Two copper complexes based on nitronyl nitroxide with different halides: structures and magnetic properties

<p>Complexes based on different halogen-substituted nitronyl nitroxide radicals and Cu(II), Cu₃(hfac)₆(NIT-Ph-F)₂ (<b>1</b>) and Cu₃(hfac)₆(NIT-Ph-Cl)₂ (<b>2</b>) (hfac = hexafluoroacetylacetonate; NIT-Ph-F = 2-(4′-fluorophenyl)-4,4,5,5-tetramethyl-imidazoline-1-oxyl-3-oxide; NIT-Ph-Cl = 2-(4′-chlorphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), were synthesized and characterized structurally and magnetically. X-ray crystal structure analyses show that <b>1</b> and <b>2</b> have similar centrosymmetric five-spin structures consisting of three Cu(II) ions bridged by two nitroxide ligands. The Cu(II) is coordinated by six oxygens to form an octahedron, while the five coordination of the terminal Cu(II) ion is square pyramidal. Magnetic measurements reveal strong antiferromagnetic interactions between Cu(II) ions and radicals in <b>1</b> (<i>J</i> = −38.9 cm⁻¹) and weak antiferromagnetic interactions between Cu(II) ions and radicals in <b>2</b> (<i>J</i> = −1.23 cm⁻¹), which may be explained by the bond length of the Cu–O_rad (2.468(2) Å) in <b>1</b>, which is shorter than that (2.514(2) Å) in <b>2</b>, and the dihedral angle (73.17(1)°) of the plane O7–O8–Cu(2)–O7A–O8A with the moiety O5–N1–C11–N2–O6 in <b>1</b> is smaller than (77.82(1)°) in <b>2</b>.</p

Three new lanthanide compounds based on nitronyl nitroxide radical: Crystal structure, magnetic properties, and luminescence properties

<p>Three new lanthanide compounds were obtained using 2-(3-methylthiophene)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) (NIT-3Methien). These compounds, [Gd(hfac)₃(NIT-3Methien)₂]∙0.5CH₃(CH₂)₅CH₃ (<b>1</b>: Half n-heptane trihexafluoroacetylacetonate-di-2-(3-methylthiophene)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide gadolinium(III)), [Tb(hfac)₃(NIT-3Methien)₂]∙0.5H₂O (<b>2</b>: Half Hydrate trihexafluoroacetylacetonate-di-2-(3-methylthiophene)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide terbium(III)), and [Dy(hfac)₃(NIT-3Methien)₂]∙0.5H₂O (<b>3</b>: Half Hydrate trihexafluoroacetylacetonate-di-2-(3-methylthiophene)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide dysprosium(III)), (CH₃(CH₂)₅CH₃ = n-heptane), (hfac = hexafluoroacetylacetonate), were characterized structurally and magnetically. The three compounds crystallize in the triclinic space group P1( - ). Ln(III) ion was eight-coordinate by six oxygens from three hfac ligands and two oxygens from two radicals. In <b>1</b>, direct current (DC) magnetic studies reveal ferromagnetic interactions between the Gd(III) ion and radicals with <i>J</i>₁ = 0.94 cm⁻¹. In <b>2</b> and <b>3</b>, there are antiferromagnetic interactions between the Tb(III), or Dy(III) ions and radicals. The luminescence characterizations show that <b>2</b> exhibits highly selective luminescent sensing of Cr₂O₇²⁻ ions.</p

Ferroelastic Phase Transition and Switchable Dielectric Constant in Heterometallic Niccolite Formate Frameworks

Four heterometallic formate frameworks templated by various alkylamine cations with the general formula [cat]­[Ga^IIIMn^II(HCOO)₆] {cat is MA (CH₃NH₃⁺) for <b>1</b>, DMA [(CH₃)₂NH₂⁺] for <b>2</b>, EtA (CH₃CH₂NH₃⁺) for <b>3</b>, and DEtA [(CH₃CH₂)₂NH₂⁺] for <b>4</b>} have been prepared and characterized by X-ray diffraction, differential scanning calorimetry, and dielectric studies. All of the complexes have niccolite-like structures, which possess the same [GaMn­(HCOO)₆]⁻ anionic framework with binodal (4¹²·6³)­(4⁹·6⁶) topology; only the counterions in the cavity are different. Complex <b>4</b> undergoes a reversible ferroelastic phase transition around 220 K accompanied by a thermally switchable dielectric constant transition triggered by the freezing of the order–disorder DEtA cations

Alkylamine-Templated Niccolite Frameworks of [Ga^IIIM^II(HCOO)₆]⁻ (M = Fe, Ni): Structure, Magnetism, and Dielectricity

The five heterometallic formate frameworks [EtA]­[Ga^IIIFe^II(HCOO)₆] (<b>1</b>; EtA = CH₃CH₂NH₃⁺), [DMA]­[Ga^IIIFe^II(HCOO)₆] (<b>2</b>; DMA = (CH₃)₂NH₂⁺), [DEtA]­[Ga^IIIFe^II(HCOO)₆] (<b>3</b>; DEtA = (CH₃CH₂)₂NH₂⁺), [MA]­[Ga^IIINi^II(HCOO)₆] (<b>4</b>; MA = CH₃NH₃⁺), and [DMA]­[Ga^IIINi^II(HCOO)₆] (<b>5</b>) were synthesized through solvothermal methods. Complexes <b>1</b>–<b>5</b> are isotructural, and all crystallize in the trigonal <i>P</i>3̅₁<i>c</i> space group. Each metal center is 6-connected, with each HCOO^– bridging ligand in an anti-anti mode to build a three-dimensional niccolite-like architecture. All of the complexes exhibit weak ferromagnetism at low temperature. A variable-temperature (VT) dielectric study indicates that the dielectric anomaly is induced by the freezing of motions from the protonated amines during the freezing process

Synthesis and Magnetic Properties of a Series of Octanuclear [Fe₆Ln₂] Nanoclusters

The reaction of polydentate ligand Bis-tris propane {(CH₂OH)₃CNH­(CH₂)₃NHC­(CH₂OH)₃} with Ln­(NO₃)₃·6H₂O and Fe₃O precursor resulted in the formation of a series of Fe₆Ln₂ nanoclusters. Magnetic measurements indicate that the Fe₆ core exhibits ferrimagnetic behavior, and slow magnetic relaxation was observed in Fe₆Dy₂ and Fe₆Tb₂

Syntheses, Structures, and Magnetic and Luminescence Properties of a New Dy^III-Based Single-Ion Magnet

Three new Ln^III complexes based on 2,2′-bipyridine [Ln­(hfac)₃(bpy)] (Ln = Dy (<b>1</b>), Tb (<b>2</b>), or Ho (<b>3</b>); hfac = hexafluoroacetylacetonate; and bpy = 2,2′-bipyridine) have been synthesized and characterized structurally and magnetically. Single-crystal X-ray analysis shows that all these complexes contain one [Ln­(hfac)₃(bpy)] unit in which a center Ln^III ion is surrounded with a slightly distorted square-antiprismatic LnO₆N₂ coordination sphere formed by three bischelate hfac anions and one bpy ligand. Both static and dynamic magnetic properties were studied for complex <b>1</b>, which is proved to be a new single-ion magnet. The luminescence characterizations of complexes <b>1</b> and <b>2</b> are also studied in this paper

Syntheses, Structures, and Magnetic and Luminescence Properties of a New Dy^III-Based Single-Ion Magnet

Three new Ln^III complexes based on 2,2′-bipyridine [Ln­(hfac)₃(bpy)] (Ln = Dy (<b>1</b>), Tb (<b>2</b>), or Ho (<b>3</b>); hfac = hexafluoroacetylacetonate; and bpy = 2,2′-bipyridine) have been synthesized and characterized structurally and magnetically. Single-crystal X-ray analysis shows that all these complexes contain one [Ln­(hfac)₃(bpy)] unit in which a center Ln^III ion is surrounded with a slightly distorted square-antiprismatic LnO₆N₂ coordination sphere formed by three bischelate hfac anions and one bpy ligand. Both static and dynamic magnetic properties were studied for complex <b>1</b>, which is proved to be a new single-ion magnet. The luminescence characterizations of complexes <b>1</b> and <b>2</b> are also studied in this paper