the spectrometer, with the wider EPR community may like adapt at a later stage. These developments are in their early trial stages. |
Sectors | Chemicals |