Chromophore-radical excited state antiferromagnetic exchange controls the sign of photoinduced ground state spin polarization

Kirk, Martin L.; Shultz, David A.; Hewitt, Patrick; Stasiw, Daniel E.; Ju, Chen; Est, Art van der

doi:10.1039/d1sc02965g

Cited by 32 publications

(67 citation statements)

References 42 publications

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“…In this series, perylene is covalently bound to seven different radicals, which are commonly used in experimental studies on molecular three-spin systems. [45][46][47][48][49][50][51][52][53][54] The goal was to determine the influence of the nature of the radical on the magnitude of the exchange interaction(s) and to verify whether systematic trends can be identified. Fig.…”

Section: Choice Of the Molecules And Methodsmentioning

confidence: 99%

Calculation of exchange couplings in the electronically excited state of molecular three-spin systems

2022

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Section: Choice Of the Molecules And Methodsmentioning

confidence: 99%

Calculation of exchange couplings in the electronically excited state of molecular three-spin systems

2022

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“…Optically pumped electron spin hyperpolarization can be generated in chromophore-radical (CR) systems during photophysical quenching processes. − The electron hyperpolarization generation in CR systems is well understood in the liquid state. − Two mechanisms contribute to the electron hyperpolarization (see energy diagram in Scheme ): (i) the spin-orbit-induced inter-system-crossing (SO-ISC) , and (ii) the D 1 –Q 1 conversion via the reverse quartet mechanism (RQM) . The first mechanism is due to the spin-orbit coupling, while the second involves the large zero-field splitting (ZFS), D ZFS , both in the excited triplet state of the chromophore.…”

Section: Resultsmentioning

confidence: 99%

Spinning-Driven Dynamic Nuclear Polarization with Optical Pumping

et al. 2022

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We propose a new, more efficient, and potentially cost effective, solid-state nuclear spin hyperpolarization method combining the cross-effect mechanism and electron spin optical hyperpolarization in rotating solids. We first demonstrate optical hyperpolarization in the solid state at low temperatures and low field and then investigate its field dependence to obtain the optimal condition for high-field electron spin hyperpolarization. The results are then incorporated into advanced magic-angle spinning dynamic nuclear polarization (MAS-DNP) numerical simulations that show that optically pumped MAS-DNP could yield breakthrough enhancements at very high magnetic fields. Based on these investigations, enhancements greater than the ratio of electron to nucleus magnetic moments (>658 for 1H) are possible without microwave irradiation. This could solve at once the MAS-DNP performance decrease with increasing field and the high cost of MAS-DNP instruments at very high fields.

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“…Lastly, given that fields like quantum computing , require selective addressing and faithful readout of spins, the current proposal of using a two-photon excitation for generating a hyperpolarized EPR signal can potentially address both of these concerns. Thus, it would not be wrong to conceive that the OH-EPRI, which assimilates the benefits of both EPR and the optical microscopy, would benefit diverse fields in the near future.…”

Section: Discussionmentioning

confidence: 99%

Harnessing Electron Spin Hyperpolarization in Chromophore–Radical Spin Probes for Subcellular Resolution in Electron Paramagnetic Resonance Imaging: Concept and Feasibility

Rane

2022

J. Phys. Chem. B

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Obtaining a subcellular resolution for biological samples doped with stable radicals at room temperature (RT) is a long-sought goal in electron paramagnetic resonance imaging (EPRI). The spatial resolution in current EPRI methods is constrained either because of low electron spin polarization at RT or the experimental limitations associated with the field gradients and the radical linewidth. Inspired by the recent demonstration of a large electron spin hyperpolarization in chromophore-nitroxyl spin probe molecules, the present work proposes a novel optically hyperpolarized EPR imaging (OH-EPRI) method, which combines the optical method of two-photon confocal microscopy for hyperpolarization generation and the rapid scan (RS) EPR method for signal detection. An important aspect of OH-EPRI is that it is not limited by the abovementioned restrictions of conventional EPRI since the large hyperpolarization in the spin probes overcomes the poor thermal spin polarization at RT, and the use of two-photon optical excitation of the chromophore naturally generates the required spatial resolution, without the need for any magnetic field gradient. Simulations based on time-dependent Bloch equations, which took into account both the RS field modulation and the hyperpolarization generation by optical means, were performed to examine the feasibility of OH-EPRI. The simulation results revealed that a spatial resolution of up to 2 fL can be achieved in OH-EPRI at RT under in vitro conditions. Notably, the majority of the requirements for an OH-EPRI experiment can be fulfilled by the currently available technologies, thereby paving the way for its easy implementation. Thus, the proposed method could potentially bridge the sensitivity gap between the optical and magnetic imaging techniques.

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Chromophore-radical excited state antiferromagnetic exchange controls the sign of photoinduced ground state spin polarization

Abstract: A change in the sign of the ground-state electron spin polarization (ESP) is reported in complexes where an organic radical (nitronylnitroxide, NN) is covalently attached to a donor acceptor...

Cited by 32 publications

References 42 publications

Calculation of exchange couplings in the electronically excited state of molecular three-spin systems

Calculation of exchange couplings in the electronically excited state of molecular three-spin systems

Spinning-Driven Dynamic Nuclear Polarization with Optical Pumping

Harnessing Electron Spin Hyperpolarization in Chromophore–Radical Spin Probes for Subcellular Resolution in Electron Paramagnetic Resonance Imaging: Concept and Feasibility

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