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Temperature-Dependent Antiferromagnetic Exchange along 1D Linear Regular Chains of the Phthalonitrile Blatter Radical
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1,3-Diphenyl-1,4-dihydrobenzo[e][1,2,4]triazin-4-yl-6,7-dicarbonitrile is an exceptionally stable electron-deficient organic radical with promising potential to be used as a building block in a range of electronic and spintronic materials. The radical has a fully reversible one-electron redox and is highly delocalized, with some spin density reaching as far as the nitrile groups. Two polymorphs, α and β, were identified and characterized by single-crystal X-ray diffractometry. Both polymorphs form one-dimensional (1D) π stacks. However, while in polymorph α radicals are located at evenly interplane distances (3.366 Å), in polymorph β radicals are located at alternate interplane distances (3.182 and 3.318 Å). Magnetic susceptibility measurements for polymorph α indicate strong antiferromagnetic interactions along the 1D regular chain. Magnetic susceptibility data cannot be fully fitted to the Bonner and Fischer model for the 2–300 K temperature range. The steeper rise in paramagnetism above 80 K was rationalized by temperature-dependent antiferromagnetic exchange interactions between radicals within the 1D π stacks, which is indeed supported by Density Functional Theory (DFT) calculations. A microscopic study of the magnetic topology of polymorph α together with the interpretation of its magnetic experimental data was pursued by using a First-Principles Bottom-Up approach. Minuscule changes in crystal packing upon changing the temperature significantly affect the magnetic interaction between spin-containing moieties. Temperature, therefore, is the key player in rationalizing the magnetism in polymorph α.
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CHRYSOCHOS, N., et al. Temperature-Dependent Antiferromagnetic Exchange along 1D Linear Regular Chains of the Phthalonitrile Blatter Radical. Crystal Growth & Design. 2023. Vol. 23, num. 12, pags. 8939-8952. ISSN 1528-7483. [consulted: 27 of May of 2026]. Available at: https://hdl.handle.net/2445/218760