Microwave-assisted hydrothermal synthesis of lead zirconate fine powders

A rapid synthesis of lead zirconate fine powders by microwave-assisted hydrothermal technique is reported. The influences of type of lead precursor, concentration of potassium hydroxide mineraliser, applied microwave power and irradiation time are described. The synthesised powders were characterised by powder X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopic microanalysis and light scattering technique. The merits of the microwave application in reducing reaction time and improving particle mono-dispersion and size uniformity as well as the drawbacks, viz. low purity of the desired phase and increasing demand of mineraliser, are discussed in relation to conventional heating method

Polymorphism in metal complexes of thiazole-4-carboxylic acid

Five new molecular complexes of chemical formula [M(4-tza)₂(H₂O)₂] (M = Co, Ni, and Cu) and a complex of [Cu(4-tza)₂]∙4H₂O using thiazole-4-carboxylic acid (4-tza) as the ligand have been successfully synthesized and structurally characterized by single crystal X-ray diffraction. Two district polymorphs (α and β) are found for both [Co(4-tza)₂(H₂O)₂] and [Ni(4-tza)₂(H₂O)₂]. The effects of solvent composition and temperature on the formation of these polymorphs have been investigated and phase behaviour of the polymorphs was studied through X-ray powder diffraction. Unlike two complexes of Co and Ni, [Cu(4-tza)₂(H₂O)₂] does not display polymorphism but exhibits irreversible structural transformation from [Cu(4-tza)₂(H₂O)₂] to the dehydrated form, [Cu(4-tza)₂], upon heating

Crystal structures and Hirshfeld surface analysis of transition-metal complexes of 1,3-azolecarboxylic acids

The crystal structures of five new transition-metal complexes synthesized using thia­zole-2-carb­oxy­lic acid (2-Htza), imidazole-2-carb­oxy­lic acid (2-H2ima) or 1,3-oxazole-4-carb­oxy­lic acid (4-Hoxa), namely di­aqua­bis­(thia­zole-2-carboxyl­ato-κ2N,O)cobalt(II), [Co(C4H2NO2S)2(H2O)2], 1, di­aqua­bis­(thia­zole-2-car­box­yl­ato-κ2N,O)nickel(II), [Ni(C4H2NO2S)2(H2O)2], 2, di­aqua­bis­(thia­zole-2-car­boxyl­ato-κ2N,O)cadmium(II), [Cd(C4H2NO2S)2(H2O)2], 3, di­aqua­bis­(1H-imidazole-2-carboxyl­ato-κ2N3,O)cobalt(II), [Co(C4H2N2O2)2(H2O)2], 4, and di­aqua­bis­(1,3-oxazole-4-carboxyl­ato-κ2N,O4)cobalt(II), [Co(C4H2NO3)2(H2O)2], 5, are reported. The influence of the nature of the heteroatom and the position of the carboxyl group in relation to the heteroatom on the self-assembly process are discussed based upon Hirshfeld surface analysis and used to explain the observed differences in the single-crystal structures and the supra­molecular frameworks and topologies of complexes 1–5

Crystal structure of (1,3-thiazole-2-carboxylato-κ N)(1,3-thiazole-2-carboxylic acid-κ N)silver(I)

© Meundaeng et al. 2019. The linear two-coordinate silver (I) complex [Ag(C 4 H 2 NO 2 S)(C 4 H 3 NO 2 S)] or [Ag(2-Htza)(2-tza)] is reported (2-Htza = 1,3-thiazole-2-carboxylic acid). The Ag I ion is coordinated by two heterocyclic N atoms from two ligands in a linear configuration, forming a discrete coordination complex. There is an O - H⋯O hydrogen bond between 2-tza - and 2tzaH of adjacent complexes. The hydrogen atom is shared between the two oxygen atoms. This interaction produces a hydrogen-bonded tape parallel to the [110] direction, which is augmented through intermolecular C - H⋯O hydrogen-bonding interactions between the bound thiazole groups. There is a further rather long Ag⋯O interaction [2.8401 (13) Å, compared with a mean of 2.54 (11) Å for 23 structures in the CSD] that assembles these tapes into columns, between which there are C - H⋯π interactions, leading to the formation of a three-dimensional supramolecular architecture

Influence of secondary ligand on structures and topologies of lanthanide coordination polymers with 1,3,5-triazine-2,4,6-triamine hexaacetic acid

© 2015 Taylor and Francis. A series of new lanthanide coordination polymers has been synthesized and structurally characterized; [Ln 4 (TTHA) 2 (pzac)(H 3 O) 2 (H 2 O)]·5H 2 O (Ln = Pr (1a) and Nd (1b)), [Sm 8 (TTHA) 4 (pzac) 0.5 (H 3 O)(H 2 O) 7.5 ]·4H 2 O (2), [Ln 4 (HTTHA) 2 (SO 4 )(H 2 O) 4 ]·5H 2 O (Ln = Pr (3a) and Nd (3b)), where H 6 TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid, and H 2 pzac = 2,5-dioxo-piperazine-1,4-diacetic acid. The compounds feature 3-D frameworks comprising the deprotonated H 6 TTHA as the primary ligand and either the in situ generated pzac 2- or sulfate as the secondary ligands. The influence of the deprotonated H 6 TTHA in directing the framework structures through preferential coordination modes and molecular conformation is described. The effect of the secondary ligands in increasing the compactness of the frameworks and in the alternation of the framework topologies based on the four-connected pts type is described

Copper coordination polymers constructed from thiazole-5-carboxylic acid: Synthesis, crystal structures, and structural transformation

© 2016 Elsevier Inc. We have successfully prepared crystals of thiazole-5-carboxylic acid (5-Htza) (L) and three new thiazole-5-carboxylate-based Cu 2+ coordination polymers with different dimensionality, namely, 1D [Cu 2 (5-tza) 2 (1,10-phenanthroline) 2 (NO 3 ) 2 ] (1), 2D [Cu(5-tza) 2 (MeOH) 2 ] (2), and 3D [Cu(5-tza) 2 ]·H 2 O (3). These have been characterized by single crystal X-ray diffraction and thermogravimetry. Interestingly, the 2D network structure of 2 can directly transform into the 3D framework of 3 upon removal of methanol molecules at room temperature. 2 can also undergo structural transformation to produce the same 2D network present in the known [Cu(5-tza) 2 ]·1.5H 2 O upon heat treatment for 2 h. This 2D network can adsorb water and convert to 3 upon exposure to air

Crystal structures and gas adsorption behavior of new lanthanide-benzene-1,4-dicarboxylate frameworks

Six new lanthanide metal organic complexes, i.e. [La2(NO2-BDC)3(H2O)4] (1) [Ln(L)0.5(NO2-BDC) (H2O)]·3H2O (Ln = Eu (2), Tb (3), Dy (4) and Ho (5); L = BDC2− or BDC2−/NO2-BDC2-) and [Tm(NO2-BDC)1.5(H2O)]·H2O (6), have been synthesized using mixed ligands of benzene-1,4-dicarboxylic acid (H2BDC) and the in situ generated 2-nitro-benzene-1,4-dicarboxylic acid (NO2-BDC2-). Single crystal structures and topologies of the complexes are presented based on the single crystal X-ray diffraction and spectroscopic data. Whilst the structures of 1 and 6 contain negligible voids, the frameworks of 2–5 are microporous in nature and stable upon the removal of all the water molecules from the structures and thermal treatment to over 400 °C. Based on the study of 2, significant adsorption capacities for carbon dioxide (95 cm3·g−1 or 4.2 mmol·g−1) and hydrogen (79 cm3·g−1 or 4 mmol·g−1), as well as the remarkable stability of the framework upon the sorption/desorption experiments are revealed

(1-Butyl-1,4-diazabicyclo[2.2.2]octon-1-ium-κN4)trichloridocobalt(II)

The title compound, [Co(C 10 H 21 N 2 )Cl3], was obtained as the by-product of the attempted synthesis of a cobalt sulfate framework using 1,4-diaza-bicyclo-[2.2.2] octane as an organic template. The asymmetric unit comprises two distinct mol-ecules, and in each, the cobalt(II) ions are tetra-hedrally coordinated by three chloride anions and one 1-butyl-diaza-bicyclo-[2.2.2]octan-1-ium cation. The organic ligands are generated in situ, and exhibit two forms differentiated by the eclipsed and staggered conformations of the butyl groups. These mol-ecules inter-act by way of C - H⋯Cl hydrogen bonds, forming a three-dimensional hydrogen-bonding array

Tris(ethyl­enediamine)cobalt(II) sulfate

The structure of the title compound, [CoII(C2H8N2)3]SO4, the cobalt example of [M(C2H8N2)3]SO4, is reported. The Co and S atoms are located at the 2d and 2c Wyckoff sites (point symmetry 32), respectively. The Co atom is coordinated by six N atoms of three chelating ethyl­enediamine mol­ecules generated from half of the ethyl­enediamine mol­ecule in the asymmetric unit. The O atoms of the sulfate anion are disordered mostly over two crystallographic sites. The third disorder site of O (site symmetry 3) has a site occupancy approaching zero. The H atoms of the ethyl­enediamine mol­ecules inter­act with the sulfate anions via inter­molecular N—H⋯O hydrogen-bonding inter­actions

Inter­calated brucite-type layered cobalt(II) hydroxy­sulfate

In an attempt to synthesize new cobalt(II) sulfate framework structures using 1,4-diaza­bicyclo­[2.2.2]octane as a template, crystals of poly[0.35-[hexa­aqua­cobalt(II)] [tri-μ-hydroxido-μ-sulfato-dicobalt(II)]], {[Co(H2O)6]0.35[Co2(OH)3(SO4)]}n, were obtained as a mixture with [Co(H2O)6]SO4 crystals. The crystal structure can be described as being constructed from discrete brucite-type [Co4(OH)6(SO4)2] layers, each of which is built up from edge-shared [Co(OH)6] and [Co(OH)4(OSO3)2] octa­hedra, with partial inter­calation by [Co(H2O)6]2+ ions. The absence of ca 30% of the [Co(H2O)6]2+ cations indicates partial oxidation of cobalt(II) to cobalt(III) within the layer