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Brown JT, Zeller M, Rosokha SV. Effects of structural variations on π-dimer formation: long-distance multicenter bonding of cation-radicals of tetrathiafulvalene analogues. Phys Chem Chem Phys 2020; 22:25054-25065. [PMID: 33118569 DOI: 10.1039/d0cp04891g] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The multicenter (pancake) bonding between cation-radicals of tetramethyltetraselenafulvalene, TMTSF+˙, tetramethyltetrathiafulvalene, TMTTF+˙, and bis(ethylenedithio)-tetrathiafulvalene, ET+,˙ was compared to that of tetrathiafulvalene, TTF+˙. To minimize counter-ion effects, the cation-radical salts with weakly coordinating anions (WCA), tetrakis(3,5-trifluoromethylphenyl)borate, dodecamethylcarborane and hexabromocarborane were prepared. Solid-state (X-ray and EPR) measurements revealed diamagnetic π-dimers in the TMTSF and ET salts and the separate monomers in the TTF salts with all WCAs, while TMTTF existed as a dimer in one and a monomer in two salts. The variable-temperature UV-Vis studies of these salts in solution showed that the thermodynamics of formation of the π-bonded dimers of TMTTF+˙ was close to that of TTF+˙, while TMTSF+˙ and ET+˙ showed a higher propensity for π-dimerization. These data indicated that the replacement of sulfur with heavier selenium or insertion of ethylenedithia-substituents into the TTF core increases the π-dimers' stability. Yet, computational analysis indicated that the weakly covalent component of π-bonding decreases in the order TTF > TMTTF > TMTSF > ET. The higher stability of the π-dimers of TMTSF+˙ and ET+˙ cation-radicals was related to a decrease of the electrostatic repulsion between cationic counter-parts and an increase of dispersion components in these associations.
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Affiliation(s)
- John T Brown
- Department of Chemistry, Ball State University, Muncie, IN 47306, USA.
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Zaytseva E, Shiomi D, Ten Y, Gatilov YV, Lomanovich A, Stass D, Bogomyakov A, Yu A, Sugisaki K, Sato K, Takui T, Bagryanskaya E, Mazhukin D. Magnetic Properties of π-Conjugated Hybrid Phenoxyl-Nitroxide Radicals with Extended π-Spin Delocalization. J Phys Chem A 2020; 124:2416-2426. [PMID: 32130857 DOI: 10.1021/acs.jpca.9b11856] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of stable and genuinely organic open-shell systems, π-conjugated phenoxyl-nitroxide free radicals (hybrid phenoxyl-nitroxide radicals), have been synthesized and their magnetic properties in the crystalline state investigated, revealing their usefulness as new building blocks for molecular magnetic materials. The salient electronic structure of the hybrid phenoxyl-nitroxide radicals is extended π-spin delocalization from the nitroxide moiety, mediating the localization effect intrinsic to nitroxide radicals. Five representative hybrid radicals containing an aliphatic, aromatic, and heteroaromatic substituent in the side part of the compact hybrid radical centers were synthesized, and their molecular/crystal structures in the crystalline state were determined by X-ray diffraction analyses. CW X-band ESR, 1H-ENDOR spectroscopy, and DFT calculations for the hybrid radicals confirmed that an unpaired spin delocalizes over the whole molecular frame including the nonconjugated fragments, suggesting the possibility of tuning their electronic properties through substituent effects in the crystalline state. Significant influence of the phenoxyl moiety on the electronic structure was analyzed in terms of the g-tensor calculations. The SQUID magnetization measurements revealed that the nitroxides bearing alkyl or aromatic substituents behave as 3D Curie-Weiss paramagnets with weak antiferromagnetic (AFM) (Θ = -1 to -2.6 K) or ferromagnetic (FM) (Θ = +0.33 K) spin-spin exchange interactions. On the other hand, heteroaromatically substituted hybrid phenoxyl-nitroxide showed significant AFM interactions with J/kB = -25.6 K. The analysis of the bulk magnetic properties based on the crystallographic data and DFT calculations revealed competition between the intermolecular AFM and FM interactions which originate from the C-O(phenoxyl)···Me(nitroxide) or (N)O-C(arom) infinite 1D head-to-tail chains and the C(arom)-C(arom) head-over-tail dimers forming 3D networks in their crystal lattices.
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Affiliation(s)
- Elena Zaytseva
- N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, 9 Acad. Lavrentyeva Ave., Novosibirsk 630090, Russia.,Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090, Russia
| | - Daisuke Shiomi
- Department of Chemistry and Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Yury Ten
- N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, 9 Acad. Lavrentyeva Ave., Novosibirsk 630090, Russia
| | - Yuri V Gatilov
- N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, 9 Acad. Lavrentyeva Ave., Novosibirsk 630090, Russia.,Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090, Russia
| | - Alyona Lomanovich
- N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, 9 Acad. Lavrentyeva Ave., Novosibirsk 630090, Russia
| | - Dmitri Stass
- Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090, Russia.,Voevodsky Institute of Chemical Kinetics and Combustion, SB RAS, 3 Institutskaya Str., Novosibirsk 630090, Russia
| | - Artem Bogomyakov
- Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090, Russia.,International Tomography Center, SB RAS, 3 Institutskaya Str., Novosibirsk 630090, Russia
| | - Aixia Yu
- Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090, Russia
| | - Kenji Sugisaki
- Department of Chemistry and Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Kazunobu Sato
- Department of Chemistry and Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Takeji Takui
- Department of Chemistry and Molecular Materials Science, Graduate School of Science, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan.,Research Support Department, University Research Administrator Center, University Administration Division, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan
| | - Elena Bagryanskaya
- N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, 9 Acad. Lavrentyeva Ave., Novosibirsk 630090, Russia.,Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090, Russia
| | - Dmitrii Mazhukin
- N.N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, 9 Acad. Lavrentyeva Ave., Novosibirsk 630090, Russia.,Novosibirsk State University, 2 Pirogova Str., Novosibirsk 630090, Russia
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8
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Sato K, Hirao R, Timofeev I, Krumkacheva O, Zaytseva E, Rogozhnikova O, Tormyshev VM, Trukhin D, Bagryanskaya E, Gutmann T, Klimavicius V, Buntkowsky G, Sugisaki K, Nakazawa S, Matsuoka H, Toyota K, Shiomi D, Takui T. Trityl-Aryl-Nitroxide-Based Genuinely g-Engineered Biradicals, As Studied by Dynamic Nuclear Polarization, Multifrequency ESR/ENDOR, Arbitrary Wave Generator Pulse Microwave Waveform Spectroscopy, and Quantum Chemical Calculations. J Phys Chem A 2019; 123:7507-7517. [PMID: 31373818 DOI: 10.1021/acs.jpca.9b07169] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Trityl and nitroxide radicals are connected by π-topologically controlled aryl linkers, generating genuinely g-engineered biradicals. They serve as a typical model for biradicals in which the exchange (J) and hyperfine interactions compete with the g-difference electronic Zeeman interactions. The magnetic properties underlying the biradical spin Hamiltonian for solution, including J's, have been determined by multifrequency CW-ESR and 1H ENDOR spectroscopy and compared with those obtained by quantum chemical calculations. The experimental J values were in good agreement with the quantum chemical calculations. The g-engineered biradicals have been tested as a prototype for AWG (Arbitrary Wave Generator)-based spin manipulation techniques, which enable GRAPE (GRAdient Pulse Engineering) microwave control of spins in molecular magnetic resonance spectroscopy for use in molecular spin quantum computers, demonstrating efficient signal enhancement of specific weakened hyperfine signals. Dynamic nuclear polarization (DNP) effects of the biradicals for 400 MHz nuclear magnetic resonance signal enhancement have been examined, giving efficiency factors of 30 for 1H and 27.8 for 13C nuclei. The marked DNP results show the feasibility of these biradicals for hyperpolarization.
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Affiliation(s)
- Kazunobu Sato
- Department of Chemistry and Molecular Materials Science, Graduate School of Science , Osaka City University , 3-3-138 Sugimoto , Sumiyoshi-ku, Osaka 558-8585 , Japan
| | - Rei Hirao
- Department of Chemistry and Molecular Materials Science, Graduate School of Science , Osaka City University , 3-3-138 Sugimoto , Sumiyoshi-ku, Osaka 558-8585 , Japan
| | - Ivan Timofeev
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry , Novosibirsk 630090 , Russia.,International Tomography Center SB RAS , Institutskaya 3A , Novosibirsk 630090 , Russia.,Novosibirsk State University , Novosibirsk 630090 , Russia
| | - Olesya Krumkacheva
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry , Novosibirsk 630090 , Russia.,International Tomography Center SB RAS , Institutskaya 3A , Novosibirsk 630090 , Russia.,Novosibirsk State University , Novosibirsk 630090 , Russia
| | - Elena Zaytseva
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry , Novosibirsk 630090 , Russia.,Novosibirsk State University , Novosibirsk 630090 , Russia
| | - Olga Rogozhnikova
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry , Novosibirsk 630090 , Russia.,Novosibirsk State University , Novosibirsk 630090 , Russia
| | - Victor M Tormyshev
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry , Novosibirsk 630090 , Russia.,Novosibirsk State University , Novosibirsk 630090 , Russia
| | - Dmitry Trukhin
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry , Novosibirsk 630090 , Russia.,Novosibirsk State University , Novosibirsk 630090 , Russia
| | - Elena Bagryanskaya
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry , Novosibirsk 630090 , Russia.,Novosibirsk State University , Novosibirsk 630090 , Russia
| | - Torsten Gutmann
- Eduard-Zintl Institute for Inorganic and Physical Chemistry , Technische Universität Darmstadt , Alarich-Weiss-Straße 8 , 64287 Darmstadt , Germany.,Institute of Chemistry and Center for Interdisciplinary Nanostructure Science and Technology , Universität Kassel , Heinrich-Plett Straße 40 , 34132 Kassel , Germany
| | - Vytautas Klimavicius
- Eduard-Zintl Institute for Inorganic and Physical Chemistry , Technische Universität Darmstadt , Alarich-Weiss-Straße 8 , 64287 Darmstadt , Germany
| | - Gerd Buntkowsky
- Eduard-Zintl Institute for Inorganic and Physical Chemistry , Technische Universität Darmstadt , Alarich-Weiss-Straße 8 , 64287 Darmstadt , Germany
| | - Kenji Sugisaki
- Department of Chemistry and Molecular Materials Science, Graduate School of Science , Osaka City University , 3-3-138 Sugimoto , Sumiyoshi-ku, Osaka 558-8585 , Japan
| | - Shigeaki Nakazawa
- Department of Chemistry and Molecular Materials Science, Graduate School of Science , Osaka City University , 3-3-138 Sugimoto , Sumiyoshi-ku, Osaka 558-8585 , Japan
| | - Hideto Matsuoka
- Department of Chemistry and Molecular Materials Science, Graduate School of Science , Osaka City University , 3-3-138 Sugimoto , Sumiyoshi-ku, Osaka 558-8585 , Japan
| | - Kazuo Toyota
- Department of Chemistry and Molecular Materials Science, Graduate School of Science , Osaka City University , 3-3-138 Sugimoto , Sumiyoshi-ku, Osaka 558-8585 , Japan
| | - Daisuke Shiomi
- Department of Chemistry and Molecular Materials Science, Graduate School of Science , Osaka City University , 3-3-138 Sugimoto , Sumiyoshi-ku, Osaka 558-8585 , Japan
| | - Takeji Takui
- Department of Chemistry and Molecular Materials Science, Graduate School of Science , Osaka City University , 3-3-138 Sugimoto , Sumiyoshi-ku, Osaka 558-8585 , Japan.,Research Support Department/University Research Administrator Center, University Administration Division , Osaka City University , 3-3-138 Sugimoto , Sumiyoshi-ku, Osaka 558-8585 , Japan
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