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The study is concerned with structural rearrangements in the crystals of heterospin complexes Cu(hfac)2 with nitroxide radicals LR (hfac is hexafluoroacetylacetonate, LR is 2-(1-R-1H-pyrazol-4-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, R is Et or Allyl) induced by increasing pressure from 10−4 to ∼1 GPa in the pressure-transmitting medium. An increase in the external pressure to only ∼0.03 GPa leads to the disappearance of the temperature-induced magnetic anomaly observed for these heterospin crystals under ambient conditions. [ABSTRACT FROM AUTHOR]

The ternary TaIr2B2 boride was prepared by the reaction between iridium and TaB2 powders. It was shown that a choice in favor of any crystal structure of TaIr2B2 boride using only X-ray powder diffraction analysis and single-crystal XRD is rather difficult to make. The DFT calculations were carried out to predict the energetically preferred crystal structure of TaIr2B2. The 11B solid-state NMR spectrum of TaIr2B2 was recorded for the first time. A combination of diffraction and spectroscopic methods, as well as theoretical calculations, allowed us to make clear choice in favor of the triclinic space group for the crystal structure of TaIr2B2. The Vickers microhardness value for TaIr2B2 was found to be 17.9 ± 2.3 GPa, and the ternary TaIr2B2 boride can be considered a hard material. Therefore, the family of hard ternary boride phases got a new member. The coefficients of thermal expansion of TaIr2B2 measured by in situ high-temperature XRD analysis are independent of temperature along the a and b axes, but the CTE along the c axis deviates noticeably at elevated temperatures. The findings for the new ternary TaIr2B2 boride are of interest for the rational design of complex structural materials containing Ta–Ir–B-based components and prediction of their high-temperature behavior. Further research into this ternary boride as well as other iridium-containing ternary borides will provide a tool to solve the problems faced by high-temperature materials science. [ABSTRACT FROM AUTHOR]

Alkali metals form mutinuclear compounds with redox-active singly and doubly reduced derivatives of sterically of hindered о-benzoquinones. Complexes [Na6(Cat)3(THF)7]•4THF, [Na5(Cat)2(SQ)(THF)5], [Na4(SQ)4(THF)4]•THF•C6H14, [Na4(3,5-SQ)4(THF)4], [K4(SQ)4(THF)4]•4THF and [Li3(SQ)3(THF)3]•THF (Cat is catecholate, SQ is semiquinonate) possessing high sensitivity to atmospheric oxygen were synthesized and their structures were determined. Magnetochemical measurements and quantum chemical calculations revealed that variation of the alkali metal and/or change in the structure of the polymetallic core significantly affect the energy of exchange interaction between the unpaired electrons of the paramagnetic ligands framing the polynuclear metal core formed by s-elements. [ABSTRACT FROM AUTHOR]

The interaction of mono- and tetranuclear hexafluoroacetylacetonates [M4(hfac)4(OMe)4(MeOH)4] (where М = Co, Ni) and [Cu4(hfac)4(OMe)4] with spin-labeled nitrophenols - nitronyl nitroxide 2-(2-hydroxy-5-nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (HL1) or with corresponding iminonitroxide (HL2) - is found to lead to the formation of solvates of binuclear complexes: [Co2(hfac)2(L2)2(H2O)2], [Ni2(hfac)2(L1)2(H2O)2], [Ni2(hfac)2(L2)2(H2O)], [Cu2(hfac)2(L1)2]. The magnetochemical analysis reveals that exchange interactions between metal ions and coordinated nitronyl nitroxides are strongly feroomagnetic and result in the compensation of spins. Imino nitroxide L2 substitution for nitronyl nitroxide L1 changes the character of exchange interactions in the heterospin molecule to the ferromagnetic one. [ABSTRACT FROM AUTHOR]

A series of paramagnetic salts of s-elements (Li, Na, K, Rb, Cs) with deprotonated nitroxide radical, 2-(2-hydroxy-5-nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide (L), were synthesized and isolated as crystals. According to X-ray diffraction data, these compounds are polymers of different dimensionality (CCDC nos. 2342497–2342506). As indicated by the results of quantum chemical calculations and magnetic measurements, weak antiferromagnetic exchange interactions predominate in the paramagnetic salts, with the interaction energy decreasing with increasing radius of the alkali metal ion. [ABSTRACT FROM AUTHOR]

A dichlorophenyl substituted nitronyl nitroxide radical 2-(2,6-dichlorophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (L) is prepared, its structure and magnetic properties are studied. It is shown that the interaction of bis(hexafluoroacetylacetonato)copper(II) [Cu(hfac)2] with L leads to the formation of the {[Cu(hfac)2][Cu(hfac)2L2]} heterospin complex whose crystal structure consists of pseudo-polymer chains formed by alternating single-spin [Cu(hfac)2] and three-spin [Cu(hfac)2L2] fragments. It is established that the temperature dependence of magnetic susceptibility of {[Cu(hfac)2][Cu(hfac)2L2]} is determined by ferromagnetic exchange interactions between unpaired electrons of Cu(II) ions and the axially coordinated L in three-spin fragments. [ABSTRACT FROM AUTHOR]

The X-ray diffraction analysis of products of the interaction between hexanuclear manganese pivalate [Mn6O2Piv10(THF)4] and 1,3-di(4′-pyridyl)triazene (LH) shows the possibility of forming 3D metal organic frameworks (MOFs), in which LH acts as di- and tritopic linkers. It is found that ROH (R = Me, Et, i-Pr, n-Bu) alcohols used as a solvent and the reaction temperature have a significant effect on the compositions and structures of the products formed. [ABSTRACT FROM AUTHOR]

Molecular and crystal structures are determined for a series of mixed-ligand mononuclear compounds of lanthanides (Ln) with the 3,6-di(tert-butyl)-1,2-benzoquinone (SQ) anion radical and bidentate nitrogen-containing ligands (L) of the composition [Ln(SQ)3(L)], where Ln is Tb or Dy, L is 2,2′-bipyridine (bipy); Ln is Eu, L is 1,10-phenanthroline (phen) or N,N,N′,N′-tetramethylethylenediamine (tmen). It is confirmed that the introduction of bidentate L significantly increases the stability of lanthanide semiquinolates in both liquid and solid phases. [ABSTRACT FROM AUTHOR]

The reaction of metal hexafluoroacetylacetonates M(hfac)2, where M = Fe, Mn, and Co, with 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) in the inert atmosphere of a dry box is found to yield mixed-ligand complexes [M(hfac)2(3,6-Q)]. When the synthesis is performed under ambient conditions or the [M(hfac)2(3,6-Q)] mother liquor is kept in air in the case of Mn(II) and Co(II), crystals of [M(hfac)2(H2O)2](3,6-Q) aqua complexes precipitate into the solid phase, in which cis-coordinated H2O molecules are hydrogen bonded to o-quinone O atoms. Single crystal X-ray diffraction data for compounds, which correlate with the results of quantum chemical calculations, show that solid [M(hfac)2(3,6-Q)] and [M(hfac)2(H2O)2](3,6-Q), where M = Co(II) and Mn(II), contain initial o-quinone molecules. In the interaction of Fe(hfac)2 with 3,6-Q, there is an intramolecular redox process during which Fe(II) is oxidized to Fe(III) and o-quinone is reduced to the respective semiquinonate radical anion, which leads to the formation of [FeIII(hfac)2(3,6-SQ)]. According to the data of magnetic measurements, a strong antiferromagnetic exchange between high-spin Fe(III) unpaired electrons and SQ provide an almost complete compensation of spin of one of the unpaired electrons of the metal ion by SQ spin. For Co a complex with 3,5-di-tert-butyl-o-benzoquinone [Co(hfac)2(3,5-Q)] is also synthesized and its structure and magnetic properties are studied. The latter prove to be similar to those of [Co(hfac)2(3,6-Q)]. [ABSTRACT FROM AUTHOR]

Molecular and crystal structures of mononuclear lanthanide (Ln) compounds with the 3,6-di(tert-butyl)-1,2-benzoquinone (SQ) radical anion of the composition [Ln(SQ)3(THF)2] (Ln = Pr, Nd, Eu, Tb, Dy), [Ln(SQ)3(Q)], (Ln = Gd, Eu; Q – 3,6-di(tert-butyl)-1,2-benzoquinone), [La(SQ)3(Q)(THF)], [CeIV(SQ)4], [NaLn(SQ)4(THF)3]·0.25C6H14 (Ln = Gd, Tb), [NaLn(SQ)4(Q)(THF)] (Ln = La, Pr) are determined. The study of the magnetic properties of isolated heterospin solid phases reveals that intramolecular antiferromagnetic exchange interactions between unpaired electrons of SQ moieties dominate in them. At T≤2 K [Dy(SQ)3(THF)2] exhibits the properties typical of a metamagnetic compound. [ABSTRACT FROM AUTHOR]

A method for the synthesis of solvates of dinuclear heterospin complexes of bis(hexafluoroacetylacetonato)copper(ii) with 2-(4-methylpyridin-3-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (LMe) and 2-(4-ethylpyridin-3-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (LEt) of the composition [Cu(hfac)2LR]2 · Solv (Solv = benzene, bromobenzene, toluene, o-xylene, p-xylene) was developed. It was found that a decrease in temperature induces structural transformations of the solid phases of the complexes followed by significant changes in the distances between the paramagnetic centers in the intramolecular exchange clusters {Cu2+-O·-} from 2.321 to 1.974 Å. As a result, the temperature dependences of the effective magnetic moment μeff(T) exhibit magnetic features similar to spin transitions. An analysis of the shape of the μeff(T) curves suggested that the magnetic properties of the compounds under study depend primarily on the molecular packing. A comparison of the magneto-structural correlations typical of the [Cu(hfac)2LR]2 · Solv complexes studied in this work with the data obtained earlier for analogous solvates of heterospin polymer chain complexes showed that the spin transition characteristics of the [Cu(hfac)2LR]2 · Solv systems are much less sensitive to the change of the solvent than the corresponding characteristics of the heterospin polymers containing solvate molecules in the interchain space. The magnetic characteristics of the heterospin dimer molecules depend primarily on which cavity between the dimers is filled with solvate molecules. For solvates with monoclinic symmetry, changes in the solvent molecules occupying same-type cavities have almost no effect on the spin transition characteristics in the heterospin exchange cluster. [ABSTRACT FROM AUTHOR]

The structure of heterospin complexes[M(DCA)2L2x]·yH2O, where M = Mn, Co, Ni, Cu, Lx is the nitronyl nitroxide radical; DCA is the dicyanamide anion, y = 0, 1, or 2 is studied. It is found that the nature of[M(DCA)2L2x]·yH2O is characterized by the formation of multiple hydrogen bonds generating ribbons, layers, or frameworks in the crystals. The analysis of magnetostructural correlations by means of band calculations of the electronic structure confirms the occurrence of ferromagnetic exchange between the unpaired electrons of paramagnetic centers in solid [Cu(DCA)2L21]·2H2O when the distances between the copper ion and the coordinated N-O group are short. [ABSTRACT FROM AUTHOR]

Hydrolysis of [M4(hfac)4(MeO)4(MeOH)4] (М = Сo, Ni and hfac is hexafluoroacetylaceton ate) is a convenient way of obtaining polynuclear complexes [Ni7(hfac)6(OH)8(H2O)6]•2H2O, [Co12(hfac)10(OH)14(H2O)8]•2H2O•2MePh, [Co12(hfac)10(OH)14(H2O)4(Me2CO)4]•3PhMe, and [Co12(hfac)10(OH)14(H2O)6(Me2CO)2]•2H2O•2Me2CO, whose structures were confirmed by X-ray analysis. [ABSTRACT FROM AUTHOR]

A mixed ligand complex of Ni(II) with 3-imidazoline nitroxide and iso-propanol [NiL2(i-C3H7OH)2] is sensitive to atmospheric moisture. It is determined that at a high humidity, the air contacts with the mother solution of the compound in iso-propanol with the precipitated [NiL2(i-C3H7OH)2] crystals leads to their spontaneous transformation into [NiL2(H2O)]·i-C3H7OH crystals whose structure is described in the present paper. [ABSTRACT FROM AUTHOR]

The synthesis of a novel nitronylnitroxyl radical 2-(2,5-di(pyridin-4-yl)phenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl (L) and the first Mn(II) complex with it [Mn(NO3)2(L)(H2O)× ×(i-PrOH)] is elaborated and performed. It is found that the complex is formed by polymeric chains in which (NO3)2(H2O)(i-PrOH) fragmentы are linked by L coordinated by N atoms of pyridine rings. The chains are combined into layers by hydrogen bonds between the coordinated water molecules, i-PrOH, and nitrate anions. The layers are joined into a framework by weak C-H⋯O contacts between O atoms of the nitronylnitroxyl fragment and the pyridine C-H group. [ABSTRACT FROM AUTHOR]

Hydrolysis of the 4-nuclear [Cu(hfac)(MeO)]4 complex (where hfac is the hexafluoroacetylacetone ion) can be used as a convenient way to obtain the 11-nuclear complex [Cu11(hfac)10(OH)8(O)2] · 2MePh. The structure of the latter is determined using X-ray diffraction. [ABSTRACT FROM AUTHOR]

The article focuses on a study which demonstrates the potentialities of the time-resolved magnetic field effect (TR MFE) method. It provides details about the radical anions of tetrafluorobenzene and pentafluoroaniline generated by X-ray irradiation of solutions. Information about the fluorescence intensity decay caused by recombination of radical ion pairs is presented.