Preparation and characterization of magnetic and magnetophotonic materials based on organic free radicals

Tretyakov, Evgeny

doi:10.1016/b978-0-443-13346-6.00005-1

Cited by 5 publications

(1 citation statement)

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“…Substituted 1,4-dihydrobenzo[ e ][1,2,4]triazin-4-yl radicals (so-called Blatter radicals) were first described in the 60s and had not attracted much attention , until the work of F. Wudl et alwho showed that the 1,3-diphenyl-1,4-dihydrobenzo[ e ][1,2,4]triazin-4-yl radical gives a pressure-sensitive semiconductor with TCNQand the papers of Neugebauer and co-workers, who reported a Blatter radical having antiferromagnetic (AF) short-range ordering. , After these key reports, there has been enormous growth in the number of research articles on the synthesis and applications of 1,4-dihydrobenzo[ e ][1,2,4]triazin-4-yls as near-infrared photodetectors, broadband emitting materials, photoconductive discotic mesogens, , and initiators of controlled radical polymerization. , Due to their excellent stability in air and water, substituted Blatter radicals are actively used as building blocks for the creation of magnetic bistable materials, , high-spin polyradicals and biradicaloids, − molecule-based electronics, and magnets. − Given that 1,4-dihydrobenzo[ e ][1,2,4]triazin-4-yl radicals can be transferred through a vapor phase to form long-lived thin films, , active research is underway regarding their use in the creation of so-called pure organic “spin interfaces” for application in spintronics. − …”

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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