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Zhang X, Chen X, Sun Y, Zhao J. Radical enhanced intersystem crossing mechanism, electron spin dynamics of high spin states and their applications in the design of heavy atom-free triplet photosensitizers. Org Biomol Chem 2024; 22:5257-5283. [PMID: 38884590 DOI: 10.1039/d4ob00520a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/18/2024]
Abstract
Heavy atom-free triplet photosensitizers (PSs) can overcome the high cost and biological toxicity of traditional molecular systems containing heavy atoms (such as Pt(II), Ir(III), Ru(II), Pd(II), Lu(III), I, or Br atoms) and, therefore, are developing rapidly. Connecting a stable free radical to the chromophore can promote the intersystem crossing (ISC) process through electron spin exchange interaction to produce the triplet state of the chromophore or the doublet (D) and quartet (Q) states when taking the whole spin system into account. These molecular systems based on the radical enhanced ISC (REISC) mechanism are important in the field of heavy atom-free triplet PSs. The REISC system has a simple molecular structure and good biocompatibility, and it is especially helpful for building high-spin quantum states (D and Q states) that have the potential to be developed as qubits in quantum information science. This review introduces the molecular structure design for the purpose of high-spin states. Time-resolved electron paramagnetic resonance (TREPR) is the most important characterization method to reveal the properties of these molecular systems, generation mechanism and electron spin polarization (ESP) of the high spin states. The spin polarization manipulation of high spin states and potential application in the field of quantum information engineering are also summarized. Moreover, molecular design principles of the REISC system to obtain long absorption wavelength, high triplet state quantum yield and long triplet state lifetime are introduced, as well as applications of the compounds in triplet-triplet annihilation upconversion, photodynamic therapy and bioimaging. This review is useful for the design of heavy atom-free triplet PSs based on the radical-chromophore molecular structure motif and the study of the photophysics of the compounds, as well as the electron spin dynamics of the multi electron system upon photoexcitation.
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Affiliation(s)
- Xue Zhang
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China.
| | - Xi Chen
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China.
| | - Yue Sun
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China.
| | - Jianzhang Zhao
- State Key Laboratory of Fine Chemicals, Frontiers Science Centre for Smart Materials, School of Chemical Engineering, Dalian University of Technology, Dalian 116024, P. R. China.
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2
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Kirk ML, Shultz DA, Marri AR, van der Est A. Photoinduced Magnetic Exchange-Jump Promotes Ground State Biradical Electron Spin Polarization. J Am Chem Soc 2024; 146:9285-9292. [PMID: 38518125 DOI: 10.1021/jacs.4c00930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2024]
Abstract
Photoinduced electron spin polarization (ESP) is reported in the electronic ground states of three Pt(II) complexes comprised of two S = 1/2 nitronyl nitroxide (NN) radicals attached through different length para-phenylethynyl bridges to the 3,6 positions of a catecholate (CAT, donor) and 4,4'-di-tert-butyl-2,2'-bipyridine (bpy, acceptor). Complexes 1-3 have from 17 to 41 bonds separating NN radicals and display cw-EPR spectra consistent with |JNN-NN| ≫ |aN|, |JNN-NN| ≥ |aN|, and |JNN-NN| < |aN|, respectively, where JNN-NN is the magnetic exchange coupling between NN radicals in the electronic ground state, and aN is the isotropic 14N hyperfine coupling constant. Light-induced transient EPR spectra characterized as enhanced ground-state absorption were observed for all three complexes using 532 nm pulsed laser excitation into the ligand-to-ligand charge transfer (LL'CT) band of the (CAT)Pt(bpy) chromophore. The magnitude of the observed ESP increases in the order 1 < 2 < 3 and is inversely correlated with the magnitude of ground-state JNN-NN. In addition to the experimental observation of net absorptive polarization in 1-3, light excitation also produces multiplet polarization in 2. Since the weak dipolar coupling leads to a strong spectral overlap of the absorptive and emissive components, the multiplet polarization is not observed in 1 and 3 and is very weak in 2. The ability to spin-polarize multiple radical spins with a single photon is anticipated to advance new photoinduced multi qubit/qudit ESP protocols for quantum information science applications.
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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
- Center for Quantum Information and Control (CQuIC), The University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
- Center for Computational Chemistry, The 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
| | - Anil Reddy Marri
- 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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3
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Kato K, Teki Y. Theoretical investigation of multi-spin excited states of anthracene radical-linked π-conjugated spin systems by computational chemistry. Phys Chem Chem Phys 2024; 26:8106-8114. [PMID: 38407399 DOI: 10.1039/d3cp06335f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2024]
Abstract
Multi-spin excited states of chromophore radical-linked π-conjugated spin systems are investigated by molecular orbital calculations based on density functional theory (DFT). The investigated systems consist of an anthracene photosensitive unit leading to a triplet-excited-state (S = 1), π-conjugated linker to propagate spin exchange-coupling, and stable organic radical with a doublet-ground-state (S = 1/2). The intramolecular exchange coupling (JDQ), g value, and fine-structure interaction of their excited states depended on the π-conjugation network (π-topology), type of radical, and molecular structure of the π-linker (length and dihedral angle). The exchange interaction was dependent on the π-topology and the type of radical species. A decrease in the dihedral angle between the anthracene moiety and phenyl linker in the photo-excited state led to larger exchange coupling. With an increase in the π-linker length (r), the magnitude of the exchange coupling gradually decreased in the photoexcited states according to JDQ = JEx0 exp(-βr), similar to the ground-state exchange. The g values of the quartet (Q) state depended only on the radical type (independent of the linker). Conversely, the fine-structure interaction of the Q state was independent of the radical type and depended on both the linker length and the dihedral angle.
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Affiliation(s)
- Ken Kato
- Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita-shi, Osaka 565-0871, Japan.
| | - Yoshio Teki
- Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
- Graduate School of Engineering, Osaka Metropolitan University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.
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4
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Reid OG, Johnson JC, Eaves JD, Damrauer NH, Anthony JE. Molecular Control of Triplet-Pair Spin Polarization and Its Optoelectronic Magnetic Resonance Probes. Acc Chem Res 2024; 57:59-69. [PMID: 38103045 PMCID: PMC10765369 DOI: 10.1021/acs.accounts.3c00556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Revised: 11/21/2023] [Accepted: 11/22/2023] [Indexed: 12/17/2023]
Abstract
ConspectusPreparing and manipulating pure magnetic states in molecular systems are the key initial requirements for harnessing the power of synthetic chemistry to drive practical quantum sensing and computing technologies. One route for achieving the requisite higher spin states in organic systems exploits the phenomenon of singlet fission, which produces pairs of triplet excited states from initially photoexcited singlets in molecular assemblies with multiple chromophores. The resulting spin states are characterized by total spin (quintet, triplet, or singlet) and its projection onto a specified molecular or magnetic field axis. These excited states are typically highly polarized but exhibit an impure spin population pattern. Herein, we report the prediction and experimental verification of molecular design rules that drive the population of a single pure magnetic state and describe the progress toward its experimental realization.A vital feature of this work is the close partnership among theory, chemical synthesis, and spectroscopy. We begin by presenting our theoretical framework for understanding spin manifold interconversion in singlet fission systems. This theory makes specific testable predictions about the intermolecular structure and orientation relative to an external magnetic field that should lead to pure magnetic state preparation and provides a powerful tool for interpreting magnetic spectra. We then test these predictions through detailed magnetic spectroscopy experiments on a series of new molecular architectures that meet one or more of the identified structural criteria. Many of these architectures rely on the synthesis of molecules with features unique to this effort: rigid bridges between chromophores in dimers, heteroacenes with tailored singlet/triplet-pair energy level matching, or side-group engineering to produce specific crystal structures. The spin evolution of these systems is revealed through our application and development of several magnetic resonance methods, each of which has different sensitivities and relevance in environments relevant to quantum applications.Our theoretical predictions prove to be remarkably consistent with our experimental results, though experimentally meeting all the structural prescriptions demanded by theory for true pure-state preparation remains a challenge. Our magnetic spectra agree with our model of triplet-pair behavior, including funneling of the population to the ms = 0 magnetic sublevel of the quintet under specified conditions in dimers and crystals, showing that this phenomenon is subject to control through molecular design. Moreover, our demonstration of novel and/or highly sensitive detection mechanisms of spin states in singlet fission systems, including photoluminescence (PL), photoinduced absorption (PA), and magnetoconductance (MC), points the way toward both a deeper understanding of how these systems evolve and technologically feasible routes toward experiments at the single-molecule quantum limit that are desirable for computational applications.
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Affiliation(s)
- Obadiah G. Reid
- National
Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, Colorado 80401, United States
- Renewable
and Sustainable Energy Institute, Boulder, Colorado 80309, United States
| | - Justin C. Johnson
- National
Renewable Energy Laboratory, Chemistry and Nanoscience Center, Golden, Colorado 80401, United States
- Renewable
and Sustainable Energy Institute, Boulder, Colorado 80309, United States
| | - Joel D. Eaves
- Renewable
and Sustainable Energy Institute, Boulder, Colorado 80309, United States
- Department
of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Niels H. Damrauer
- Renewable
and Sustainable Energy Institute, Boulder, Colorado 80309, United States
- Department
of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - John E. Anthony
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
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5
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Orihashi K, Yamauchi A, Fujiwara S, Asada M, Nakamura T, Ka-Ho Hui J, Kimizuka N, Tateishi K, Uesaka T, Yanai N. Spin-Polarized Radicals with Extremely Long Spin-Lattice Relaxation Time at Room Temperature in a Metal-Organic Framework. J Am Chem Soc 2023; 145:27650-27656. [PMID: 38079364 DOI: 10.1021/jacs.3c09563] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
The generation of spin polarization is key in quantum information science and dynamic nuclear polarization. Polarized electron spins with long spin-lattice relaxation times (T1) at room temperature are important for these applications but have been difficult to achieve. We report the realization of spin-polarized radicals with extremely long T1 at room temperature in a metal-organic framework (MOF) in which azaacene chromophores are densely integrated. Persistent radicals are generated in the MOF by charge separation after photoexcitation. Spin polarization of a triplet generated by photoexcitation is successfully transferred to the persistent radicals. Pulse electron spin resonance measurements reveal that the T1 of the polarized radical in the MOF is as long as 214 μs with a relatively long spin-spin relaxation time T2 of the radicals of up to 0.98 μs at room temperature. The achievement of extremely long spin polarization in MOFs with nanopores accessible to guest molecules will be an important cornerstone for future highly sensitive quantum sensing and efficient dynamic nuclear polarization.
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Affiliation(s)
- Kana Orihashi
- Department of Applied Chemistry, Graduate School of Engineering and Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Akio Yamauchi
- Department of Applied Chemistry, Graduate School of Engineering and Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Saiya Fujiwara
- RIKEN Center for Emergent Matter Science, Riken, Wako, Saitama 351-0198, Japan
| | - Mizue Asada
- Institute for Molecular Science, Nishigonaka 38, Myodaiji, Okazaki 444-8585, Japan
| | - Toshikazu Nakamura
- Institute for Molecular Science, Nishigonaka 38, Myodaiji, Okazaki 444-8585, Japan
| | - Joseph Ka-Ho Hui
- Department of Applied Chemistry, Graduate School of Engineering and Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Nobuo Kimizuka
- Department of Applied Chemistry, Graduate School of Engineering and Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Kenichiro Tateishi
- Cluster for Pioneering Research, Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Tomohiro Uesaka
- Cluster for Pioneering Research, Nishina Center for Accelerator-Based Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Nobuhiro Yanai
- Department of Applied Chemistry, Graduate School of Engineering and Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan
- FOREST, JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012, Japan
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6
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Miller PD, Shultz DA, Mengell J, Kirk ML, Wojtas L. Variation from closed-shell to open shell electronic structures in oligothiophene bis(dioxolene) complexes. Chem Sci 2023; 14:12264-12276. [PMID: 37969598 PMCID: PMC10631215 DOI: 10.1039/d3sc02341a] [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: 05/05/2023] [Accepted: 10/07/2023] [Indexed: 11/17/2023] Open
Abstract
A series of oligothiophene bis(dioxolene) complexes, SQ-Thn-SQ (SQ = S = ½TpCum,MeZnII(3-tert-butyl-orthosemiquinonate); TpCum,Me = tris(5-cumenyl-3-methylpyrazolyl)borate anion) have been synthesized, structurally characterized, and studied as a function of the number of thiophene bridging units, n (n = 0-3) using a combination of variable-temperature (VT) electronic absorption and EPR spectroscopies, and VT magnetic susceptibility measurements. The thiophene bridge bond lengths determined by X-ray crystallography display dramatic differences across the SQ-Thn-SQ series. Bridge bond deviation values (Σ|Δi|) display a progressive change in the nature of the bridge fragment bonding as the number of thiophene groups increases, with quinoidal bridge character for n = 1 (SQ-Th-SQ) and biradical character with "aromatic" bridge bond lengths for n = 3 (SQ-Th3-SQ). Remarkably, for n = 2 (SQ-Th2-SQ) the nature of the bridge fragment is intermediate between quinoid and biradical aromatic, which we describe as having open-shell character as opposed to biradicaloid since the open-shell biradical configuration does not have the correct symmetry to mix with the quinoidal ground-state configuration. This bridge bonding character is reflected in the energies of the lowest lying open-shell states for these three molecules. The SQ-Th-SQ molecule is diamagnetic at all temperatures studied, and we provide evidence for SQ-SQ antiferromagnetic exchange coupling and population of triplet states in SQ-Th2-SQ and SQ-Th3-SQ, with JSQ-SQ(ave) = -279 cm-1 (VT EPR/electronic absorption/magnetic susceptibility) and JSQ-SQ = -117 cm-1 (VT EPR/electronic absorption/magnetic susceptibility), respectively. The results have been interpreted in the context of state configurational mixing within a simplified 4-electron, 3-orbital model that explicitly contains contributions of a bridge fragment. Variable-temperature spectroscopic- and magnetic susceptibility data are consistent with two low-lying open-shell states for SQ-Th3-SQ, but three low-lying states (one closed-shell and two open-shell) for SQ-Th2-SQ. This model provides a simple symmetry-based framework to understand the continuum of electronic and geometric structures of this class of molecules as a function of the number of thiophene units in the bridge.
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Affiliation(s)
- Paul D Miller
- Department of Chemistry, North Carolina State University Raleigh North Carolina 27695-8204 USA
| | - David A Shultz
- Department of Chemistry, North Carolina State University Raleigh North Carolina 27695-8204 USA
| | - Joshua Mengell
- Department of Chemistry and Chemical Biology, The University of New Mexico MSC03 2060, 1 University of New Mexico Albuquerque NM 87131-0001 USA
| | - 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
- The Center for High Technology Materials, The University of New Mexico Albuquerque New Mexico 87106 USA
- Center for Quantum Information and Control (CQuIC), The University of New Mexico Albuquerque New Mexico 87131-0001 USA
| | - Lukasz Wojtas
- Department of Chemistry, University of South Florida 4202 E. Fowler Avenue, CHE 205 Tampa FL 33620-5250 USA
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7
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Kirk ML, Shultz DA, Hewitt P, Marri AR, van der Est A. Competitive reversed quartet mechanisms for photogenerated ground state electron spin polarization. Chem Sci 2023; 14:9689-9695. [PMID: 37736649 PMCID: PMC10510625 DOI: 10.1039/d3sc03049k] [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: 06/14/2023] [Accepted: 08/06/2023] [Indexed: 09/23/2023] Open
Abstract
Photoinduced electron spin polarization (ESP) of a spin-½ organic radical (nitronyl nitroxide, NN) in a series of Pt(ii) complexes comprised of 4,4'-di-tert-butyl-2,2'-bipyridine (bpy) and 3-tert-butylcatecholate (CAT) ligands, where the CAT ligand is substituted with (CH3)n-meta-phenyl-NN (bridge-NN) groups, is presented and discussed. We show the importance of attenuating the energy gap between localized NN radical and chromophoric excited states to control both the magnitude and sign of the optically-generated ESP, and to provide deeper insight into the details of the ESP mechanism. Understanding electronic structure contributions to optically generated ESP will enhance our ability to control the nature of prepared states for a variety of quantum information science applications, where strong ESP facilitates enhanced sensitivity and readout capabilities at low applied magnetic fields and higher temperatures.
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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
- The Center for High Technology Materials, The University of New Mexico Albuquerque New Mexico 87106 USA
- Center for Quantum Information and Control (CQuIC), The University of New Mexico Albuquerque New Mexico 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
| | - Anil Reddy Marri
- Department of Chemistry, North Carolina State University Raleigh North Carolina 27695-8204 USA
| | - Art van der Est
- Department of Chemistry, Brock University St. Catharines Ontario Canada L2S 3A1
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8
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Eills J, Budker D, Cavagnero S, Chekmenev EY, Elliott SJ, Jannin S, Lesage A, Matysik J, Meersmann T, Prisner T, Reimer JA, Yang H, Koptyug IV. Spin Hyperpolarization in Modern Magnetic Resonance. Chem Rev 2023; 123:1417-1551. [PMID: 36701528 PMCID: PMC9951229 DOI: 10.1021/acs.chemrev.2c00534] [Citation(s) in RCA: 64] [Impact Index Per Article: 64.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Indexed: 01/27/2023]
Abstract
Magnetic resonance techniques are successfully utilized in a broad range of scientific disciplines and in various practical applications, with medical magnetic resonance imaging being the most widely known example. Currently, both fundamental and applied magnetic resonance are enjoying a major boost owing to the rapidly developing field of spin hyperpolarization. Hyperpolarization techniques are able to enhance signal intensities in magnetic resonance by several orders of magnitude, and thus to largely overcome its major disadvantage of relatively low sensitivity. This provides new impetus for existing applications of magnetic resonance and opens the gates to exciting new possibilities. In this review, we provide a unified picture of the many methods and techniques that fall under the umbrella term "hyperpolarization" but are currently seldom perceived as integral parts of the same field. Specifically, before delving into the individual techniques, we provide a detailed analysis of the underlying principles of spin hyperpolarization. We attempt to uncover and classify the origins of hyperpolarization, to establish its sources and the specific mechanisms that enable the flow of polarization from a source to the target spins. We then give a more detailed analysis of individual hyperpolarization techniques: the mechanisms by which they work, fundamental and technical requirements, characteristic applications, unresolved issues, and possible future directions. We are seeing a continuous growth of activity in the field of spin hyperpolarization, and we expect the field to flourish as new and improved hyperpolarization techniques are implemented. Some key areas for development are in prolonging polarization lifetimes, making hyperpolarization techniques more generally applicable to chemical/biological systems, reducing the technical and equipment requirements, and creating more efficient excitation and detection schemes. We hope this review will facilitate the sharing of knowledge between subfields within the broad topic of hyperpolarization, to help overcome existing challenges in magnetic resonance and enable novel applications.
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Affiliation(s)
- James Eills
- Institute
for Bioengineering of Catalonia, Barcelona
Institute of Science and Technology, 08028Barcelona, Spain
| | - Dmitry Budker
- Johannes
Gutenberg-Universität Mainz, 55128Mainz, Germany
- Helmholtz-Institut,
GSI Helmholtzzentrum für Schwerionenforschung, 55128Mainz, Germany
- Department
of Physics, UC Berkeley, Berkeley, California94720, United States
| | - Silvia Cavagnero
- Department
of Chemistry, University of Wisconsin, Madison, Madison, Wisconsin53706, United States
| | - Eduard Y. Chekmenev
- Department
of Chemistry, Integrative Biosciences (IBio), Karmanos Cancer Institute
(KCI), Wayne State University, Detroit, Michigan48202, United States
- Russian
Academy of Sciences, Moscow119991, Russia
| | - Stuart J. Elliott
- Molecular
Sciences Research Hub, Imperial College
London, LondonW12 0BZ, United Kingdom
| | - Sami Jannin
- Centre
de RMN à Hauts Champs de Lyon, Université
de Lyon, CNRS, ENS Lyon, Université Lyon 1, 69100Villeurbanne, France
| | - Anne Lesage
- Centre
de RMN à Hauts Champs de Lyon, Université
de Lyon, CNRS, ENS Lyon, Université Lyon 1, 69100Villeurbanne, France
| | - Jörg Matysik
- Institut
für Analytische Chemie, Universität
Leipzig, Linnéstr. 3, 04103Leipzig, Germany
| | - Thomas Meersmann
- Sir
Peter Mansfield Imaging Centre, University Park, School of Medicine, University of Nottingham, NottinghamNG7 2RD, United Kingdom
| | - Thomas Prisner
- Institute
of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic
Resonance, Goethe University Frankfurt, , 60438Frankfurt
am Main, Germany
| | - Jeffrey A. Reimer
- Department
of Chemical and Biomolecular Engineering, UC Berkeley, and Materials Science Division, Lawrence Berkeley National
Laboratory, Berkeley, California94720, United States
| | - Hanming Yang
- Department
of Chemistry, University of Wisconsin, Madison, Madison, Wisconsin53706, United States
| | - Igor V. Koptyug
- International Tomography Center, Siberian
Branch of the Russian Academy
of Sciences, 630090Novosibirsk, Russia
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9
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Shultz DA, Stephenson R, Kirk ML. Dinuclear ligand-to-ligand charge transfer complexes. Dalton Trans 2023; 52:1970-1976. [PMID: 36691821 DOI: 10.1039/d2dt03385b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The synthesis and characterization of dinuclear ligand-to-ligand charge transfer complexes are described. Each complex is comprised of square-planar platinum(II) coordinated to a 3-tert-butyl-orthocatecholate donor and a 4,4'-di-tert-butyl-2,2'-bipyridine acceptor. Both complexes exhibit donor → acceptor ligand-to-ligand charge transfer (LL'CT) bands in the visible spectrum. The platinum complexes are covalently attached at the catecholate 5-position to either a meta- or para-phenylene bridge fragment. Both cyclic voltammetry and electronic absorption spectroscopy exhibit features characteristic of intramolecular interaction between the platinum centres. The LL'CT excited state lifetimes are ∼twofold longer than the mononuclear parent complex. The properties of these complexes are discussed and compared to similar complexes in the literature.
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Affiliation(s)
- David A Shultz
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA.
| | - Riley Stephenson
- Department of Chemistry, North Carolina State University, Raleigh, North Carolina 27695-8204, USA.
| | - 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.,The Center for High Technology Materials, The University of New Mexico, Albuquerque, New Mexico 87106, USA.,Center for Quantum Information and Control (CQuIC), The University of New Mexico, Albuquerque, New Mexico 87131-0001, USA
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10
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Chen J, Yang J, Yadav M, Shultz DA, Kirk ML. Origin of Ferromagnetic Exchange Coupling in Donor-Acceptor Biradical Analogues of Charge-Separated Excited States. Inorg Chem 2023; 62:739-747. [PMID: 36598509 DOI: 10.1021/acs.inorgchem.2c02903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
A new donor-acceptor biradical complex, TpCum,MeZn(SQ-VD) (TpCum,MeZn+ = zinc(II) hydro-tris(3-cumenyl-5-methylpyrazolyl)borate complex cation; SQ = orthosemiquinone; VD = oxoverdazyl), which is a ground-state analogue of a charge-separated excited state, has been synthesized and structurally characterized. The magnetic exchange interaction between the S = 1/2 SQ and the S = 1/2 VD within the SQ-VD biradical ligand is observed to be ferromagnetic, with JSQ-VD = +77 cm-1 (H = -2JSQ-VDŜSQ·ŜVD) determined from an analysis of the variable-temperature magnetic susceptibility data. The pairwise biradical exchange interaction in TpCum,MeZn(SQ-VD) can be compared with that of the related donor-acceptor biradical complex TpCum,MeZn(SQ-NN) (NN = nitronyl nitroxide, S = 1/2), where JSQ-NN ≅ +550 cm-1. This represents a dramatic reduction in the biradical exchange by a factor of ∼7, despite the isolobal nature of the VD and NN acceptor radical SOMOs. Computations assessing the magnitude of the exchange were performed using a broken-symmetry density functional theory (DFT) approach. These computations are in good agreement with those computed at the CASSCF NEVPT2 level, which also reveals an S = 1 triplet ground state as observed in the magnetic susceptibility measurements. A combination of electronic absorption spectroscopy and CASSCF computations has been used to elucidate the electronic origin of the large difference in the magnitude of the biradical exchange coupling between TpCum,MeZn(SQ-VD) and TpCum,MeZn(SQ-NN). A Valence Bond Configuration Interaction (VBCI) model was previously employed to highlight the importance of mixing an SQSOMO → NNLUMO charge transfer configuration into the electronic ground state to facilitate the stabilization of the high-spin triplet (S = 1) ground state in TpCum,MeZn(SQ-NN). Here, CASSCF computations confirm the importance of mixing the pendant radical (e.g., VD, NN) LUMO (VDLUMO and NNLUMO) with the SOMO of the SQ radical (SQSOMO) for stabilizing the triplet, in addition to spin polarization and charge transfer contributions to the exchange. An important electronic structure difference between TpCum,MeZn(SQ-VD) and TpCum,MeZn(SQ-NN), which leads to their different exchange couplings, is the reduced admixture of excited states that promote ferromagnetic exchange into the TpCum,MeZn(SQ-VD) ground state, and the intrinsically weaker mixing between the VDLUMO and the SQSOMO compared to that observed for TpCum,MeZn(SQ-NN), where this orbital mixing is significant. The results of this comparative study contribute to a greater understanding of biradical exchange interactions, which are important to our understanding of excited-state singlet-triplet energy gaps, electron delocalization, and the generation of electron spin polarization in both the ground and excited states of (bpy)Pt(CAT-radical) complexes.
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Affiliation(s)
- Ju Chen
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico87131-0001, United States
| | - Jing Yang
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico87131-0001, United States
| | - Munendra Yadav
- Department of Chemistry and Chemical Biology, The University of New Mexico, MSC03 2060, 1 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
| | - 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.,The 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
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Mao H, Young RM, Krzyaniak MD, Wasielewski MR. Optical Initialization of Molecular Qubit Spin States Using Weak Exchange Coupling to Photogenerated Fullerene Triplet States. J Phys Chem B 2022; 126:10519-10527. [DOI: 10.1021/acs.jpcb.2c07096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Affiliation(s)
- Haochuan Mao
- Department of Chemistry, Center for Molecular Quantum Transduction, and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Ryan M. Young
- Department of Chemistry, Center for Molecular Quantum Transduction, and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Matthew D. Krzyaniak
- Department of Chemistry, Center for Molecular Quantum Transduction, and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Michael R. Wasielewski
- Department of Chemistry, Center for Molecular Quantum Transduction, and Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208-3113, United States
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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, Chen J, van der Est A. Excited State Magneto-Structural Correlations Related to Photoinduced Electron Spin Polarization. J Am Chem Soc 2022; 144:12781-12788. [PMID: 35802385 DOI: 10.1021/jacs.2c03490] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Photoinduced electron spin polarization (ESP) is reported in the ground state of a series of complexes consisting of an organic radical (nitronylnitroxide, NN) covalently attached to a donor-acceptor chromophore either directly or via para-phenylene bridges substituted with 0-4 methyl groups. These molecules represent a class of chromophores that undergo visible light excitation to produce an initial exchange-coupled, three-spin [bpy•-, CAT•+ (= semiquinone, SQ) and NN•], charge-separated doublet 2S1 (S = chromophore spin singlet configuration) excited state that rapidly decays by magnetic exchange-enhanced internal conversion to a 2T1 (T = chromophore excited spin triplet configuration) state. The 2T1 state equilibrates with chromophoric and NN radical-derived excited states, resulting in absorptive ESP of the recovered ground state, which persists for greater than a millisecond and can be measured by low-temperature time-resolved electron paramagnetic resonance spectroscopy. The magnitude of the ground state ESP is found to correlate with the excited state magnetic exchange interaction between the CAT+• and NN• radicals, which in turn is controlled by the structure of the bridge fragment.
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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.,Center for Quantum Information and Control (CQuIC), The 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
| | - Patrick Hewitt
- 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, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
| | - Art van der Est
- Department of Chemistry, Brock University, St. Catharines, Ontario L2S 3A1, Canada
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