Anomalous chemically induced electron spin polarization in proton-coupled electron transfer reactions: insight into radical pair dynamics

Brugh, Alexander M.; Forbes, Malcolm D. E.

doi:10.1039/d0sc02691c

Cited by 7 publications

(4 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This hypothesis agrees with the observed polarisation pattern as described above, since the different intrinsic PDA radicals have a similar g ‐factor [15–17, 23] . SQRs polarised by the radical pair mechanism have been previously observed in systems involving PCET events [39] . We therefore propose that PCET which occurs between QH 2 and Q species in PDA is responsible for the polarisation observed in our transient ESR results.…”

Section: Figuresupporting

confidence: 93%

“…[15][16][17]23] SQRs polarised by the radical pair mechanism have been previously observed in systems involving PCET events. [39] We therefore propose We next sought to investigate the potential for using photo-activated PDA as a photosensitiser for polymerisation reactions. We selected photo-initiated free radical polymerisation as an exemplary reaction owing to the broad utility of this procedure for materials synthesis.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Polydopamine as a Visible‐Light Photosensitiser for Photoinitiated Polymerisation

et al. 2023

View full text Add to dashboard Cite

Polydopamine (PDA) is a synthetic model for melanin and has a wide range of opto‐electronic properties that underpin its utility in applied and biological settings, from broadband light absorbance to possessing stable free radical species. Here, we show that PDA free radicals are photo‐responsive under visible light irradiation, enabling PDA to serve as a photo‐redox catalyst. Steady‐state and transient electron spin resonance spectroscopy reveals a reversible amplification in semiquinone radical population within PDA under visible light. This photo‐response modifies the redox potential of PDA and supports sensitisation of exogenous species via photoinduced electron transfer (PET). We demonstrate the utility of this discovery by employing PDA nanoparticles to photosensitise a common diaryliodonium photoinitiator and initiate free‐radical polymerisation (FRP) of vinylic monomers. In situ 1H nuclear magnetic resonance spectroscopy reveals an interplay between PDA‐driven photosensitising and radical quenching during FRP under blue, green, and red light. This work provides crucial insights into the photoactive free radical properties of melanin‐like materials and reveals a promising new application for polydopamine as a photosensitiser.

show abstract

Section: Figuresupporting

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Polydopamine as a Visible‐Light Photosensitiser for Photoinitiated Polymerisation

et al. 2023

View full text Add to dashboard Cite

show abstract

“…These include transient or even stable free radicals, radical-ions, biradicals, and triplet molecular species. Quite often, several CIDEP mechanisms can operate at the same time . This significant perturbation of the population of electron spin states can be a useful tool in organic photochemistry. , Specifically, CIDEP is useful to explore the mechanisms of chemical reactions including the direct and sensitive detection of short-lived reaction intermediates.…”

Section: Hyperpolarization Techniquesmentioning

confidence: 99%

Spin Hyperpolarization in Modern Magnetic Resonance

et al. 2023

View full text Add to dashboard Cite

Magnetic resonance techniques are successfully utilized in a broad range of scientific disciplines and in various practical applications, with medical magnetic resonance imaging being the most widely known example. Currently, both fundamental and applied magnetic resonance are enjoying a major boost owing to the rapidly developing field of spin hyperpolarization. Hyperpolarization techniques are able to enhance signal intensities in magnetic resonance by several orders of magnitude, and thus to largely overcome its major disadvantage of relatively low sensitivity. This provides new impetus for existing applications of magnetic resonance and opens the gates to exciting new possibilities. In this review, we provide a unified picture of the many methods and techniques that fall under the umbrella term "hyperpolarization" but are currently seldom perceived as integral parts of the same field. Specifically, before delving into the individual techniques, we provide a detailed analysis of the underlying principles of spin hyperpolarization. We attempt to uncover and classify the origins of hyperpolarization, to establish its sources and the specific mechanisms that enable the flow of polarization from a source to the target spins. We then give a more detailed analysis of individual hyperpolarization techniques: the mechanisms by which they work, fundamental and technical requirements, characteristic applications, unresolved issues, and possible future directions. We are seeing a continuous growth of activity in the field of spin hyperpolarization, and we expect the field to flourish as new and improved hyperpolarization techniques are implemented. Some key areas for development are in prolonging polarization lifetimes, making hyperpolarization techniques more generally applicable to chemical/biological systems, reducing the technical and equipment requirements, and creating more efficient excitation and detection schemes. We hope this review will facilitate the sharing of knowledge between subfields within the broad topic of hyperpolarization, to help overcome existing challenges in magnetic resonance and enable novel applications.

show abstract

“…[15][16][17]23] SQRs polarised by the radical pair mechanism have been previously observed in systems involving PCET events. [39] We therefore propose that PCET which occurs between QH 2 and Q species in PDA is responsible for the polarisation observed in our transient ESR results. Overall, the steady-state and transient ESR results indicate a previously unknown photoreactivity in PDA, where light absorption drives amplification of the intrinsic free-radical population and alteration of bulk redox properties.…”

mentioning

confidence: 56%

Polydopamine as a Visible‐Light Photosensitiser for Photoinitiated Polymerisation

et al. 2023

View full text Add to dashboard Cite

Polydopamine (PDA) is a synthetic model for melanin and has a wide range of opto-electronic properties that underpin its utility in applied and biological settings, from broadband light absorbance to possessing stable free radical species. Here, we show that PDA free radicals are photo-responsive under visible light irradiation, enabling PDA to serve as a photo-redox catalyst. Steady-state and transient electron spin resonance spectroscopy reveals a reversible amplification in semiquinone radical population within PDA under visible light. This photo-response modifies the redox potential of PDA and supports sensitisation of exogenous species via photoinduced electron transfer (PET). We demonstrate the utility of this discovery by employing PDA nanoparticles to photosensitise a common diaryliodonium photoinitiator and initiate free-radical polymerisation (FRP) of vinylic monomers. In situ 1 H nuclear magnetic resonance spectroscopy reveals an interplay between PDA-driven photosensitising and radical quenching during FRP under blue, green, and red light. This work provides crucial insights into the photoactive free radical properties of melanin-like materials and reveals a promising new application for polydopamine as a photosensitiser.

show abstract

Anomalous chemically induced electron spin polarization in proton-coupled electron transfer reactions: insight into radical pair dynamics

Abstract: Time-resolved electron paramagnetic resonance (TREPR) spectroscopy has been used to study the proton coupled electron transfer (PCET) reaction between a Ruthenium complex (Ru(bpz)(bpy)2) and several substituted hydroquinones (HQ).

Cited by 7 publications

References 39 publications

Polydopamine as a Visible‐Light Photosensitiser for Photoinitiated Polymerisation

Polydopamine as a Visible‐Light Photosensitiser for Photoinitiated Polymerisation

Spin Hyperpolarization in Modern Magnetic Resonance

Polydopamine as a Visible‐Light Photosensitiser for Photoinitiated Polymerisation

Contact Info

Product

Resources

About