Search

Reactions of CuCl2·2H2O or Cu(NO3)2·6H2O with 3,5-diiodosalicylic acid (DISA) in the presence of different amines result in structurally diverse products.

Functionalized perfluoroalkyl lithium β-diketonates (LiL) react with lanthanide(III) salts (Ln = Eu, Gd, Tb, Dy) in methanol to give heterobimetallic Ln-Li complexes of general formula [(LnL3)(LiL)(MeOH)]. The length of fluoroalkyl substituent in ligand was found to affect the crystal packing of complexes. Photoluminescent and magnetic properties of heterobimetallic β-diketonates in the solid state are reported. The effect of the geometry of the [LnO8] coordination environment of heterometallic β-diketonates on the luminescent properties (quantum yields, phosphorescence lifetimes for Eu, Tb, Dy complexes) and single-ion magnet behavior (Ueff for Dy complexes) is revealed.

The coordination diversity of a novel N4-ligand and its sodium complex toward cobalt(ii) ions was studied.

Fast crystallization of the monoclathrochelate cobalt(II) intracomplex [Co(Cl

New coordination compounds of copper(II) halides with 2-(3,5-dimethylpyrazol-1-yl)benzimidazole (L) are synthesized: CuLCl2 (I), [CuL2Cl]Cl⋅H2O⋅C2H5OH (II), and CuLBr2 (III). The compounds are characterized by IR spectroscopy, X-ray diffraction analysis, and static magnetic susceptibility. The crystal structure of compound II is determined by X-ray structure analysis (CIF file CCDC no. 2043452). The cytotoxic properties of ligands L and complexes I and II are studied.

Magnetic topological insulators (MTIs) have recently become a subject of poignant interest; among them, Z

The reactions of monomeric [(dpp-Bian)M(thf)4] (M = Ca (1a), Sr (1b); dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) with 4,4'-bipyridyl (4,4'-bipy) proceed with electron transfer from dpp-Bian2- to 4,4'-bipy0 to afford calcium and strontium complexes containing simultaneously radical-anionic dpp-Bian- and 4,4'-bipy- ligands. In tetrahydrofuran (thf) the reactions result in 1D coordination polymers [{(dpp-Bian)M(4,4'-bipy)(thf)2}·4thf]n (M = Ca (2a), Sr (2b)), while in a thf/benzene mixture the reaction between 1a and 4,4'-bipy affords the 2D metal-organic framework [{(dpp-Bian)Ca(4,4'-bipy)2}·2thf·2C6H6]n (3). The structures of compounds 2a,b and 3 have been determined by single-crystal X-ray analyses. The presence of the ligand-localized unpaired electrons allows the use of ESR spectroscopy for characterization of the compounds 2a,b and 3. DFT calculations of model calcium complexes with the dpp-Bian, 4,4'-bipy, and thf ligands confirm the energetically favorable open-shell configurations of the molecules bearing the 4,4'-bipy fragments. The magnetic susceptibility measurements confirm the presence of two unpaired electrons per monomeric unit in 2a,b and 3. The thermal stability of compounds 2a,b and 3 was studied by thermogravimetric analysis (TGA). To the best of our knowledge, 3 is the first MOF simultaneously containing two different paramagnetic bridging ligands inside the framework.

Five-coordinate iron(III) complexes, (ImPh)2FeX (X = Cl (I), Br (II), I (III), N3 (IV)) containing two bidentate Schiff bases (N-benzylidene-2-hydroxy-3,5-di-tert-butylaniline (ImPh)H) and a halogen atom/azide group in the coordination sphere were synthesized and characterized in detail. According to the magnetic susceptibility measurements for polycrystalline samples of I–IV and Mossbauer spectroscopy data in the 2–300 K range, the complexes contain a high-spin metal ion (HS Fe3+, d5, SFe = 5/2). Compounds I–IV are stable in the crystalline state in the absence of oxygen or air moisture; however, in solution, they undergo symmetrization, resulting in the formation of the tris-ligand complex (ImPh)3Fe (V), which was also synthesized by the reaction (ImPh)H and FeCl3 (3 : 1). Unlike five-coordinate complexes I–IV, six-coordinate complex V contains low-spin iron(III) ion (LS Fe3+, d5, SFe = 1/2). The molecular structure of I was determined by X-ray diffraction (CIF file CCDC no. 1996527).

The Cu(hfac)2 complex with a paramagnetic ligand 2-(1-ethyl-imidazol-5-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl (L5Et) was synthesized in the form of two polymorphs: α-[Cu(hf...

Thermally stable organic diradicals with a triplet ground state along with large singlet-triplet energy gap have significant potential for advanced technological applications. A series of phenylene-bridged diradicals with oxoverdazyl and nitronyl nitroxide units were synthesized via a palladium-catalyzed cross-coupling reaction of iodoverdazyls with a nitronyl nitroxide-2-ide gold(I) complex with high yields. The diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 °C. For the diradicals, both substantial AF (ΔEST ≈-64 cm-1 ) and FM (ΔEST ≥25 and 100 cm-1 ) intramolecular exchange interactions were observed. The sign of the exchange interaction is determined both by the bridging moiety (para- or meta-phenylene) and by the type of oxoverdazyl block (C-linked or N-linked). Upon crystallization, diradicals with the triplet ground state form unique one-dimensional exchange-coupled chains with strong intra- and weak inter-diradical ferromagnetic coupling.

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.

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.

Heterospin polymeric complexes based on Ni(II) and Co(II) hexafluoroacetylacetonates and deprotonated iminonitroxide, 2-(2-hydroxy-5-nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl (HL), were synthesized. The [MII(Hfac)L2]– anions (Hfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate) in the complexes are linked into 1D–3D polymers by Na+, K+, Rb+, or Cs+ cations (I–V). An X-ray diffraction study of MI[MII(Hac)L2] ∙ n(Me2CO) (n = 0–2.5) demonstrated that the polymer structural motif is determined by alkali metal cation (CIF files CCDC nos. 1974139–1974143 for I–V). According to magnetic measurements, ferromagnetic interactions in the {LML} exchange clusters predominate in the solid phase, which gives rise to increase in the effective magnetic moment with decreasing temperature.

Metal tris-o-dioxolene (o-quinone, o-semiquinone, and catecholate) complexes represent an interesting and vivid model system for the demonstration of a relationship between the structure and magnetic properties when considering a series of objects of the same type. After publishing the reviews [1, 2], the metal tris-o-dioxolene complexes containing the symmetric 3,6-di-tert-butyl-o-benzoquinone derivatives with substituents in positions 4 and 5 are described in a number of works. In addition, some earlier unpublished structures of the complexes of this type are reviewed. The substituents in the lateral chains enhance the steric protection of the metal center and, as a consequence, result in the formation of coordination polyhedra uncharacteristic of the tris(dioxolene) complexes, such as a trigonal prism. In turn, the distortion of the structure affects the magnetic properties of the complexes. Only the complexes with the derivatives of sterically hindered o-quinones, 3,5- and 3,6-di-tert-butyl-o-benzoquinones, are considered in the present review. On the one hand, bulky tert-butyl groups prevent the formation of direct intermolecular contacts and, on the other hand, prevent organic reactions to occur at the benzoquinone cycle.

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)].

The interaction of Cu(acF6)2 with the stable imino nitroxide 2-(pyridin-3-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl (ImN-mPy) at a ratio of 2:1 led to the formation of a new complex [...

The synthesis, crystal structure, thermal stability, porosity and magnetic properties of three new layered coordination polymers [(M2(pQ)3)·4DMAA]n (M3+ = La3+ (1), Pr3+ (2), Nd3+ (3); pQ2− – the dianionic form of 2,5-dihydroxy-3,6-di-tert-butyl-para-quinone; DMAA = N,N′-dimethylacetamide) are reported. The coordination polymers obtained were investigated by solid-state electrochemistry which demonstrates multistep one-electron transformations caused by the presence of redox-active dioxolene ligands.

An interaction of M(hfac)2 (M = Mn or Ni) with N-(bis(4,4,5,5-tetramethyl-3-oxido-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)methylene)-2-methyl-propan-2-amine oxide (a nitronyl nitroxide diradical with theC[double bond, length as m-dash]N(O)-tert-Bu coupler) was investigated under various conditions. It was found that prolongation of reaction time caused transformation of the initial diradical into new diradicals with the uniqueC[double bond, length as m-dash]N-OH coupling unit and formation of binuclear Mn(ii) and Ni(ii) complexes, which were characterized by X-ray diffraction analysis. The resulting binuclear heterospin complexes have a complicated magnetic structure with six paramagnetic centers and a number of exchange interaction channels between them, as well as between neighboring complexes. To adequately describe the magnetic properties of these complexes, high-level ab initio calculations of their electronic structure and parameters of the spin-Hamiltonian were carried out. The accuracy of the conventional broken-symmetry density functional theory approach in the calculation of the exchange interaction parameters was also verified.

This paper reveals and describes the features of NicoreAushell nanoparticles’ magnetic properties. Their activation energy of monodomain thermal relaxation (5.1 × 10–20 J) and constant of magnetic ...

By the metal salt metathesis reaction between tin(IV) bis-o-iminobenzosemiquinonates imSQi−Pr2SnCl2 (1) or imSQMe2SnCl2 (2) (where imSQi-Pr – radical-anion of N-2,6-di-iso-propylphenylsubstituted o-iminobenzoquinone, imSQMe - radical-anion of N-2,6-dimethylphenylsubstituted o-iminobenzoquinone) and an excess of sodium azide, potassium isocyanate or potassium thiocyanate new hexacoordinated tin(IV) bis-o-iminobenzosemiquinonates imSQi−Pr2SnX2 (3, 5 and 7) and imSQMe2SnX2 (4, 6 and 8) (where X - azide, isocyanate or thioisocyanate group) were synthesized and characterized including X-ray diffraction analysis. The magnetic susceptibility measurements for new compounds 2–8 and related previously known complexes imSQi−Pr2SnX2 (X = Me (9), Br (11), I (12)) were performed. All tin(IV) bis-o-iminobenzosemiquinonates were found to be characterized by antiferromagnetic exchange interaction between unpaired electrons of two imSQ ligands independently on the X substituent nature. However known tin(IV) complexes imSQi−Pr2Sn(Me)2 (9) and imSQi−Pr2Sn(Ph)2 (10) containing organic ligands bonded to the metal atom demonstrate quite strong magnetic interaction compared with complexes including halide or pseudohalide substituents. Due to their great kinetic stability the diradical tin(IV) derivatives obtained have a possible application as potential components for molecular electronics and spintronics, lithium batteries, nonlinear optics and magnetic materials.

It is found that on cooling from 295 K to 100 K, [Fe(hfac)2(THF)2] crystals undergo reversible phase transitions during which their symmetry changes and one of the unit cell parameters doubles.

A series of heterospin bis-o-semiquinone cobalt, nickel, and copper complexes (4-TEMPO-oxy-3,6-di-tert-butyl-o-benzoquinone derivatives) is synthesized: (DMSO)Cu(4-TEMPO-O-3,6-DBSQ)2 (I), (THF)2Ni(4-TEMPO-O-3,6-DBSQ)2 (II), (Py)2Ni(4-TEMPO-O-3,6-DBSQ)2 (III), and (Py)2Ni(4-TEMPO-O-3,6-DBSQ)2 (IV) (4-TEMPO-O-3,6-DBQ is 4-(3,6-di-tert-butyl-1,2-dioxocyclohexa-3,5-dien-4-yloxy)-2,2,6,6-tetramethylpiperidine-1-oxyl 4-oxy-2,2',6,6'-tetramethylpiperidine-1-oxyl). All complexes are characterized by elemental analysis, IR spectroscopy, magnetochemistry, and EPR. The structure of complex I is determined by X-ray diffraction analysis (CIF file CCDC no. 1882878). The coordination polyhedron of the copper atom in the molecular structure of the Cu(II) bis-o-semiquinone complex with dimethyl sulfoxide (DMSO) is a distorted tetragonal pyramid, whose equatorial plane contains the o-semiquinone ligands, and the DMSO molecule occupies the apical position. The magnetic properties of complexes I–IV are consistent with their compositions and structures. The magnetic behavior of copper complex I and nickel complexes II and III is determined by the balance of two contributions: metal–ligand ferromagnetic exchange interaction and ligand–ligand antiferromagnetic interaction. The temperature dependence of the magnetic moment of cobalt complex IV shows the redox isomeric transformation conjugated with the spin transition, which is characteristic of complexes of this type. No participation of nitroxyl radical centers is observed in intermolecular coordination.

Ionic complexes of the composition [LnL2(NO3)2]2[Ln(NO3)5]3Me2CO (Ln = Sm (1), Eu (2), Tb (3), Dy (4)) with an optically active ligand L containing 1,10-phenanthroline and (+)−3-carene moieties are synthesized. According to the X-ray crystallographic data, the crystal structure of compound 2 is composed of complex [EuL2(NO3)2]+ cations (N6O4 polyhedron) and complex [Eu(NO3)5]2− anions (O10 polyhedron), and also Me2CO molecules. The L and NO3 ligands perform both tridentate and bidentate chelating functions respectively. Complexes 1–4 are isostructural and crystallize in the non-centrosymmetric space group P1; their magnetic properties are studied in the temperature range 2–300 K. The μeff values for 1–4 at 300 K are 3.14 μB, 6.08 μB, 16.76 μB, and 18.30 μB respectively and are typical of Ln3+ ions. For complex 3 significant anisotropy results in a nonlinear field dependence of the magnetization at 2 K. Complexes 1–4 exhibit metal-centered orange (Sm3+), red (Eu3+), green (Tb3+), and yellow (Dy3+) luminescence in the solid state at room temperature. Luminescence quantum yield decreases for solid samples in the order 2 > 1 > 3 ≈ 4.

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.