Polyfluorinated organic paramagnets

Tretyakov, E. V.; Fedyushin, Pavel

doi:10.1007/s11172-021-3346-5

Cited by 15 publications

(4 citation statements)

References 77 publications

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“…Hence, the introduction of F atoms into 1,4-dihydrobenzo[ e ][1,2,4]triazin-4-yls can be an effective way to influence intermolecular magnetic couplings. In the current paper, following this approach and as part of our systematic exploration of the “structure–property” relations characteristic of organic polyfluorinated radicals, − we report the synthesis, structure, and complete characterization of polyfluorinated Blatter radicals, namely, 1-(2,3,4-trifluorophenyl)-3-phenyl-1,4-dihydrobenzo[ e ][1,2,4]triazin-4-yl ( 2a ) and 1-(2,3,5,6-tetrafluorophenyl)-3-phenyl-1,4-dihydrobenzo[ e ][1,2,4]triazin-4-yl ( 2b ). Moreover, we performed SQUID magnetometry of 2c and analyzed the magnetic structural correlations inherent in the entire series of compounds 1a – c and 2a – c .…”

Section: Introductionmentioning

confidence: 99%

Polyfluorophenyl-Substituted Blatter Radicals: Synthesis and Structure–Property Correlations

Gulyaev,

Serykh,

Gorbunov

et al. 2024

Crystal Growth & Design

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Blatter radicals are extremely stable organic electrondeficient paramagnets having good potential as a spin-bearing building block in diverse applications. The packing mode and molecular conformation of such radicals are appropriate for attaining distinctive magnetic and electronic properties. Herein, within the framework of systematic exploration of the "structure−property" correlations inherent in fluorinated Blatter radicals, 1-(2,3,4trifluorophenyl)-(2a) and 1-(2,3,5,6-tetrafluorophenyl)-3-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (2b) were synthesized and completely characterized. The crystal structure of both radicals 2a and 2b was found to consist of two different centrosymmetric dimers with relatively short intermolecular distances between atoms of the benzotriazinyl moieties. SQUID magnetometry in the range of 2− 300 K revealed that crystals of the two radicals, just as crystals of previously synthesized 1-(pentafluorophenyl)-3-phenyl-1,4dihydrobenzo[e][1,2,4]triazin-4-yl (2c), are dominated by rather strong antiferromagnetic interactions. For the two dimer types, spin-unrestricted broken-symmetry DFT calculations predicted similar parameters J differing by less than 20%. Subsequent fitting of χT vs T dependences using theoretically predicted magnetic motifs resulted in equal values of J for two types of dimers and yielded the following best-fit J/k B parameters: −156.4 ± 0.8 K for 2a, −230 ± 3 K for 2b, and −58.3 ± 0.6 K for 2c. For comparison, in the corresponding nonfluorinated radical (1a), only weak intermolecular interactions were observed (J/k B = −2.2 ± 0.2 K). By contrast, previously studied radicals 1b and 1c (containing two fluorine atoms) are dominated by strong antiferromagnetic interactions (J/k B = −292 ± 10 and −222 ± 17 K, respectively). The reason for the difference in magnetic properties of 1a and fluorinated radicals is that the introduction of fluorine atoms into the phenyl substituent in 1a has a considerable effect on its electrostatic potential, thereby leading to changes in the crystal structure and in bulk magnetic properties.

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Section: Introductionmentioning

confidence: 99%

Polyfluorophenyl-Substituted Blatter Radicals: Synthesis and Structure–Property Correlations

Gulyaev,

Serykh,

Gorbunov

et al. 2024

Crystal Growth & Design

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“…In a series of other works, a trifluoromethyl group was introduced to the C7 position of the Blatter radical to give radicals with significantly improved chemical stability [38,39]. Herein, as part of our increasing interest in "structure-property" correlations inherent in fluorinated organic radicals [40][41][42][43][44][45][46][47][48][49][50][51][52], we report synthesis, structure and complete characterization of novel difluorophenyl-substituted Blatter radicals, namely 1-(3,4-difluorophenyl)-3-phenyl-1,4-dihydrobenzo[e] [1,2,4]triazin-4-yl (1a) and 1-(2,4-difluorophenyl)-3-phenyl-1,4-dihydrobenzo[e] [1,2,4]triazin-4-yl (1b).…”

Section: Introductionmentioning

confidence: 99%

Effects of Difluorophenyl Substituents on Structural, Redox, and Magnetic Properties of Blatter Radicals

et al. 2023

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Blatter radicals 1-(3,4-difluorophenyl)-(1a) and 1-(2,4-difluorophenyl)-3-phenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl (1b) were prepared in good yields through oxidation of the corresponding amidrazones using MnO2 in dry CH2Cl2. Cyclic voltammetry showed that both radicals are oxidized and reduced chemically and electrochemically reversibly in accordance with −1/0 and 0/+1 processes. EPR spectroscopy indicated that spin density is mainly delocalized on the triazinyl moiety of the heterocycle. The structure of all paramagnets was unambiguously confirmed by single-crystal X-ray diffraction, and two different 1D chains of alternating radicals were identified. 3,4-difluorophenyl-derivatives 1a are packed into columns composed of two kinds of alternating centrosymmetric dimers, having comparatively short intermolecular distances. In crystals of 2,4-difluorophenyl-derivative 1b, the parallel arrangement of bicyclic moieties and phenyl rings favors the formation of 1D regular chains wherein the radicals are related by translation parallel to the crystallographic stacking axis. Magnetic susceptibility measurements in the 2–300 K region showed that in crystals of the radicals, strong antiferromagnetic interactions are dominant. Subsequent fitting of the dependence of χT on T with 12-membered looped stacks gave the following best-fit parameters: for 1a, g = 2.01 ± 0.05, J1/kB = −292 ± 10 K (according to BS-DFT calculations J2 = 0.12 × J1 and J3 = 0.61 × J1); for 1b, g = 2.04 ± 0.01 J1/kB = −222 ± 17 K. For comparison, in a nonfluorinated related radical, there are only very weak intermolecular interactions along the columns (J/kB = −2.2 ± 0.2 K). These results illustrate the magnitude of the influence of the difluorophenyl substituents introduced into Blatter radicals on their structure and magnetic properties.

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“…In a preceding paper, we investigated the influence of step-by-step fluorination of different paramagnetic systems on their structure and magnetism [14][15][16]. The motivation was that the introduction of fluorine atom(s) into molecules alters physical and chemical properties of the compounds because of fluorine's electronegativity, its low polarisability and high bond strength [17].…”

Section: Introductionmentioning

confidence: 99%

“…The complexation reaction of [Mn(hfac) 2 ] with these radicals under identical conditions led to the formation of complexes of dimer structure, head-to-head chain-polymeric structure or head-to-tail chain-polymeric structure depending on the structure of the fluorinated alkyl substituent. Magnetic analyses showed that there is a strong antiferromagnetic interaction between the Mn(II) ion and the directly coordinated N-O group in the high-temperature region and weak ferro-or antiferromagnetic exchange interactions below 100 K. In a preceding paper, we investigated the influence of step-by-step fluorination of different paramagnetic systems on their structure and magnetism [14][15][16]. The motivation was that the introduction of fluorine atom(s) into molecules alters physical and chemical properties of the compounds because of fluorine's electronegativity, its low polarisability and high bond strength [17].…”

Section: Introductionmentioning

confidence: 99%

An Influence of Fluorinated Alkyl Substituents on Structure and Magnetic Properties of Mn(II) Complexes with Pyrazolyl-Substituted Nitronyl Nitroxides

Kudryavtseva,

Serykh,

Ugrak

et al. 2023

Crystals

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New complexes of manganese(II) hexafluoroacetylacetonate [Mn(hfac)2] with 2-(1-R-3-pyrazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl (R = CHF2, CH2CH2F, CH2CHF2 or CH2CF3) were synthesised and characterised structurally and magnetically. All complexes were prepared under similar conditions. Nonetheless, their crystal structures were considerably different. Depending on the structure of fluorinated alkyl substituent R, the complexation reaction led to complexes of three types: chain-polymeric complexes with the head-to-head or head-to-tail motif and complexes of molecular structure. All complexes show strong antiferromagnetic behaviour in a high-temperature region (150–300 K) and weak ferro- or antiferromagnetic exchange interactions at low temperatures. The stronger antiferromagnetic exchange, −101.7 ± 1.5 or −136 ± 10 cm−1, −82.3 ± 1.3 cm−1 and −87.4 ± 1.3 cm−1, was attributed to the magnetic interaction in three- or two-spin clusters: {>N∸O–Mn2+–O∸N<} or {>N∸O–Mn2+}, respectively. The weaker antiferromagnetic interaction, −0.005, between three-spin clusters or ferromagnetic interactions, 0.18–0.81 cm−1, between two-spin clusters are realised through the pyrazole ring or intermolecular contacts.

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Polyfluorinated organic paramagnets

Cited by 15 publications

References 77 publications

Polyfluorophenyl-Substituted Blatter Radicals: Synthesis and Structure–Property Correlations

Polyfluorophenyl-Substituted Blatter Radicals: Synthesis and Structure–Property Correlations

Effects of Difluorophenyl Substituents on Structural, Redox, and Magnetic Properties of Blatter Radicals

An Influence of Fluorinated Alkyl Substituents on Structure and Magnetic Properties of Mn(II) Complexes with Pyrazolyl-Substituted Nitronyl Nitroxides

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