A black-box approach to the construction of metal-radical multispin systems and analysis of their magnetic properties

Kadilenko, Evgeny M.; Gritsan, Nina P.; Tretyakov, E. V.; Fokin, S. V.; Романенко, Г. В.; Bogomyakov, A. S.; Gorbunov, Dmitry; Schollmeyer, Dieter; Baumgarten, Martin; Овчаренко, В. И.

doi:10.1039/d0dt03184d

Cited by 9 publications

(5 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As mentioned above, the polymeric chain consists of repeating blocks containing four paramagnetic species (Scheme 2); and in each block there are two types of exchange interactions of Cu(hfac) 2 with iminoxyl radicals with parameters J 1 and J 2 . To estimate these parameters from the experiment, the dependence of χT versus T (Figure 4) was approximated using custom-designed software 64 and a model magnetic motif in the form of looped chains of n blocks (n = 1−3). The g-factor of the copper ion (g Cu ) was also used as an approximation parameter.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Two Discoveries in One Crystal: σ-Type Oxime Radical as an Unforeseen Building Block in Molecular Magnetics and Its Spatial Structure

Budnikov,

Krylov,

Ushakov

et al. 2023

Inorg. Chem.

Self Cite

View full text Add to dashboard Cite

In the present work, the study of the unusual interaction between copper hexafluoroacetylacetonate and the diacetyliminoxyl radical resulted in two discoveries from different fields: the determination of the oxime radical spatial structure and the introduction of an oxime radical into the field of molecular magnetic material design. Oxime radicals are key plausible intermediates in the processes of oxidative CH-functionalization and in the synthesis of functionalized isoxazolines from oximes. Due to the lack of X-ray diffraction data for oxime radicals, the knowledge about their structure is based mainly on indirect approaches, spectroscopic methods (electron paramagnetic resonance and IR), and quantum chemical calculations. The structure of the oxime radical was determined for the first time by stabilizing the diacetyliminoxyl radical in the form of its complex with copper (II) hexafluoroacetylacetonate (Cu(hfac)2), followed by single-crystal X-ray diffraction analysis. Although oxime radicals are known to undergo oxidative coupling with acetylacetonate ligands in transition-metal complexes, a complex is formed with intact hfac ligands. X-ray diffraction studies have shown that the oxime radical is coordinated with copper ions through the oxygen atoms of the carbonyl groups without the direct involvement of the CN–O• radical moiety. The structure of the coordinated diacetyliminoxyl is in good agreement with the density functional theory (DFT) prediction for free diacetyliminoxyl due to the very weak interaction of the radical molecule with copper ions. Remarkably, both weak ferromagnetic and antiferromagnetic interactions between Cu (II) and oxime radicals have been revealed by modeling the temperature dependence of magnetic susceptibility and confirmed by DFT calculations, rendering diacetyliminoxyl a promising building block for the design of molecular magnets.

show abstract

Section: ■ Results and Discussionmentioning

confidence: 99%

Two Discoveries in One Crystal: σ-Type Oxime Radical as an Unforeseen Building Block in Molecular Magnetics and Its Spatial Structure

Budnikov,

Krylov,

Ushakov

et al. 2023

Inorg. Chem.

Self Cite

View full text Add to dashboard Cite

show abstract

Section: Methodsmentioning

confidence: 99%

“…Accordingly, in this work, the fitting was carried out using a numerical model for magnetic motifs in the form of looped FM chains of N radicals, where N varies from 5 to 12. To simulate the χ(T) × T dependences, we utilized our new customdesigned software 50 with spin-Hamiltonian Moreover, to estimate the accuracy of the previously obtained parameters J, 16,28,40,49 the high-temperature Pade expansion formula 41 was employed too. In both cases, the interaction between radicals of neighboring chains was introduced through the mean field approximation 51 T T = + = .…”

Section: 455-tetramethyl-2-(4-fluorobenzo[d]imidazol-2-yl)-45-dihydro...mentioning

confidence: 99%

Series of Fluorinated Benzimidazole-Substituted Nitronyl Nitroxides: Synthesis, Structure, Acidity, Redox Properties, and Magnetostructural Correlations

et al. 2022

Self Cite

View full text Add to dashboard Cite

A special series of nitronyl nitroxides was synthesized: 2-(benzimidazol-2′-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1Himidazole-3-oxide-1-oxyls mono-, di-, tri-, or tetrafluorinated on the benzene ring. The structure of all paramagnets was unambiguously confirmed by single-crystal X-ray diffraction. It was found that in crystals, the radicals are assembled into chains due to intermolecular H-bonds between the benzimidazole moiety (H-bond donor) and the nitronyl nitroxide group or benzimidazole ring (H-bond acceptor). The magnetic properties of nitronyl nitroxides depend on the type of binding of radicals by H-bonds. The magnetic motif of 4-fluoro-, 5-fluoro-, 4,6-difluoro-, 4,5,6trifluoro-, 4,5,7-trifluoro-, and 4,5,6,7-tetrafluoro-derivatives, as well as the nonfluorinated compound, consists of ferromagnetic chains (J/k B ≈ 20−40 K) formed by the McConnell type I mechanism. In the 5,6-difluoro-and 4,5-difluoro-derivatives, the distances between the paramagnetic centers are large, as a result of which the exchange interactions are weak. According to cyclic voltammetry, paramagnets are oxidized reversibly, while their reduction is a quasi-reversible electron transfer (EC mechanism); experimental redox potentials of radicals correlate well with the calculated values. Quantum chemical assessment of the acidity of benzimidazolylsubstituted nitronyl nitroxides revealed that the introduction of fluorine atoms into the benzene ring enhances the acidity of the paramagnets by more than 5 orders of magnitude.

show abstract

“…To simulate the temperature dependence of the molar magnetic susceptibility, χ(T), in the form of product χ(T) × T, we utilized custom-designed software [82]. For both radicals, the magnetic motifs consist of stacks of exchange-coupled radicals.…”

Section: Computational Detailsmentioning

confidence: 99%

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

et al. 2023

Self Cite

View full text Add to dashboard Cite

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.

show abstract

A black-box approach to the construction of metal-radical multispin systems and analysis of their magnetic properties

Abstract: The metal cation-induced transformation of nitronyl-nitroxide diradicals led to formation of the binuclear Mn(ii) and Ni(ii) complexes with six paramagnetic centres, their magnetic properties were analysed using high-level calculations.

Cited by 9 publications

References 33 publications

Two Discoveries in One Crystal: σ-Type Oxime Radical as an Unforeseen Building Block in Molecular Magnetics and Its Spatial Structure

Two Discoveries in One Crystal: σ-Type Oxime Radical as an Unforeseen Building Block in Molecular Magnetics and Its Spatial Structure

Series of Fluorinated Benzimidazole-Substituted Nitronyl Nitroxides: Synthesis, Structure, Acidity, Redox Properties, and Magnetostructural Correlations

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

Contact Info

Product

Resources

About