1
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Liu L, Liu X, Kurganskii I, Chen X, Gurzadyan GG, Zhao J, Wan Y, Fedin M. Charge Transfer and Intersystem Crossing in Compact Naphthalenediimide-Phenothiazine Triads: Synthesis and Study of the Photophysical Property with Transient Optical and Electron Paramagnetic Resonance Spectroscopic Methods. J Phys Chem B 2024; 128:7237-7253. [PMID: 39016740 DOI: 10.1021/acs.jpcb.4c03145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/18/2024]
Abstract
In order to obtain a long-lived charge separation (CS) state in compact electron donor-acceptor molecular systems, we prepared a series of naphthalenediimide (NDI)-phenothiazine (PTZ) triads, with phenylene as the linker between the donor and acceptor. Conformation restriction is imposed to control the mutual orientation of the NDI and PTZ units by attaching methyl groups on the phenylene linker to tune the electronic coupling between the donor and the acceptor. Moreover, the PTZ moiety was oxidized to sulfoxide to tune the ordering of the CS state and the 3LE state (LE: locally excited state). UV-vis absorption spectra indicate electronic coupling between NDI with the phenylene linker as well as the PTZ units, manifested by the appearance of a charge-transfer (CT) absorption band, whereas this coupling is devoid in the triads with conformation restriction imposed. Fluorescence is strongly quenched in the triads compared to the reference compound, indicating electron transfer upon photoexcitation. Femtosecond transient absorption spectra indicate that the CS takes 0.8 ps, and then the 3LE state is formed by charge recombination in 83 ps. Nanosecond transient absorption (ns-TA) spectra show that the 3NDI state was observed in nonpolar solvents such as cyclohexane (triplet state lifetime: 95.7 μs), whereas the CS state was observed in more polar solvents. The CS state lifetimes are up to 1.2 μs (in toluene). Time-resolved electron paramagnetic resonance spectra of the triads in toluene consist of two types of signals: CS states (narrower signals, ∼10 mT) and 3LE states (broader signals, ∼50 to 200 mT). In the spectra of the triads containing PTZ, the CS state signals dominate, whereas for the triads containing oxidized PTZ, the 3NDI signals (zero-field splitting D ≈ 2000 MHz) prevail, both observations being in agreement with the ns-TA spectral studies. The electron spin polarization phase pattern of the 3NDI states of the triads indicates that the intersystem crossing (ISC) mechanism is spin-orbit charge-transfer ISC. Considering the 3CS state as ion pairs, the electron-exchange energy (J) is determined to be -39 to -59 MHz, and the electron spin dipolar interaction is 83-92 MHz.
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Affiliation(s)
- Lezhang Liu
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China
| | - Xi Liu
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Ivan Kurganskii
- International Tomography Center, SB RAS, Institutskaya Street, 3A, Novosibirsk 630090, Russia
| | - Xi Chen
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China
| | - Gagik G Gurzadyan
- State Key Laboratory of Fine Chemicals, Institute of Artificial Photosynthesis, Dalian University of Technology, Dalian 116024, P. R. China
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals, Frontier Science Center for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China
| | - Yan Wan
- College of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - Matvey Fedin
- International Tomography Center, SB RAS, Institutskaya Street, 3A, Novosibirsk 630090, Russia
- Novosibirsk State University, Pirogova Street 2, Novosibirsk 630090, Russia
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2
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Thielert P, El Bitar Nehme M, Mayländer M, Franz M, Zimmermann SL, Fisch F, Gilch P, Vargas Jentzsch A, Rickhaus M, Richert S. Influence of the substitution position on spin communication in photoexcited perylene-nitroxide dyads. Chem Sci 2024; 15:7515-7523. [PMID: 38784753 PMCID: PMC11110163 DOI: 10.1039/d4sc00328d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Accepted: 03/25/2024] [Indexed: 05/25/2024] Open
Abstract
By virtue of the modularity of their structures, their tunable optical and magnetic properties, and versatile applications, photogenerated triplet-radical systems provide an ideal platform for the study of the factors controlling spin communication in molecular frameworks. Typically, these compounds consist of an organic chromophore covalently attached to a stable radical. After formation of the chromophore triplet state by photoexcitation, two spin centres are present in the molecule that will interact. The nature of their interaction is governed by the magnitude of the exchange interaction between them and can be studied by making use of transient electron paramagnetic resonance (EPR) techniques. Here, we investigate three perylene-nitroxide dyads that only differ with respect to the position where the nitroxide radical is attached to the perylene core. The comparison of the results from transient UV-vis and EPR experiments reveals major differences in the excited state properties of the three dyads, notably their triplet state formation yield, excited state deactivation kinetics, and spin coherence times. Spectral simulations and quantum chemical calculations are used to rationalise these findings and demonstrate the importance of considering the structural flexibility and the contribution of rotational conformers for an accurate interpretation of the data.
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Affiliation(s)
- Philipp Thielert
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
| | - Mélissa El Bitar Nehme
- Department of Chemistry, University of Zurich Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Maximilian Mayländer
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
| | - Michael Franz
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
| | - Simon L Zimmermann
- Institute of Physical Chemistry, Heinrich Heine University Düsseldorf Universitätsstraße 1 40225 Düsseldorf Germany
| | - Fabienne Fisch
- Department of Chemistry, University of Zurich Winterthurerstrasse 190 8057 Zurich Switzerland
| | - Peter Gilch
- Institute of Physical Chemistry, Heinrich Heine University Düsseldorf Universitätsstraße 1 40225 Düsseldorf Germany
| | - Andreas Vargas Jentzsch
- SAMS Research Group, Université de Strasbourg, CNRS, Institut Charles Sadron UPR 22 67000 Strasbourg France
| | - Michel Rickhaus
- Department of Chemistry, University of Zurich Winterthurerstrasse 190 8057 Zurich Switzerland
- Department of Organic Chemistry, University of Geneva 30 Quai Ernest-Ansermet 1211 Geneva 4 Switzerland
| | - Sabine Richert
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
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3
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Medagedara H, Teferi MY, Wanasinghe ST, Burson W, Kizi S, Zaslona B, Mardis KL, Niklas J, Poluektov OG, Rury AS. Decorrelated singlet and triplet exciton delocalization in acetylene-bridged Zn-porphyrin dimers. Chem Sci 2024; 15:1736-1751. [PMID: 38303928 PMCID: PMC10829018 DOI: 10.1039/d3sc03327a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Accepted: 12/12/2023] [Indexed: 02/03/2024] Open
Abstract
The controlled delocalization of molecular excitons remains an important goal towards the application of organic chromophores in processes ranging from light-initiated chemical transformations to classical and quantum information processing. In this study, we present a methodology to couple optical and magnetic spectroscopic techniques and assess the delocalization of singlet and triplet excitons in model molecular chromophores. By comparing the steady-state and time-resolved optical spectra of Zn-porphyrin monomers and weakly coupled dimers, we show that we can use the identity of substituents bound at specific positions of the macromolecules' rings to control the inter-ring delocalization of singlet excitons stemming from their B states through acetylene bridges. While broadened steady-state absorption spectra suggest the presence of delocalized B state excitons in mesityl-substituted Zn-tetraphenyl porphyrin dimers (Zn2U-D), we confirm this conclusion by measuring an enhanced ultrafast non-radiative relaxation from these inter-ring excitonic states to lower lying electronic states relative to their monomer. In contrast to the delocalized nature of singlet excitons, we use time-resolved EPR and ENDOR spectroscopies to show that the triplet states of the Zn-porphyrin dimers remain localized on one of the two macrocyclic sub-units. We use the analysis of EPR and ENDOR measurements on unmetallated model porphyrin monomers and dimers to support this conclusion. The results of DFT calculations also support the interpretation of localized triplet states. These results demonstrate researchers cannot conclude triplet excitons delocalize in macromolecular based on the presence of spatially extended singlet excitons, which can help in the design of chromophores for application in spin conversion and information processing technologies.
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Affiliation(s)
- Hasini Medagedara
- Department of Chemistry, Wayne State University Detroit MI 48202 USA
| | - Mandefro Y Teferi
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | | | - Wade Burson
- Department of Chemistry, Wayne State University Detroit MI 48202 USA
| | - Shahad Kizi
- Department of Chemistry, Wayne State University Detroit MI 48202 USA
| | - Bradly Zaslona
- Department of Chemistry, Wayne State University Detroit MI 48202 USA
| | - Kristy L Mardis
- Department of Chemistry, Physics, and Engineering Sciences, Chicago State University Chicago IL 60628 USA
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
| | - Aaron S Rury
- Department of Chemistry, Wayne State University Detroit MI 48202 USA
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4
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Palmer JR, Williams ML, Young RM, Peinkofer KR, Phelan BT, Krzyaniak MD, Wasielewski MR. Oriented Triplet Excitons as Long-Lived Electron Spin Qutrits in a Molecular Donor-Acceptor Single Cocrystal. J Am Chem Soc 2024; 146:1089-1099. [PMID: 38156609 DOI: 10.1021/jacs.3c12277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
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 T2 varies nonlinearly with the optical excitation density due to exciton annihilation. Overall, an optimized coherence time of T2 = 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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Affiliation(s)
- Jonathan R Palmer
- Department of Chemistry, Center for Molecular Quantum Transduction, and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Malik L Williams
- Department of Chemistry, Center for Molecular Quantum Transduction, and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Ryan M Young
- Department of Chemistry, Center for Molecular Quantum Transduction, and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Kathryn R Peinkofer
- Department of Chemistry, Center for Molecular Quantum Transduction, and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Brian T Phelan
- Department of Chemistry, Center for Molecular Quantum Transduction, and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Matthew D Krzyaniak
- Department of Chemistry, Center for Molecular Quantum Transduction, and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R Wasielewski
- Department of Chemistry, Center for Molecular Quantum Transduction, and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, Illinois 60208-3113, United States
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5
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Actis A, Melchionna M, Filippini G, Fornasiero P, Prato M, Chiesa M, Salvadori E. Singlet-Triplet Energy Inversion in Carbon Nitride Photocatalysts. Angew Chem Int Ed Engl 2023; 62:e202313540. [PMID: 37801043 DOI: 10.1002/anie.202313540] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 10/05/2023] [Accepted: 10/06/2023] [Indexed: 10/07/2023]
Abstract
Time-resolved EPR (TR-EPR) demonstrates the formation of well-defined spin triplet excitons in carbon nitride. This permits to experimentally probe the extent of the triplet wavefunction which delocalizes over several tri-s-triazine units. Analysis of the temperature dependence of the TR-EPR signal reveals the mobility of the triplet excitons. By employing monochromatic light excitation in the range 430-600 nm, the energy of the spin triplet is estimated to be ≈0.2 eV above the conduction band edge, proving that the triplet exciton lies above the corresponding singlet. Comparison between amorphous and graphitic forms establishes the singlet-triplet inversion as a general feature of carbon nitride materials.
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Affiliation(s)
- Arianna Actis
- Department of Chemistry and NIS Centre, University of Torino, Via Pietro Giuria 7, 10125, Torino, Italy
| | - Michele Melchionna
- Department of Chemical and Pharmaceutical, INSTM UdR, University of Trieste, Via Licio Giorgieri 1, 34127, Trieste, Italy
| | - Giacomo Filippini
- Department of Chemical and Pharmaceutical, INSTM UdR, University of Trieste, Via Licio Giorgieri 1, 34127, Trieste, Italy
| | - Paolo Fornasiero
- Department of Chemical and Pharmaceutical, INSTM UdR, University of Trieste, Via Licio Giorgieri 1, 34127, Trieste, Italy
- ICCOM-CNR URT, Via Licio Giorgieri 1, 34127, Trieste, Italy
| | - Maurizio Prato
- Department of Chemical and Pharmaceutical, INSTM UdR, University of Trieste, Via Licio Giorgieri 1, 34127, Trieste, Italy
- Center for Cooperative Research in Biomaterials (CIC biomaGUNE), Basque Research and Technology Alliance (BRTA), Paseo Miramon 194, 20014, Donostia San Sebastián, Spain
- Basque Fdn Sci, Ikerbasque, 48013, Bilbao, Spain
| | - Mario Chiesa
- Department of Chemistry and NIS Centre, University of Torino, Via Pietro Giuria 7, 10125, Torino, Italy
| | - Enrico Salvadori
- Department of Chemistry and NIS Centre, University of Torino, Via Pietro Giuria 7, 10125, Torino, Italy
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6
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Ren Y, Hore PJ. Conditions for EPR detection of chirality-induced spin selectivity in spin-polarized radical pairs in isotropic solution. J Chem Phys 2023; 159:145104. [PMID: 37819000 DOI: 10.1063/5.0171700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 09/19/2023] [Indexed: 10/13/2023] Open
Abstract
Chiral molecules can act as spin filters, preferentially transmitting electrons with spins polarized along their direction of travel, an effect known as chirality-induced spin selectivity (CISS). In a typical experiment, injected electrons tunnel coherently through a layer of chiral material and emerge spin-polarized. It is also possible that spin polarization arises in radical pairs formed photochemically when electrons hop incoherently between donor and acceptor sites. Here we aim to identify the magnetic properties that would optimise the visibility of CISS polarization in time-resolved electron paramagnetic resonance (EPR) spectra of transient radical pairs without the need to orient or align their precursors. By simulating spectra of actual and model systems, we find that CISS contributions to the polarization should be most obvious when at least one of the radicals has small g-anisotropy and an inhomogeneous linewidth larger than the dipolar coupling of the two radicals. Under these conditions there is extensive cancellation of absorptive and emissive enhancements making the spectrum sensitive to small changes in the individual EPR line intensities. Although these cancellation effects are more pronounced at lower spectrometer frequencies, the spectral changes are easier to appreciate with the enhanced resolution afforded by high-frequency EPR. Consideration of published spectra of light-induced radical pairs in photosynthetic bacterial reaction centres reveals no significant CISS component in the polarization generated by the conventional spin-correlated radical pair mechanism.
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Affiliation(s)
- Yi Ren
- Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - P J Hore
- Department of Chemistry, University of Oxford, Oxford, United Kingdom
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7
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Eckvahl HJ, Tcyrulnikov NA, Chiesa A, Bradley JM, Young RM, Carretta S, Krzyaniak MD, Wasielewski MR. Direct observation of chirality-induced spin selectivity in electron donor-acceptor molecules. Science 2023; 382:197-201. [PMID: 37824648 DOI: 10.1126/science.adj5328] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2023] [Accepted: 08/23/2023] [Indexed: 10/14/2023]
Abstract
The role of chirality in determining the spin dynamics of photoinduced electron transfer in donor-acceptor molecules remains an open question. Although chirality-induced spin selectivity (CISS) has been demonstrated in molecules bound to substrates, experimental information about whether this process influences spin dynamics in the molecules themselves is lacking. Here we used time-resolved electron paramagnetic resonance spectroscopy to show that CISS strongly influences the spin dynamics of isolated covalent donor-chiral bridge-acceptor (D-Bχ-A) molecules in which selective photoexcitation of D is followed by two rapid, sequential electron-transfer events to yield D•+-Bχ-A•-. Exploiting this phenomenon affords the possibility of using chiral molecular building blocks to control electron spin states in quantum information applications.
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Affiliation(s)
- Hannah J Eckvahl
- Department of Chemistry, Center for Molecular Quantum Transduction and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL 60208-3113, USA
| | - Nikolai A Tcyrulnikov
- Department of Chemistry, Center for Molecular Quantum Transduction and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL 60208-3113, USA
| | - Alessandro Chiesa
- Università di Parma, Dipartimento di Scienze Matematiche, Fisiche e Informatiche, I-43124 Parma, Italy
| | - Jillian M Bradley
- Department of Chemistry, Center for Molecular Quantum Transduction and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL 60208-3113, USA
| | - Ryan M Young
- Department of Chemistry, Center for Molecular Quantum Transduction and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL 60208-3113, USA
| | - Stefano Carretta
- Università di Parma, Dipartimento di Scienze Matematiche, Fisiche e Informatiche, I-43124 Parma, Italy
| | - Matthew D Krzyaniak
- Department of Chemistry, Center for Molecular Quantum Transduction and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL 60208-3113, USA
| | - Michael R Wasielewski
- Department of Chemistry, Center for Molecular Quantum Transduction and Paula M. Trienens Institute for Sustainability and Energy, Northwestern University, Evanston, IL 60208-3113, USA
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8
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Mayländer M, Kopp K, Nolden O, Franz M, Thielert P, Vargas Jentzsch A, Gilch P, Schiemann O, Richert S. PDI-trityl dyads as photogenerated molecular spin qubit candidates. Chem Sci 2023; 14:10727-10735. [PMID: 37829028 PMCID: PMC10566479 DOI: 10.1039/d3sc04375d] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 09/21/2023] [Indexed: 10/14/2023] Open
Abstract
Owing to their potential applications in the field of quantum information science, photogenerated organic triplet-radical conjugates have attracted an increasing amount of attention recently. Typically, these compounds are composed of a chromophore appended to a stable radical. After initialisation of the system by photoexcitation, a highly spin-polarised quartet state may be generated, which serves as a molecular spin qubit candidate. Here, we investigate three perylene diimide (PDI)-based chromophore-radical systems with different phenylene linkers and radical counterparts by both optical spectroscopy and transient electron paramagnetic resonance (EPR) techniques. Femtosecond transient absorption measurements demonstrate chromophore triplet state formation on a picosecond time scale for PDI-trityl dyads, while excited state deactivation is found to be slowed down considerably in a PDI-nitroxide analogue. The subsequent investigation of the coherent spin properties by transient EPR confirms quartet state formation by triplet-doublet spin mixing for all investigated dyads and the suitability of the two studied PDI-trityl dyads as spin qubit candidates. In particular, we show that using tetrathiaryl trityl as the radical counterpart, an intense spin polarisation is observed even at room temperature and quartet state coherence times of 3.0 μs can be achieved at 80 K, which represents a considerable improvement compared to previously studied systems.
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Affiliation(s)
- Maximilian Mayländer
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
| | - Kevin Kopp
- Clausius Institute of Physical and Theoretical Chemistry, University of Bonn Wegelerstraße 12 53115 Bonn Germany
| | - Oliver Nolden
- Institute of Physical Chemistry, Heinrich Heine University Düsseldorf Universitätsstraße 1 40225 Düsseldorf Germany
| | - Michael Franz
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
| | - Philipp Thielert
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
| | - Andreas Vargas Jentzsch
- SAMS Research Group, Université de Strasbourg, CNRS, Institut Charles Sadron UPR 22 67000 Strasbourg France
| | - Peter Gilch
- Institute of Physical Chemistry, Heinrich Heine University Düsseldorf Universitätsstraße 1 40225 Düsseldorf Germany
| | - Olav Schiemann
- Clausius Institute of Physical and Theoretical Chemistry, University of Bonn Wegelerstraße 12 53115 Bonn Germany
| | - Sabine Richert
- Institute of Physical Chemistry, University of Freiburg Albertstraße 21 79104 Freiburg Germany
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9
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Moise G, Redman AJ, Richert S, Myers WK, Bulut I, Bolls PS, Rickhaus M, Sun J, Anderson HL, Timmel CR. The impact of spin-orbit coupling on fine-structure and spin polarisation in photoexcited porphyrin triplet states. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 355:107546. [PMID: 37797559 DOI: 10.1016/j.jmr.2023.107546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Revised: 08/24/2023] [Accepted: 08/31/2023] [Indexed: 10/07/2023]
Abstract
The photoexcited triplet states of porphyrins show great promise for applications in the fields of opto-electronics, photonics, molecular wires, and spintronics. The magnetic properties of porphyrin triplet states are most conveniently studied by time-resolved continuous wave and pulse electron spin resonance (ESR). This family of techniques is singularly able to probe small yet essential details of triplet states: zero-field splittings, g-anisotropy, spin polarisation, and hyperfine interactions. These characteristics are linked to spin-orbit coupling (SOC) which is known to have a strong influence on photophysical properties such as intersystem crossing rates. The present study explores SOC effects induced by the presence of Pd2+ in various porphyrin architectures. In particular, the impact of this relativistic interaction on triplet state fine-structure and spin polarisation is investigated. These properties are probed using time-resolved ESR complemented by electron-nuclear double resonance. The findings of this study could influence the future design of molecular spintronic devices. The Pd2+ ion may be incorporated into porphyrin molecular wires as a way of controlling spin polarisation.
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Affiliation(s)
- Gabriel Moise
- Centre for Advanced Electron Spin Resonance (CAESR), Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom.
| | - Ashley J Redman
- Centre for Advanced Electron Spin Resonance (CAESR), Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom
| | - Sabine Richert
- Centre for Advanced Electron Spin Resonance (CAESR), Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom; Institute of Physical Chemistry, University of Freiburg, Albertstraße 21, Freiburg, 79104, Germany
| | - William K Myers
- Centre for Advanced Electron Spin Resonance (CAESR), Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom
| | - Ibrahim Bulut
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Pernille S Bolls
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Michel Rickhaus
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Jibin Sun
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Harry L Anderson
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford, OX1 3TA, United Kingdom
| | - Christiane R Timmel
- Centre for Advanced Electron Spin Resonance (CAESR), Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom.
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10
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Majumder K, Mukherjee S, Panjwani NA, Lee J, Bittl R, Kim W, Patil S, Musser AJ. Controlling Intramolecular Singlet Fission Dynamics via Torsional Modulation of Through-Bond versus Through-Space Couplings. J Am Chem Soc 2023; 145:20883-20896. [PMID: 37705333 DOI: 10.1021/jacs.3c06075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/15/2023]
Abstract
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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Affiliation(s)
- Kanad Majumder
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Soham Mukherjee
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Naitik A Panjwani
- Berlin Joint EPR Lab, Fachbereich Physik, Freie Universität, Berlin, Berlin 14195, Berlin, Germany
| | - Jieun Lee
- Department of Chemistry, Yonsei University, Seoul 03722, Republic of Korea
| | - Robert Bittl
- Berlin Joint EPR Lab, Fachbereich Physik, Freie Universität, Berlin, Berlin 14195, Berlin, Germany
| | - Woojae Kim
- Department of Chemistry, Yonsei University, Seoul 03722, Republic of Korea
| | - Satish Patil
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560012, India
| | - Andrew J Musser
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
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Carella A, Ciuti S, Wiedemann HTA, Kay CWM, van der Est A, Carbonera D, Barbon A, Poddutoori PK, Di Valentin M. The electronic structure and dynamics of the excited triplet state of octaethylaluminum(III)-porphyrin investigated with advanced EPR methods. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 353:107515. [PMID: 37364432 DOI: 10.1016/j.jmr.2023.107515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 06/14/2023] [Accepted: 06/18/2023] [Indexed: 06/28/2023]
Abstract
The photoexcited triplet state of octaethylaluminum(III)-porphyrin (AlOEP) was investigated by time-resolved Electron Paramagnetic Resonance, Electron Nuclear Double Resonance and Electron Spin Echo Envelope Modulation in an organic glass at 10 and 80 K. This main group element porphyrin is unusual because the metal has a small ionic radius and is six-coordinate with axial covalent and coordination bonds. It is not known whether triplet state dynamics influence its magnetic resonance properties as has been observed for some transition metal porphyrins. Together with density functional theory modelling, the magnetic resonance data of AlOEP allow the temperature dependence of the zero-field splitting (ZFS) parameters, D and E, and the proton AZZ hyperfine coupling (hfc) tensor components of the methine protons, in the zero-field splitting frame to be determined. The results provide evidence that the ZFS, hfc and spin-lattice relaxation are indeed influenced by the presence of a dynamic process that is discussed in terms of Jahn-Teller dynamic effects. Thus, these effects should be taken into account when interpreting EPR data from larger complexes containing AlOEP.
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Affiliation(s)
- Angelo Carella
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Susanna Ciuti
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Haakon T A Wiedemann
- Department of Chemistry, Saarland University, Campus B 2.2, 66123 Saarbrücken, Germany
| | - Christopher W M Kay
- Department of Chemistry, Saarland University, Campus B 2.2, 66123 Saarbrücken, Germany; London Centre for Nanotechnology, University College London, 17-19 Gordon Street, London WC1H 0AH, UK
| | - Arthur van der Est
- Department of Chemistry, Brock University, 1812 Sir Isaac Brock Way, St. Catharines, Ontario, Canada
| | - Donatella Carbonera
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Antonio Barbon
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy.
| | - Prashanth K Poddutoori
- Department of Chemistry & Biochemistry, University of Minnesota Duluth, 1038 University Drive, Duluth, MN 55812, USA
| | - Marilena Di Valentin
- Department of Chemical Sciences, University of Padova, Via Marzolo 1, 35131 Padova, Italy.
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