Photoexcited Triplet State Kinetics Studied by Electron Paramagnetic Resonance Spectroscopy

Hintze, Christian; Steiner, Ulrich; Drescher, Malte

doi:10.1002/cphc.201600868

Cited by 44 publications

(47 citation statements)

References 118 publications

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“…Next to these technical differences between LaserIMD and LiDEER, another important point to note is the fact that different spin species are observed in the two experiments. For LiDEER, the number of observable (triplet) spins is determined by the light excitation and triplet quantum yield, while at the same time, a signal enhancement is expected due to OSP [13,16]. A further parameter that becomes crucial when measuring longer dipolar traces required for detecting longer distances [28] is the phase memory time of the observer spins.…”

Section: Resultsmentioning

confidence: 99%

Light-induced dipolar spectroscopy – A quantitative comparison between LiDEER and LaserIMD

Bieber

Bücker

Drescher

2018

Journal of Magnetic Resonance

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Nanometric distance measurements with EPR spectroscopy yield crucial information on the structure and interactions of macromolecules in complex systems. The range of suitable spin labels for such measurements was recently expanded with a new class of light-inducible labels: the triplet state of porphyrins. Importantly, accurate distance measurements between a triplet label and a nitroxide have been reported with two distinct light-induced spectroscopy techniques, (light-induced) triplet-nitroxide DEER (LiDEER) and laser-induced magnetic dipole spectroscopy (LaserIMD). In this work, we set out to quantitatively compare the two techniques under equivalent conditions at Q band. Since we find that LiDEER using a rectangular pump pulse does not reach the high modulation depth that can be achieved with LaserIMD, we further explore the possibility of improving the LiDEER experiment with chirp inversion pulses. LiDEER employing a broadband pump pulse results in a drastic improvement of the modulation depth. The relative performance of chirp LiDEER and Laser-IMD in terms of modulation-to-noise ratio is found to depend on the dipolar evolution time: While LaserIMD yields higher modulation-to-noise ratios than LiDEER at short dipolar evolution times (τ=2μs), the high phase memory time of the triplet spins causes the situation to revert at τ=6μs.

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Section: Resultsmentioning

confidence: 99%

Light-induced dipolar spectroscopy – A quantitative comparison between LiDEER and LaserIMD

Bieber

Bücker

Drescher

2018

Journal of Magnetic Resonance

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“…Both drawbacks can be successfully remedied by using another type of photoexcited triplets—the fullerenes. Their ZFS values are approximately 4 times smaller resulting in much narrower EPR spectrum of approximately 20 mT . Compared to porphyrins, such a spectrum width would allow more efficient excitation and a significant increase of the signal‐to‐noise ratio.…”

Section: Methodsmentioning

confidence: 63%

“…Compared to porphyrins, such a spectrum width would allow more efficient excitation and a significant increase of the signal‐to‐noise ratio. Moreover, EPR spectra of photoexcited fullerenes are known to be detectable up to a room temperature, and the possibility to carry out PD EPR experiments at closely native conditions is strongly desired in biological applications …”

Section: Methodsmentioning

confidence: 99%

Triplet Fullerenes as Prospective Spin Labels for Nanoscale Distance Measurements by Pulsed Dipolar EPR Spectroscopy

et al. 2019

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Precise nanoscale distance measurements by pulsed electron paramagnetic resonance (EPR) spectroscopy play a crucial role in structural studies of biomolecules. The properties of the spin labels used in this approach determine the sensitivity limits, attainable distances, and proximity to biological conditions. Herein, we propose and validate the use of photoexcited fullerenes as spin labels for pulsed dipolar (PD) EPR distance measurements. Hyperpolarization and the narrower spectrum of fullerenes compared to other triplets (e.g., porphyrins) boost the sensitivity, and superior relaxation properties allow PD EPR measurements up to a near‐room temperature. This approach is demonstrated using fullerene–nitroxide and fullerene–triarylmethyl pairs, as well as a supramolecular complex of fullerene with nitroxide‐labeled protein. Photoexcited triplet fullerenes can be considered as new spin labels with outstanding spectroscopic properties for future structural studies of biomolecules.

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“…This effect has been investigated extensively on anthracene and, specifically, on haloanthracenes. [ 13 ] In this work we set out to systematically investigate the photoexcited triplet state kinetics of a series of haloanthracenes by means of electron paramagnetic resonance (EPR) spectroscopy [ 14 ]. We chose anthracene because the photochemistry of anthracene has been studied in detail [ 15 – 17 ], its triplet state is well-known (more than 500 corresponding publications in Thomson Reuters Web of Science) and the intersystem crossing (ISC) of haloanthracenes (among other haloaromatics) is understood [ 18 ].…”

Section: Introductionmentioning

confidence: 99%

“…Experiments to record the excited triplet state kinetics are well-known in EPR [ 14 ] as well as in optically detected magnetic resonance (ODMR) [ 19 – 21 ]. In this work, transient EPR (TR-EPR) is used to obtain EPR spectra of haloanthracenes, and electron spin echo (ESE) EPR for the actual kinetic measurements.…”

Section: Introductionmentioning

confidence: 99%

Heavy-atom effect on optically excited triplet state kinetics

2017

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In several fields of research, like e.g. photosensitization, photovoltaics, organic electroluminescent devices, dynamic nuclear polarization, or pulsed dipolar electron paramagnetic resonance spectroscopy, triplet state kinetics play an important role. It is therefore desirable to tailor the kinetics of photoexcited triplet states, e.g. by exploiting the intramolecular heavy-atom effect, and to determine the respective kinetic parameters. In this work, we set out to systematically investigate the photoexcited triplet state kinetics of a series of haloanthracenes by time-resolved electron paramagnetic resonance spectroscopy in combination with synchronized laser excitation. For this purpose, a procedure to simulate time traces by solving the differential equation system governing the triplet kinetics numerically is developed. This way, spin lattice relaxation rates and zero-field triplet life times are obtained concurrently by a global fit to experimental data measured at three different cryogenic temperatures.

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Photoexcited Triplet State Kinetics Studied by Electron Paramagnetic Resonance Spectroscopy

Cited by 44 publications

References 118 publications

Light-induced dipolar spectroscopy – A quantitative comparison between LiDEER and LaserIMD

Light-induced dipolar spectroscopy – A quantitative comparison between LiDEER and LaserIMD

Triplet Fullerenes as Prospective Spin Labels for Nanoscale Distance Measurements by Pulsed Dipolar EPR Spectroscopy

Heavy-atom effect on optically excited triplet state kinetics

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