Synthesis,crystal structure and magnetic properties of a cobalt(II) complex with pyridine-substituted imino nitroxide radicals

The mononuclear Co(im4-py)₄(N₃)₂ complex [im4-py = 2-(p-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl] has been synthesized and structurally characterized. It crystallizes in the triclinic space group Pl¯ with the Co^II ion octahedrally coordinated and bound to four radical ligands through the nitrogen atom of the pyridine rings; the azido groups occupy the apical positions. The complex exhibits weak intramolecular antiferromagnetic interactions between the Co^II ion and the imino nitroxide radicals; intermolecular antiferromagnetic interactions are observed.     

Synthesis,crystal structure and magnetic properties of a nickel(II) complex containing a 2-pyridyl-substituted nitronyl nitroxide

A new complex of formula [Ni(NIT2Py)₂Cl(H₂O)]Cl·2CH₃OH, where NIT2Py is 2-(2′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, was synthesized and characterized structurally and magnetically. The structure consists of a [Ni(NIT2Py)₂Cl(H₂O)]⁺ ion, a chloride anion and two methanol molecules. The nickel(II) ion lies in a distorted octahedral environment; two nitrogen atoms and two oxygen atoms from NIT2Py ligands from the basal plane; one oxygen atom from a water molecule and one chloride anion occupy axial positions. Variable temperature magnetic susceptibility data show that there is strong antiferromagnetic coupling between the nickel(II) ion and nitronyl nitroxide radicals. The results suggest that the sign of the magnetic interaction depends on structural and ligand effects.     

Synthesis, crystal structures, and magnetic properties of a new nickel(II) complex with nitronyl nitroxide

A new nickel(II) complex [Ni(NIT-1′-MeBzIm)₂(H₂O)₂] · ClO₄ · H₂O (NIT-1′-MeBzIm = 2-{2′-[(l′-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) has been prepared and structurally characterized by single-crystal X-ray diffraction. Complex I crystallizes in monoclinic, space group C2/c, Z = 4. Crystal data: C₃₀H₄₆N₈O₁₆ClNi, Mr = 869.06, a = 13.958(3), b = 15.904(4), c = 18.514(5) Å, β = 101.047(3)°. The X-ray analysis reveals that Ni²⁺ ion resides in a distorted octahedron center, the complex was linked by intermolecular hydrogen bonds, resulting in a 2D network configuration. Magnetic investigation indicates the existence of interamolecular interactions is antiferromagnetic with J = ?40.76 cm^?1.     

A new zinc(II) complex containing nitronyl nitroxide radicals: Synthesis, crystal structure, and magnetic properties

A new one-dimensional dicyanamide bridged zinc(II) complex containing nitronyl nitroxide radicals [Zn(Hfac)₂(NIT-1′-MeBzIm)] (NIT-1′-MeBzIm = 2-{2′-[(l′-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, Hfac = hexafluoroacetylacetonate) has been prepared and structurally characterized by single-crystal X-ray diffraction. The complex crystallizes in monoclinic, space group P2₁/c, Z = 4. Crystal data: C₂₅H₂₁F₁₂N₄O₆Zn, Mr = 766.83, a = 12.1812(13) Å, b = 16.8770(18) Å, c = 15.5230(16) Å, β = 98.009(2)°, V = 3160.1(6) ų, ρ _c = 1.612 g/cm³, μ(MoK _α) = 0.893 mm^?1, F(000) = 1540, R = 0.0925 and wR = 0.2652 for 5875 observed reflections with I > 2σ(I). The X-ray analysis reveals that the zinc(II) ion is six-coordinated with a distorted octahedral geometry. These units develop as 1D species by intermolecular hydrogen bonds. Magnetic investigation indicates the existence of weak intermolecular interactions is antiferromagnetic with J = ?1.35 cm^?1, where the spin Hamitonian is defined as H = ?2Σ _i,j J _i,j S _i S within the complex.     

Synthesis, crystal structure, and magnetic properties of a new manganese(II) complex with nitronyl nitroxide

A new manganese(II) complex [MnCl₂(NIT-1′-MeBzIm)₂] · 3H₂O (NIT-1′-MeBzIm = 2-{2′-[(l′-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) has been prepared and structurally characterized by single-crystal X-ray diffraction. The complex crystallizes in monoclinic, space group C2/c, Z = 4. Crystal data: C₃₀H₃₈Cl₂MnN₈O₈, M = 764.52, a = 17.261(3) Å, b = 21.317(4) Å, c = 11.744(2) Å, β = 108.464(2)°. The X-ray analysis reveals that Mn(II) atom is six-coordinated with a distorted octahedral geometry. The complex was linked by intermolecular hydrogen bonds, leading to a 2D network configuration. Magnetic investigation indicates the existence of interamolecular interactions is ferromagnetic with J = 1.11 cm^?1.     

Synthesis,structure and magnetic properties of a Pr(III) complex with chelating nitronyl nitroxide radicals

The synthesis and structure of Pr(III) complex with chelating nitronyl nitroxide radicals of formula [Pr(III)(NIT2Py)₂(NO₃)₃] (NIT2Py?=?2-(2′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) is reported. Pr(III) is ten-coordinate with three bidentate nitrate anions and two radicals. The radical behaves as a bidentate chelating ligand through one oxygen atom of the nitronyl nitroxide group and one nitrogen atom of a pyridine ring. The electronic spectrum for the complex in THF and magnetic susceptibilities from 77–300?K are reported.     

Synthesis and crystal structures of the nickel(II) complex with nitronyl nitroxide

Two nickel(II) complexes [Ni(NIT-l′-MeBzlrn)₂(Dca)₂] (I, II) (NIT-l′-MeBzIm = 2-{2′-[(l′methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-l-oxyl-3-oxide) have been prepared and structurally characterized by single-crystal X-ray diffraction. They are structural epimers. The complexe crystallizes in monoclinic, space group P2₁/n, Z = 4. Crystal data: C₃₄H₃₈N₁₄NiO₄, M _r = 765.49, a = 15.019(3), b = 18.803(4), c = 15.756(3) Å, β = 109.399(3)°, γ = 90° (I); a = 13.934(3), b = 11.046(2), c = 24.570(5) Å, β = 90.024(2)° (II). The X-ray analysis reveals that Ni²⁺ ion resides in a distorted octahedral center. The complex was linked by intermolecular hydrogen bonds, resulting in a ID chain structure for I and a 2D network configuration for II.     

Synthesis,structure, and properties of a 1-D copper(II) complex with nitronyl nitroxide radicals

A 1-D chain complex [Cu(NIT4Py)(IDA)]_∞ (NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and IDA = iminodiacetate) has been prepared and characterized by single-crystal X-ray diffraction, IR, TGA, and magnetic analysis. Each Cu(II) is five-coordinate with distorted square pyramidal geometry. Each IDA bridges two Cu(II) ions via one carboxylate which occupies the axial site of Cu(II), leading to a chain structure composed of Cu(II)-radical cations and IDA anions. In the complex, there exist three magnetic exchange pathways, (i) interaction between units of (Cu(II)-NIT4Py) through IDA, (ii) Cu(II)-NIT4Py interaction, and (iii) NIT4Py-NIT4Py interaction through space. Compared with the first two magnetic interactions, the last magnetic exchange interaction should be too weak to be counted because of the large distance of the neighboring NIT4Py molecules (4.993 Å). Analysis of the magnetic properties was performed using the Bleany–Bowers (dimer) model, showing that the complex exhibited both weak antiferromagnetic interaction between the Cu(II) and NIT4Py, and between the units of (Cu(II)-NIT4Py) through IDA with exchange coupling parameters J = ?7.28 cm^?1 and zJ′ = ?0.40 cm^?1.     

1D chlorine bridged mercury(II) complex containing nitronyl nitroxide radicals: Synthesis, crystal structures, and magnetic properties

A novel 1D chlorine bridged mercury(II) complex containing nitronyl nitroxide radicals, [Hg₂(NIT-1′-MeBzIm)Cl₄] _n (NIT-1′-MeBzIm = 2-{2′-[(1′-methyl)benzimidazolyl]}-4,4,5,5-tetrameth-ylimidazoline-1-oxyl-3-oxide), has been prepared and characterized by magnetic and single-crystal X-ray diffraction studies. The complex crystallizes in triclinic, space group P $\bar 1$ , Z = 2. Crystal data: C₁₅H₁₉C₁₄Hg₂N₄O₂, M = 830.32, a = 7.4454(16), b = 9.463(2), c = 16.180(3) Å, α = 94.245(2)°, β = 100.747(2)°, γ = 102.523(2)°, V = 1085.5(4) ų, ρ _c = 2.540 g/cm³, μ(MoK_α) = 14.636 mm^?1, F(000) = 762, R = 0.0312 and wR = 0.0779 for 3990 observed reflections with I > 2σ(I). The X-ray analysis reveals that the Hg²⁺ ions shows two coordination geometries of five-coordinated with a distorted square pyramidal coordination geometry and quadrilateral geometry. The units of [Hg₂(NIT-1′-MeBzIm)C_l4] _n were connected as 1D chain structure by the chlorine bridges. Magnetic investigation indicates the existence of weak intramolecular interactions is antiferromagnetic with J = ?1.23 cm^?1, where the spin Hamitonian is defined as H = $ - 2\sum\nolimits_{i,j} {J_{i,j} S_i S} $ within the complex.     

Synthesis,crystal structure and magnetic properties of a novel complex containing a diamagnetic metal ion and thiazole-substituted nitronyl nitroxide radicals

The synthesis, crystal structure and magnetic properties of a novel diamagnetic metal complex containing thiazole-substituted nitronyl nitroxide radicals, [HgCl₂(NIT2-thz)₂] (NIT2-thz?= 2-(2′-thiazole)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), is reported. The mercury(II) ion has distorted tetrahedral coordination involving two chloride atoms and two thiazole nitrogen atoms. Magnetic susceptibility data show that there are intramolecular antiferromagnetic interactions between the radicals in the complex.     

Synthesis,crystal structure and ferromagnetic properties of a novel acetate bridged dicadmium(II) complex with nitronyl nitroxide

The novel dinuclear cadmium(II) complex [Cd₂(NIT-1′-MeBzIm)₂(CH₃COO)₄] (I), where NIT-1′-MeBzIm = 2-{2′-[(1′-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, has been prepared and structurally characterized by single-crystal X-ray diffraction. The complex crystallizes in monoclinic crystal system, space group C2/c, Z = 4. Crystal data: C₃₈H₅₀Cd₂N₈O₁₂, M _r = 1035.66, a = 18.6492(16), b = 11.9605(10), c = 19.9208(17) Å, β = 92.1650(10)°. The X-ray analysis reveals that two Cd(II) atoms were bridged by two acetate groups to form a centrosymmetric Cd(II)-Cd(II) dinuclear entity, Cadmium atom is six-coordinated with a distorted octahedral geometry. The complex is linked by intermolecular hydrogen bonds leading to a 2D network configuration. Magnetic investigation indicates the existence of weak intramolecular interactions; i.e., the complex I is ferromagnetic with J = 1.97 cm^?1.     

Synthesis,crystal structures and magnetic properties of nitronyl nitroxide radical-coordinated copper(II) complexes

Transition Metal Chemistry - The coordination compound constructed for nitronyl nitroxide radical NIT-Ph-4-Br and CuII(hfac)2(H2O)2 building blocks...     

A novel one-dimensional dicyanamide bridged lead(II) complex containing nitronyl nitroxide radicals: Syntheses,crystal structures,and magnetic properties

A novel one-dimensional dicyanamide bridged lead(II) complex containing nitronyl nitroxide radicals, [Pb(NIT-1′-MeBzIm)(Dca)₂] _n (Dca = dicyanamide anion, NIT-1′-MeBzIm = 2-{2′-[(l′-methyl)benzimidazolyl]}-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), has been prepared and characterized by magnetic and single-crystal X-ray diffraction studies. In the complex, Pb²⁺ ion shows seven-coordinate geometry. A chain structure with single, symmetrical, end-to-end Dca bridges is found in the compound. These units develop as 1D species, where dicyanamide ligands bridge Pb²⁺ ions. Otherwise, molecules are linked by π-π-piling interactions to form 2D network structure. Magnetic investigation indicates the existence of intramolecular interactions, wich are ferromagnetic with J = 23.6 cm⁻¹, where the spin Hamitonian is defined as H = −2Σ _i,j J _i,j S _i S within the complex.     

Syntheses,crystal structures and magnetic properties of a new thienyl-substituted nitronyl nitroxide and its copper(II) complex

A new building block for molecule-based magnetic materials???thiophene-substituted nitronyl nitroxide, NIT2-thp, [1, NIT2-thp?=?4,4,5,5-tetramethyl-2-(thiophenal-2-yl)imidazoline-1-oxyl-3-oxide] and its copper(II) complex [Cu(hfac)₂]₃(NIT2-thp)₂ (2) (hfac?=?hexafluoroacetylacetonate) have been synthesized and characterized structurally and magnetically. For 1, dimers were formed and arranged through intermolecular interactions, the shortest contact between nitroxide groups is 4.115?Å among adjacent dimers. In 2 two types of copper interaction with 1 give three colinear Cu(II) ions linked by two μ???1,4 bridging nitroxide ligands. The central metal ion is in a distorted octahedron, axially coordinated by two nitroxide oxygen atoms, while the two external metal ions are in distorted square-pyramidal environments with the nitroxide oxygen atom coordinated in the basal plane. Magnetic susceptibility data for 1 and 2 have been measured in the range 3–300?K. There are antiferromagnetic interactions (J?=??3.89?cm^?1) between the dimers of 1 and also ferromagnetic interactions in 2. The magnetic properties of 1 and 2 are discussed in connection with their crystal structures.     

Synthesis,structure and magnetic properties of an iron(II) complex with nitronyl nitroxides

An iron(II) complex with nitronyl nitroxides, [Fe^II(dppNN)₂](BF₄)₂ · CH₃COCH₃ (1) (dppNN = 2,6-di(pyrazol-1-yl)-4-(4,4,5,5-tetramethyl-1-oxido-3-ylooxy-4,5-dihydro-3H-imidazol-2′-yl)pyridine) was synthesized. In 1 the central iron(II) ion was coordinated by two tridentate ligands with nitronyl nitroxides. Magnetic susceptibility measurements showed that χ_mT values below 130 K was almost temperature independent, while upon increasing temperature χ_mT values showed gradual increase, suggesting an occurrence of a spin transition from low to high spin state. Green light irradiation on powder sample at 5 K resulted in spin conversion (LIESST).     

Synthesis,structure, and magnetic properties of two dimer paddle-wheel CuII toluate complexes with nitronyl nitroxide radicals

Two new paddle-wheel dimeric copper complexes, [Cu₂(4-MePhCOO)₄(NITmPy)₂] (1) and [Cu₂(3-MePhCOO)₄(NITmPy)₂] (2) (NITmPy?=?2-(3-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro1H-imidazolyl-1-oxyl-3-oxide), were synthesized by reaction of copper toluate and NITmPy. Single crystal X-ray analyses revealed that both complexes are symmetrical dimers. Cu with four deprotonated methyl-benzoate bridging ligands form a paddle-wheel core and pyridyl nitrogen of radical ligands at the apical position. Based on the Cu–Cu axis of 1 and 2, we exploited the steric constraints of the methyl groups and induced the paddle-wheel. Two magnetic exchange pathways with strong antiferromagnetic interaction between dimeric Cu^II ions and weak antiferromagnetic interaction between NITmPy ligands exist in the complexes. IR and powder X-ray diffraction of the complexes were also studied.     

Synthesis,crystal structure and magnetic properties of N -benzesulfonyl-L-glutamic acid-bridged binuclear nickel(II) complex

N-benzesulfonyl-L-glutamic acid-bridged binuclear nickel(II) complex, [Ni₂(Bs-Glu)₂(bipy)₂ (H₂O)₂]?·?3H₂O (Bs-Glu?=?N-benzesulfonyl-L-glutamic acid dianion, bipy?=?2,2′-bipyridine), has been synthesized and characterized structurally and magnetically. It crystallizes in the triclinic space group P 1. The α-carboxyl group coordinates to Ni(II) in a monodentate mode, while the γ-carboxyl group coordinates in a chelating mode. In the temperature range 2–300?K, magnetic measurements show that the exchange interaction of the two Ni(II) ions is antiferromagnetic, and the values for J, g are ?2.47?cm^?1 and 2.18, respectively.     

Synthesis,crystal structures,and magnetic properties of cobalt(II)-hexafluoro-acetylacetonate complexes with two new triazole-substituted nitronyl and imino nitroxide

Two new chelating radical ligands, NITphtrz (4,4,5,5-tetramethyl-2-(2-phenyl-1,2,3-triazole-4-yl)imidazoline-1-oxyl-3-oxide) and IMphtrz (4,4,5,5-tetramethyl-2-(2-phenyl-1,2,3-triazole-4-yl)imidazoline-1-oxyl), and their cobalt(II) complexes [Co(Hfac)₂(NITphtrz)] (I) and [Co(Hfac)₂(IMphtrz)] (II) (Hfac = hexafluoroacetylacetonate) have been prepared and characterized by IR, magnetic, and single-crystal X-ray analysis. The magnetic behaviors of the lignad NITphtrz and complex I have been discussed.