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Properties and applications of photoexcited chromophore–radical systems. Nat Rev Chem 2023; 7:75-90. [PMID: 37117913 DOI: 10.1038/s41570-022-00453-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2022] [Indexed: 02/11/2023]
Abstract
Photoexcited organic chromophore-radical systems hold great promise for a range of technological applications in molecular spintronics, including quantum information technology and artificial photosynthesis. However, further development of such systems will depend on the ability to control the magnetic properties of these materials, which requires a profound understanding of the underlying excited-state dynamics. In this Review, we discuss photogenerated triplet-doublet systems and their potential to be used for applications in molecular spintronics. We outline the theoretical description of the spin system in the different coupling regimes and the invoked excited-state mechanisms governing the generation and transfer of spin polarization. The main characterization techniques used to evaluate the optical and magnetic properties of chromophore-radical systems are discussed. We conclude by giving an overview of previously investigated covalently linked triplet-radical systems, and highlight the need for further systematic investigations to improve our understanding of the magnetic interactions in such systems.
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Kirk ML, Shultz DA, Marri AR, Hewitt P, van der Est A. Single-Photon-Induced Electron Spin Polarization of Two Exchange-Coupled Stable Radicals. J Am Chem Soc 2022; 144:21005-21009. [DOI: 10.1021/jacs.2c09680] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Martin L. Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico87131-0001, United States
- Center for High Technology Materials, The University of New Mexico, Albuquerque, New Mexico87106, United States
- Center for Quantum Information and Control (CQuIC), The University of New Mexico, Albuquerque, New Mexico87131-0001, United States
| | - David A. Shultz
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina27695-8204, United States
| | - Anil Reddy Marri
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina27695-8204, United States
| | - Patrick Hewitt
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina27695-8204, United States
| | - Art van der Est
- Department of Chemistry, Brock University, St. Catharines, Ontario, CanadaL2S 3A1
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Kirk ML, Shultz DA, Hewitt P, van der Est A. Excited State Exchange Control of Photoinduced Electron Spin Polarization in Electronic Ground States. J Phys Chem Lett 2022; 13:872-878. [PMID: 35045702 DOI: 10.1021/acs.jpclett.1c03491] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Ground-state electron spin polarization (ESP) is generated in radical elaborated (bpy)Pt(CAT-NN) and (bpy)Pt(CAT-p-Me2PhMe2-NN) (bpy = 5,5'-di-tert-butyl-2,2'-bipyridine, CAT = 3-tert-butylcatecholate, p-Ph = para-phenylene, NN = nitronylnitroxide). Photoexcitation produces an exchange-coupled, three-spin, charge-separated doublet 2S1 (S = chromophore excited spin singlet configuration) excited state that rapidly decays to a 2T1 (T = chromophore excited spin triplet configuration) excited state. The SQ-bridge-NN bond torsions affect the magnitude of the excited state exchange interaction (JSQ-NN), which determines the 2T1-4T1 energy gap. Ground state ESP is dependent on the magnitude of JSQ-NN, and we postulate that this results from differences in 2T1 and 4T1 state mixing. Mechanisms that lead to the rapid transfer of the excited state ESP to the ground state are discussed. Although subnanosecond 2T1 state lifetimes are measured optically in solution, the ground state ESP decays very slowly at 20 K and is observable for more than a millisecond.
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Affiliation(s)
- Martin L Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
- The Center for High Technology Materials, The University of New Mexico, Albuquerque, New Mexico 87106, United States
| | - David A Shultz
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Patrick Hewitt
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Art van der Est
- Department of Chemistry, Brock University, St. Catharines, Ontario L2S 3A1, Canada
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Kirk ML, Shultz DA, Hewitt P, Stasiw DE, Chen J, van der Est A. Chromophore-radical excited state antiferromagnetic exchange controls the sign of photoinduced ground state spin polarization. Chem Sci 2021; 12:13704-13710. [PMID: 34760154 PMCID: PMC8549796 DOI: 10.1039/d1sc02965g] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 09/01/2021] [Indexed: 11/21/2022] Open
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 chromophore via two different meta-phenylene bridges in (bpy)Pt(CAT-m-Ph-NN) (mPh-Pt) and (bpy)Pt(CAT-6-Me-m-Ph-NN) (6-Me-mPh-Pt) (bpy = 5,5'-di-tert-butyl-2,2'-bipyridine, CAT = 3-tert-butylcatecholate, m-Ph = meta-phenylene). These molecules represent a new class of chromophores that can be photoexcited with visible light to produce an initial exchange-coupled, 3-spin (bpy˙-, CAT+˙ = semiquinone (SQ), and NN), charge-separated doublet 2S1 (S = chromophore excited spin singlet configuration) excited state. Following excitation, the 2S1 state rapidly decays to the ground state by magnetic exchange-mediated enhanced internal conversion via the 2T1 (T = chromophore excited spin triplet configuration) state. This process generates emissive ground state ESP in 6-Me-mPh-Pt while for mPh-Pt the ESP is absorptive. It is proposed that the emissive polarization in 6-Me-mPh-Pt results from zero-field splitting induced transitions between the chromophoric 2T1 and 4T1 states, whereas predominant spin-orbit induced transitions between 2T1 and low-energy NN-based states give rise to the absorptive polarization observed for mPh-Pt. The difference in the sign of the ESP for these molecules is consistent with a smaller excited state 2T1 - 4T1 gap for 6-Me-mPh-Pt that derives from steric interactions with the 6-methyl group. These steric interactions reduce the excited state pairwise SQ-NN exchange coupling compared to that in mPh-Pt.
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Affiliation(s)
- Martin L Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico MSC03 2060, 1 University of New Mexico Albuquerque NM 87131-0001 USA
| | - David A Shultz
- Department of Chemistry, North Carolina State University Raleigh North Carolina 27695-8204 USA
| | - Patrick Hewitt
- Department of Chemistry, North Carolina State University Raleigh North Carolina 27695-8204 USA
| | - Daniel E Stasiw
- Department of Chemistry, North Carolina State University Raleigh North Carolina 27695-8204 USA
| | - Ju Chen
- Department of Chemistry and Chemical Biology, The University of New Mexico MSC03 2060, 1 University of New Mexico Albuquerque NM 87131-0001 USA
| | - Art van der Est
- Department of Chemistry, Brock University St. Catharines Ontario Canada L2S 3A1
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Kandrashkin YE, van der Est A. Enhanced Intersystem Crossing due to Resonant Energy Transfer to a Remote Spin. J Phys Chem Lett 2021; 12:7312-7318. [PMID: 34319743 DOI: 10.1021/acs.jpclett.1c02032] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A new mechanism for enhanced intersystem crossing in coupled three-spin systems consisting of a chromophore and an attached radical is proposed. It is shown that if the unpaired electron of the radical experiences spin-orbit coupling and different exchange interactions with the two unpaired electron spins of the chromophore, energy transfer from the chromophore to the radical can occur together with singlet-triplet intersystem crossing in the chromophore. The efficiency of this process increases dramatically when the electronic excitation of the radical is resonant with the S1-T1 energy gap of the chromophore. The types of systems in which this resonance could be achieved are discussed, and it is suggested that the mechanism could result in improved sensitization in near-IR emitting lanthanide dyes.
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Affiliation(s)
- Yuri E Kandrashkin
- Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center of RAS, Kazan 420029, Russian Federation
| | - Art van der Est
- Department of Chemistry Brock University, St. Catharines, ON L2S 3A1, Canada
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Kirk ML, Shultz DA, Chen J, Hewitt P, Daley D, Paudel S, van der Est A. Metal Ion Control of Photoinduced Electron Spin Polarization in Electronic Ground States. J Am Chem Soc 2021; 143:10519-10523. [PMID: 34251803 DOI: 10.1021/jacs.1c04149] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Both the sign and intensity of photoinduced electron spin polarization (ESP) in the electronic ground state doublet (2S0/D0) of chromophore-radical complexes can be controlled by changing the nature of the metal ion. The complexes consist of an organic radical (nitronyl nitroxide, NN) covalently attached to a donor-acceptor chromophore via a m-phenylene bridge, (bpy)M(CAT-m-Ph-NN) (1) (bpy = 4,4'-di-tert-butyl-2,2'-bipyridine, M = PdII (1-Pd) or PtII (1-Pt), CAT = 3-tert-butylcatecholate, m-Ph = meta-phenylene). In both complexes, photoexcitation with visible light produces an initial exchange-coupled, three-spin (bpy•-, CAT•+ = semiquinone (SQ), and NN•), charge-separated doublet 2S1 (S = chromophore excited spin singlet configuration) excited state that rapidly decays to the ground state via a 2T1 (T = chromophore excited spin triplet configuration) state. This process is not expected to be spin selective, and only very weak emissive ESP is found for 1-Pd. In contrast, strong absorptive ESP is generated in 1-Pt. It is postulated that zero-field-splitting-induced transitions between the chromophoric 2T1 and 4T1 states (1-Pd and 1-Pt) and spin-orbit-induced transitions between 2T1 and NN-based quartet states (1-Pt) account for the differences in polarization.
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Affiliation(s)
- Martin L Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, Albuquerque, New Mexico 87131-0001, United States.,The Center for High Technology Materials, The University of New Mexico, Albuquerque, New Mexico 87106, United States
| | - David A Shultz
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Ju Chen
- Department of Chemistry and Chemical Biology, The University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - Patrick Hewitt
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - David Daley
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Sangita Paudel
- Department of Chemistry and Chemical Biology, The University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - Art van der Est
- Department of Chemistry, Brock University, St. Catharines, Ontario, Canada L2S 3A1
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Kandrashkin YE, Di Valentin M, van der Est A. Reversible triplet energy hopping in photo-excited molecules: A two-site model for the spin polarization. J Chem Phys 2020; 153:094304. [PMID: 32891093 DOI: 10.1063/5.0022164] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effect of reversible energy hopping between different local environments on the properties of spin-polarized excited states is investigated theoretically using a two-site model. The kinetic equations for the populations of the spin sublevels of the excited state are derived and then used to obtain analytical expressions for the evolution of the spin polarization of excited triplet states under specific conditions. The time dependence of the triplet state polarization patterns is also obtained by numerical solution of the kinetic equations. It is shown that the reversible energy hopping can lead to significant changes in the properties of the triplet state, including changes in the shape of the observed spectrum and, in some cases, the inversion of the sign of the polarization, the generation of the net polarization, and anisotropic spin-lattice relaxation. The relations between the parameters that can be observed experimentally by time-resolved electron paramagnetic resonance spectroscopy and the kinetic and dynamic parameters of the system are discussed.
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Affiliation(s)
- Yuri E Kandrashkin
- Zavoisky Physical-Technical Institute FRC Kazan Scientific Center of RAS, Sibirsky Tract 10/7, Kazan 420029, Russia
| | - Marilena Di Valentin
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova, Via Marzolo 1, 35131 Padova, Italy
| | - Art van der Est
- Department of Chemistry Brock University, St. Catharines, Ontario L2S 3A1, Canada
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Teki Y. Excited‐State Dynamics of Non‐Luminescent and Luminescent π‐Radicals. Chemistry 2019; 26:980-996. [DOI: 10.1002/chem.201903444] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 08/28/2019] [Indexed: 11/11/2022]
Affiliation(s)
- Yoshio Teki
- Division of Molecular Materials ScienceGraduate School of ScienceOsaka City University 3-3-138 Sugimoto Sumiyoshi-ku Osaka 558-8585 Japan
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Tichnell CR, Daley DR, Stein BW, Shultz DA, Kirk ML, Danilov EO. Wave Function Control of Charge-Separated Excited-State Lifetimes. J Am Chem Soc 2019; 141:3986-3992. [DOI: 10.1021/jacs.8b13011] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Christopher R. Tichnell
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - David R. Daley
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Benjamin W. Stein
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - David A. Shultz
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Martin L. Kirk
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - Evgeny O. Danilov
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
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Tichnell CR, Shultz DA, Popescu CV, Sokirniy I, Boyle PD. Synthesis, Characterization, and Photophysical Studies of an Iron(III) Catecholate–Nitronylnitroxide Spin-Crossover Complex. Inorg Chem 2015; 54:4466-74. [DOI: 10.1021/acs.inorgchem.5b00298] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Christopher R. Tichnell
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - David A. Shultz
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
| | - Codrina V. Popescu
- Department of Chemistry, Colgate University, 13 Oak Drive, Hamilton, New York 13346, United States
| | - Ivan Sokirniy
- Department of Chemistry, Ursinus College, Collegeville, Pennsylvania 19426, United States
| | - Paul D. Boyle
- Department
of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, United States
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Katayama K, Hirotsu M, Kinoshita I, Teki Y. Synthesis, magnetic properties and dynamic behavior of cobalt complexes with an anthracene-containing dioxolene ligand. Dalton Trans 2014; 43:13384-91. [DOI: 10.1039/c4dt01574f] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Colvin MT, Carmieli R, Miura T, Richert S, Gardner DM, Smeigh AL, Dyar SM, Conron SM, Ratner MA, Wasielewski MR. Electron Spin Polarization Transfer from Photogenerated Spin-Correlated Radical Pairs to a Stable Radical Observer Spin. J Phys Chem A 2013; 117:5314-25. [DOI: 10.1021/jp4045012] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Michael T. Colvin
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Raanan Carmieli
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Tomoaki Miura
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Sabine Richert
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Daniel M. Gardner
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Amanda L. Smeigh
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Scott M. Dyar
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Sarah M. Conron
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Mark A. Ratner
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R. Wasielewski
- Department
of Chemistry and Argonne-Northwestern Solar
Energy Research (ANSER) Center, Northwestern University, Evanston, Illinois 60208-3113, United States
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Matsumoto T, Teki Y. Theoretical study of dynamic electron-spin-polarization via the doublet-quartet quantum-mixed state (II). Population transfer and magnetic field dependence of the spin polarization. Phys Chem Chem Phys 2012; 14:10178-86. [DOI: 10.1039/c2cp41121k] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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14
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Kanemoto K, Fukunaga A, Yasui M, Kosumi D, Hashimoto H, Tamekuni H, Kawahara Y, Takemoto Y, Takeuchi J, Miura Y, Teki Y. Ultrafast photoexcitation dynamics of π-conjugated bodipy-anthracene-radical triad system. RSC Adv 2012. [DOI: 10.1039/c2ra20473h] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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Katayama K, Hirotsu M, Kinoshita I, Teki Y. Design, synthesis, magnetic properties of a π-radical ligand with photo-excited high-spin state and its Fe(ii) complex. The first stage of a new strategy for LIESST materials. Dalton Trans 2012; 41:13465-73. [DOI: 10.1039/c2dt31831h] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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