Conservation of [(C2H4NH3)3N]2·(ZrF7)2·H2O layers during the topotactic dehydration of [(C2H4NH3)3N]2·(ZrF7)2·9H2O

Tren amine cations [(C₂H₄NH₃)₃N]³⁺ and zirconate or tantalate anions adopt a ternary symmetry in two hydrates, [H₃tren]₂·(ZrF₇)₂·9H₂O and [H₃tren]₆·(ZrF₇)₂·(TaOF₆)₄·3H₂O, which crystallise in R32 space group with a_H = 8.871 (2) Å, c_H = 38.16 (1) Å and a_H = 8.758 (2) Å, c_H = 30.112 (9) Å, respectively. Similar [H₃tren]₂·(MX₇)₂·H₂O (M = Zr, Ta; X = F, O) sheets are found in both structures; they are separated by a water layer (O_w(2)-O_w(3)) in [H₃tren]₂·(ZrF₇)₂·9H₂O. Dehydration of [H₃tren]₂·(ZrF₇)₂·9H₂O starts at room temperature and ends at 90 °C to give [H₃tren]₂·(ZrF₇)₂·H₂O. [H₃tren]₂·(ZrF₇)₂·H₂O layers remain probably unchanged during this dehydration and the existence of one intermediate [H₃tren]₂·(ZrF₇)₂·3H₂O hydrate is assumed. O_w(1) molecules are tightly hydrogen bonded with -NH₃⁺ groups and decomposition of [H₃tren]₂·(ZrF₇)₂·H₂O occurs from 210 °C to 500 °C to give successively [H₃tren]₂·(ZrF₆)·(Zr₂F₁₂) (285 °C), an intermediate unknown phase (320 °C) and ZrF₄.     

Synthesis, crystal structure, and structural conversion of Ni molybdate hydrate NiMoO4·nH2O

The synthesis and crystal structure of NiMoO₄·nH₂O were investigated. The hydrate crystallized in the triclinic system with space group P−1, Z=4 with unit cell parameters of a=6.7791(2) Å, b=6.8900(2) Å, c=9.2486(2) Å, α=76.681(2)°, β=83.960(2)°, γ=74.218(2)°. Its ideal chemical composition was NiMoO₄·3/4H₂O rather than NiMoO₄·1H₂O. Under hydrothermal conditions the hydrate turned directly into α-NiMoO₄ above 483 K, giving nanorods thinner than the crystallites of the mother hydrate. On the other hand, it turned into Anderson type of polyoxomolybdate via a solid-solution process in a molybdate solution at room temperature.     

Syntheses and crystal structures of straight or zigzag one-dimensional coordination polymers based on Cu(II) square pyramidal or Cu(I) tetrahedral coordination environments

Two coordination polymers containing copper ions, [Cu(SO₄)(pyz)(H₂O)]_n (1) and [Cu₂(SO₄)(pyz)₂(H₂O)₂]_n (2) (pyz = pyrazine), have been synthesized and characterized by single-crystal X-ray analyses. Compound 1 was synthesized by the reaction of Cu(SO₄) · 5H₂O with pyz (ratio = 1:2) in H₂O at room temperature. The structure of 1 consists of linear chains of [Cu(pyz)(H₂O)]²⁺, with coordinated sulfate ions bridging the chains. Compound 2 was obtained as dark red blocks from the reaction of Cu(SO₄) · 5H₂O and pyz (ratio = 1:2) in H₂O, after heating to 180 °C in a Teflon autoclave for 48 h. The structure of 2 consists of zigzag chains of [Cu(pyz)(H₂O)]⁺ with sulfate ions. Only the difference in the synthesis temperature, room temperature or 180 °C, determines whether Cu(II) or Cu(I) coordination polymers are formed, with the reduction of Cu(II) to Cu(I) being explained by the Gillard mechanism.     

The reaction of MgCl2·4H2O with CCl2F2

A new reaction of MgCl₂·4H₂O with CCl₂F₂ is investigated by DTA and TG from room temperature to 350 °C. It is observed that MgF₂ was obtained between 252 and 350 °C, Below the temperature, MgCl₂·4H₂O dehydrates and hydrolyzes to MgCl₂ and Mg(OH)Cl, which are the real reactants of the reaction with CCl₂F₂. The formation of MgF₂ is ascribed to the reaction of MgCl₂ and Mg(OH)Cl with HF, which forms by decomposition of CCl₂F₂ with the taking part in of H₂O released from dehydration of hydrated magnesium chloride on the surface of MgCl₂ and Mg(OH)Cl, which catalyzes the decomposition of CCl₂F₂ in this case. Consequently, the reactions are tested in the fluid-bed condition. It is found that MgF₂ formed at temperatures down to 200 °C in a fluid-bed reactor. This reaction may be used as a method of disposing of the environmentally sensitive CCl₂F₂ (rather than release into the atmosphere). It is also a method for the preparation of MgF₂.     

Influence of some reaction conditions on the obtaining of tetra- and dinuclear zinc complexes of some Schiff bases derived from 2,6-diformyl-4-alkyl-phenols

A template 2:2:4 condensation of 2,6-diformyl-4-methyl-phenol, triethylenetetramine and zinc acetate gave rise to the crystallisation of [{Zn₄(H₄L¹)(OAc)₄}{Zn(OAc)₃(H₂O)}(OAc)] · 7H₂O (1 · 7H₂O), being H₆L¹ a macrocyclic diphenolate Schiff base ligand. Changing some operation conditions, other template reactions yielded dinuclear complexes of the type Zn₂(Lⁿ)(OAc) · xH₂O, where H₃Lⁿ (n = 2, 3) are podant triphenolate Schiff base ligands derived from a 3:1 condensation of the corresponding 2,6-diformyl-4-alkyl-phenol (alkyl = Me or Bu^t, respectively) and triethylenetetramine. After recrystallisation, these two latter complexes could be X-ray characterised as Zn₂(L²)(OAc) · 1.25H₂O · 0.5MeCN (2 · 1.25H₂O · 0.5MeCN), and Zn₂(L³)(OAc) (3). Furthermore, after addition of a 3:1 molar ratio of 2-amino-4-methyl-phenol to 3, this underwent imidazolidine hydrolysis and a double imine condensation, yielding Zn₂(L⁴)(OAc)(HOAc) · 2H₂O (4 · 2H₂O), where H₃L⁴ is an acyclic pentadentate Schiff base derived from the 1:2 condensation of 2,6-diformyl-4-tert-butyl-phenol and 2-amino-4-methyl-phenol.     

From discrete entity to three-dimensional architecture: Syntheses,crystal structures and optical properties of a series of transition metal complexes constructed from 4-carboxymethylbenzoic acid and 4,4′-bipyidine

Five new interesting transition metal coordination polymers [MnL₂(bpy)₂(H₂O)₂]_n (1) (H₂L = 4-carboxymethylbenzoic acid) (bpy = 4,4′-bipyidine), [CoL(bpy)(H₂O)₃ · H₂O]_n (2), [CdL(bpy)(H₂O)₃ · H₂O]_n (3), [Cu₂L(bpy)₂ · 3H₂O]_n (4) and [Zn₂L₂(bpy) · H₂O]_n (5) have been synthesized under solvothermal conditions and structurally characterized. This series of complexes has shown an intriguing variety of architectures, which firstly form zero- to two-dimensional frameworks by metal–ligand interactions, and secondly form three-dimensional supramolecular frameworks by intermolecular interactions such as hydrogen bonds. Compound 3 shows strong blue fluorescent emissions in the solid state upon photo-excitation at 359 nm at room temperature and may be an excellent candidate for blue-fluorescent materials. Compound 4 appears to be a good candidate for new hybrid inorganic–organic NLO materials.     

Synthesis and magnetic properties of ZnFe2O4 obtained by mechanochemically assisted low-temperature annealing of mixtures of Zn and Fe oxalates

The mechanism of formation of zinc ferrite (ZnFe₂O₄) from ZnC₂O₄·1.8H₂O-2Fe^IIC₂O₄·2H₂O and ZnC₂O₄·1.8H₂O-Fe₂^III(C₂O₄)₃·6H₂O mixtures is investigated. By combination of TG and XRPD measurements it has been shown that microcrystalline ZnFe₂O₄ forms from physical mixtures after prolonged annealing at 1000 °C while nanocrystalline ZnFe₂O₄ powders are produced by mild annealing (1 h at 500 °C in air) of mechanically activated mixtures. The magnetic properties of ZnFe₂O₄ powders obtained from physical and from milled mixtures are compared.     

Two-dimensional composition diagram of the Al(OH)3-dien-HFaq.-ethanol system: Evidence of a new tetrahedral (Al4F18) polyanion

Six domains appear in the 2D composition diagram of the Al(OH)₃-dien-HF_aq.-ethanol system at 190 °C and [Al³⁺] = 1 mol L⁻¹ under microwave heating. Four organic-inorganic fluorides crystallise: [H₃dien]·(AlF₆) (P2₁/c, Z = 4), [H₃dien]₂·(AlF₅(H₂O))₃·2H₂O (P2₁/n, Z = 4), [H₃dien]·(AlF₆)·2H₂O, which was previously known, and [H₃dien]₂·(Al₄F₁₈) (C2/c, Z = 4). A new (Al₄F₁₈)⁶⁻ polyanion, which results from the tetrahedral association of four AlF₆ octahedra linked by corners, is evidenced in [H₃dien]₂·(Al₄F₁₈).     

Assembly and structures of five new Cu(II) complexes based on the V-shaped building block [Cu(dbsf)]

Five new copper(II) complexes [Cu(dbsf)(H₂O)]_n · 0.5n(i-C₃H₇OH) (1), [Cu(dbsf)(4,4′-bpy)_0.5]_n · nH₂O (2), [Cu(dbsf)(2,2′-bpy)(H₂O)]₂ · (n-C₃H₇OH) · 0.5H₂O (3), [Cu(dbsf)(phen)(H₂O)]₂ · 1.5H₂O (4) and [Cu(dbsf)(2,2′-bpy)(H₂O)]_n · n(i-C₃H₇OH) (5) (H₂dbsf = 4,4′-dicarboxybiphenyl sulfone, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline, i-C₃H₇OH = isopropanol, n-C₃H₇OH = n-propanol) have been synthesized under hydro/solvothermal conditions. All of the complexes are assembled from V-shaped building blocks, [Cu(dbsf)]. Complex 1 is composed of 1D double-chains. In complex 2, dbsf²⁻ ligands and 4,4′-bpy ligands connect Cu(II) ions into catenane-like 2D layers. These catenane-like 2D layers stack in an ABAB fashion to form a 3D supramolecular network. Complexes 3 and 4 are 0D dimers, in which two [Cu(dbsf)] units encircle to form dimetal macrocyclic molecules. However, in complex 5, the V-shaped building blocks [Cu(dbsf)] are joined head-to-tail, resulting in the formation of infinite tooth-like chains. The different structures of complexes 3 and 5 may be attributed to the different solvent molecules included.     

Synthesis,structural characterisation and thermal decomposition of a new organic–inorganic hybrid material (C5H14N2)[Cu(SO4)2(H2O)4] · H2O

The crystal structure of copper sulfate templated by 2-methylpiperazine, (C₅H₁₄N₂)[Cu(SO₄)₂(H₂O)₄] · H₂O, was investigated using single crystal X-ray diffraction data. At room temperature, it crystallises in the monoclinic P2₁/n space group with the following unit-cell parameters: a = 6.9153(1), b = 23.1295(3), c = 10.4472(1) Å, β = 104.227(1)°, V = 1619.75(4) Å³ and Z = 4. The Cu^II cation adopts a slightly distorted octahedral geometry, arising from four water molecules and two sulfate tetrahedra leading to the formation of [Cu(SO₄)₂(H₂O)₄] units. The structure consists of isolated [Cu(SO₄)₂(H₂O)₄]²⁻ anions, 2-methylpiperazinediium cations (C₅H₁₄N₂)²⁺ and water molecules connected by a three-dimensional hydrogen-bond network. The thermal decomposition of the precursor, studied by thermogravimetry and temperature-dependent X-ray powder diffraction, proceeds through four stages giving rise to the copper oxide.     

Ruthenium-catalyzed generation of hydrogen from iso-propanol

The dehydrogenation reaction of iso-propanol has been investigated in the absence of a hydrogen acceptor. Among different transition metals tested various ruthenium precursors in the presence of phosphine ligands proved to be active catalysts. Best results (turnover frequencies up to 155 h⁻¹ after 2 h) were achieved with RuCl₃·xH₂O and 2-di-tert-butyl-phosphinyl-1-phenyl-1H-pyrrole 4 at low temperature (90 °C).     

H2O + Fe(NO3)3 + Ni(NO3)2 ternary system isotherms at 0 °C and 30 °C

H₂O + Ni(NO₃)₂ binary system were investigated in the temperature range from −25 °C to 55 °C. The solid-liquid equilibria of the ternary system H₂O + Fe(NO₃)₃ + Ni(NO₃)₂ were studied using a synthetic method based on conductivity measurements. Tow isotherms were established at 0 °C and 30 °C, and the appearing stable solid phases are iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O), iron nitrate hexahydrate (Fe(NO₃)₃·6H₂O), nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and nickel nitrate tetrahydrate (Ni(NO₃)₂·4H₂O).     

One-dimensional coordination polymers of praseodymium(III)–vanadium(V) complexes with pyridine-2,6-dicarboxylic acid

This paper represents the hydrothermal synthesis of new isomorphous lanthanide–vanadium complexes with one-dimensional coordination polymers: [Pr₂(VO₂)₂(dipic)₄(H₂O)₉] · nH₂O with dipic = pyridine-2,6-dicarboxylic acid and n = 7.75. The structure determination shows a unique one-dimensional structure in which three types of chains run along the c-axis: the chain of positively charged praseodymium complexes bridged by a dipic ligand ([Pr(dipic)(H₂O)₅]⁺), the chain of negatively charged, stacked vanadium complexes ([VO₂(dipic)]⁻), and the chain of neutral praseodymium complexes with a bridged dipic ligand and a coordinating dipic ligand ([Pr(dipic)[VO₂(dipic)](H₂O)₄]). Such one-dimensional chains provide open channels which can accommodate water molecules. Not only accommodated water molecules but also ones coordinated to praseodymium ions were easily removed and absorbed upon heating at 200 °C and exposure of humidity at room temperature, respectively.     

Four distinctive 1-D lanthanide carboxylate coordination polymers: Synthesis,crystal structures and spectral properties

Four novel lanthanide coordination polymers [Pr(mal)(OH)(bipy) · 2H₂O]_n (1), {[Dy¹(SBA)₃(H₂O)₂][Dy²(SBA)₃(H₂O)₂] · 4H₂O}_n (2), {[Tb(OHnic)(Onic)(H₂O)₅ · (OHnicH)] · H₂O}_n (3) and {[Sm(OHnic)(Onic)(H₂O)₅ · (OHnicH)] · H₂O}_n (4) (Hmal = maleic acid, HSBA = 4-sulfobenzoic acid, OHnicH = 6-hydroxynicotinic acid and bipy = 2,2′-bipyridine) have been synthesized and determined by single crystal X-ray diffraction. Complex 1 is a 1-D helical chain with seven-coordinated praseodymium centers. Complex 2 forms 1-D chain-like molecular structure containing two crystallographically unique dysprosium centers, the Dy¹ center is seven-coordinated while Dy² is eight-coordinated. The isomorphous complexes 3 and 4 exhibit an unprecedented 1-D chain-like polymeric structure through hydroxyl oxygen atoms of bridging Onic²⁻ anions linking up the neighboring central ions, and there exist three types of 6-OHnicH ligands in the structural unit which is rare for lanthanide carboxylate complexes. The photophysical properties of these complexes were studied using ultraviolet absorption spectra, fluorescence excitation and emission spectra.     

Sol-gel synthesis of hydrous ruthenium oxide nanonetworks from 1,2-epoxides

Hydrous ruthenium oxide (RuO₂·xH₂O) xerogels were synthesized through the addition of a 1,2-epoxide, propylene oxide, to commercial hydrated ruthenium chloride, “RuCl₃·xH₂O,” in ethanol. After a blue-black monolithic gel formed in 4 h, the samples were allowed to age for 24 h and were dried in ambient conditions. The dried samples were then characterized by XPS, XRD, DTA and TGA. XPS showed the Ru(3d_5/2) peak at a binding energy of 281.7 eV, corresponding to that of hydrous ruthenium oxide. XRD data revealed the synthesized material as amorphous. Heating the sample in inert atmospheres caused the complete reduction of the oxide to the zero-valent state, whereas heating the sample in air resulted in both crystalline anhydrous RuO₂ and zero-valent ruthenium, depending on the method of heating. DTA traces showed an endotherm ending at 150 °C, corresponding to the loss of coordinated water, as well as two higher temperature crystallization exotherms when the sample was heated in both inert and oxygen-rich atmospheres. TGA runs also confirmed the complete reduction of the hydrous oxide when heated in nitrogen below 270 °C and the formation of anhydrous ruthenium oxide when heated in air, confirming the XRD results.     

Coordination studies of 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine towards Cu cation. X-ray studies,spectroscopic characterization and DFT calculations

The reactions of 5,6-diphenyl-3-(2-pyridyl)-1,2,4-triazine with CuCl₂ · 2H₂O, Cu(NO₃)₂ · 3H₂O and CuSO₄ · 5H₂O have been examined, and four [CuCl₂(dppt)] (1), [CuCl₂(dppt)₂] · 2MeOH (2), [Cu(dppt)₂(H₂O)₂](NO₃)₂ (3) and [Cu(SO₄)(dppt)(H₂O)]_n · nH₂O (4) complexes have been obtained. All the complexes have been structurally and spectroscopically characterized, and compound 4 has been additionally studied by magnetic measurements. The electronic structure of 1 has been calculated with the density functional theory (DFT) method, and the time-dependent DFT calculations have been employed to calculate the electronic spectrum of 1.     

Experimental study on preparation of LaMO3 (M = Fe, Co, Ni) nanocrystals and their catalytic activity

The perovskite-type oxides LaMO₃ (M = Fe, Co, Ni) were prepared by a glycine combustion method using La (NO₃)₃·6H₂O and Fe (NO₃)₃·9H₂O, Co (NO₃)₂·6H₂O, Ni (NO₃)₂·6H₂O as the raw materials, respectively, and C₂H₅NO₂ as gelating agent. The products were characterized by XRD, TEM, HRTEM, SEM and BET. The catalytic activity of LaMO₃ (M = Fe, Co, Ni) nanocrystals on thermal decomposition of NH₄CIO₄ (AP) were carried out by DTA and TG. The burning rate of the propellant modified by obtained LaCoO₃ was measured by strand burner method. The experimental results showed that the obtained products can play a catalytic role in the thermal decomposition of AP and combustion of AP-based propellant. The order of the catalytic performance of obtained products on AP thermal decomposition is LaCoO₃ > LaNiO₃ ≈ LaFeO₃. Adding 2% of LaCoO₃ nanocrystals to AP decreases the decomposition temperature by 134 °C and increases the heat of decomposition by 0.8 kJ g⁻¹. Compared with basic propellant, the burning rate of propellant modified by 1% LaCoO₃ nanocrystals increases around 8%.     

Syntheses, crystal structures of a series of copper(II) complexes and their catalytic activities in the green oxidative coupling of 2,6-dimethylphenol

Three mixed-ligand Cu^II complexes bearing iminodiacetato (ida) and N-heterocyclic ligands, namely, [Cu₂(ida)₂(bbbm)(H₂O)₂] · H₂O (1), [Cu₂(ida)₂(btx)(H₂O)₂] · 2H₂O (2) and [Cu₂(ida)₂(pbbm)(H₂O)₂] · H₂O · 3CH₃OH (3) (bbbm = 1,1^′-(1,4-butanediyl)bis-1H-benzimidazole, btx = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene, pbbm = 1,1^′-(1,3-propanediyl)bis-1H-benzimidazole), in addition to three fcz-based Cu^II complexes, namely, {[Cu(fcz)₂(H₂O)₂] · 2NO₃}_n (4), {[Cu(fcz)₂(H₂O)] · SO₄ · DMF · 2CH₃OH · 2H₂O}_n (5) and {[Cu(fcz)₂Cl₂] · 2CH₃OH}_n (6) (fcz = 1-(2,4-difluorophenyl)-1,1-bis[(1H-1,2,4-triazol-l-yl) methyl]ethanol) have been prepared according to appropriate synthetic strategies with the aim of exploiting new and potent catalysts. Single crystal X-ray diffraction shows that 1 and 2 possess similar binuclear structures, 3 features a 2D pleated network, and 4 exhibits a 1D polymeric double-chain structure. Complexes 1-6 are tested as catalysts in the green catalysis process of the oxidative coupling of 2,6-dimethylphenol (DMP). Under the optimized reaction conditions, these complexes are catalytically active by showing high conversion of DMP and high selectivity of PPE. The preliminary study of the catalytic-structural correlations suggests that the coordination environment of the copper center have important influences on their catalytic activities.     

Low temperature synthesis of bilayer hydrated cesium cobalt oxide

Bilayer hydrated Na_0.35CoO₂·1.3H₂O structure has re-directed superconductivity research in recent years. Here, we develop a low temperature synthesis method to prepare a novel hydrous Cs_0.2CoO₂·0.63H₂O compound in one step. The bilayer-hydrate of Cs_0.2CoO₂·0.63H₂O with a greatest interlayer spacing d=10.0(2) Å among alkali cobalt oxides has been grown in crystal form. Magnetic susceptibility measurement of Cs_0.2CoO₂·0.63H₂O displays a paramagnetic behavior down to 1.9 K. With the assistance of low temperature molten CsOH solvent, crystals of Rb_0.30CoO₂·0.36H₂O and K_0.35CoO₂·0.4H₂O can be grown. The results provide the capability for preparing a novel hydrous structure and the systematic investigation of interlayer coupling effect of alkali ion insertion compounds.     

Lanthanide N,N′-piperazine-bis(methylenephosphonates) (Ln=La, Ce, Nd) that display flexible frameworks, reversible hydration and cation exchange

Hydrothermal syntheses of lanthanide bisphosphonate metal organic frameworks comprising the light lanthanides lanthanum, cerium and neodymium and N,N′-piperazine bis(methylenephosphonic acid) (H₂L(1) and its 2-methyl and 2,5-dimethyl derivatives (H₂L(2) and H₂L(3)) gives three new structure types. At elevated starting pH (ca. 5 and above) syntheses give ‘type I’ materials with all metals and acids of the study (MLnLxH₂O, M=Na, K, Cs; Ln=La, Ce, Nd; x≈4: KCeL(1)·4H₂O, C2/c, a=23.5864(2) Å, b=12.1186(2) Å, c=5.6613(2) Å, β=93.040(2)°). The framework of structure type I shows considerable flexibility as the ligand is changed, due mainly to rotation around the -N-CH₂- bond of the linker in response to steric considerations. Type I materials demonstrate cation exchange and dehydration and rehydration behaviour. Upon dehydration of KCeL·4H₂O, the space group changes to P2₁/n, a=21.8361(12) Å, b=9.3519(4) Å, c=5.5629(3) Å, β=96.560(4)°, as a result of a change of the piperazine ring from chair to boat configuration. When syntheses are performed at lower pH, two other structure types crystallise. With the ‘non-methyl’ ligand 1, type II materials result (LnL(1)H₂L(1)·4.5H₂O: Ln=La, P−1, a=5.7630(13) Å, b=10.213(2) Å, c=11.649(2) Å, α=84.242(2)°, β=89.051(2)°, γ=82.876(2)°) in which one half of the ligands coordinate via the piperazine nitrogen atoms. With the 2-methyl ligand, structure type III crystallises (LnHL(2)·4H₂O: Ln=Nd, Ce, P2₁/c, a=5.7540(9) Å, b=14.1259(18) Å, c=21.156(5) Å, β=90.14(2)°) due to unfavourable steric interactions of the methyl group in structure type II.