1
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Zhang D, Zhu Z, Xiao X, Fang YH, Xiao T, Wang X, Jiang SD, Zhao D. An Air-Stable Carbon-Centered Triradical with a Well-Addressable Quartet Ground State. J Am Chem Soc 2024; 146:21752-21761. [PMID: 39056815 DOI: 10.1021/jacs.4c05898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2024]
Abstract
Organic polyradicals with a high-spin ground state and quantum magnetic properties suitable for spin manipulation are valuable materials for diverse innovative technologies, including quantum devices. However, the typically high reactivity and low stability of conventional polyradicals present a major obstacle to such applications. In this study, a highly stable carbon-centered triradical TR with a quartet ground state and excellent stability (τ1/2 of ∼90 days in air-saturated toluene at room temperature) is achieved, which shows apposite magnetic anisotropy and Zeeman splitting partition with favorable addressability. By virtue of the optimal stability, thorough structural and magnetic characterizations are realized. With X-ray crystallography unambiguously proving the molecular structure, the quartet ground state (ΔED-Q = 0.78 kcal/mol) is confirmed by the SQUID measurements, while the cw- and pulsed EPR techniques offer additional supportive evidence for the high-spin nature. Remarkably, owing to the easily attained magnetic anisotropy, selective excitations between different Zeeman splitting levels are successfully demonstrated with TR in its frozen toluene solution without the requirement for special alignment, which is unprecedented for organic polyradicals. Along with the millisecond spin-lattice relaxation and microsecond coherence time manifested by TR, this triradical is promising for potential coherent spin manipulation applications as a multienergy-level quantum information carrier.
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Affiliation(s)
- Di Zhang
- Beijing National Laboratory for Molecular Sciences, Centre for the Soft Matter Science and Engineering, the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
| | - Ziqi Zhu
- Beijing National Laboratory for Molecular Sciences, Centre for the Soft Matter Science and Engineering, the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
| | - Xiao Xiao
- Beijing National Laboratory for Molecular Sciences, Centre for the Soft Matter Science and Engineering, the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
| | - Yu-Hui Fang
- Beijing National Laboratory for Molecular Sciences, Centre for the Soft Matter Science and Engineering, the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
| | - Tongtong Xiao
- Beijing National Laboratory for Molecular Sciences, Centre for the Soft Matter Science and Engineering, the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
| | - Xiaoge Wang
- Beijing National Laboratory for Molecular Sciences, Centre for the Soft Matter Science and Engineering, the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
| | - Shang-Da Jiang
- Spin-X Institute, School of Chemistry and Chemical Engineering, State Key Laboratory of Luminescent Materials and Devices, Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials, South China University of Technology, Guangzhou 510641, China
| | - Dahui Zhao
- Beijing National Laboratory for Molecular Sciences, Centre for the Soft Matter Science and Engineering, the Key Laboratory of Polymer Chemistry and Physics of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China
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2
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Tran P, Wang Y, Dzikovski B, Lahm ME, Xie Y, Wei P, Klepov VV, Schaefer HF, Robinson GH. A Stable Aluminum Tris(dithiolene) Triradical. J Am Chem Soc 2024; 146:16340-16347. [PMID: 38820231 PMCID: PMC11177253 DOI: 10.1021/jacs.4c05631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Revised: 05/21/2024] [Accepted: 05/22/2024] [Indexed: 06/02/2024]
Abstract
A stable aluminum tris(dithiolene) triradical (3) was experimentally realized through a low-temperature reaction of the sterically demanding lithium dithiolene radical (2) with aluminum iodide. Compound 3 was characterized by single-crystal X-ray diffraction, UV-vis and EPR spectroscopy, SQUID magnetometry, and theoretical computations. The quartet ground state of triradical 3 has been unambiguously confirmed by variable-temperature continuous wave EPR experiments and SQUID magnetometry. Both SQUID magnetometry and broken-symmetry DFT computations reveal a small doublet-quartet energy gap [ΔEDQ = 0.18 kcal mol-1 (SQUID); ΔEDQ = 0.14 kcal mol-1 (DFT)]. The pulsed EPR experiment (electron spin echo envelop modulation) provides further evidence for the interaction of these dithiolene-based radicals with the central aluminum nucleus of 3.
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Affiliation(s)
- Phuong
M. Tran
- Department
of Chemistry and the Center for Computational Chemistry, The University of Georgia, Athens, Georgia 30602-2556, United States
| | - Yuzhong Wang
- Department
of Chemistry and the Center for Computational Chemistry, The University of Georgia, Athens, Georgia 30602-2556, United States
| | - Boris Dzikovski
- Department
of Chemistry and Chemical Biology, and ACERT, National Biomedical
Center for Advanced Electron Spin Resonance Technology, Cornell University, Ithaca, New York 14853-1301, United States
| | - Mitchell E. Lahm
- Department
of Chemistry and the Center for Computational Chemistry, The University of Georgia, Athens, Georgia 30602-2556, United States
| | - Yaoming Xie
- Department
of Chemistry and the Center for Computational Chemistry, The University of Georgia, Athens, Georgia 30602-2556, United States
| | - Pingrong Wei
- Department
of Chemistry and the Center for Computational Chemistry, The University of Georgia, Athens, Georgia 30602-2556, United States
| | - Vladislav V. Klepov
- Department
of Chemistry and the Center for Computational Chemistry, The University of Georgia, Athens, Georgia 30602-2556, United States
| | - Henry F. Schaefer
- Department
of Chemistry and the Center for Computational Chemistry, The University of Georgia, Athens, Georgia 30602-2556, United States
| | - Gregory H. Robinson
- Department
of Chemistry and the Center for Computational Chemistry, The University of Georgia, Athens, Georgia 30602-2556, United States
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3
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Wei D, Qin Y, Xu Z, Liu H, Chen R, Yu Y, Wang D. Study of Molecular Dimer Morphology Based on Organic Spin Centers: Nitronyl Nitroxide Radicals. Molecules 2024; 29:2042. [PMID: 38731533 PMCID: PMC11085200 DOI: 10.3390/molecules29092042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 04/24/2024] [Accepted: 04/27/2024] [Indexed: 05/13/2024] Open
Abstract
In this work, in order to investigate the short-range interactions between molecules, the spin-magnetic unit nitronyl nitroxide (NN) was introduced to synthesize self-assembly single radical molecules with hydrogen bond donors and acceptors. The structures and magnetic properties were extensively investigated and characterized by UV-Vis absorption spectroscopy, electron paramagnetic resonance (EPR), and superconducting quantum interference devices (SQUIDs). Interestingly, it was observed that the single molecules can form two different dimers (ring-closed dimer and "L"-type dimer) in different solvents, due to hydrogen bonding, when using EPR to track the molecular spin interactions. Both dimers exhibit ferromagnetic properties (for ring-closed dimer, J/kB = 0.18 K and ΔES-T = 0.0071 kcal/mol; for "L"-type dimer, the values were J/kB = 9.26 K and ΔES-T = 0.037 kcal/mol). In addition, the morphologies of the fibers formed by the two dimers were characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM).
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Affiliation(s)
- Dongdong Wei
- School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Yongliang Qin
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, China
| | - Zhipeng Xu
- School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Hui Liu
- School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Ranran Chen
- School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China
| | - Yang Yu
- School of Advanced Manufacturing Engineering, Hefei University, Hefei 230601, China
| | - Di Wang
- School of Materials Science and Chemical Engineering, Anhui Jianzhu University, Hefei 230601, China
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4
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Guo H, Lovell JB, Shu C, Pink M, Morton M, Rajca S, Rajca A. Chiral π-Conjugated Double Helical Aminyl Diradical with the Triplet Ground State. J Am Chem Soc 2024; 146:9422-9433. [PMID: 38501228 DOI: 10.1021/jacs.4c02057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
We report a neutral high-spin diradical of chiral C2-symmetric bis[5]diazahelicene with ΔEST ≈ 0.4 kcal mol-1, as determined by EPR spectroscopy/SQUID magnetometry. The diradical is the most persistent among all high-spin aminyl radicals reported to date by a factor of 20, with a half-life of up to 6 days in 2-MeTHF at room temperature. Its triplet ground state and excellent persistence may be associated with the unique spin density distribution within the dihydrophenazine moiety, which characterizes two effective 3-electron C-N bonds analogous to the N-O bond of a nitroxide radical. The enantiomerically enriched (ee ≥ 94%) (MM)- and (PP)-enantiomers of the precursors to the diradicals are obtained by either preparative chiral supercritical fluid chromatography or resolution via functionalization with the chiral auxiliary of the C2-symmetric racemic tetraamine. The barrier for the racemization of the solid tetraamine is ΔG‡ = 43 ± 0.01 kcal mol-1 in the 483-523 K range. The experimentally estimated lower limit of the barrier for the racemization of a diradical, ΔG‡ ≥ 26 kcal mol-1 in 2-MeTHF at 293 K, is comparable to the DFT-determined barrier of ΔG‡ = 31 kcal mol-1 in the gas phase at 298 K. While the enantiomerically pure tetraamine displays strong chiroptical properties, with anisotropy factor |g| = |Δε|/ε = 0.036 at 376 nm, |g| ≈ 0.005 at 548 nm of the high-spin diradical is comparable to that recently reported triplet ground-state diradical dication. Notably, the radical anion intermediate in the generation of diradical exhibits a large SOMO-HOMO inversion, SHI = 35 kcal mol-1.
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Affiliation(s)
- Haoxin Guo
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Joshua B Lovell
- Teledyne ISCO, 4700 Superior Street, Lincoln, Nebraska 68504-1328, United States
| | - Chan Shu
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Maren Pink
- IUMSC, Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, United States
| | - Martha Morton
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
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5
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Tretyakov EV, Zayakin IA, Dmitriev AA, Fedin MV, Romanenko GV, Bogomyakov AS, Akyeva AY, Syroeshkin MA, Yoshioka N, Gritsan NP. A Nitronyl Nitroxide-Substituted Benzotriazinyl Tetraradical. Chemistry 2024; 30:e202303456. [PMID: 37988241 DOI: 10.1002/chem.202303456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 11/20/2023] [Accepted: 11/21/2023] [Indexed: 11/23/2023]
Abstract
High-spin organic tetraradicals with significant intramolecular exchange interactions have high potential for advanced technological applications and fundamental research, but those synthesized to date possess limited stability and processability. In this work, we have designed a tetraradical based on the Blatter's radical and nitronyl nitroxide radical moieties and successfully synthesized it by using the palladium-catalyzed cross-coupling reaction of a triiodo-derivative of the 1,2,4-benzotriazinyl radical with gold(I) nitronyl nitroxide-2-ide complex in the presence of a newly developed efficient catalytic system. The molecular and crystal structure of the tetraradical was confirmed by X-ray diffraction analysis. The tetraradical possesses good thermal stability with decomposition onset at ∼150 °C under an inert atmosphere and exhibits reversible redox waves at -0.54 and 0.45 V versus Ag/AgCl. The magnetic properties of the tetraradical were characterized by SQUID magnetometry of polycrystalline powders and EPR spectroscopy in various matrices. The collected data, analyzed by using high-level quantum chemical calculations, confirmed that the tetraradical has a triplet ground state and a nearby excited quintet state. The unique high stability of the prepared triazinyl-nitronylnitroxide tetraradical is a new milestone in the field of creating high-spin systems.
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Affiliation(s)
- Evgeny V Tretyakov
- N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Ave. 47, 119991, Moscow, Russian Federation
| | - Igor A Zayakin
- N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Ave. 47, 119991, Moscow, Russian Federation
| | - Alexey A Dmitriev
- V.V. Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of Russian Academy of Sciences, Institutskaya Str. 3, 630090, Novosibirsk, Russian Federation
| | - Matvey V Fedin
- International Tomography Center, Siberian Branch of Russian Academy of Sciences, Institutskaya Str. 3a, 630090, Novosibirsk, Russian Federation
| | - Galina V Romanenko
- International Tomography Center, Siberian Branch of Russian Academy of Sciences, Institutskaya Str. 3a, 630090, Novosibirsk, Russian Federation
| | - Artem S Bogomyakov
- International Tomography Center, Siberian Branch of Russian Academy of Sciences, Institutskaya Str. 3a, 630090, Novosibirsk, Russian Federation
| | - Anna Ya Akyeva
- N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Ave. 47, 119991, Moscow, Russian Federation
| | - Mikhail A Syroeshkin
- N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Ave. 47, 119991, Moscow, Russian Federation
| | - Naoki Yoshioka
- Department of Applied Chemistry Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, 223-8522 Kanagawa, Japan
| | - Nina P Gritsan
- V.V. Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of Russian Academy of Sciences, Institutskaya Str. 3, 630090, Novosibirsk, Russian Federation
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6
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Sun Q, Chen H, Zhao Y, Wang T, Pei R, Zhao Y, Ye S, Wang X. A Discrete, Boron-Containing Triangular Triradical. Chemistry 2024; 30:e202302582. [PMID: 37842967 DOI: 10.1002/chem.202302582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 10/11/2023] [Accepted: 10/13/2023] [Indexed: 10/17/2023]
Abstract
A neutral boron-containing triangular triradical based on a triptycene derivative has been designed and synthesized. Its structure, bonding and physical property have been studied by EPR spectroscopy, SQUID magnetometry and single crystal X-ray diffraction, as well as theoretical calculations. The triradical has a series of isosceles triangle conformations in the solution due to the Jahn-Teller distortion, leading to the splitting of the two low-lying doublet states. This factor together with negligible spin-orbit coupling (SOC) of composing light atoms quenches the spin frustration. The work represents a rare example of a neutral through-space triangular triradical.
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Affiliation(s)
- Quanchun Sun
- State Key Laboratory of Coordination Chemistry Jiangsu Key Laboratory of Advanced Organic Materials School of Chemistry and Chemical Engineering Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210023, China
| | - Haowen Chen
- State Key Laboratory of Catalysis Dalian Institute of Chemical Physics University of Chinese Academy of Sciences, Chinese Academy of Sciences, Dalian, 116023, China
| | - Yu Zhao
- State Key Laboratory of Coordination Chemistry Jiangsu Key Laboratory of Advanced Organic Materials School of Chemistry and Chemical Engineering Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210023, China
| | - Tao Wang
- State Key Laboratory of Coordination Chemistry Jiangsu Key Laboratory of Advanced Organic Materials School of Chemistry and Chemical Engineering Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210023, China
| | - Runbo Pei
- State Key Laboratory of Coordination Chemistry Jiangsu Key Laboratory of Advanced Organic Materials School of Chemistry and Chemical Engineering Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210023, China
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry Jiangsu Key Laboratory of Advanced Organic Materials School of Chemistry and Chemical Engineering Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210023, China
| | - Shengfa Ye
- State Key Laboratory of Catalysis Dalian Institute of Chemical Physics University of Chinese Academy of Sciences, Chinese Academy of Sciences, Dalian, 116023, China
| | - Xinping Wang
- State Key Laboratory of Coordination Chemistry Jiangsu Key Laboratory of Advanced Organic Materials School of Chemistry and Chemical Engineering Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210023, China
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7
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Zayakin I, Romanenko G, Bagryanskaya I, Ugrak B, Fedin M, Tretyakov E. Catalytic System for Cross-Coupling of Heteroaryl Iodides with a Nitronyl Nitroxide Gold Derivative at Room Temperature. Molecules 2023; 28:7661. [PMID: 38005383 PMCID: PMC10675334 DOI: 10.3390/molecules28227661] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 11/16/2023] [Accepted: 11/16/2023] [Indexed: 11/26/2023] Open
Abstract
A simple and highly effective methodology for the cross-coupling of heteroaryl iodides with NN-AuPPh3 at room temperature is reported. The protocol is based on a novel catalytic system consisting of Pd2(dba)3·CHCl3 and the phosphine ligand MeCgPPh having an adamantane-like framework. The present protocol was found to be well compatible with various heteroaryl iodides, thus opening new horizons in directed synthesis of functionalized nitronyl nitroxides and high-spin molecules.
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Affiliation(s)
- Igor Zayakin
- N. D. Zelinsky Institute of Organic Chemistry, Leninsky Ave. 47, Moscow 119991, Russia; (I.Z.); (B.U.)
| | - Galina Romanenko
- International Tomography Center, Institutskaya Str. 3a, Novosibirsk 630090, Russia;
| | - Irina Bagryanskaya
- N. N. Vorozhtsov Institute of Organic Chemistry, 9 Ac. Lavrentiev Avenue, Novosibirsk 630090, Russia;
| | - Bogdan Ugrak
- N. D. Zelinsky Institute of Organic Chemistry, Leninsky Ave. 47, Moscow 119991, Russia; (I.Z.); (B.U.)
| | - Matvey Fedin
- International Tomography Center, Institutskaya Str. 3a, Novosibirsk 630090, Russia;
| | - Evgeny Tretyakov
- N. D. Zelinsky Institute of Organic Chemistry, Leninsky Ave. 47, Moscow 119991, Russia; (I.Z.); (B.U.)
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8
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Shu C, Yang Z, Rajca A. From Stable Radicals to Thermally Robust High-Spin Diradicals and Triradicals. Chem Rev 2023; 123:11954-12003. [PMID: 37831948 DOI: 10.1021/acs.chemrev.3c00406] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2023]
Abstract
Stable radicals and thermally robust high-spin di- and triradicals have emerged as important organic materials due to their promising applications in diverse fields. New fundamental properties, such as SOMO/HOMO inversion of orbital energies, are explored for the design of new stable radicals, including highly luminescent ones with good photostability. A relation with the singlet-triplet energy gap in the corresponding diradicals is proposed. Thermally robust high-spin di- and triradicals, with energy gaps that are comparable to or greater than a thermal energy at room temperature, are more challenging to synthesize but more rewarding. We summarize a number of high-spin di- and triradicals, based on nitronyl nitroxides that provide a relation between the experimental pairwise exchange coupling constant J/k in the high-spin species vs experimental hyperfine coupling constants in the corresponding monoradicals. This relation allows us to identify outliers, which may correspond to radicals where J/k is not measured with sufficient accuracy. Double helical high-spin diradicals, in which spin density is delocalized over the chiral π-system, have been barely explored, with the sole example of such high-spin diradical possessing alternant π-system with Kekulé resonance form. Finally, we discuss a high-spin diradical with electrical conductivity and derivatives of triangulene diradicals.
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Affiliation(s)
- Chan Shu
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Zhimin Yang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
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9
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Abstract
Robust organic triradicals with high-spin quartet ground states provide promising applications in molecular magnets, spintronics, etc. In this context, a triradical based on Blatter's radical has been synthesized recently, having two low-lying non-degenerate doublet states with a quartet ground state. The traditional broken-symmetry (BS)-DFT computed doublet-quartet energy gaps are reported to be somewhat overestimated in comparison to the experimentally observed values. In this work, we have employed different ab initio methods on this prototypical system to obtain more accurate doublet-quartet energy gaps for this triradical. The spin-constraint broken-symmetry (CBS)-DFT method has been used to reduce the overestimation of energy gaps from BS-DFT. To address the issues of spin-contamination and the multireference nature of low-spin states affecting the DFT methods, we have computed the energy gaps using appropriately state-averaged CASSCF and NEVPT2 computations. Using a series of active spaces, our calculations are shown to provide quite accurate values in concordance with the experimentally observed results. Furthermore, we have proposed and modeled another two triradicals based on Blatter's radical, which are of interest for experimental synthesis and characterization. Our computations show that all these triradicals also have a quartet ground state with a similar energy difference between the excited doublet states.
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Affiliation(s)
- Rishu Khurana
- Institute of Nano Science and Technology, Sector-81, Mohali, Punjab 140306, India
| | - Ashima Bajaj
- Institute of Nano Science and Technology, Sector-81, Mohali, Punjab 140306, India
| | - K R Shamasundar
- Indian Institute of Science Education and Research Mohali, Sector-81, Mohali, Punjab 140306, India
| | - Md Ehesan Ali
- Institute of Nano Science and Technology, Sector-81, Mohali, Punjab 140306, India
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10
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Han H, Huang Y, Tang C, Liu Y, Krzyaniak MD, Song B, Li X, Wu G, Wu Y, Zhang R, Jiao Y, Zhao X, Chen XY, Wu H, Stern CL, Ma Y, Qiu Y, Wasielewski MR, Stoddart JF. Spin-Frustrated Trisradical Trication of PrismCage. J Am Chem Soc 2023; 145:18402-18413. [PMID: 37578165 DOI: 10.1021/jacs.3c04340] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Organic trisradicals featuring threefold symmetry have attracted significant interest because of their unique magnetic properties associated with spin frustration. Herein, we describe the synthesis and characterization of a triangular prism-shaped organic cage for which we have coined the name PrismCage6+ and its trisradical trication─TR3(•+). PrismCage6+ is composed of three 4,4'-bipyridinium dications and two 1,3,5-phenylene units bridged by six methylene groups. In the solid state, PrismCage6+ adopts a highly twisted conformation with close to C3 symmetry as a result of encapsulating one PF6- anion as a guest. PrismCage6+ undergoes stepwise reduction to its mono-, di-, and trisradical cations in MeCN on account of strong electronic communication between its 4,4'-bipyridinium units. TR3(•+), which is obtained by the reduction of PrismCage6+ employing CoCp2, adopts a triangular prism-shaped conformation with close to C2v symmetry in the solid state. Temperature-dependent continuous-wave and nutation-frequency-selective electron paramagnetic resonance spectra of TR3(•+) in frozen N,N-dimethylformamide indicate its doublet ground state. The doublet-quartet energy gap of TR3(•+) is estimated to be -0.08 kcal mol-1, and the critical temperature of spin-state conversion is found to be ca. 50 K, suggesting that it displays pronounced spin frustration at the molecular level. To the best of our knowledge, this example is the first organic radical cage to exhibit spin frustration. The trisradical trication of PrismCage6+ opens up new possibilities for fundamental investigations and potential applications in the fields of both organic cages and spin chemistry.
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Affiliation(s)
- Han Han
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yuheng Huang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Center for Molecular Quantum Transduction, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208, United States
| | - Chun Tang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yiming Liu
- Beijing National Laboratory for Molecular Sciences, Centre for the Soft Matter Science and Engineering, The Key Lab of Polymer Chemistry & Physics of the Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Matthew D Krzyaniak
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Center for Molecular Quantum Transduction, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208, United States
| | - Bo Song
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Xuesong Li
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Guangcheng Wu
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yong Wu
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Ruihua Zhang
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yang Jiao
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Xingang Zhao
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Xiao-Yang Chen
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Huang Wu
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Charlotte L Stern
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Yuguo Ma
- Beijing National Laboratory for Molecular Sciences, Centre for the Soft Matter Science and Engineering, The Key Lab of Polymer Chemistry & Physics of the Ministry of Education, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Yunyan Qiu
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Republic of Singapore
| | - Michael R Wasielewski
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Center for Molecular Quantum Transduction, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Institute for Sustainability and Energy at Northwestern, Northwestern University, Evanston, Illinois 60208, United States
| | - J Fraser Stoddart
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
- Stoddart Institute of Molecular Science, Department of Chemistry, Zhejiang University, Hangzhou 310027, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Hangzhou 311215, China
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
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11
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Dong X, Luo QC, Zhao Y, Wang T, Sun Q, Pei R, Zhao Y, Zheng YZ, Wang X. A Dynamic Triradical: Synthesis, Crystal Structure, and Spin Frustration. J Am Chem Soc 2023; 145:17292-17298. [PMID: 37493570 DOI: 10.1021/jacs.3c04692] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
Polyradicals, i.e., multispin organic molecules, are playing important roles in radical-based material applications for their spin-spin interaction. A dynamic covalently bonded multispin molecule may endow materials with added function such as memory and switching. However, such a species has yet to be reported. We here report the synthesis, characterization, and crystal structure of a dynamic triradical species. It is generated by the self-assembly of two molecules through a Lewis acid coupled electron transfer. The crystalline species is spin-frustrated without Jahn-Teller distortion at low temperature, while it dissociates back to diamagnetic starting material in solution at high temperature. The reversible process is tracked by variable-temperature NMR, EPR, and UV-vis-NIR spectroscopy. Isolation, property study, and dynamic bonding investigation on such a species lay the foundation for the design of functional polyradicals with potential application as memory or switching devices.
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Affiliation(s)
- Xue Dong
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Science, Shanghai 200032, China
| | - Qian-Cheng Luo
- Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an 710049, China
| | - Yu Zhao
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Tao Wang
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Quanchun Sun
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Runbo Pei
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Yan-Zhen Zheng
- Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an 710049, China
| | - Xinping Wang
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Science, Shanghai 200032, China
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12
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Yang Z, Pink M, Nowik-Boltyk EM, Lu S, Junghoefer T, Rajca S, Stoll S, Casu MB, Rajca A. Thermally Ultrarobust S = 1/2 Tetrazolinyl Radicals: Synthesis, Electronic Structure, Magnetism, and Nanoneedle Assemblies on Silicon Surface. J Am Chem Soc 2023; 145:13335-13346. [PMID: 37285418 PMCID: PMC10438971 DOI: 10.1021/jacs.3c03402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Open-shell organic molecules, including S = 1/2 radicals, may provide enhanced properties for several emerging technologies; however, relatively few synthesized to date possess robust thermal stability and processability. We report the synthesis of S = 1/2 biphenylene-fused tetrazolinyl radicals 1 and 2. Both radicals possess near-perfect planar structures based on their X-ray structures and density-functional theory (DFT) computations. Radical 1 possesses outstanding thermal stability as indicated by the onset of decomposition at 269 °C, based on thermogravimetric analysis (TGA) data. Both radicals possess very low oxidation potentials <0 V (vs. SCE) and their electrochemical energy gaps, Ecell ≈ 0.9 eV, are rather low. Magnetic properties of polycrystalline 1 are characterized by superconducting quantum interference device (SQUID) magnetometry revealing a one-dimensional S = 1/2 antiferromagnetic Heisenberg chain with exchange coupling constant J'/k ≈ -22.0 K. Radical 1 in toluene glass possesses a long electron spin coherence time, Tm ≈ 7 μs in the 40-80 K temperature range, a property advantageous for potential applications as a molecular spin qubit. Radical 1 is evaporated under ultrahigh vacuum (UHV) forming assemblies of intact radicals on a silicon substrate, as confirmed by high-resolution X-ray photoelectron spectroscopy (XPS). Scanning electron microscope (SEM) images indicate that the radical molecules form nanoneedles on the substrate. The nanoneedles are stable for at least 64 hours under air as monitored by using X-ray photoelectron spectroscopy. Electron paramagnetic resonance (EPR) studies of the thicker assemblies, prepared by UHV evaporation, indicate radical decay according to first-order kinetics with a long half-life of 50 ± 4 days at ambient conditions.
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Affiliation(s)
- Zhimin Yang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA
| | - Maren Pink
- IUMSC, Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, USA
| | | | - Shutian Lu
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Tobias Junghoefer
- Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA
| | - Stefan Stoll
- Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
| | - Maria Benedetta Casu
- Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA
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13
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Nowik-Boltyk EM, Junghoefer T, Glaser M, Giangrisostomi E, Ovsyannikov R, Zhang S, Shu C, Rajca A, Calzolari A, Casu MB. Long-Term Degradation Mechanisms in Application-Implemented Radical Thin Films. ACS APPLIED MATERIALS & INTERFACES 2023. [PMID: 37319383 DOI: 10.1021/acsami.3c02057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Blatter radical derivatives are very attractive due to their potential applications, ranging from batteries to quantum technologies. In this work, we focus on the latest insights regarding the fundamental mechanisms of radical thin film (long-term) degradation, by comparing two Blatter radical derivatives. We find that the interaction with different contaminants (such as atomic H, Ar, N, and O and molecular H2, N2, O2, H2O, and NH2) affects the chemical and magnetic properties of the thin films upon air exposure. Also, the radical-specific site, where the contaminant interaction takes place, plays a role. Atomic H and NH2 are detrimental to the magnetic properties of Blatter radicals, while the presence of molecular water influences more specifically the magnetic properties of the diradical thin films, and it is believed to be the major cause of the shorter diradical thin film lifetime in air.
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Affiliation(s)
| | - Tobias Junghoefer
- Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Mathias Glaser
- Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Erika Giangrisostomi
- Institute Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin, 12489 Berlin, Germany
| | - Ruslan Ovsyannikov
- Institute Methods and Instrumentation for Synchrotron Radiation Research, Helmholtz-Zentrum Berlin, 12489 Berlin, Germany
| | - Shuyang Zhang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - Chan Shu
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, United States
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588, United States
| | | | - M Benedetta Casu
- Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
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14
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Boudalis AK, Constantinides CP, Chrysochos N, Carmieli R, Leitus G, Kourtellaris A, Lawson DB, Koutentis PA. Deciphering the ground state of a C 3-symmetrical Blatter-type triradical by CW and pulse EPR spectroscopy. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2023; 349:107406. [PMID: 36841142 DOI: 10.1016/j.jmr.2023.107406] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Revised: 02/08/2023] [Accepted: 02/13/2023] [Indexed: 06/18/2023]
Abstract
3,3',3''-(Benzene-1,3,5-triyl)tris(1-phenyl-1H-benzo[e][1,2,4]triazin-4-yl) (1) is a C3-symmetrical triradical comprised of three Blatter radical units connected at the 1, 3, 5 positions of a central trimethylenebenzene core. This triradical has an excellent air, moisture, and thermal stability. Single-crystal XRD indicates that triradical 1 adopts a propeller-like geometry with the benzotriazinyl moieties twisted by 174.1(2)° and packs in 1D chains along the c axis to form an extensive network of weak intermolecular interactions. Frozen solution continuous wave (CW) EPR spectra and variable-temperature field-sweep echo-detected (FSED) spectra revealed an intramolecular ferromagnetic exchange within the spin system, supporting a quartet S = 3/2 ground state. DFT calculations further supported these experimental findings.
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Affiliation(s)
- Athanassios K Boudalis
- Institut de Chimie de Strasbourg (UMR 7177, CNRS-Unistra), Université de Strasbourg, 4 rue Blaise Pascal, CS 90032, F-67081 Strasbourg, France.
| | - Christos P Constantinides
- Department of Natural Sciences, University of Michigan - Dearborn, 4901 Evergreen Rd, Dearborn, MI 48128, United States.
| | - Nicolas Chrysochos
- Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
| | - Raanan Carmieli
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Gregory Leitus
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Andreas Kourtellaris
- Department of Chemistry, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
| | - Daniel B Lawson
- Department of Natural Sciences, University of Michigan - Dearborn, 4901 Evergreen Rd, Dearborn, MI 48128, United States
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15
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Zayakin I, Tretyakov E, Akyeva A, Syroeshkin M, Burykina J, Dmitrenok A, Korlyukov A, Nasyrova D, Bagryanskaya I, Stass D, Ananikov V. Overclocking Nitronyl Nitroxide Gold Derivatives in Cross-Coupling Reactions. Chemistry 2023; 29:e202203118. [PMID: 36259387 DOI: 10.1002/chem.202203118] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Indexed: 12/12/2022]
Abstract
Nitronyl nitroxides are functional building blocks in cutting-edge research fields, such as the design of molecular magnets, the development of redox and photoswitchable molecular systems and the creation of redox-active components for organic and hybrid batteries. The key importance of the nitronyl nitroxide function is to translate molecular-level-optimized structures into nano-scale devices and new technologies. In spite of great importance, efficient and versatile synthetic approaches to these compounds still represent a challenge. Particularly, methods for the direct introduction of a nitronyl nitroxide moiety into aromatic systems possess many limitations. Here, we report gold derivatives of nitronyl nitroxide that can enter Pd(0)-catalysed cross-coupling reactions with various aryl bromides, affording the corresponding functionalized nitronyl nitroxides. Based on the high thermal stability and enhanced reactivity in catalytic transformation, a new reagent is suggested for the synthesis of radical systems via a universal cross-coupling approach.
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Affiliation(s)
- Igor Zayakin
- N. D. Zelinsky Institute of Organic Chemistry, 47 Leninsky Prosp., 119991, Moscow, Russia
| | - Evgeny Tretyakov
- N. D. Zelinsky Institute of Organic Chemistry, 47 Leninsky Prosp., 119991, Moscow, Russia
| | - Anna Akyeva
- N. D. Zelinsky Institute of Organic Chemistry, 47 Leninsky Prosp., 119991, Moscow, Russia
| | - Mikhail Syroeshkin
- N. D. Zelinsky Institute of Organic Chemistry, 47 Leninsky Prosp., 119991, Moscow, Russia
| | - Julia Burykina
- N. D. Zelinsky Institute of Organic Chemistry, 47 Leninsky Prosp., 119991, Moscow, Russia
| | - Andrey Dmitrenok
- N. D. Zelinsky Institute of Organic Chemistry, 47 Leninsky Prosp., 119991, Moscow, Russia
| | - Alexander Korlyukov
- A. N. Nesmeyanov Institute of Organoelement Compounds, 28 Vavilov Str., 119991, Moscow, Russia
| | - Darina Nasyrova
- N. D. Zelinsky Institute of Organic Chemistry, 47 Leninsky Prosp., 119991, Moscow, Russia
| | - Irina Bagryanskaya
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, 9 Akad. Lavrentyev Prosp., 630090, Novosibirsk, Russia
| | - Dmitri Stass
- V. V. Voevodsky Institute of Chemical Kinetics and Combustion, 3 Institutskaya Str., 630090, Novosibirsk, Russia
| | - Valentine Ananikov
- N. D. Zelinsky Institute of Organic Chemistry, 47 Leninsky Prosp., 119991, Moscow, Russia
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16
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Zhang H, Pink M, Wang Y, Rajca S, Rajca A. High-Spin S = 3/2 Ground-State Aminyl Triradicals: Toward High-Spin Oligo-Aza Nanographenes. J Am Chem Soc 2022; 144:19576-19591. [PMID: 36251959 PMCID: PMC10438970 DOI: 10.1021/jacs.2c09241] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report high-spin aminyl triradicals with near-planar triphenylene backbones. Near-planarity of the fused aminyl radicals and the 2,6,10-triphenylene ferromagnetic coupling unit (FCU), magnetically equivalent to three fused 3,4'-biphenyl FCUs, assures an effective 2pπ-2pπ overlap within the cross-conjugated π-system, leading to an S = 3/2 (quartet) ground state that is well separated from low-spin excited doublet states. Thermal populations of the low-spin (S = 1/2) excited states are detectable both by SQUID magnetometry and electron paramagnetic resonance (EPR) spectroscopy, providing doublet-quartet energy gaps, ΔEDQ, corresponding to >85% population of the quartet ground states at room temperature. Notably, EPR-based determination of ΔEDQ relies on direct detection of the quartet ground state and doublet excited states. The ΔEDQ values are 1.0-1.1 kcal mol-1, with the more sterically shielded triradical having the larger value. The half-life of the more sterically shielded triradical in 2-methyltetrahydrofuran (2-MeTHF) is about 6 h at room temperature. The less sterically shielded triradical in 2-MeTHF decomposes at 158 K with a half-life of about 4 h, while at 195 K, the half-life is still about 2 h. The dominant products of the decay of triradicals are the corresponding triamines, suggesting hydrogen atom abstraction from the solvent as the primary mechanism. This study expands the frontier of the open-shell PAHs/nanographenes, of which the unique electronic, nonlinear optical, and magnetic properties could be useful in the development of novel organic electronics, photonics, and spintronics.
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Affiliation(s)
- Hui Zhang
- Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304, United States
| | - Maren Pink
- IUMSC, Department of Chemistry, Indiana University, Bloomington, IN 47405-7102, United States
| | - Ying Wang
- Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304, United States
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304, United States
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, NE 68588-0304, United States
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17
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Kasemthaveechok S, Abella L, Crassous J, Autschbach J, Favereau L. Organic radicals with inversion of SOMO and HOMO energies and potential applications in optoelectronics. Chem Sci 2022; 13:9833-9847. [PMID: 36128246 PMCID: PMC9430691 DOI: 10.1039/d2sc02480b] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Accepted: 07/06/2022] [Indexed: 11/21/2022] Open
Abstract
Organic radicals possessing an electronic configuration in which the energy of the singly occupied molecular orbital (SOMO) is below the highest doubly occupied molecular orbital (HOMO) level have recently attracted significant interest, both theoretically and experimentally. The peculiar orbital energetics of these SOMO-HOMO inversion (SHI) organic radicals set their electronic properties apart from the more common situation where the SOMO is the highest occupied orbital of the system. This review gives a general perspective on SHI, with key fundamental aspects regarding the electronic and structural factors that govern this particular electronic configuration in organic radicals. Selected examples of reported compounds with SHI are highlighted to establish molecular guidelines for designing this type of radical, and to showcase the potential of SHI radicals in organic spintronics as well as for the development of more stable luminescent radicals for OLED applications.
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Affiliation(s)
| | - Laura Abella
- Department of Chemistry, University at Buffalo, State University of New York Buffalo New York 14260 USA
| | | | - Jochen Autschbach
- Department of Chemistry, University at Buffalo, State University of New York Buffalo New York 14260 USA
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18
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Wang Y, Chen S, Chen X, Zangarelli A, Ackermann L. Photo-Induced Ruthenium-Catalyzed Double Remote C(sp 2 )-H / C(sp 3 )-H Functionalizations by Radical Relay. Angew Chem Int Ed Engl 2022; 61:e202205562. [PMID: 35527721 PMCID: PMC9401009 DOI: 10.1002/anie.202205562] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Indexed: 12/25/2022]
Abstract
Distal C(sp2 )-H and C(sp3 )-H functionalizations have recently emerged as step-economical tools for molecular synthesis. However, while the C(sp2 )-C(sp3 ) construction is of fundamental importance, its formation through double remote C(sp2 )-H/C(sp3 )-H activation has proven elusive. By merging the ruthenium-catalyzed meta-C(sp2 )-H functionalization with an aliphatic hydrogen atom transfer (HAT) process, we, herein, describe the catalyzed twofold remote C(sp2 )-H/C(sp3 )-H functionalizations via photo-induced ruthenium-mediated radical relay. Thus, meta-C(sp2 )-H arene bonds and remote C(sp3 )-H alkane bonds were activated by a single catalyst in a single operation. This process was accomplished at room temperature by visible light-notably without exogenous photocatalysts. Experimental and computational theory studies uncovered a manifold comprising ortho-C-H activation, single-electron-transfer (SET), 1,n-HAT (n=5-7) and σ-activation by means of a single ruthenium(II) catalyst.
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Affiliation(s)
- Yulei Wang
- Institut für Organische und Biomolekulare Chemie and Wöhler Research Institute for Sustainable Chemistry (WISCh)Georg-August-UniversitätTammanstraße 237077GöttingenGermany
| | - Shan Chen
- Institut für Organische und Biomolekulare Chemie and Wöhler Research Institute for Sustainable Chemistry (WISCh)Georg-August-UniversitätTammanstraße 237077GöttingenGermany
| | - Xinran Chen
- Institut für Organische und Biomolekulare Chemie and Wöhler Research Institute for Sustainable Chemistry (WISCh)Georg-August-UniversitätTammanstraße 237077GöttingenGermany
- Department of ChemistryZhejiang UniversityHangzhou310027China
| | - Agnese Zangarelli
- Institut für Organische und Biomolekulare Chemie and Wöhler Research Institute for Sustainable Chemistry (WISCh)Georg-August-UniversitätTammanstraße 237077GöttingenGermany
| | - Lutz Ackermann
- Institut für Organische und Biomolekulare Chemie and Wöhler Research Institute for Sustainable Chemistry (WISCh)Georg-August-UniversitätTammanstraße 237077GöttingenGermany
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19
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Wang Y, Chen S, Chen X, Zangarelli A, Ackermann L. Foto‐Induzierte Ruthenium‐Katalysierte Doppel C(sp
2
)−H/C(sp
3
)−H Funktionalisierungen durch Radikalübertragungen. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202205562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Yulei Wang
- Institut für Organische und Biomolekulare Chemie und Wöhler Research Institute for Sustainable Chemistry (WISCh) Georg-August-Universität Tammanstraße 2 37077 Göttingen Deutschland
| | - Shan Chen
- Institut für Organische und Biomolekulare Chemie und Wöhler Research Institute for Sustainable Chemistry (WISCh) Georg-August-Universität Tammanstraße 2 37077 Göttingen Deutschland
| | - Xinran Chen
- Institut für Organische und Biomolekulare Chemie und Wöhler Research Institute for Sustainable Chemistry (WISCh) Georg-August-Universität Tammanstraße 2 37077 Göttingen Deutschland
- Department of Chemistry Zhejiang University Hangzhou 310027 China
| | - Agnese Zangarelli
- Institut für Organische und Biomolekulare Chemie und Wöhler Research Institute for Sustainable Chemistry (WISCh) Georg-August-Universität Tammanstraße 2 37077 Göttingen Deutschland
| | - Lutz Ackermann
- Institut für Organische und Biomolekulare Chemie und Wöhler Research Institute for Sustainable Chemistry (WISCh) Georg-August-Universität Tammanstraße 2 37077 Göttingen Deutschland
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20
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Fershtat LL. Synthesis of 1,4-dihydro-1,2,4-benzotriazin-4-yl radicals (microreview). Chem Heterocycl Compd (N Y) 2022. [DOI: 10.1007/s10593-022-03072-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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21
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Kasemthaveechok S, Abella L, Jean M, Cordier M, Vanthuyne N, Guizouarn T, Cador O, Autschbach J, Crassous J, Favereau L. Carbazole Isomerism in Helical Radical Cations: Spin Delocalization and SOMO-HOMO Level Inversion in the Diradical State. J Am Chem Soc 2022; 144:7253-7263. [PMID: 35413200 DOI: 10.1021/jacs.2c00331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report a new molecular design to afford persistent chiral organic open-shell systems with configurational stability and an inversion in energy of the singly occupied molecular orbital (SOMO) and the highest doubly occupied molecular orbital (HOMO) for both mono- and diradical states. The unpaired electron delocalization within the designed extended helical π-conjugated systems is a crucial factor to reach chemical stabilities, which is not obtained using the classical steric protection approach. The unique features of the obtained helical monoradicals allow an exploration of the chiral intramolecular electron transfer (IET) process in solvents of different polarity by means of optical and chiroptical spectroscopies, resulting in an unprecedented electronic circular dichroism (ECD) sign inversion for the radical transitions. We also characterized the corresponding helical diradicals, which show near-infrared electronic circular dichroism at wavelengths up to 1100 nm and an antiferromagnetic coupling between the spins, with an estimated singlet-triplet gap (ΔEST) of about -1.2 kcal mol-1. The study also revealed an intriguing double SOMO-HOMO inversion (SHI) electronic configuration for these diradicals, providing new insight regarding the peculiar energetic ordering of radical orbitals and the impact on the corresponding (chiral) optoelectronic properties.
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Affiliation(s)
| | - Laura Abella
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, United States
| | - Marion Jean
- Aix Marseille University, CNRS Centrale Marseille, iSm2, 13284 Marseille, France
| | - Marie Cordier
- Univ Rennes, CNRS, ISCR - UMR 6226, F-35000 Rennes, France
| | - Nicolas Vanthuyne
- Aix Marseille University, CNRS Centrale Marseille, iSm2, 13284 Marseille, France
| | | | - Olivier Cador
- Univ Rennes, CNRS, ISCR - UMR 6226, F-35000 Rennes, France
| | - Jochen Autschbach
- Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, United States
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22
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Zhang S, Pink M, Junghoefer T, Zhao W, Hsu SN, Rajca S, Calzolari A, Boudouris BW, Casu MB, Rajca A. High-Spin ( S = 1) Blatter-Based Diradical with Robust Stability and Electrical Conductivity. J Am Chem Soc 2022; 144:6059-6070. [PMID: 35333507 PMCID: PMC10439714 DOI: 10.1021/jacs.2c01141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Triplet ground-state organic molecules are of interest with respect to several emerging technologies but usually show limited stability, especially as thin films. We report an organic diradical, consisting of two Blatter radicals, that possesses a triplet ground state with a singlet-triplet energy gap, ΔEST ≈ 0.4-0.5 kcal mol-1 (2J/k ≈ 220-275 K). The diradical possesses robust thermal stability, with an onset of decomposition above 264 °C (TGA). In toluene/chloroform, glassy matrix, and fluid solution, an equilibrium between two conformations with ΔEST ≈ 0.4 kcal mol-1 and ΔEST ≈ -0.7 kcal mol-1 is observed, favoring the triplet ground state over the singlet ground-state conformation in the 110-330 K temperature range. The diradical with the triplet ground-state conformation is found exclusively in crystals and in a polystyrene matrix. The crystalline neutral diradical is a good electrical conductor with conductivity comparable to the thoroughly optimized bis(thiazolyl)-related monoradicals. This is surprising because the triplet ground state implies that the underlying π-system is cross-conjugated and thus is not compatible with either good conductance or electron delocalization. The diradical is evaporated under ultra-high vacuum to form thin films, which are stable in air for at least 18 h, as demonstrated by X-ray photoelectron and electron paramagnetic resonance (EPR) spectroscopies.
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Affiliation(s)
- Shuyang Zhang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | - Maren Pink
- IUMSC, Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, United States
| | - Tobias Junghoefer
- Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Wenchao Zhao
- Charles D. Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, United States
| | - Sheng-Ning Hsu
- Charles D. Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, United States
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
| | | | - Bryan W. Boudouris
- Charles D. Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN 47907, United States
- Department of Chemistry, Purdue University, West Lafayette, IN 47907, United States
| | - Maria Benedetta Casu
- Institute of Physical and Theoretical Chemistry, University of Tübingen, 72076 Tübingen, Germany
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States
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Kodama T, Aoba M, Hirao Y, Rivero SM, Casado J, Kubo T. Molecular and Spin Structures of a Through‐Space Conjugated Triradical System. Angew Chem Int Ed Engl 2022; 61:e202200688. [DOI: 10.1002/anie.202200688] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Indexed: 12/15/2022]
Affiliation(s)
- Takuya Kodama
- Department of Chemistry, Graduate School of Science Osaka University Toyonaka Osaka 560-0043 Japan
- Current Address: Department of Applied Chemistry Graduate School of Engineering Osaka University Suita Osaka 565-0871 Japan
- Innovative Catalysis Science Division (ICS) Institute for Open and Transdisciplinary Research Initiatives (OTRI) Osaka University Suita Osaka 565-0871 Japan
| | - Mitsuya Aoba
- Department of Chemistry, Graduate School of Science Osaka University Toyonaka Osaka 560-0043 Japan
| | - Yasukazu Hirao
- Department of Chemistry, Graduate School of Science Osaka University Toyonaka Osaka 560-0043 Japan
| | - Samara Medina Rivero
- Department of Physical Chemistry University of Málaga Andalucia-Tech Campus de Teatinos s/n 29071 Málaga Spain
| | - Juan Casado
- Department of Physical Chemistry University of Málaga Andalucia-Tech Campus de Teatinos s/n 29071 Málaga Spain
| | - Takashi Kubo
- Department of Chemistry, Graduate School of Science Osaka University Toyonaka Osaka 560-0043 Japan
- Innovative Catalysis Science Division (ICS) Institute for Open and Transdisciplinary Research Initiatives (OTRI) Osaka University Suita Osaka 565-0871 Japan
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24
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Kumagai T, Suzuki S, Kanzaki Y, Shiomi D, Sato K, Takui T, Tanaka R, Okada K, Kozaki M. Heteroatom-Incorporated Trimethylenemethane: Synthesis and Properties of Triphenylphenylnitroxide–(Nitronyl Nitroxide) Dyad. CHEM LETT 2022. [DOI: 10.1246/cl.220021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Tasuku Kumagai
- Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Osaka 558-8585, Japan
| | - Shuichi Suzuki
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Yuki Kanzaki
- Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Osaka 558-8585, Japan
| | - Daisuke Shiomi
- Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Osaka 558-8585, Japan
| | - Kazunobu Sato
- Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Osaka 558-8585, Japan
| | - Takeji Takui
- Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Osaka 558-8585, Japan
| | - Rika Tanaka
- Graduate School of Engineering, Osaka City University, Sumiyoshi-ku, Osaka, Osaka 558-8585, Japan
| | - Keiji Okada
- Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Osaka 558-8585, Japan
| | - Masatoshi Kozaki
- Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka, Osaka 558-8585, Japan
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25
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Tang S, Ruan H, Hu Z, Zhao Y, Song Y, Wang X. A cationic sulfur-hydrocarbon triradical with an excited quartet state. Chem Commun (Camb) 2022; 58:1986-1989. [PMID: 35045147 DOI: 10.1039/d1cc06904g] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The triptycene-bridged tris(thianthrene) compound 1 was designed and synthesized. Three-electron oxidation of 1 by NO[Al(OC(CF3)3)4], followed by crystallization at two different temperatures resulted in the triradical trication salts 2a and 2b respectively, which feature different crystal packing patterns. The triradical trications in 2a and 2b both feature a doublet ground state which can be thermally populated to a quartet state, representing the first examples of cationic main-group triradicals.
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Affiliation(s)
- Shuxuan Tang
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, China.
| | - Huapeng Ruan
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, China.
| | - Zhaobo Hu
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, China.
| | - Yue Zhao
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, China.
| | - You Song
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, China.
| | - Xinping Wang
- State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210023, China.
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26
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Kodama T, Aoba M, Hirao Y, Rivero SM, Casado J, Kubo T. Molecular and Spin Structures of a Through‐Space Conjugated Triradical System. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202200688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Takuya Kodama
- Osaka University: Osaka Daigaku Department of Applied Chemistry, Graduate School of Engineering JAPAN
| | - Mitsuya Aoba
- Osaka University: Osaka Daigaku Department of Chemistry, Graduate School of Science JAPAN
| | - Yasukazu Hirao
- Osaka University: Osaka Daigaku Department of Chemistry, Graduate School of Science JAPAN
| | - Samara Medina Rivero
- University of Malaga: Universidad de Malaga Department of Physical Chemistry SPAIN
| | - Juan Casado
- University of Malaga: Universidad de Malaga Department of Physical Chemistry SPAIN
| | - Takashi Kubo
- Osaka University: Osaka Daigaku Department of Chemistry, Graduate School of Science 1-1 Machikaneyama 560-0043 Toyonaka JAPAN
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27
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Tan Y, Hsu SN, Tahir H, Dou L, Savoie BM, Boudouris BW. Electronic and Spintronic Open-Shell Macromolecules, Quo Vadis? J Am Chem Soc 2022; 144:626-647. [PMID: 34982552 DOI: 10.1021/jacs.1c09815] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Open-shell macromolecules (i.e., polymers containing radical sites either along their backbones or at the pendant sites of repeat units) have attracted significant attention owing to their intriguing chemical and physical (e.g., redox, optoelectronic, and magnetic) properties, and they have been proposed and/or implemented in a wide range of potential applications (e.g., energy storage devices, electronic systems, and spintronic modules). These successes span multiple disciplines that range from advanced macromolecular chemistry through nanoscale structural characterization and on to next-generation solid-state physics and the associated devices. In turn, this has allowed different scientific communities to expand the palette of radical-containing polymers relatively quickly. However, critical gaps remain on many fronts, especially regarding the elucidation of key structure-property-function relationships that govern the underlying electrochemical, optoelectronic, and spin phenomena in these materials systems. Here, we highlight vital developments in the history of open-shell macromolecules to explain the current state of the art in the field. Moreover, we provide a critical review of the successes and bring forward open opportunities that, if solved, could propel this class of materials in a meaningful manner. Finally, we provide an outlook to address where it seems most likely that open-shell macromolecules will go in the coming years. Our considered view is that the future of radical-containing polymers is extremely bright and the addition of talented researchers with diverse skills to the field will allow these materials and their end-use devices to have a positive impact on the global science and technology enterprise in a relatively rapid manner.
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Affiliation(s)
- Ying Tan
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Sheng-Ning Hsu
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Hamas Tahir
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Letian Dou
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States.,Birck Nanotechnology Center, Purdue University, 1205 West State Street, West Lafayette, Indiana 47907, United States
| | - Brett M Savoie
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States
| | - Bryan W Boudouris
- Charles D. Davidson School of Chemical Engineering, Purdue University, 480 Stadium Avenue, West Lafayette, Indiana 47907, United States.,Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
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28
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Tretyakov EV, Ovcharenko VI, Terent'ev AO, Krylov IB, Magdesieva TV, Mazhukin DG, Gritsan NP. Conjugated nitroxide radicals. RUSSIAN CHEMICAL REVIEWS 2022. [DOI: 10.1070/rcr5025] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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29
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Hewitt P, Shultz DA, Kirk ML. Rules for Magnetic Exchange in Azulene-Bridged Biradicals: Quo Vadis? J Org Chem 2021; 86:15577-15587. [PMID: 34644082 DOI: 10.1021/acs.joc.1c02085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Electronic coupling through organic bridges facilitates magnetic exchange interactions and controls electron transfer and single-molecule device electron transport. Electronic coupling through alternant π-systems (e.g., benzene) is better understood than the corresponding coupling through nonalternant π-systems (e.g., azulene). Herein, we examine the structure, spectroscopy, and magnetic exchange coupling in two biradicals (1,3-SQ2Az and 1,3-SQ-Az-NN; SQ = the zinc(II) complex of spin-1/2 semiquinone radical anion, NN = spin-1/2 nitronylnitroxide; Az = azulene) that possess nonalternant azulene π-system bridges. The SQ radical spin density in both molecules is delocalized into the Az π-system, while the NN spin is effectively localized onto the five-atom ONCNO π-system of NN radical. The spin distributions and interactions are probed by EPR spectroscopy and magnetic susceptibility measurements. We find that J = +38 cm-1 for 1,3-SQ2Az and J = +9 cm-1 for 1,3-SQ-Az-NN (H=-2JS^SQ·S^SQorNN). Our results highlight the differences in exchange coupling mediated by azulene compared to exchange coupling mediated by alternant π-systems.
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Affiliation(s)
- Patrick Hewitt
- 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
| | - Martin L Kirk
- Department of Chemistry, The University of New Mexico, MSC03 2060, 1 University of New Mexico, Albuquerque, New Mexico 87131-0001, United States
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30
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Huang S, Pink M, Ngendahimana T, Rajca S, Eaton GR, Eaton SS, Rajca A. Bis-Spiro-Oxetane and Bis-Spiro-Tetrahydrofuran Pyrroline Nitroxide Radicals: Synthesis and Electron Spin Relaxation Studies. J Org Chem 2021; 86:13636-13643. [PMID: 34546727 PMCID: PMC10441184 DOI: 10.1021/acs.joc.1c01670] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Synthesis of bis-spiro-oxetane and bis-spiro-tetrahydrofuran pyrroline nitroxide radicals relies on the Mitsunobu reaction-mediated double cyclizations of N-Boc protected pyrroline tetraols. Structures of the nitroxide radicals are supported by X-ray crystallography. In a trehalose/sucrose matrix at room temperature, the bis-spiro-oxetane nitroxide radical possesses electron spin coherence time, Tm ≈ 0.7 μs. The observed enhanced Tm is most likely associated with strong hydrogen bonding of oxetane moieties to the trehalose/sucrose matrix.
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Affiliation(s)
- Shengdian Huang
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304
| | - Maren Pink
- IUMSC, Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102
| | - Thacien Ngendahimana
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208-2436
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304
| | - Gareth R. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208-2436
| | - Sandra S. Eaton
- Department of Chemistry and Biochemistry, University of Denver, Denver, CO 80208-2436
| | - Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304
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31
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Rajca A, Shu C, Zhang H, Zhang S, Wang H, Rajca S. Thiophene-Based Double Helices: Radical Cations with SOMO-HOMO Energy Level Inversion †. Photochem Photobiol 2021; 97:1376-1390. [PMID: 34152605 DOI: 10.1111/php.13475] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 06/17/2021] [Indexed: 11/29/2022]
Abstract
We report relatively persistent, open-shell thiophene-based double helices, radical cations 1•+ -TMS12 and 2•+ -TMS8 . Closed-shell neutral double helices, 1-TMS12 and 2-TMS8 , have nearly identical first oxidation potentials, E+/0 ≈ +1.33 V, corresponding to reversible oxidation to their radical cations. The radical cations are generated, using tungsten hexachloride in dichloromethane (DCM) as an oxidant, E+/0 ≈ +1.56 V. EPR spectra consist of a relatively sharp singlet peak with an unusually low g-value of 2.001-2.002, thus suggesting exclusive delocalization of spin density over π-conjugated system consisting of carbon atoms only. DFT computations confirm these findings, as only negligible fraction of spin density is found on sulfur and silicon atoms and the spin density is delocalized over a single tetrathiophene moiety. For radical cation, 1•+ -TMS12 , energy level of the singly occupied molecular orbital (SOMO) lies below the four highest occupied molecular orbitals (HOMOs), thus indicating the SOMO-HOMO inversion (SHI) and therefore, violating the Aufbau principle. 1•+ -TMS12 has a half-life of the order of only 5 min at room temperature. EPR peak intensity of 2•+ -TMS8 , which does not show SHI, is practically unchanged over at least 2 h.
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Affiliation(s)
- Andrzej Rajca
- Department of Chemistry, University of Nebraska, Lincoln, NE, USA
| | - Chan Shu
- Department of Chemistry, University of Nebraska, Lincoln, NE, USA
| | - Hui Zhang
- Department of Chemistry, University of Nebraska, Lincoln, NE, USA
| | - Sheng Zhang
- Engineering Research Center for Nanomaterials, Henan University, Kaifeng, China
| | - Hua Wang
- Engineering Research Center for Nanomaterials, Henan University, Kaifeng, China
| | - Suchada Rajca
- Department of Chemistry, University of Nebraska, Lincoln, NE, USA
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