Synthesis of nanocrystalline nickel ferrite by thermal decomposition of organic precursors

Nickel ferrite powders were synthesized by thermal decomposition of the precursors obtained in the redox reaction between the mixture of Ni(NO₃)₂·6H₂O and Fe(NO₃)₃·9H₂O with polyalcohol: 1,4-butanediol, polyvinyl alcohol and also with their mixture. During this reaction the primary C?COH groups were oxidized at ?CCOOH, while secondary C?COH groups at C=O groups. The carboxylic groups formed coordinate to the present Ni(II) and Fe(III) cations leading to carboxylate type compounds, further used as precursors for NiFe₂O₄. These precursors were characterized by thermal analysis and FT-IR spectrometry. All precursors thermally decomposed up to 350?°C leading to nickel ferrite weakly crystallized. By annealing at higher temperatures, nanocrystalline nickel ferrite powders were obtained, as resulted from XRD. SEM images have evidenced the formation of nanoparticulate powders; these powders present magnetic properties characteristic to the oxidic system formed by magnetic nanoparticles.     

Thermal analysis of some polynuclear coordination compounds as precursors of iron garnets (M3Fe5O12, M=Y3+ or Er3+)

The thermal behaviour of four coordination compounds (NH₄)₆[Y₃Fe₅(C₄O₅H₄)₆(C₄O₅H₃)₆]·12H₂O, (NH₄)₆[Y₃Fe₅(C₆O₇H₁₀)₆(C₆O₇H₉)₆]·8H₂O, (NH₄)₆[Er₃Fe₅(C₄O₅H₄)₆(C₄O₅H₃)₆]·10H₂O and (NH₄)₆[Er₃Fe₅(C₄O₆H₄)₆(C₄O₆H₃)₆]·22H₂O has been studied to evaluate their suitability for garnet synthesis. The thermal decomposition and the phase composition of the resulted decomposition compounds are influenced by the nature of metallic cations (yttrium-iron or erbium-iron) and ligand anions (malate or gluconate).     

Preparation of nanocrystalline BiFeO3 and kinetics of thermal process of precursor

The Bi₂Fe₂(C₂O₄)₅·5H₂O was synthesized by solid-state reaction at low heat using Bi(NO₃)₃·5H₂O, FeSO₄·7H₂O, and Na₂C₂O₄ as raw materials. The nanocrystalline BiFeO₃ was obtained by calcining Bi₂Fe₂(C₂O₄)₅·5H₂O at 600 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, FT-IR, X-ray powder diffraction, and vibrating sample magnetometer. The data showed that highly crystallized BiFeO₃ with hexagonal structure [space group R3c(161)] was obtained when the precursor was calcined at 600 °C in air for 1.5 h. The thermal process of the precursor in air experienced five steps which involved, at first, the dehydration of an adsorption water molecule, then dehydration of four crystal water molecules, decomposition of FeC₂O₄ into Fe₂O₃, decomposition of Bi₂(C₂O₄)₃ into Bi₂O₃, and at last, reaction of Bi₂O₃ and Fe₂O₃ into hexagonal BiFeO₃. Based on Starink equation, the values of the activation energies associated with the thermal process of Bi₂Fe₂(C₂O₄)₅·5H₂O were determined. Besides, the most probable mechanism functions and thermodynamic functions (ΔS ^≠, ΔH ^≠, and ΔG ^≠) of thermal processes of Bi₂Fe₂(C₂O₄)₅·5H₂O were also determined.     

Thermal stability of amino acid-(tyrosine and tryptophan) coated magnetites

The thermal stability of two amino acid-(tyrosine and tryptophan) coated magnetite and their corresponding precursors, [Fe₂^IIIFe^II(Tyr)₈]·9H₂O and [Fe₂^IIIFe^II(Trp)₂(OH)₄](NO₃)₂·8H2O (where tyrosine=Tyr and tryptophan=Trp), was analyzed in comparison with free amino acids. The complexes present a lower thermal stability relative to the free ligand, due to the catalytic effect introduced by the iron cation and the presence of NO₃⁻ groups. The presence of NO₃⁻ group determines also a different degradation’s stoichiometry of the amino acid anion comparative with the one expressed by the free ligand molecule. The amino acid bonded to magnetite decomposes in two steps, its presence inducing an increasing of γ-Fe₂O₃→Fe₂O₃ conversion temperature.     

Three 1-D molybdenum(V) phosphates with copper/nickel coordination cations

Three 1-D reduced molybdenum(V) phosphates, [Ni(OH)₂][Na₂(H₂O)₃]₂{Ni[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?5H₂O (1), [Ni(H₂O)₂][K(H₂O)₅]₂{Ni[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?4H₂O (2), and [Cu(H₂O)₂][Na(H₂O)₅]₂{Cu[(MoO₂)₆(OH)₃(HPO₄)₃(PO₄)]₂}?·?2C₆H₁₄N₂?·?2H₃O?·?4H₂O (3), have been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction. The crystallographic analysis reveals that 1 is based on {Ni[Mo₆O₁₂(OH)₃(HPO₄)₃(PO₄)]₂} clusters connected through {[Ni(OH)₂][Na₂(H₂O)₃]₂} pentanuclear mixed-metal cluster units to yield unusual 1-D chains along the c-axis, which further form 3-D supramolecular networks via hydrogen-bonding. Compounds 2 and 3 are heterogeneous isostructural compounds. Both are built from M[Mo₆P₄]₂ (M?=?Ni or Cu) blocks as the structural motif combined with [MO₄(H₂O)₂] (M?=?Ni or Cu) octahedra to form 1-D chains, where M[Mo₆P₄]₂ (M?=?Ni or Cu) is bonded by [M′(H₂O)₅] (M′?=?K or Na). Furthermore, bulk carbon paste electrode modified with 1 (1-CPE) displays good electrocatalytic activity toward reduction of nitrite or bromate.     

Structure,Magnetic and Spectral Properties of Ethyl Phosphite Nitrate Tri(1,10-phenanthroline) Nickel(II) Solvate Trihydrate: [Ni(phen)3]NO3·C2H5OP(O)O·3H2O

The compound, [Ni(phen)₃]NO₃ · C₂H₅OP(O)O · 3H₂O, was obtained by the reaction of Ni(NO₃)₂, C₂H₅OP(OH)₂ and 1,10-phenanthroline in 95% EtOH solution, and was characterized using IR and UV spectra and magnetic susceptibility measurements over the temperature range 75-300 K. The red crystal is triclinic of space group P&1macr;, with lattice parameters a = 12.462(3), b = 13.416(3), c = 13.422(3) Å, f = 75.88(3), g = 64.75(3), n = 65.87(3)°, and Z = 2. The coordinated cation contains a six-coordinate nickel atom chelated by three phenanthroline ligands, resulting in a distorted octahedral arrangement with the six Ni-N distances ranging from 2.086(2) to 2.113(3) Å. In addition to the nickel coordination complex, there are two anions, NO₃ and C₂H₅OP(O)O^-, and three water molecules which complete the crystal structure. In the solid state, the title compound forms a three dimensional network structure through hydrogen bonds. The intermolecular hydrogen bonds connect the [Ni(phen)₃]²⁺, NO₃, C₂H₅OP(O)O^- and H₂O molecules.     

IR- und Ramanspektren isotop markierter Tetra- und Pentaborate

IR and Raman spectra of solid H₃BO, Na[B(OH)₄], Na₂[B₄O₅(OH)₄]·8H₂O, Na[B₅O₆(OH)₄]·3H₂O, K[B₅O₆(OH)₄]·2H₂O, (NH₄)₂[B₄O₅(OH)₄]·2H₂O, β-NH₄[B₅O₆(OH)₄]· 2H₂O, NH₄[B₅O₆(OH)₄]·.0,67H₂O and NH₄[B₅O₆(OH)₄] were recorded between 300 and 1550 cm⁻¹ as well as the spectra of H₃¹¹BO₃, H₃¹⁰BO₃, Na[¹¹B(OH)₄], Na[¹⁰B(OH)₄], Na₂[¹¹B₄O₅(OH)₄]·8H₂O, Na₂[¹⁰B₄O₅(OH)₄]·8H₂O, (NH₄)₂[¹¹B₄O₅(OH)₄]·2H₂O, (NH₄)₂[¹⁰B₄O₅(OH)₄]·2H₂O, K[¹¹B₅O₆(OH)₄]·2H₂O or K[¹⁰B₅O₆(OH)₄]·2H₂O.The spectra were interpreted by comparisons with known structures, by comparisons within the series, and by interpretations of isotopic shifts. Thus a large number of lines could be assigned, and it was possible to arrive at general hints for the interpretation of the spectra. Finally, a very important and characteristic line called pulsation vibration could be explained.     

Iron,nickel and zinc malates coordination compounds cynthesis,characterization and thermal behaviour

The coordinations compounds (NH₄)[Fe(C₄H₄O₅)(OH)₂]·0.5H₂O, [Ni(C₄H₄O₅)]·3H₂O and [Zn(C₄H₄O₅)]·5H₂O were synthesized by a precipitation method and characterized by chemical analysis, spectral (IR, UV-VIS) and magnetical investigations. In the range 50-600°C stepped thermal decompositions occur with formation of anhydrous malates, malonates, oxoacetates (iron and nickel compounds) and hydroxocarbonate (Zn compound) as intermediates observed by FT-IR spectroscopy. α-Fe₂O₃, NiO and ZnO constitute the final decomposition products. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and crystal structure of [Fe4O2(H2O)10(C5H5NCOO)4](NO3)8 · 2H2O

Crystals of the tetranuclear complex [Fe₄O₂(H₂O)₁₀(C₅H₅NCOO)₄](NO₃)₈ · 2H₂O are obtained by the slow evaporation of an aqueous solution of iron(III) nitrate and isonicotinic acid. According to the X-ray diffraction data, four metal atoms lie in the same plane and together with two μ₃-O oxygen atoms form the fragment [Fe₄(μ₃-O)₂]¹⁰⁺. The [Fe₄O₂(H₂O)₁₀(C₅H₅NCOO)₄]⁸⁺ cation has been obtained and structurally characterized for the first time.     

Preparation of CoxFe3?xO4 nanoparticles by thermal decomposition of some organo-metallic precursors

This paper presents a study for the preparation of Co_xFe_3−xO₄ (x = 0.02, 0.2, 0.5, 0.8, 1.0, 1.1, 1.5) nanoparticles, starting from metal nitrates: Co(NO₃)₂·6H₂O, Fe(NO₃)₃·9H₂O and ethylene glycol (C₂H₆O₂). By heating the solutions metal nitrates-ethylene glycol, the redox reaction took place between the anion NO₃ ⁻ and OH–(CH₂)₂–OH with formation of carboxylate anions. The resulted carboxylate anions reacted with Co(II) and Fe(III) cations to form coordinative compounds which are precursors for cobalt ferrite. XRD and magnetic measurements have evidenced the formation of cobalt ferrite for all studied molar ratios. The average diameter of the cobalt ferrite crystallites was estimated from XRD data and showed values in the range 10–20 nm. The crystallites size depends on the annealing temperature. The magnetization of the synthesized samples depends on the molar ratio Co/Fe and on the annealing temperature.     

Bis(1,10‐phenanthroline‐N,N′)(thiosulfato‐O,S)­nickel(II)–water–methanol (1/0.92/1.4) and bis(2,2′‐bi­pyridyl‐N,N′)(thiosulfato‐O,S)nickel(II)–water–methanol (1/2/0.55)

The title compounds, [Ni(S₂O₃)­(C₁₂H₈N₂)₂]·­0.92H₂O·­1.4CH₄O and [Ni(S₂O₃)­(C₁₀H₈N₂)₂]·­2H₂O·­0.55CH₄O, are monomeric, containing nickel(II) in a distorted octahedral coordination environment provided by the four N atoms of two bidentate bipy or phen groups and one S and one O atom from a chelating thio­sulfate anion. The crystals are highly unstable outside their mother liquors and are stabilized in solution by a not fully determined number of water and methanol solvate mol­ecules. The phenanthroline structure includes two independent moieties related by a non‐crystallographic inversion center. The thio­sulfate anions display the usual S—O lengthening found when the anion acts in a bidentate mode.     

Solid complexes of iron(II) and iron(III) with rutin

Solid complex compounds of Fe(II) and Fe(III) ions with rutin were obtained. On the basis of the elementary analysis and thermogravimetric investigation, the following composition of the compounds was determined: (1) FeOH(C₂₇H₂₉O₁₆)·5H₂O, (2) Fe₂OH(C₂₇H₂₇O₁₆)·9H₂O, (3) Fe(OH)₂(C₂₇H₂₉O₁₆)·8H₂O, (4) [Fe₆(OH)₂(4H₂O)(C₁₅H₇O₁₂)SO₄]·10H₂O. The coordination site in a rutin molecule was established on the basis of spectroscopic data (UV–Vis and IR). It was supposed that rutin was bound to the iron ions via 4C=O and 5C—oxygen in the case of (1) and (3). Groups 5C–OH and 4C=O as well as 3′C–OH and 4′C–OH of the ligand participate in binding metals ions in the case of (2). At an excess of iron(III) ions with regard to rutin under the synthesis conditions of (4), a side reaction of ligand oxidation occurs. In this compound, the ligands’ role plays a quinone which arose after rutin oxidation and the substitution of Fe(II) and Fe(III) ions takes place in 4C=O, 5C–OH as well as 4′C–OH, 3′C–OH ligands groups. The magnetic measurements indicated that (1) and (3) are high-spin complexes.     

Clathrate compounds of tetracyano complexes of nickel and platinum with phenol

The double cyanides of nickel and platinum form structures capable of enclosing also phenol, for example, as guest molecule. Such clathrates are Ni(NH₃)₂Pt(CN)₄ 2 C₆H₅OH and Ni(en)₂Pt(CN)₄ · 0.14 C₆H₅OH. In the case of the tetracyano complexes, different thermal stabilities of their clathrate compounds could be achieved by alteration of the constituents of the cage structure and also of the guest molecules. According to the thermal behaviour, the clathrates may be divided into two groups: those which release the guest molecules in the first step of thermal decomposition (Ni(NH₃)₂Pt(CN)₄· 2 C₆H₅OH), and those which lose the guest component only after partial destruction of the host cage (Ni(en)₂Pt(CN)₄ · 0.14 C₆H₅OH). The temperature ranges of loss of the guest component may determine the interval for their use in sorptive experiments. The temperature range for release of phenol from Ni(NH₃)₂Pt(CN)₄ · · 2 C₆H₅OH is 55–244°, and from Ni(en)₂Pt(CN)₄ · 0.14 C₆H₅OH is 139–284°. The model host molecules NiPt(CN)₄ · 6 H₂O and Ni(en)₃Pt(CN)₄ · 3 H₂O were also studied by thermal analysis.     

Cobalt(II) and nickel(II) complexes of isoquinoline‐1‐carboxylate

trans‐Di­aqua­bis­(iso­quinoline‐1‐carboxyl­ato‐κ²N,O)­cobalt(II) dihydrate, [Co(C₁₀H₆NO₂)₂(H₂O)₂]·2H₂O, and trans‐di­aqua­bis­(iso­quinoline‐1‐carboxyl­ato‐κ²N,O)­nickel(II) dihydrate, [Ni(C₁₀H₆NO₂)₂(H₂O)₂]·2H₂O, contain the same isoquinoline ligand, with both metal atoms residing on a centre of symmetry and having the same distorted octahedral coordination. In the former complex, the Co—O(water) bond length in the axial direction is 2.167 (2) Å, which is longer than the Co—O(carboxylate) and Co—N bond lengths in the equatorial plane [2.055 (2) and 2.096 (2) Å, respectively]. In the latter complex, the corresponding bond lengths for Ni—O(water), Ni—O(carboxylate) and Ni—N are 2.127 (2), 2.036 (2) and 2.039 (3) Å, respectively. Both crystals are stabilized by similar stacking interactions of the ligand, and also by hydrogen bonds between the hydrate and coordinated water molecules.     

Co(en)3[B4O5(OH)4]Cl·3H2O和[Ni(en)3][B5O6(OH)4]2·2H2O的合成、结构以及热力学性质

利用水热法合成了两种过渡金属配合物为模板剂的含水硼酸盐晶体Co(en)3[B4O5(OH)4]Cl·3H2O(1) 和 [Ni(en)3][B5O6(OH)4]2·2H2O (2),并通过元素分析、X射线单晶衍射、红外光谱及热重分析对其进行了表征。化合物1晶体结构的主要特点是在所有组成Co(en)33+, [B4O5(OH)4]2–, Cl– 和 H2O之间通过O–H…O、O–H…Cl、N–H…Cl和N–H…O四种氢键连接形成网状超分子结构。化合物2晶体结构的特点是[B5O6(OH)4]–阴离子通过O–H…O氢键连接形成沿a方向有较大通道的三维超分子骨架,模板剂[Ni(en)3]2+阳离子和结晶水分子填充在通道中。     

Tetranitratogoldsäure, (H5O2)[Au(NO3)4]·H2O: Synthese,Kristallstruktur und thermisches Verhalten des ersten sauren Nitrates des Goldes

Tetranitratogold(III) Acid, (H₅O₂)[Au(NO₃)₄]·H₂O: Synthesis, Crystal Structure, and Thermal Behaviour of the First Acidic Nitrate of Gold Yellow single crystals of (H₅O₂)[Au(NO₃)₄]·H₂O grow upon cooling of a solution of Au(OH)₃ in conc. nitric acid. The crystal structure contains (monoclinic, C2/c, Z = 4, a = 1214.5(2), b = 854.4(1), c = 1225.7(2) pm, β = 117.75(1)°, R_all = 0.0331) the Au³⁺ ion in coordination of four monodentate NO₃^— ligands. The [Au(NO₃)₄]^— units are linked by H₅O₂⁺‐ions. Significant hydrogen bonding is observed in the crystal structure between the H₅O₂⁺ ions and the H₂O molecules. The thermal analysis reveals a five step decomposition leading to elemental gold.     

Synthesis and Crystal Structure of [Ni(H2O)6][Ni(H2O)2(C4H2O4)]·4H2O

Reaction of a freshly prepared Ni(OH)_{2?2 x} (CO₃) _x ·yH₂O with maleic acid in H₂O at room temperature afforded [Ni(H₂O)₆][Ni(H₂O)₂(C₄H₂O₄)]·4H₂O, which consists of [Ni(H₂O)₆]²⁺ cations, [Ni(H₂O)₂(C₄H₂O₄)]^2? anions and lattice H₂O molecules. Ni atoms in cations are octahedrally coordinated and Ni atoms in anions are each octahedrally coordinated by bidentate chelating maleato ligands and two water molecules at trans positions. Cations and anions are interlinked by hydrogen bonds to form 1D chains, which are hexagonally arranged and connected by the lattice water molecules. When heated in a flowing argon stream, the compound decomposes, with complete dehydration being followed by dissociation of nickel maleate into NiO and maleic anhydride.     

Thermal analysis of some polynuclear coordination compounds

The thermal behaviour of five polynuclear coordination compounds containing tartaric anion as ligand, namely (NH₄)₃[LnFe(C₄O₆H₄)₃(OH)₃] (Ln=La and Eu), (NH₄)₂[PrFe(C₄O₆H₄)₃(OH)₂] and (NH₄)[LnFe(C₄O₆H₄)₃(OH)]·3H₂O (Ln=Nd and Gd) was investigated. The reaction progress was studied by TG/DTA and FTIR measurements. Oxalates and oxocarbonates were identified as intermediates. In the case of Ln=La, Nd, Pr, Eu and Gd, pure LnFeO₃ was obtained as final decomposition product. The thermal decomposition of Eu-Fe compound, leads to a mixture of mixed (ortho-ferrite (EuFeO₃) and garnet (Eu₃Fe₅O₁₂)) and simple oxides (Eu₂O₃ and α-Fe₂O₃).     

Untersuchung von Hydrolysereaktionen zum Aufbau von Eisen(III)‐Oxo‐Aggregaten

Investigation of the Hydrolytic Build‐up of Iron(III)‐Oxo‐Aggregates The synthesis and structures of five new iron/hpdta complexes [{Fe^III₄(μ‐O)(μ‐OH)(hpdta)₂(H₂O)₄}₂Fe^II(H₂O)₄]·21H₂O ( 2 ), (pipH₂)₂[Fe₂(hpdta)₂]·8H₂O ( 4 ), (NH₄)₄[Fe₆(μ‐O)(μ‐OH)₅(hpdta)₃]·20.5H₂O ( 5 ), (pipH₂)_1.5[Fe₄(μ‐O)(μ‐OH)₃(hpdta)₂]·6H₂O ( 7 ), [{Fe₆(μ₃‐O)₂(μ‐OH)₂(hpdta)₂(H₄hpdta)₂}₂]·py·50H₂O ( 9 ) are described and the formation of these is discussed in the context of other previously published hpdta‐complexes (H₅hpdta = 2‐Hydroxypropane‐1, 3‐diamine‐N, N, N′, N′‐tetraacetic acid). Terminal water ligands are important for the successive build‐up of higher nuclearity oxy/hydroxy bridged aggregates as well as for the activation of substrates such as DMA and CO₂. The formation of the compounds under hydrolytic conditions formally results from condensation reactions. The magnetic behaviour can be quantified analogously up to the hexanuclear aggregate 5 . The iron(III) atoms in 1 ‐ 7 are antiferromagnetically coupled giving rise to S = 0 spin ground states. In the dodecanuclear iron(III) aggregate 9 we observe the encapsulation of inorganic ionic fragments by dimeric{M₂hpdta}‐units as we recently reported for Al^III/hpdta‐system.     

Two furo­pyridine complexes of nickel(II) iso­thio­cyanate

Pyridine fused with a furan ring (fupy), and its di­methyl derivative, have been used for the first time as ligands to synthesize potentially new Werner clathrates. The extended aromatic system of pyridine‐like ligands influences considerably the molecular structure of prepared nickel complexes. The molecular structure of tetrakis­(furo­[3,2‐c]­pyridine)­bis(iso­thio­cyanato)­nickel(II) tetra­hydro­furan (THF) solvate, [Ni(NCS)₂(C₇H₅NO)₄]·C₄H₈O or [Ni(NCS)₂(fupy)₄]·THF, (I), reveals a `four‐blade propeller' arrangement of ligands, with the angles between the fupy planes and the basal octahedron plane spanning the range 38.7–55.3°. These angles are much larger (69.9–78.8°) in the centrosymmetric complex tetrakis(2,3‐di­methyl­furo­[3,2‐c]­pyridine)­bis­(iso­thio­cyanato)nickel(II) 6.6‐hydrate, [Ni(NCS)₂(C₉H₉NO)₄]·6.6H₂O or [Ni(NCS)₂(Me₂fupy)₄]·6.6H₂O, (II), in which crystallographically imposed inversion symmetry is present.