Computational tools for the simulation and analysis of spin-polarized EPR spectra

Tait, Claudia E.; Krzyaniak, Matthew D.; Stoll, Stefan

doi:10.1016/j.jmr.2023.107410

Cited by 33 publications

(22 citation statements)

References 115 publications

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“…At early times (0.8–1.1 μs, Figure a), the spectra are dominated by a ∼35 mT wide spectral signature, which for most dimers has the ESP pattern of aae / aea , where a is enhanced absorption and e is emission. The early time spectra are simulated using the MATLAB toolbox EasySpin, , confirming the ∼35 mT wide features are arising due to quintet manifold transitions. Quintet features in trEPR prove that SF is active in all eight pentacene dimers.…”

Section: Resultsmentioning

confidence: 75%

Controlling Intramolecular Singlet Fission Dynamics via Torsional Modulation of Through-Bond versus Through-Space Couplings

Majumder,

Mukherjee,

Panjwani

et al. 2023

J. Am. Chem. Soc.

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Covalent dimers, particularly pentacenes, are the dominant platform for developing a mechanistic understanding of intramolecular singlet fission (iSF). Numerous studies have demonstrated that a photoexcited singlet state in these structures can rapidly and efficiently undergo exciton multiplication to form a correlated pair of triplets within a single molecule, with potential applications from photovoltaics to quantum information science. One of the most significant barriers limiting such dimers is the fast recombination of the triplet pair, which prevents spatial separation and the formation of long-lived triplet states. There is an ever-growing need to develop general synthetic strategies to control the evolution of triplets following iSF and enhance their lifetime. Here, we rationally tune the dihedral angle and interchromophore separation between pairs of pentacenes in a systematic series of bridging units to facilitate triplet separation. Through a combination of transient optical and spin-resonance techniques, we demonstrate that torsion within the linker provides a simple synthetic handle to tune the fine balance between through-bond and through-space interchromophore couplings that steer iSF. We show that the full iSF pathway from femtosecond to microsecond timescales is tuned through the static coupling set by molecular design and structural fluctuations that can be biased through steric control. Our approach highlights a straightforward design principle to generate paramagnetic spin pair states with higher yields.

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Section: Resultsmentioning

confidence: 75%

Controlling Intramolecular Singlet Fission Dynamics via Torsional Modulation of Through-Bond versus Through-Space Couplings

Majumder,

Mukherjee,

Panjwani

et al. 2023

J. Am. Chem. Soc.

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“…Revealing the characteristics and formation dynamics of intermediate triplet states is critical for understanding the TADF mechanism, while EPR spectroscopy is the ideal tool for characterizing these properties. 22 The EPR spectra of organic triplet states are dominated by the zero-field splitting (ZFS) interaction, which can be characterized by using two ZFS parameters D and E. Here, the ZFS parameters of the 3 LE and the 3 CT states were simulated using the ORCA 5.0 package. 34 Then the simulation and fitting of EPR spectra were carried out using open-source MATLAB version 9.5, treating them as absorption powder spectra via the ''pepper'' function from the EasySpin 5.0 package.…”

Section: Zero-field Splitting and Epr Parametersmentioning

confidence: 99%

“…In this investigation, we systematically compared the TADF mechanism of three compact dyads, namely, AQ-PTZ, AQ-PTZ-O, and AQ-PTZ-O 2 by means of quantum chemical calculations in conjunction with electron paramagnetic resonance (EPR) spectroscopy. 22 The objectives are to provide new gateways for designing effective TADF materials and studying TADF mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Spin–orbit charge transfer intersystem crossing and thermal activation delayed fluorescence (TADF) studies of compact orthogonal anthraquinone phenothiazine derivatives

Lv,

Yuan,

Zhao

et al. 2023

New J. Chem.

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“…Data processing and fitting were performed in MATLAB using lab-written scripts and EasySpin v6.0-dev. 51,52 The triplet TREPR spectra were simulated and fit using the pepper function in EasySpin, which was modeled using the Hamiltonian:…”

Section: ■ Introductionmentioning

confidence: 99%

Oriented Triplet Excitons as Long-Lived Electron Spin Qutrits in a Molecular Donor–Acceptor Single Cocrystal

Palmer,

Williams,

Young

et al. 2023

J. Am. Chem. Soc.

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The photogeneration of multiple unpaired electron spins within molecules is a promising route to applications in quantum information science because they can be initialized into well-defined, multilevel quantum states (S > 1/2) and reproducibly fabricated by chemical synthesis. However, coherent manipulation of these spin states is difficult to realize in typical molecular systems due to the lack of selective addressability and short coherence times of the spin transitions.Here, these challenges are addressed by using donor−acceptor single cocrystals composed of pyrene and naphthalene dianhydride to host spatially oriented triplet excitons, which exhibit promising photogenerated qutrit properties. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy demonstrates that spatially orienting triplet excitons in a single crystal platform imparts narrow, well-resolved, tunable resonances in the triplet EPR spectrum, allowing selective addressability of the spin sublevel transitions. Pulse-EPR spectroscopy reveals that at temperatures above 30 K, spin decoherence of these triplet excitons is driven by exciton diffusion. However, coherence is limited by electronic spin dipolar coupling below 30 K, where T 2 varies nonlinearly with the optical excitation density due to exciton annihilation. Overall, an optimized coherence time of T 2 = 7.1 μs at 20 K is achieved. These results provide important insights into designing solid-state molecular excitonic materials with improved spin qutrit properties.

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Computational tools for the simulation and analysis of spin-polarized EPR spectra

Cited by 33 publications

References 115 publications

Controlling Intramolecular Singlet Fission Dynamics via Torsional Modulation of Through-Bond versus Through-Space Couplings

Controlling Intramolecular Singlet Fission Dynamics via Torsional Modulation of Through-Bond versus Through-Space Couplings

Spin–orbit charge transfer intersystem crossing and thermal activation delayed fluorescence (TADF) studies of compact orthogonal anthraquinone phenothiazine derivatives

Oriented Triplet Excitons as Long-Lived Electron Spin Qutrits in a Molecular Donor–Acceptor Single Cocrystal

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