Mössbauer studies of some iron(II) complexes of cyclohexanonesemicarbazone

Summary Mössbauer studies of high-spin iron(II) complexes of the type FeL₂X₂ [L = cyclohexanonesemicarbazone (CHSC); X = Cl, NO₃, 0.5 SO₄, NCS] have been carried out at room and at liquid nitrogen temperature. The results reveal doublet ground states for Fe(CHSC)₂Cl₂ and Fe(CHSC)₂(NO₃)₂ and singlet ground states for Fe(CHSC)₂SO₄ and Fe(CHSC)₂(NCS)₂.     

Fixation of Sulphur Dioxide by Manganese(II)‐Schiff Base Complexes: Thermal Stability of these Adducts and the Possible Conversion of the Coordinated SO2 to Sulphate

A series of manganese(II) complexes of general formula MnLⁿ(H₂O)_m (where H₂Lⁿ are substituted N,N′‐bis(salicylidene)‐1,2‐diimino‐2,2‐dimethylethane) have been prepared by electrochemical synthesis and characterized by analytical and spectroscopic techniques, magnetism and by studying their redox reversibility character by cyclic and normal pulse voltammetry. The reactivity of these complexes with sulphur dioxide has been investigated in the solid state and in toluene slurries at room temperature. The studies of the reversibility of the reaction (desorption studies) by thermogravimetrical analysis (TGD) have shown a different behaviour among the SO₂‐adducts (from irreversible to totally reversible fixing), pointing to different SO₂ binding modes. Thus, adducts 10 , 12 and 14 , kept the SO₂ after TGD, signifying S–bridged SO₂ binding mode, while TGD for 8 , 9 and 13 revealed the lability of their SO₂, attributable to ligand bound SO₂ coordination. The manganese(II) precursor 4 is that one which has the ability of reversily fixing a major quantity of SO₂ and undergoes the sulphato reaction to form 11 also.     

Catalytic hydrogenation of crotonaldehyde in the liquid phase using Pt and Ru/SnO<Subscript>2</Subscript> catalysts

Effects of the precursor of active metal and of the reduction temperature upon activity and selectivity in selective hydrogenation of crotonaldehyde by Pt/SnO₂ and Ru/SnO₂ catalysts were studied. Experiments were performed in the liquid phase with a group of solvents tested: propan-2-ol, toluene, hexane and tetrahydrofuran. The best results were achieved with catalysts from ex-nitrate precursors/Pt(NH₃)₄(NO₃)₂ and Ru(NO)(NO₃)₂/reduced at 150° C. Propan-2-ol was evaluated as the most appropriate solvent to gain high yields of crotylalcohol in this study. A new hydrogenation product, 2-methylprop-2-en-1-ol (methallylalcohol), was observed.     

Iron(III) complexes withN-Methyl-4-mercaptopiperidine

Summary Complexes of iron(III), containingN-methyl-4-mercaptopiperidine in its zwitterionic form (HRS), of stoichiometry Fe(HRS)₄XA₄ · nD, Fe(HRS)₃(BPh₄)₃ · 3DMF and (Fe(HRS)SO₄)₂SO₄ · 3MeOH · 2H₂O (X=Cl or NO₃; A=BPh₄ or PF₆; D=H₂O, MeOH or DMF) have been prepared and characterized by i.r. and electronic spectra, magnetic susceptibilities at room temperature and by cyclic voltammetry measurements.     

Synthesis and Thermal Decomposition of Mn-Al Layered Double Hydroxides

In this paper, the synthesis and thermal decomposition behavior of hydrotalcite-like Mn-Al layered double hydroxide (LDH) have been investigated. First, the Mn-Al LDH was synthesized by the coprecipitation method using various anions such as Cl⁻, CO²⁻₃, NO⁻₃, SO²⁻₄ or dicarboxylic acids (DCA). The single phase of the Mn-Al LDH was obtained when Cl⁻, NO⁻₃ or DCA was used as a guest anion. In the case of CO²⁻₃ or SO²⁻₄, the solid products included MnCO₃ or shigaite as a by-product. The crystallinity of the Cl/Mn-Al LDH was greatly influenced by a drying temperature and that the crystallinity of the Cl/Mn-Al LDH dried at room temperature was found to rise about 6 times in comparison with that dried at 333 K. The DCA/Mn-Al LDH was found to have an expanding LDH structure, supporting that the LDH basal layers were bridged by the intercalated DCA anion. Then, the thermal decomposition of the DCA/Mn-Al LDH has been examined, and the intercalated DCA was found to be decomposed at lower temperature than DCA itself. The oxidation number of Mn ion rose with increasing the heat treatment temperature and was +2.70 with crystallizing Mn₃O₄ after being heated at 973 K. The thermal decomposition of guest DCA was thought to be accelerated by the strong catalytic action of Mn ion in the host hydroxide basal layers.     

The crystal structure of μ-Oxo-bis{diethoxy[salicylaldoximato(2-)]-tantalum(V)}

Stochiometric reaction of salicylaldoxime and tantalum or niobium ethoxide in toluene at room temperature resulted in formation of [M₂O(C₇H₅NO₂)₂(C₂H₅O)₄], M=Ta and Nb which were crystallized from CH₂Cl₂ at −5 °C and characterized by spectroscopic techniques. The molecular structures of [Ta₂O(C₇H₅NO₂)₂(C₂H₅O)₄] was determined by single-crystal X-ray diffraction and compared with molecular structure of [Nb₂O(C₇H₅NO₂)₂(C₂H₅O)₄]. The geometries at metal atoms are distorted octahedron which shared an apex through bridged oxygen. Each dianionic salicylaldoximate ligand chelates to the one metal ion through its phenolic oxygen and oximate nitrogen atoms, and to another metal ion through its oximate oxygen atom.     

Adsorption and electrophysical studies of the sensitivity and selectivity of the surface of the InSb-CdTe system with respect to toxic gases

The piezoquartz microweighing and probe compensation methods were used to study the adsorption properties with respect to NO₂ and changes in the electrical conductivity of solid solutions and the binary components of the InSb-CdTe system under the influence of NO₂ and NO₂ + SO₂ and NO₂ + CO mixtures at various temperatures and relative gas contents. Solid solutions were prepared by isothermal diffusion and certified using the results of X-ray, thermographic, IR spectroscopic, and electrophysical measurements. The (InSb)_0.03(CdTe)_0.97 component of the system was found to possess high selective sensitivity (adsorption and electronic) already at room temperature. This component was recommended for creating a sensor for NO₂ microimpurities.     

Studies on solid state synthesis and the oxygenation property of cobalt (II) Schiff base (vanilline polyamine) complexes

Three new cobalt complexes were synthesized by solid-state reaction at room temperature and the resultant Co complexes reacted with two equivalent oxygen molecules at room temperature to produce the oxygenated complexes [Co·(L₁)₂·(O₂)₂](NO₃)₂·2H₂O (L₁ = N, N’-bis(4-hydroxyl-3-methoxy-benzyl)-diethylenetriamine), [Co·(L₂)₂·(O₂)₂](NO₃)₂·2H₂O (L₂ = N, N’-bis(4-hydroxyl-3-methoxy-benzyl)-triethylenetetramine), and [Co·(L₃)₂·(O₂)₂](NO₃)₂·2H₂O (L₃ = N, N’-bis(4-hydroxyl-3-methoxy-benzyl-tetraethylenepentamine). The oxygenated complexes were characterized by elemental analysis, IR (Infrared), ¹H-NMR (Nuclear Magnetic Resonance), and UV-Vis (Ultraviolet Visual) spectrometry, and TG/DTA (Thermogravimetry/Differential Thermal Analysis) analysis, and molar conductance. The coordinated oxygen contents in the oxygenated complexes were also determined by weight method. It was supposed that only one O₂ molecule coordinated to the Co ion forming a superoxo type oxygenated complex. Translated from Acta Chimica Sinica, 2006, 64(15): 1517–1522 (in Chinese)     

Electrochemical synthesis of manganese(II)-Schiff base complexes and their behaviour towards H2O,H2O2 and SO2

Manganese(II) complexes with ONNO tetradentate Schiff bases have been prepared by electrochemical synthesis and characterised by analytical and spectroscopic techniques, magnetism and by studying their redox reversibility character by cyclic and normal pulse voltammetry. The ability of these systems to catalyse the decomposition of water, to yield dioxygen, and their catalase-like activity was checked. Reaction of the complexes with sulfur dioxide was studied in the solid state and in toluene slurries at room temperature. The adducts formed underwent thermogravimetric desorption analyses that highlights the SO₂-irreversible linkage present in all complexes.     

Synthesis,structures, photoluminescence,and theoretical investigations on two new Zn(II)/Mn(II) complexes with pyridine-2-amidoxine and carboxylate ligands

Abstract  

Two new neutral mononuclear Zn(II) and Mn(II) complexes with pyridine-2-amidoxine and carboxylate ligands, [Zn(paH)₂(OAc)₂]·2CH₃OH (paH = pyridine-2-amidoxine, HOAc = acetic acid) (1), and [Mn(paH)₂(OAc)₂]·C₂H₅OH·2H₂O (2), have been prepared and characterized structurally by X-ray crystallography. 1 and free paH exhibit photoluminescence at room temperature in solid state, which is rare so fare for metal complexes with oxime-based ligand. The emissions of 1 and free paH arise from the metal-perturbed paH-based π → π* ligand-to-ligand charge transfer transition (LLCT) and π → π* charge transfer transition in nature, respectively, in terms of the density functional theory level calculations and molecular orbital analyses.     

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.     

Synthesis and structure of trinuclear pyrazolate-bridged acetates M<Subscript>3</Subscript>(μ-dmpz)<Subscript>4</Subscript>(Hdmpz)<Subscript>2</Subscript>(OOCMe)<Subscript>2</Subscript> (M = Zn or Co; Hdmpz = 3,5-dimethylpyrazole)

We discovered that reactions of hydrous cobalt and zinc acetates with 3,5-dimethylpyrazole (Hdmpz) in boiling xylene or toluene or upon the thermolysis of solid precursors (150°C) yield trinuclear pyrazolate-bridged complexes M₃ (μ-dmpz)₄(Hdmpz)₂ (OOCMe)₂(M = Zn or Co). Depending on the crystallization conditions, these complexes contain various solvating molecules (benzene, toluene, or Hdmpz), which influences the character of intramolecular and intermolecular hydrogen bonding, as shown by X-ray crystallography.     

Syntheses and Structures of Terpyridine‐Metal Complexes

Seven complexes, [Ln(ctpy)(NO₃)₂]_n and M(ctpy)₂ · 4H₂O [Ln = Gd ( 1 ), Dy ( 2 ), Er ( 3 ); M = Co ( 4 ), Ni ( 5 ), Cu ( 6 ), Zn ( 7 )] with the ligand 2, 2′:6′,2′′‐terpyridine‐4′‐carboxylic acid (Hctpy) were hydrothermally synthesized. X‐ray diffractional analysis reveals that the isomorphous compounds 1 – 3 adopt one‐dimensional chain‐like structures, whereas 4 – 7 are isomorphic monomers. Luminescence spectroscopy measurements indicates that compound 7 exhibits photoluminescence in the solid state at room temperature.     

Three new coordination complexes based on 2-methyl-4, 5-imidazoledicarboxylic acid varying from zero- to two-dimensionality

Reaction of 2-methyl-imidazole-4,5-dicarboxylic acid (H₃MIDC) with different salts (Zn and Mn) has led to three new H _n MIDC–metal complexes varying from zero- to two-dimensional structures under hydrothermal and solvothermal conditions. The complex [Zn(H₂MIDC)₂(H₂O)₂] (1) is a 0-D complex constructed by H₂MIDC^? and Zn centers and the complex [Mn(HMIDC)(H₂O)₂]?·?H₂O (2) is a polymeric 1-D chiral chain constructed by HMIDC^2? and Mn centers connected into a 3-D supramolecular framework with a 1-D channel. The complex [Zn₃(MIDC)₂(H₂O)₂(DMF)₂]?·?0.5H₂O (3) shows a 2-D puckered structure composed of MIDC^3? and Zn. The differences of the three complexes demonstrate that reaction solvent and temperature have important effects on the structure of these complexes. Complex 3 shows strong fluorescence in the solid state at room temperature.     

Iridium Cluster Chemistry: The Synthesis and the Solid State Structures of [HIr5(CO)12]2− and [HIr4(CO)10PPh3]−

The cluster [HIr₅(CO)₁₂]^2- (1) was prepared by condensation of [HIr₄(CO)₁₁]^- and [Ir(CO)₄]^- (molar ratio 1:1) in refluxing THF, with almost quantitative yields. Its solid state structure was determined by X-ray diffraction at low temperature on the salt [PPh₃CH₂Ph]₂[HIr₅(CO)₁₂]. The metal atoms define a trigonal bipyramidal arrangement. The hydride ligand was located indirectly as a bridge between apical and equatorial metal atoms. The phosphine-substituted cluster [HIr₄(CO)₁₀PPh₃]^- (2) was synthetized by CO displacement on [HIr₄(CO)₁₁]^-, in THF at room temperature. This reaction is selective, with no traces of polysubstitution products. In the solid state, the hydride and the triphenylphosphine are axially bound on basal iridium atoms; the terminal hydrogen atom was directly located by X-ray analysis at a Ir–H distance of 1.57(9) Å. On the contrary, two isomers are present in THF solution, and they interconvert rapidly at room temperature, as shown by¹H and ³¹P NMR spectra.     

Jahn‐Teller‐Ordnung in Mangan(III)‐fluoridsulfaten. II. Phasenübergang und Verzwillingung bei K2[MnF3(SO4)] und 1D Magnetismus in Verbindungen A2[MnF3(SO4)] (A = K,NH4, Rb,Cs)

Jahn‐Teller Ordering in Manganese(III) Fluoride Sulfates. II. Phase Transition and Twinning of K₂[MnF₃(SO₄)] and 1D Magnetism in Compounds A₂[MnF₃(SO₄)] (A = K, NH₄, Rb, Cs) According to single‐crystal X‐ray investigations, K₂[MnF₃(SO₄)] crystallizes at low temperature, like the isostructural Rb, NH₄, and Cs analogues in space group P2₁/c, Z = 4, e.g. at 100 K with a = 7.197, b = 10.704, c = 8.427Å, β = 91.84°. Below about 300 K, the crystals are found to be [001] axis twins. Using a new integration method for area detector records, nearly complete intensity data could be gained allowing for structure refinements of similar quality as for untwinned crystals (e.g. at 100 K: wR₂ = 0.050, R = 0.020 for all reflections). With rising temperature, the monoclinic angle approaches continuously 90°. For an ordering parameter Δβ = β?90° a 2^nd‐order phase transition is observed with an exponent λ = 0.17. At the transition temperature of 280 K resulting from the fit, the monoclinic structure changes – with delay – to orthorhombic with the minimum super‐group Pnca, a = 7.243, b = 10.763, c = 8.457Å, R = 0.024, as found in an early structure determination at room temperature by Edwards 1971. In the chain‐like [MnF₃(SO₄)]^2? anions, manganese(III) is octahedrally coordinated by two trans‐terminal and two trans‐bridging fluorine ligands as well as by the O atoms of two trans‐bridging sulfate ligands. At low temperature, the octahedral elongation by the Jahn‐Teller effect alternates between a F–Mn–F and an O–Mn–O axis (antiferrodistortive ordering). All bridges are asymmetric. From about 320 K on they become symmetric. Due to 2D dynamical Jahn‐Teller effect all octahedra appear compressed. All compounds A₂[MnF₃(SO₄)] show 1D antiferromagnetism. The antiferrodistortive Jahn‐Teller order at low temperatures and the small bridge angles explain the much lower magnetic exchange energies and their inverse relation to the bridge angles as compared with other fluoromanganate(III) chain compounds with the usual ferrodistortive ordering.     

Neue Alkalimetallorthonitrate und ihre schwingungsspektroskopische Charakterisierung

New Alkali Metal Orthonitrates nad their Characterization by Vibrational Spectroscopy For the first time the alkali metal orthonitrates Rb₃NO₄, Cs₃NO₄, AA′₂NO₄ (A,A′=Na, K, Rb), A₃A′₃(NO₄)₂ (A=K, Rb, Cs; A′=Na, K, Rb except Cs₃Na₃(NO₄)₂ and AA′₅(NO₄)₂ (A,A′=Na, K) have been prepared by solid state reactions of alkali metal oxides with alkali metal nitrates. All new compounds were proved to contain NO₄^3?-groups by vibrational spectroscopy. The wavenumbers of the fundamental vibrations are strongly depending on the radius of the cations in an unexpected amount.     

Magnesium(II), Calcium(II), and Barium(II) Coordination Compounds Constructed by 1H‐Tetrazolate‐5‐acetic Acid Ligand

Reactions of H₂tza (H₂tza = 1H‐tetrazolate‐5‐acetic acid) with Mg(NO₃)₂ · 6H₂O, Ca(NO₃)₂ · 4H₂O, or Ba(NO₃)₂ with the presence of KOH under hydrothermal conditions, produced three new coordination compounds, [M(tza)(H₂O)₂] (M = Mg ( 1 ), Ca ( 2 ), Ba ( 3 )). These compounds were structurally characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction. Compounds 1 and 3 display 2D structures, whereas 2 reveals a 1D structure with bridging tza ligand molecules as linkers. Furthermore, the luminescence properties of 1 – 3 at room temperature in the solid state were also investigated. The results show that the nature of metal ions play an important role in governing the molecular frameworks of 1 – 3 , and the strong coordinate abilities of carboxylate and tetrazolate group, endow tza with abundant coordination modes.     

Single Crystal Growth and Crystal Structure of Anhydrous Mercury(I) Nitrate,Hg2(NO3)2

Polycrystalline anhydrous Hg₂(NO₃)₂ was prepared by drying Hg₂(NO₃)₂·2H₂O over concentrated sulphuric acid. Evaporation of a concentrated and slightly acidified mercury(I) nitrate solution to which the same volumetric amount of pyridine was added, led to the growth of colourless rod‐like single crystals of Hg₂(NO₃)₂. Besides the title compound, crystals of hydrous Hg₂(NO₃)₂·2H₂O and the basic (Hg₂)₂(OH)(NO₃)₃ were formed as by‐products after a crystallization period of about 2 to 4 days at room temperature. The crystal structure was determined from two single crystal diffractometer data sets collected at —100°C and at room temperature: space group P2₁, Z = 4, —100°C [room temperature]: a = 6.2051(10) [6.2038(7)]Å, b = 8.3444(14) [8.3875(10)]Å, c = 11.7028(1) [11.7620(14)]Å, ß = 93.564(3) [93.415(2)]°, 3018 [3202] structure factors, 182 [182] parameters, R[Fμ² > 2σ(Fμ²)] = 0.0266 [0.0313]. The structure is built up of two crystallographically inequivalent Hg₂²⁺ dumbbells and four NO₃^— groups which form molecular [O₂N‐O‐Hg‐Hg‐O‐NO₂] units with short Hg‐O bonds. Via long Hg‐O bonds to adjacent nitrate groups the crystal packing is achieved. The Hg‐Hg distances with an average of d(Hg‐Hg) = 2.5072Å are in the typical range for mercurous oxo compounds. The oxygen coordination around the mercury dumbbells is asymmetric with four and six oxygen atoms as ligands for the two mercury atoms of each dumbbell. The nitrate groups deviate slightly from the geometry of an equilateral triangle with an average distance of d(N‐O) = 1.255Å.     

3D Coordination Polymers with Chiral Structures, [Ln2(tda)2(H2O)3]·5H2O: Hydrothermal Synthesis,Structural Characterization,and Luminescent Properties

Reactions of H₃tda (H₃tda = 1H‐1, 2, 3‐triazole‐4, 5‐dicarboxylic acid) with Sm(NO₃)₃ · 6H₂O, Eu(NO₃)₃ · 6H₂O, and Tb(NO₃)₃ · 6H₂O, in the presence of NaOH under hydrothermal conditions, produced three new coordination polymers, [Ln₂(tda)₂(H₂O)₃] · 5H₂O [Ln = Sm ( 1 ), Eu ( 2 ), Tb ( 3 )]. These compounds were structurally characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis (TGA), PXRD and single‐crystal X‐ray diffraction. The single‐crystal X‐ray diffraction studies of compounds 1 – 3 reveal that all compounds are three‐dimensional porous structures with chiral frameworks. Furthermore, the luminescence studies of compound 2 and 3 in the solid state reveal that they are potential luminescent materials at room temperature.