Synthesis and thermal decomposition of neodymium(III) peroxotitanate to Nd<Subscript>2</Subscript>TiO<Subscript>5</Subscript>

Neodymium(III) peroxotitanate is used as a precursor for obtaining Nd₂TiO₅. The last one possesses numerous valuable electrophysical properties. TiCl₄, Nd(NO₃)₃·6H₂O and H₂O₂ in mol ratio 1:2:10 were used as starting materials. The reaction ambience was alkalized to pH = 9 with a solution of NH₃. The obtained neodymium(III) peroxotitanate and intermediate compounds of the isothermal heating were proved by the help of quantitative analysis and infrared spectroscopy (IRS). It has Nd₄[Ti₂(O₂)₄(OH)₁₂]·7H₂O composition. The absorption band observed in IRS at 831 cm^?1 relates to a triangular bonding of the peroxo group of Ti, at 1062 cm^?1—terminal groups Ti–OH and at 1491 and 1384 cm^?1—the bridging OH^?-groups Ti–O(H)–Ti. Nd₂TiO₅ was obtained by thermal decomposition of neodymium(III) peroxotitanate. The isothermal conditions for decomposition were determined on the base of differential thermal analysis, thermogravimetric and differential scanning calorimetry results in the temperature range of 20–1000 °C. The mechanism of thermal decomposition of Nd₄[Ti₂(O₂)₄(OH)₁₂]·7H₂O to Nd₂TiO₅ was studied. In the temperature range of 20–208 °C, a simultaneous decomposition of the peroxo groups by the separation of oxygen and hydrate water is conducted and Nd₄[Ti₂O₄(OH)₁₂] is obtained. From 208 to 390 °C, the terminal OH^?-groups are separated and Nd₄[Ti₂O₇(OH)₆] is formed. In the range of 390–824 °C, the bridging OH^?-groups are completely decomposed to Nd₂TiO₅. The optimal conditions for obtaining nanocrystalline Nd₂TiO₅ are 900 °C for 6 h and 20–80 nm.     

Intermolecular complexes of nido-C<Subscript>2</Subscript>B<Subscript>3</Subscript>H<Subscript>7</Subscript> with HF and LiH molecules: the theoretical studies,bonding properties and natural bond orbital (NBO) analysis

The changes in stabilization energy upon the formation of intermolecular hydrogen, dihydrogen and lithium bond complexes between C₂B₃H₇, LiH and HF have been investigated using MP2 method with aug-cc-pVDZ basis set. The interaction of HF with nido-C₂B₃H₇ could occur through the formation of B–H^?δ···^+δH–F, C–H^+δ···F^?δ–H and B–C···H–F classical and non-classical hydrogen bonds. The B–C bonds in backbone of the C₂B₃H₇ as electron donor interact with σ* orbital of HF as electron acceptor. Also interaction of LiH with nido-C₂B₃H₇ resulted in B–C···Li–H and B–H···LiH lithium bonds as well as C–H···H–Li dihydrogen bond complexes. In some of these complexes, LiH interacts with B–C bonds. Results are indicating that more stable complexes belong to interaction of HF and LiH with backbone of the nido-C₂B₃H₇. The AIM and NBO methods were used to analyze the intermolecular interactions; also the electron density at the bond critical point and the charge transfer of obtained complexes were studied.     

Hydrate schwacher und starker Basen. XI. Die Kristallstrukturen von NaOH · 3,5H2O und NaOH · 7 H2O. Eine Präzisierung

Hydrates of Weak and Strong Bases. XI. The Crystal Structures of NaOH · 3,5H₂O and NaOH · 7 H₂O. A Refinement The crystal structures of the hydrates NaOH · 3,5 H₂O (space group P2₁/c, Z = 8 formula units per unit cell; lattice parameters: a = 6.481, b = 12.460, c = 11.681 Å, β = 104.12° at ?100°C) and NaOH · 7 H₂O (P2₁/c, Z = 4; a = 7.344, b = 16.356, c = 6.897 Å, β = 92.91° at ?150°C) have been redetermined using MoKα diffractometer data. The obtained refinement of the structures, including the localization also of the H atoms for the first time, has led to new findings with respect to the H bonds. In particular, in both hydrates there is one such interaction of the rare type OH^? …? OH₂, from an OH^? ion to an H₂O molecule, i. e. with the OH^? ion as the proton donor.     

Ein ungewöhnliches H-Brückenbindungssystem in Rubidium-hydroxiddihydrat,RbOH · 2 H2O

An Unusual System of Hydrogen Bonds in Rubidium Hydroxide Dihydrate, RbOH · 2 H₂O RbOH · 2H₂O was obtained by the reaction of Rb with H₂O and dehydration of the resulting solution by concentrated sulfuric acid. The compound melts at 310 K. The structure was determined by X-ray single crystal methods: The H positions of H₂O were found. The structure consists of a threedimensional H-bonded network of H₂O molecules and OH^?ions. Hydroxide ions are acceptors for four protons of four adjacent water molecules with d(O? O) = 2×2.59 Å and 2×2.82 Å. Oxygen of OH-ions is disordered over a distance of 1.27 Å. Rb has 8 H₂O molecules as nearest neighbours, d(Rb? O) = 3.03 Å to 3.07 Å, OH^?ions are further removed with d(Rb? O) ≥ 3.45 Å.     

Charakterisierung von Distorsionsisomeren der Anionen Pentacyano-oxo-molybdat(IV) sowie Tetracyano-oxo-aqua-molybdat(IV) im festen Zustand. Kristallstrukturen von [(C6H5)4P]3[MoO(CN)5] · 7 H2O(grün), [(C6H5)4As]2 [MoO(OH2)(CN)4] · 4 H2O (blau) und [(C6H5)4P]2[MoO(OH2)(CN)4] · 4 H2O (grün)

Characterization of Distortional Isomers of the Anions Pentacyano-oxo-molybdate(IV) and of Tetracyano-aqua-oxo-molybdate(IV) in the Solid State. Crystal Structures of [(C₆H₅)₄P]₃[MoO(CN)₅] · 7 H₂O (green), [(C₆H₅)₄As]₂[MoO(OH₂)(CN)₄] · 4 H₂O (blue), and [(C₆H₅)₄P]₂[MoO(OH₂) (CN)₄] · 4 H₂O (green) Preparation of a series of salts containing the new pentacyano-oxo-molybdate(IV) anion is described: Cs₂H[MoO(CN)₅] (blue), [(CH₃)₄N]₂H[MoO(CN)₅] · 2 H₂O (blue) and [Cr(en)₃] [MoO(CN)₅] · 4 H₂O (green). The green [(C₆H₅)₄P]₃[MoO(CN)₅] · 7 H₂O crystallizes triclinic in the space group P1 . The molybdenum(IV) center is in an pseudo-octahedral environment of a terminal oxo-group (d(Mo?O); 1.705(4) Å), a CN^? group in the trans-position (d(Mo? C): 2.373(6) Å), and four equatorial CN^? groups (averaged d(Mo? C): 2.178 (Å). The blue and green salts exhibit v(Mo?O) stretching frequencies at 948 cm^?1 and 920 cm^?1, respectively. Blue and green salts containing the [MoO(OH₂)(CN)₄]^2? anion and [(C₆H₅)₄P]⁺ or [(C₆H₅)₄As]⁺ cations have been prepared and characterized by single crystal crystallography. [(C₆H₅)₄P]₂[MoO(OH₂)(CN)₄] · 4 H₂O (green) and [(C₆H₅)₄As]₂[MoO(OH₂)(CN)₄] · 4 H₂O (blue) crystallize monoclinic in the space group C—P2₁/n. They are considered to be distortional isomers of the complex anion: the green species has a Mo?O bond distance of 1.72(2) Å whereas for the blue species d(Mo?O) = 1.60(2) Å is found; the corresponding v(Mo?O) frequencies are at 920 cm^?1 and 980 cm^?1.     

Ungewöhnliche H-Brückenbindungen in Natriumhydroxidmonohydrat: Röntgen- und Neutronenbeugung an NaOH · H2O bzw. NaOD · D2O

Unusual H-Bonds in Sodium Hydroxide Monohydrate: X-Ray and Neutron Diffraction on NaOH · H₂O and NaOD · D₂O, respectively X-ray data revealed the structure of NaOH · H₂O including the H positions. Neutron diffraction on microcrystalline NaOD · D₂O was used for comparison of H with D positions: The compound crystallizes in a layer-type structure with the sequence …? /O Na O O Na O/ …? closely related to that of hydrargillite Al(OH)₃ with …? /O 2/3 Al O O 2/3 Al O/ …?. Between OH^? ions as acceptors and H₂O molecules mäandric, one-dimensional infinite strong H-bonds occur with d(O…?O) = 2.66 Å and 2.69 Å. These lie within O-layers that coordinate Na⁺ ions. Bridge-bonds between OH^? ions as donors and H₂O molecules as acceptors connect the /O Na O/-layers with d(O…?O) = 3.18 Å.     

Synthesis,structures and characterization of two new supramolecular coordination complexes with the ambidentate ligand 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot)

Two new coordination supramolecular complexes based on a versatile and unsymmetrical 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) and Mn^II and Ni^II have been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of MnCl₂?· 4H₂O with Hpot afforded a neutral mononuclear complex [Mn(pot)₂(H₂O)₄]?·?2H₂O (1), which exhibits a three-dimensional (3-D) supramolecule through versatile intermolecular O–H?···?X (X=O, N and S) hydrogen bond interactions. When using NiCl₂?·?6H₂O instead of MnCl₂?· 4H₂O under similar reaction conditions, a neutral mononuclear complex [Ni(pot)₂(H₂O)₄] (2) is also obtained, which does not exhibit intermolecular hydrogen bonds and π–π stacking interactions. It is very interesting that the pot anion exhibits different coordination modes in complexes 1 and 2. The IR spectra and the TGA for 1 and 2 have been investigated and discussed in detail.     

Cu(II) and Ni(II)‐1,10‐phenanthroline‐ 5,6‐dione‐amino acid ternary complexes exhibiting pH‐sensitive redox properties

Syntheses, and electrochemical properties of two novel complexes, [Cu(phendio)(L ‐Phe)(H₂O)](ClO₄) ·H₂O (1) and [Ni(phendio)(Gly)(H₂O)](ClO₄)·H₂O (2) (where phendio = 1,10‐phenanthroline‐5,6‐dione, L ‐Phe = L ‐phenylalanine, Gly = glycine), are reported. Single‐crystal X‐ray diffraction results of (1) suggest that this complex structure belongs to the orthorhombic crystal system. The electrochemical properties of free phendio and these complexes in phosphate buffer solutions in a pH range between 2 and 9 have been investigated using cyclic voltammetry. The redox potential of these compounds is strongly dependent on the proton concentration in the range of ? 0.3–0.4 V vs SCE (saturated calomel reference electrode). Phendiol reacts by the reduction of the quinone species to the semiquinone anion followed by reduction to the fully reduced dianion. At pH lower than 4 and higher than 4, reduction of phendio proceeds via 2e^?/3H⁺ and 2e^?/2H⁺ processes. For complexes (1) and (2), being modulated by the coordinated amino acid, the reduction of the phendio ligand proceeds via 2e^?/2H⁺ and 2e^?/H⁺ processes, respectively. Copyright © 2006 John Wiley & Sons, Ltd.     

NEt4OH·4H2O containing infinite hydro­xide–water ribbons

In tetraethyl­ammonium hydro­xide tetrahydrate, C₈H₂₀N⁺·­OH^?·­4H₂O, the array of mirror symmetric NEt₄⁺ cations gives rise to a system of parallel channels which are filled with hydrogen‐bonded anionic ribbons. The central part of each ribbon is constituted by a [OH^?(HOH)_4/2] spiro‐chain, with each hydro­xide ion accepting four strong linear hydrogen bonds [d(O?O) between 2.692 (1) and 2.727 (1) Å] but donating none. Additional (two‐coordinate) H₂O mol­ecules bridge between the (four‐coordinate) H₂O mol­ecules of the spiro‐chain [d(O?O) between 2.831 (1) and 2.835 (1) Å].     

Kristallstrukturen des Sr(OH)2 · H2O,Ba(OH)2 · H2O (o.-rh. und mon.) und Ba(OH)2 · 3 H2O

Crystal Structures of Sr(OH)₂ · H₂O, Ba(OH)₂ · H₂O (o.-rh. and mon.), and Ba(OH)₂ · 3 H₂O The crystal structures of Ba(OH)₂ · 3 H₂O (Pnma, Z = 4), γ-Ba(OH)₂ · H₂O (P2₁/m, Z = 2) and the isotypic Sr(OH)₂ · H₂O and β-Ba(OH)₂ · H₂O (Pmc2₁, Z = 2) were determined using X-ray single crystal data. Ba(OH)₂ · 3 H₂O and Ba(OH)₂ · H₂O mon. crystallize in hitherto unknown structure types. The structure of Ba(OH)₂ · H₂O mon. is strongly related to that of rare earth hydroxides M(OH)₃ with space group P6₃/m (super group of P2₁/m). The metal-oxygen distances are significantly shorter for OH^? ions (mean Ba—O bond lengths of all hydroxides under investigation 278.1 pm) than for H₂O molecules (289.9 pm). Corresponding to other hydrates of ionic hydroxides, the water molecules form strong hydrogen bonds to adjacent OH^? ions whereas the hydroxide are not H-bonded.     

Synthesis,spectroscopic properties,and antimicrobial activity of some new 5-phenylazo-6-aminouracil-vanadyl complexes

Six complexes, [VO(L¹-H)₂]?·?5H₂O (1), [VO(OH)(L^2,3?H)(H₂O)]?·?H₂O (2,3), [VO(OH)(L^4,5?H)(H₂O)]?·?H₂O (4,5), [VO(OH)(L⁶?H)(H₂O)]?·?H₂O (6), were prepared by reacting different derivatives of 5-phenylazo-6-aminouracil ligands with VOSO₄?·?5H₂O. The infrared and ¹H NMR spectra of the complexes have been assigned. Thermogravimetric analyses (TG, DTG) were also carried out. The data agree quite well with the proposed structures and show that the complexes were finally decomposed to the corresponding divanadium pentoxide. The ligands and their vanadyl complexes were screened for antimicrobial activities by the agar-well diffusion technique using DMSO as solvent. The minimum inhibitory concentration (MIC) values for 1–4 and 6 were calculated at 30°C for 24–48?h. The activity data show that the complexes are more potent antimicrobials than the parent ligands.     

High-Pressure Stopped-Flow Study of the Kinetics of Base Hydrolysis of the Dichromate Ion by Hydroxide Ion,Ammonia, Water,and 2,6-Lutidine in Aqueous Solution

Volumes of activation for the base hydrolysis of the dichromate anion have been measured at 298.2 K, using high-pressure stopped-flow spectrophotometry. The values of ΔV* (cm³ · mol^?1), ? 17.9 ± 0.6, ? 19.2 ± 0.9, ? 24.9 ± 0.9 and ? 26.0 ± 0.7 for OH^?, NH₃, H₂O and 2,6-lutidine, respectively, are consistent with an interchange mechanism with associative activation mode (I^a).     

Competition between H<Subscript>2</Subscript>O and CH<Subscript>3</Subscript>OH molecules in the formation of the simplest stable proton disolvates and their solvation in aqueous methanol solutions of KOH and CH<Subscript>3</Subscript>OK

IR spectroscopic and quantum chemical methods are used to study the competition between water and methanol molecules in the formation of the simplest stable proton disolvates and their subsequent solvation in the case of solutions of KOH in CH₃OH and CH₃OK in H₂O with similar stoichiometries (~1:3-3.5). The complexes found in these solutions are analysed to determine their composition and structure: they are found to be heteroions (CH₃O?H?OH)^– solvated by two similar solvent molecules. In both cases, there are virtually no complexes of the second possible type (CH₃OH·(CH₃O?H?OCH₃)^–··H₂O or CH₃OH·(HO?H?OH)^–·H₂O), which appears to be due to the stoichiometric compositions of the solutions. It is shown that a DFT calculation (B3LYP/6-31++G(d,p)) of linear complexes with strong (~15-30 kcal/mol) H bonds reproduces, with good accuracy, the IR spectra of the solutions, which consist mainly of these complexes.     

Mass spectral fragmentation pattern of 3-(2′-hydroxyethyl)quinolin-2(1H)-one and its derivatives

Fragmentation patterns resulting from electron impact ionization of 3-(2′-hydroxyethyl)quinolin-2(1H)-one, three of its monosubstituted derivatives and four of its disubstituted derivatives were studied. The molecular ion of quinolinone-2-etbanol undergoes initial fragmentation with the loss of OH^·, H₂O, CO, ^·CHO, CH₂O, CH₂OH^·, CH₂?CHOH and HCNO species. The [M – CHO]⁺ ion is tentatively suggested to have been formed by the expulsion of H^· from the [M – CO]^+· ion and the [M - CHO]⁺ peak may be considered as diagnostic of a 2-quinolone-3-ethanol.     

Hydro­gen bonding in ethyl­ene­di­ammonium bis­(hydrogen malonate) mono­hydrate

In the title compound, C₂H₁₀N₂²⁺·2C₃H₃O₄^?·H₂O, the hydrogen malonate anion has an intramolecular O—H?O hydrogen bond of 2.430 (2) Å. The water mol­ecule lies on a twofold axis and connects the anions into pairs through hydrogen bonds of 2.734 (1) Å. The ethyl­enedi­ammonium cation lies across an inversion centre. Each of the ammonium protons is involved in hydrogen bonding to an anion or a water mol­ecule [N?O 2.815 (2)–2.875 (2) Å].     

Supramolecular networks constructed by cationic copper(II) complexes incorporating hybrid water–anionic polymeric assemblies

Two complexes, [Cu₂(TFSA)(2,2′-bpy)₄]?·?TFSA?·?8H₂O (1) and {[Cu(4,4′-bpy)(H₂O)₂]?·?TFSA?·?6H₂O} _n (2) (H₂TFSA?=?tetrafluorosuccinic acid, 2,2′-bpy?=?2,2′-bipyridine, and 4,4′-bpy?=?4,4′-bipyridine), have been synthesized and structurally characterized by X-ray structural analyses. Complex 1 is a binuclear molecule bridged by TFSA ligands; 2 is a 1-D chain bridged by 4,4′-bpy ligands. The asymmetric units of the two complexes are composed of cationic complexes [Cu₂(TFSA)(2,2′-bpy)₄]²⁺ (1) and [Cu(4,4′-bpy)(H₂O)₂]²⁺ (2), free TFSA anion, and independent crystallization water molecules. A unique 2-D hybrid water–TFSA anionic layer by linkage of {[(H₂O)₈(TFSA)]^2?} _n fragments consisting of 1-D T6(0)A2 water tape and TFSA anionic units by hydrogen bonds in 1 was observed. Unique 2-D hybrid water–TFSA anionic layer generated by the linkage of {[(H₂O)₆(TFSA)]^2?} _n fragments consisting of cyclic water tetramers with appended water molecules and TFSA anionic units, and 1-D metal–water tape [Cu–H₂O?···?(H₂O)₆?···?H₂O^?] _n in 2 were found. 3-D supramolecular networks of the two complexes consist of cationic complexes and water–TFSA anionic assemblies connected by hydrogen bonds.     

Homo- and heteronuclear iron complexes {Fe<Subscript>2</Subscript>MO} with salicylic acid: Synthesis,structures, and physicochemical properties

A reaction of iron nitrate with magnesium salicylate and reactions of iron and cobalt chlorides with ammonium salicylate in the presence of water, methanol, DMAA, and DMF gave the trinuclear heterometallic complexes: [hexa-μ-salicylato-μ₃-oxo-0.4-dimethylacetamide-2.6-aquadiiron(III)magnesium(II)] tetra(dimethylacetamide), [Fe₂MgO(SalH)₆(DMAA)_0.4(H₂O)_2.6]·4DMAA (I); [hexa-μ]-salicylato-μ₃-oxo(dimethanol)aquadiiron(III)cobalt(II)] dimethylformamide · 2.5-hydrate, [Fe₂CoO(SalH)₆(CH₃OH)₂(H₂O)] · DMF · 2.5H₂O (II); and [hexa-μ-salicylato-μ₃-oxotriaquatriiron(III)] chloride dimethylacetamide monohydrate, [Fe₃O(SalH)₆(H₂O)₃]Cl · DMAA · H₂O (III). The X-ray study revealed that the molecular structures of complexes I and II are [Fe₂ ^IIIM^II(μ₃-O)(RCOO)₆L₃] · nSolv. The IR and Mössbauer spectra of complexes I–III were examined; their magnetochemical and thermal properties were studied. The parameters of the Mössbauer spectra (δ_Na ⁺ = 0.69 ± 0.03 mm/s, ΔE _Q = 0.76–1.08 mm/s, 300 K) suggest the high-spin state of the Fe³⁺ ions in complexes I–III (S = 5/2). The paramagnetic Fe³⁺ ions are involved in antiferromagnetic exchange interactions with the parameter J = ?44 cm^?1, g = 2.05 (for I). Complexes I–III are thermally unstable.     

Thermolysis of cobalt(II) cyanuric acid complexes

Thermolysis during continuous heating in air from room temperature to ～1000°C was studied for cobalt(II) complexes with cyanuric acid: [CoL₂(OH₂)₂]Cl₂ · 4H₂O, [CoL₂(OH₂)₂]SO₄ · 3H₂O, and [CoL₂(OH₂)₂](NO₃)₂ (L stands for cyanuric acid C₃H₃N₃O₃). Thermoanalytical and thermogravimetric curves for these complexes and IR absorption spectra (400–4000 cm^?1) for their thermolysis products at various stages were described.     

Crystal structure of bis[Ba(Aet)(OH2)5]bis(Aet)·4H2O

An X-ray crystallographic study is conducted of single crystals with the composition [Ba₂(Aet^?)₂·10(H₂O)]²⁺·2(Aet^?)·4H₂O, where Aet^? = (C₁₀H₁₁N₄O₂S₂)^? is the ethazole (2-(para-aminobenzenesulfamido)-5-ethyl-1,3,4-tiadiazole) anion. The crystals are monoclinic; the space group is P2₁/c, Z = 2; a = 9.793(2) Å, b = 15.408(4) Å, and c = 22.553(6) Å; β = 94.98(2)°; and R = 0.047. The independent part of the compound’s structural formula, [Ba(Aet)(OH₂)₅](Aet)·2H₂O, is isostructural with the analogous compound with the Sr atom. The ethazole anion is coordinated to the complexing metal atom by oxygen and nitrogen atoms to form a four-membered ring.