Ferro- or antiferromagnetism? Heisenberg chains in the crystal structures of verdazyl radicals

2018 ◽  
Vol 20 (35) ◽  
pp. 22902-22908 ◽  
Author(s):  
Steffen Eusterwiemann ◽  
Carsten Doerenkamp ◽  
Thomas Dresselhaus ◽  
Oliver Janka ◽  
Constantin G. Daniliuc ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Exchange Coupling ◽  
Verdazyl Radicals ◽  
Verdazyl Radical ◽  
Heisenberg Chains

Quantum chemically calculated exchange-coupling maps are employed to design verdazyl radical crystals with either ferromagnetic or antiferromagnetic behaviour.

Strong Ferromagnetic and Antiferromagnetic Exchange Coupling between Transition Metals and Coordinated Verdazyl Radicals

2000 ◽  
Vol 122 (33) ◽  
pp. 8077-8078 ◽  
Author(s):  
Robin G. Hicks ◽  
Martin T. Lemaire ◽  
Laurence K. Thompson ◽  
Tosha M. Barclay
Keyword(s):  
Transition Metals ◽  
Exchange Coupling ◽  
Antiferromagnetic Exchange ◽  
Verdazyl Radicals

Exploiting verdazyl radicals to assemble 2p–3d–4f one-dimensional chains

2015 ◽  
Vol 44 (12) ◽  
pp. 5364-5368 ◽  
Author(s):  
Chao Wang ◽  
Shuang-Yan Lin ◽  
Wei Shi ◽  
Peng Cheng ◽  
Jinkui Tang
Keyword(s):  
Transition Metal ◽  
One Dimensional ◽  
Efficient Approach ◽  
Verdazyl Radicals ◽  
Verdazyl Radical

Exploiting the coordination abilities of an isopropyl substituted verdazyl radical to transition metal and lanthanide(iii) ions represents an efficient approach to produce a system incorporating 2p, 3d and 4f spin carriers.

Crystal structures, magnetic properties, and absorption spectra of nickel(II) thiocyanato complexes: a comparison of different coordination geometries

2003 ◽  
Vol 81 (11) ◽  
pp. 1168-1179 ◽  
Author(s):  
Bruno Larue ◽  
Lan-Tâm Tran ◽  
Dominique Luneau ◽  
Christian Reber
Keyword(s):  
Magnetic Properties ◽  
Crystal Structures ◽  
Absorption Spectra ◽  
Exchange Coupling ◽  
Molecular Magnetism ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Space Group ◽  
Trigonal Bipyramidal ◽  
Ferromagnetic Interactions

Thiocyanatonickel(II) compounds with composition {(AsPh4)2[Ni(NCS)4]} 1, {(Cat)[Ni(NCS)4]} 2, {(AsPh4)4 [Ni2(NCS)8]} 3, {(Cat)2[Ni2(NCS)8]·2CH3NO2} 4, and {(Et4N)4[Ni(NCS)6]} 5 (Cat2+ = (p-xylylenebis(triphenyphosphonium))2+) were prepared. The crystal structures of compounds 1, 3, and 4 were determined. Compound 1 crystallizes in the monoclinic C2/c space group with a = 22.761(2) Å, b = 15.055(1) Å, c = 15.054(1) Å, β = 108.915(1)°, V = 4879.9(6) Å3, and Z = 4. Compound 3 crystallizes in the triclinic P–1 space group with a = 11.2183(6) Å, b = 14.2551(8) Å, c = 16.629(1) Å, α = 79.326(1)°, β = 73.605(1)°, γ = 75.496(1)°, V = 2451.0(2) Å3, Z = 2. Compound 4 crystallizes in the monoclinic P21/n space group with a = 13.1148(9) Å, b = 27.128(2) Å, c = 14.882(1) Å, β = 114.056(2)°, V = 4834.8(6) Å3, Z = 4. The magnetic properties of compounds 1-4 were studied over the 2–300 K temperature range. Compounds 1 and 2 with monometallic [Ni(NCS)4]2– complex units have similar magnetic properties, in agreement with nickel(II) ions in pseudo-tetrahedral environments. Compounds 3 and 4 with bimetallic [Ni2(NCS)8]4– complex units exhibit magnetic properties, which are indicative of Ni(II)–Ni(II) ferromagnetic interactions with zero-field splitting effects caused by the pseudo-square-pyramidal or pseudo-trigonal-bipyramidal coordination environments of the nickel(II) ion in compounds 3 and 4, respectively. The structures and magnetic results for all compounds are correlated with NIR–UV–vis absorption spectra.Key words: nickel(II) thiocyanato complexes, crystal structures, paramagnetism, molecular magnetism, exchange coupling, absorption spectroscopy.

scholarly journals Syntheses, spectroscopy, and crystal structures of 3-(4-bromophenyl)-1,5-diphenylformazan and the 3-(4-bromophenyl)-1,5-diphenylverdazyl radical and the crystal structure of the by-product 5-anilino-3-(4-bromophenyl)-1-phenyl-1H-1,2,4-triazole

2018 ◽  
Vol 74 (3) ◽  
pp. 292-297 ◽  
Author(s):  
Gregor Schnakenburg ◽  
Andreas Meyer
Keyword(s):  
Crystal Structure ◽  
Crystal Structures ◽  
Organic Compounds ◽  
Spectroscopic Data ◽  
Structural Data ◽  
The Other ◽  
Side Product ◽  
Axis Direction ◽  
Verdazyl Radical ◽  
First Time

The title compounds, C19H15BrN4, C20H16BrN4and C20H15BrN4, are nitrogen-rich organic compounds that are related by their synthesis. The verdazyl radical, in which stacking leads to antiferromagnetic interactions, was reported previously [Iwaseet al.(2013).Phys. Rev. B,88, 184431]. For this compound, improved structural data and spectroscopic data are presented. The other two compounds have been crystallized for the first time and form stacks of dimers, roughly along thea-axis direction of the crystal. The formazan molecule shows signs of rapid intramolecular H-atom exchange typical for this class of compounds and spectroscopic data are provided in addition to the crystal structure. The triazole compound appears to be a side-product of the verdazyl synthesis.

scholarly journals SYNTHESIS OF 1,5-DIPHENYL-3-ARYLVERDAZILS

2017 ◽  
Vol 61 (1) ◽  
pp. 23 ◽  
Author(s):  
Yuliya V. Tsebulayeva ◽  
Margarita K. Pryanichnikova ◽  
Boris S. Tanaseichuk
Keyword(s):  
Spin Density ◽  
Electron Donor ◽  
Phenyl Ring ◽  
Reaction Centers ◽  
Verdazyl Radicals ◽  
Ch Acids ◽  
Verdazyl Radical ◽  
Phenyl Rings ◽  
Potassium Hydrogen ◽  
Density Values

The reaction between verdazyls and CH-acids was studied for checking common views on the stable radicals reactivity which is usually associated with the spin density values of the reaction centers and its alterations due to the influence of substituents. The synthesis of row l,5-diphenyl-3-arylverdazyls that contains the different types of substituents in the phenyl rings that are situated at C3 verdazyl radical atom was carried out for this purpose. This also includes the previously non-described 1,5-diphenyl-3-(4-hydroxyl)phenyl-, 1,5-diphenyl-3-(4-bromo)phenyl-, 1,5-diphenyl-3-(3- nitro)phenylverdazyls. In this case, the availability and nature of the substituents in the phenyl rings at C3 verdazyl radical atom may not be affected by the change in the spin density values on the N2 and N4 nitrogen atoms that are verdazyl radicals’ reaction centers. The synthesis of verzdazyls was carried out according to the conventional scheme, on the basis of arylhydrazones. It was observed that during azocoupling reacting of phenyldiazonium chloride with arylhydrazones in the synthesis of formazans the reaction proceeds with a higher yield when the solvent dimethylformamide-pyridine is being used. Transformation of formazans into verdazyl radicals was being carried out at room temperature with formaldehyde exposured to formazan in the presence of potassium hydrogen sulfate under the constant air going through the reactor feed. The availability of substituents in the phenyl ring at C3 formazan atom was increasing reaction time significantly in comparison with 1,3,5- trifenylformazan regardless of the substituent’s nature at C3 formazan atom. During the reaction between 1,5-diphenyl-3-arilverdazyls and CH-acids (acetylacetone and dimedone), it was discovered that the reaction rate depends on both the acidity of the CH-acid (dimedone reacts faster than acetylacetone) and the nature of the substituents situated in phenyl ring at C3 verdazyl atom. At the same time, the electron-donating substituents increase the rate of reaction between verdazyls and CH-acids while electron-donor substituents decrease it. Therefore, as it was formerly reported, when we deal with monochloroacetic acid, the rate of a reaction between verdazyl radicals and CH-acids is increasing in front of the electron-donor substituents and decreasing in front of electron-acceptor substituents. These regularities are not connected with the spin density values of the verdazyls’ reaction centers.Forcitation:Tsebulayeva Yu.V., Pryanichnikova M.K., Tanaseichuk B.S. Synthesis of 1,5-diphenyl-3-arylverdazils. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 23-29

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